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 // SPDX-License-Identifier: GPL-2.0
 /*
  * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
  *
  *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  *
  *  Interactivity improvements by Mike Galbraith
  *  (C) 2007 Mike Galbraith <efault@gmx.de>
  *
  *  Various enhancements by Dmitry Adamushko.
  *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
  *
  *  Group scheduling enhancements by Srivatsa Vaddagiri
  *  Copyright IBM Corporation, 2007
  *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
  *
  *  Scaled math optimizations by Thomas Gleixner
  *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
  *
  *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
  */
 #include <linux/energy_model.h>
 #include <linux/mmap_lock.h>
 #include <linux/hugetlb_inline.h>
 #include <linux/jiffies.h>
 #include <linux/mm_api.h>
 #include <linux/highmem.h>
 #include <linux/spinlock_api.h>
 #include <linux/cpumask_api.h>
 #include <linux/lockdep_api.h>
 #include <linux/softirq.h>
 #include <linux/refcount_api.h>
 #include <linux/topology.h>
 #include <linux/sched/clock.h>
 #include <linux/sched/cond_resched.h>
 #include <linux/sched/cputime.h>
 #include <linux/sched/isolation.h>
 #include <linux/sched/nohz.h>
 
 #include <linux/cpuidle.h>
 #include <linux/interrupt.h>
 #include <linux/mempolicy.h>
 #include <linux/mutex_api.h>
 #include <linux/profile.h>
 #include <linux/psi.h>
 #include <linux/ratelimit.h>
 #include <linux/task_work.h>
 
 #include <asm/switch_to.h>
 
 #include <linux/sched/cond_resched.h>
 
 #include "sched.h"
 #include "stats.h"
 #include "autogroup.h"
 
 /*
  * Targeted preemption latency for CPU-bound tasks:
  *
  * NOTE: this latency value is not the same as the concept of
  * 'timeslice length' - timeslices in CFS are of variable length
  * and have no persistent notion like in traditional, time-slice
  * based scheduling concepts.
  *
  * (to see the precise effective timeslice length of your workload,
  *  run vmstat and monitor the context-switches (cs) field)
  *
  * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
  */
 unsigned int sysctl_sched_latency           = 6000000ULL;
 static unsigned int normalized_sysctl_sched_latency = 6000000ULL;
 
 /*
  * The initial- and re-scaling of tunables is configurable
  *
  * Options are:
  *
  *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
  *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
  *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
  *
  * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
  */
 unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
 
 /*
  * Minimal preemption granularity for CPU-bound tasks:
  *
  * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
  */
 unsigned int sysctl_sched_min_granularity           = 750000ULL;
 static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
 
 /*
  * Minimal preemption granularity for CPU-bound SCHED_IDLE tasks.
  * Applies only when SCHED_IDLE tasks compete with normal tasks.
  *
  * (default: 0.75 msec)
  */
 unsigned int sysctl_sched_idle_min_granularity          = 750000ULL;
 
 /*
  * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
  */
 static unsigned int sched_nr_latency = 8;
 
 /*
  * After fork, child runs first. If set to 0 (default) then
  * parent will (try to) run first.
  */
 unsigned int sysctl_sched_child_runs_first __read_mostly;
 
 /*
  * SCHED_OTHER wake-up granularity.
  *
  * This option delays the preemption effects of decoupled workloads
  * and reduces their over-scheduling. Synchronous workloads will still
  * have immediate wakeup/sleep latencies.
  *
  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
  */
 unsigned int sysctl_sched_wakeup_granularity            = 1000000UL;
 static unsigned int normalized_sysctl_sched_wakeup_granularity  = 1000000UL;
 
 const_debug unsigned int sysctl_sched_migration_cost    = 500000UL;
 
 int sched_thermal_decay_shift;
 static int __init setup_sched_thermal_decay_shift(char *str)
 {
     int _shift = 0;
 
     if (kstrtoint(str, 0, &_shift))
         pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
 
     sched_thermal_decay_shift = clamp(_shift, 0, 10);
     return 1;
 }
 __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
 
 #ifdef CONFIG_SMP
 /*
  * For asym packing, by default the lower numbered CPU has higher priority.
  */
 int __weak arch_asym_cpu_priority(int cpu)
 {
     return -cpu;
 }
 
 /*
  * The margin used when comparing utilization with CPU capacity.
  *
  * (default: ~20%)
  */
 #define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
 
 /*
  * The margin used when comparing CPU capacities.
  * is 'cap1' noticeably greater than 'cap2'
  *
  * (default: ~5%)
  */
 #define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078)
 #endif
 
 #ifdef CONFIG_CFS_BANDWIDTH
 /*
  * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
  * each time a cfs_rq requests quota.
  *
  * Note: in the case that the slice exceeds the runtime remaining (either due
  * to consumption or the quota being specified to be smaller than the slice)
  * we will always only issue the remaining available time.
  *
  * (default: 5 msec, units: microseconds)
  */
 static unsigned int sysctl_sched_cfs_bandwidth_slice        = 5000UL;
 #endif
 
 #ifdef CONFIG_SYSCTL
 static struct ctl_table sched_fair_sysctls[] = {
     {
         .procname       = "sched_child_runs_first",
         .data           = &sysctl_sched_child_runs_first,
         .maxlen         = sizeof(unsigned int),
         .mode           = 0644,
         .proc_handler   = proc_dointvec,
     },
 #ifdef CONFIG_CFS_BANDWIDTH
     {
         .procname       = "sched_cfs_bandwidth_slice_us",
         .data           = &sysctl_sched_cfs_bandwidth_slice,
         .maxlen         = sizeof(unsigned int),
         .mode           = 0644,
         .proc_handler   = proc_dointvec_minmax,
         .extra1         = SYSCTL_ONE,
     },
 #endif
     {}
 };
 
 static int __init sched_fair_sysctl_init(void)
 {
     register_sysctl_init("kernel", sched_fair_sysctls);
     return 0;
 }
 late_initcall(sched_fair_sysctl_init);
 #endif
 
 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
 {
     lw->weight += inc;
     lw->inv_weight = 0;
 }
 
 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
 {
     lw->weight -= dec;
     lw->inv_weight = 0;
 }
 
 static inline void update_load_set(struct load_weight *lw, unsigned long w)
 {
     lw->weight = w;
     lw->inv_weight = 0;
 }
 
 /*
  * Increase the granularity value when there are more CPUs,
  * because with more CPUs the 'effective latency' as visible
  * to users decreases. But the relationship is not linear,
  * so pick a second-best guess by going with the log2 of the
  * number of CPUs.
  *
  * This idea comes from the SD scheduler of Con Kolivas:
  */
 static unsigned int get_update_sysctl_factor(void)
 {
     unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
     unsigned int factor;
 
     switch (sysctl_sched_tunable_scaling) {
     case SCHED_TUNABLESCALING_NONE:
         factor = 1;
         break;
     case SCHED_TUNABLESCALING_LINEAR:
         factor = cpus;
         break;
     case SCHED_TUNABLESCALING_LOG:
     default:
         factor = 1 + ilog2(cpus);
         break;
     }
 
     return factor;
 }
 
 static void update_sysctl(void)
 {
     unsigned int factor = get_update_sysctl_factor();
 
 #define SET_SYSCTL(name) \
     (sysctl_##name = (factor) * normalized_sysctl_##name)
     SET_SYSCTL(sched_min_granularity);
     SET_SYSCTL(sched_latency);
     SET_SYSCTL(sched_wakeup_granularity);
 #undef SET_SYSCTL
 }
 
 void __init sched_init_granularity(void)
 {
     update_sysctl();
 }
 
 #define WMULT_CONST (~0U)
 #define WMULT_SHIFT 32
 
 static void __update_inv_weight(struct load_weight *lw)
 {
     unsigned long w;
 
     if (likely(lw->inv_weight))
         return;
 
     w = scale_load_down(lw->weight);
 
     if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
         lw->inv_weight = 1;
     else if (unlikely(!w))
         lw->inv_weight = WMULT_CONST;
     else
         lw->inv_weight = WMULT_CONST / w;
 }
 
 /*
  * delta_exec * weight / lw.weight
  *   OR
  * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
  *
  * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
  * we're guaranteed shift stays positive because inv_weight is guaranteed to
  * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
  *
  * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
  * weight/lw.weight <= 1, and therefore our shift will also be positive.
  */
 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
 {
     u64 fact = scale_load_down(weight);
     u32 fact_hi = (u32)(fact >> 32);
     int shift = WMULT_SHIFT;
     int fs;
 
     __update_inv_weight(lw);
 
     if (unlikely(fact_hi)) {
         fs = fls(fact_hi);
         shift -= fs;
         fact >>= fs;
     }
 
     fact = mul_u32_u32(fact, lw->inv_weight);
 
     fact_hi = (u32)(fact >> 32);
     if (fact_hi) {
         fs = fls(fact_hi);
         shift -= fs;
         fact >>= fs;
     }
 
     return mul_u64_u32_shr(delta_exec, fact, shift);
 }
 
 
 const struct sched_class fair_sched_class;
 
 /**************************************************************
  * CFS operations on generic schedulable entities:
  */
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
 /* Walk up scheduling entities hierarchy */
 #define for_each_sched_entity(se) \
         for (; se; se = se->parent)
 
 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
     struct rq *rq = rq_of(cfs_rq);
     int cpu = cpu_of(rq);
 
     if (cfs_rq->on_list)
         return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
 
     cfs_rq->on_list = 1;
 
     /*
      * Ensure we either appear before our parent (if already
      * enqueued) or force our parent to appear after us when it is
      * enqueued. The fact that we always enqueue bottom-up
      * reduces this to two cases and a special case for the root
      * cfs_rq. Furthermore, it also means that we will always reset
      * tmp_alone_branch either when the branch is connected
      * to a tree or when we reach the top of the tree
      */
     if (cfs_rq->tg->parent &&
         cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
         /*
          * If parent is already on the list, we add the child
          * just before. Thanks to circular linked property of
          * the list, this means to put the child at the tail
          * of the list that starts by parent.
          */
         list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
             &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
         /*
          * The branch is now connected to its tree so we can
          * reset tmp_alone_branch to the beginning of the
          * list.
          */
         rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
         return true;
     }
 
     if (!cfs_rq->tg->parent) {
         /*
          * cfs rq without parent should be put
          * at the tail of the list.
          */
         list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
             &rq->leaf_cfs_rq_list);
         /*
          * We have reach the top of a tree so we can reset
          * tmp_alone_branch to the beginning of the list.
          */
         rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
         return true;
     }
 
     /*
      * The parent has not already been added so we want to
      * make sure that it will be put after us.
      * tmp_alone_branch points to the begin of the branch
      * where we will add parent.
      */
     list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
     /*
      * update tmp_alone_branch to points to the new begin
      * of the branch
      */
     rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
     return false;
 }
 
 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
     if (cfs_rq->on_list) {
         struct rq *rq = rq_of(cfs_rq);
 
         /*
          * With cfs_rq being unthrottled/throttled during an enqueue,
          * it can happen the tmp_alone_branch points the a leaf that
          * we finally want to del. In this case, tmp_alone_branch moves
          * to the prev element but it will point to rq->leaf_cfs_rq_list
          * at the end of the enqueue.
          */
         if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
             rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
 
         list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
         cfs_rq->on_list = 0;
     }
 }
 
 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
 {
     SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
 }
 
 /* Iterate thr' all leaf cfs_rq's on a runqueue */
 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)          \
     list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list,    \
                  leaf_cfs_rq_list)
 
 /* Do the two (enqueued) entities belong to the same group ? */
 static inline struct cfs_rq *
 is_same_group(struct sched_entity *se, struct sched_entity *pse)
 {
     if (se->cfs_rq == pse->cfs_rq)
         return se->cfs_rq;
 
     return NULL;
 }
 
 static inline struct sched_entity *parent_entity(struct sched_entity *se)
 {
     return se->parent;
 }
 
 static void
 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 {
     int se_depth, pse_depth;
 
     /*
      * preemption test can be made between sibling entities who are in the
      * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
      * both tasks until we find their ancestors who are siblings of common
      * parent.
      */
 
     /* First walk up until both entities are at same depth */
     se_depth = (*se)->depth;
     pse_depth = (*pse)->depth;
 
     while (se_depth > pse_depth) {
         se_depth--;
         *se = parent_entity(*se);
     }
 
     while (pse_depth > se_depth) {
         pse_depth--;
         *pse = parent_entity(*pse);
     }
 
     while (!is_same_group(*se, *pse)) {
         *se = parent_entity(*se);
         *pse = parent_entity(*pse);
     }
 }
 
 static int tg_is_idle(struct task_group *tg)
 {
     return tg->idle > 0;
 }
 
 static int cfs_rq_is_idle(struct cfs_rq *cfs_rq)
 {
     return cfs_rq->idle > 0;
 }
 
 static int se_is_idle(struct sched_entity *se)
 {
     if (entity_is_task(se))
         return task_has_idle_policy(task_of(se));
     return cfs_rq_is_idle(group_cfs_rq(se));
 }
 
 #else   /* !CONFIG_FAIR_GROUP_SCHED */
 
 #define for_each_sched_entity(se) \
         for (; se; se = NULL)
 
 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
     return true;
 }
 
 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
 }
 
 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
 {
 }
 
 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)  \
         for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
 
 static inline struct sched_entity *parent_entity(struct sched_entity *se)
 {
     return NULL;
 }
 
 static inline void
 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 {
 }
 
 static inline int tg_is_idle(struct task_group *tg)
 {
     return 0;
 }
 
 static int cfs_rq_is_idle(struct cfs_rq *cfs_rq)
 {
     return 0;
 }
 
 static int se_is_idle(struct sched_entity *se)
 {
     return 0;
 }
 
 #endif  /* CONFIG_FAIR_GROUP_SCHED */
 
 static __always_inline
 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
 
 /**************************************************************
  * Scheduling class tree data structure manipulation methods:
  */
 
 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 {
     s64 delta = (s64)(vruntime - max_vruntime);
     if (delta > 0)
         max_vruntime = vruntime;
 
     return max_vruntime;
 }
 
 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
 {
     s64 delta = (s64)(vruntime - min_vruntime);
     if (delta < 0)
         min_vruntime = vruntime;
 
     return min_vruntime;
 }
 
 static inline bool entity_before(struct sched_entity *a,
                 struct sched_entity *b)
 {
     return (s64)(a->vruntime - b->vruntime) < 0;
 }
 
 #define __node_2_se(node) \
     rb_entry((node), struct sched_entity, run_node)
 
 static void update_min_vruntime(struct cfs_rq *cfs_rq)
 {
     struct sched_entity *curr = cfs_rq->curr;
     struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
 
     u64 vruntime = cfs_rq->min_vruntime;
 
     if (curr) {
         if (curr->on_rq)
             vruntime = curr->vruntime;
         else
             curr = NULL;
     }
 
     if (leftmost) { /* non-empty tree */
         struct sched_entity *se = __node_2_se(leftmost);
 
         if (!curr)
             vruntime = se->vruntime;
         else
             vruntime = min_vruntime(vruntime, se->vruntime);
     }
 
     /* ensure we never gain time by being placed backwards. */
     u64_u32_store(cfs_rq->min_vruntime,
               max_vruntime(cfs_rq->min_vruntime, vruntime));
 }
 
 static inline bool __entity_less(struct rb_node *a, const struct rb_node *b)
 {
     return entity_before(__node_2_se(a), __node_2_se(b));
 }
 
 /*
  * Enqueue an entity into the rb-tree:
  */
 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     rb_add_cached(&se->run_node, &cfs_rq->tasks_timeline, __entity_less);
 }
 
 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
 }
 
 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
 {
     struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
 
     if (!left)
         return NULL;
 
     return __node_2_se(left);
 }
 
 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
 {
     struct rb_node *next = rb_next(&se->run_node);
 
     if (!next)
         return NULL;
 
     return __node_2_se(next);
 }
 
 #ifdef CONFIG_SCHED_DEBUG
 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 {
     struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
 
     if (!last)
         return NULL;
 
     return __node_2_se(last);
 }
 
 /**************************************************************
  * Scheduling class statistics methods:
  */
 
 int sched_update_scaling(void)
 {
     unsigned int factor = get_update_sysctl_factor();
 
     sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
                     sysctl_sched_min_granularity);
 
 #define WRT_SYSCTL(name) \
     (normalized_sysctl_##name = sysctl_##name / (factor))
     WRT_SYSCTL(sched_min_granularity);
     WRT_SYSCTL(sched_latency);
     WRT_SYSCTL(sched_wakeup_granularity);
 #undef WRT_SYSCTL
 
     return 0;
 }
 #endif
 
 /*
  * delta /= w
  */
 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
 {
     if (unlikely(se->load.weight != NICE_0_LOAD))
         delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
 
     return delta;
 }
 
 /*
  * The idea is to set a period in which each task runs once.
  *
  * When there are too many tasks (sched_nr_latency) we have to stretch
  * this period because otherwise the slices get too small.
  *
  * p = (nr <= nl) ? l : l*nr/nl
  */
 static u64 __sched_period(unsigned long nr_running)
 {
     if (unlikely(nr_running > sched_nr_latency))
         return nr_running * sysctl_sched_min_granularity;
     else
         return sysctl_sched_latency;
 }
 
 static bool sched_idle_cfs_rq(struct cfs_rq *cfs_rq);
 
 /*
  * We calculate the wall-time slice from the period by taking a part
  * proportional to the weight.
  *
  * s = p*P[w/rw]
  */
 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     unsigned int nr_running = cfs_rq->nr_running;
     struct sched_entity *init_se = se;
     unsigned int min_gran;
     u64 slice;
 
     if (sched_feat(ALT_PERIOD))
         nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
 
     slice = __sched_period(nr_running + !se->on_rq);
 
     for_each_sched_entity(se) {
         struct load_weight *load;
         struct load_weight lw;
         struct cfs_rq *qcfs_rq;
 
         qcfs_rq = cfs_rq_of(se);
         load = &qcfs_rq->load;
 
         if (unlikely(!se->on_rq)) {
             lw = qcfs_rq->load;
 
             update_load_add(&lw, se->load.weight);
             load = &lw;
         }
         slice = __calc_delta(slice, se->load.weight, load);
     }
 
     if (sched_feat(BASE_SLICE)) {
         if (se_is_idle(init_se) && !sched_idle_cfs_rq(cfs_rq))
             min_gran = sysctl_sched_idle_min_granularity;
         else
             min_gran = sysctl_sched_min_granularity;
 
         slice = max_t(u64, slice, min_gran);
     }
 
     return slice;
 }
 
 /*
  * We calculate the vruntime slice of a to-be-inserted task.
  *
  * vs = s/w
  */
 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     return calc_delta_fair(sched_slice(cfs_rq, se), se);
 }
 
 #include "pelt.h"
 #ifdef CONFIG_SMP
 
 static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
 static unsigned long task_h_load(struct task_struct *p);
 static unsigned long capacity_of(int cpu);
 
 /* Give new sched_entity start runnable values to heavy its load in infant time */
 void init_entity_runnable_average(struct sched_entity *se)
 {
     struct sched_avg *sa = &se->avg;
 
     memset(sa, 0, sizeof(*sa));
 
     /*
      * Tasks are initialized with full load to be seen as heavy tasks until
      * they get a chance to stabilize to their real load level.
      * Group entities are initialized with zero load to reflect the fact that
      * nothing has been attached to the task group yet.
      */
     if (entity_is_task(se))
         sa->load_avg = scale_load_down(se->load.weight);
 
     /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
 }
 
 static void attach_entity_cfs_rq(struct sched_entity *se);
 
 /*
  * With new tasks being created, their initial util_avgs are extrapolated
  * based on the cfs_rq's current util_avg:
  *
  *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
  *
  * However, in many cases, the above util_avg does not give a desired
  * value. Moreover, the sum of the util_avgs may be divergent, such
  * as when the series is a harmonic series.
  *
  * To solve this problem, we also cap the util_avg of successive tasks to
  * only 1/2 of the left utilization budget:
  *
  *   util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
  *
  * where n denotes the nth task and cpu_scale the CPU capacity.
  *
  * For example, for a CPU with 1024 of capacity, a simplest series from
  * the beginning would be like:
  *
  *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
  * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
  *
  * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
  * if util_avg > util_avg_cap.
  */
 void post_init_entity_util_avg(struct task_struct *p)
 {
     struct sched_entity *se = &p->se;
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
     struct sched_avg *sa = &se->avg;
     long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
     long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
 
     if (cap > 0) {
         if (cfs_rq->avg.util_avg != 0) {
             sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
             sa->util_avg /= (cfs_rq->avg.load_avg + 1);
 
             if (sa->util_avg > cap)
                 sa->util_avg = cap;
         } else {
             sa->util_avg = cap;
         }
     }
 
     sa->runnable_avg = sa->util_avg;
 
     if (p->sched_class != &fair_sched_class) {
         /*
          * For !fair tasks do:
          *
         update_cfs_rq_load_avg(now, cfs_rq);
         attach_entity_load_avg(cfs_rq, se);
         switched_from_fair(rq, p);
          *
          * such that the next switched_to_fair() has the
          * expected state.
          */
         se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
         return;
     }
 
     attach_entity_cfs_rq(se);
 }
 
 #else /* !CONFIG_SMP */
 void init_entity_runnable_average(struct sched_entity *se)
 {
 }
 void post_init_entity_util_avg(struct task_struct *p)
 {
 }
 static void update_tg_load_avg(struct cfs_rq *cfs_rq)
 {
 }
 #endif /* CONFIG_SMP */
 
 /*
  * Update the current task's runtime statistics.
  */
 static void update_curr(struct cfs_rq *cfs_rq)
 {
     struct sched_entity *curr = cfs_rq->curr;
     u64 now = rq_clock_task(rq_of(cfs_rq));
     u64 delta_exec;
 
     if (unlikely(!curr))
         return;
 
     delta_exec = now - curr->exec_start;
     if (unlikely((s64)delta_exec <= 0))
         return;
 
     curr->exec_start = now;
 
     if (schedstat_enabled()) {
         struct sched_statistics *stats;
 
         stats = __schedstats_from_se(curr);
         __schedstat_set(stats->exec_max,
                 max(delta_exec, stats->exec_max));
     }
 
     curr->sum_exec_runtime += delta_exec;
     schedstat_add(cfs_rq->exec_clock, delta_exec);
 
     curr->vruntime += calc_delta_fair(delta_exec, curr);
     update_min_vruntime(cfs_rq);
 
     if (entity_is_task(curr)) {
         struct task_struct *curtask = task_of(curr);
 
         trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
         cgroup_account_cputime(curtask, delta_exec);
         account_group_exec_runtime(curtask, delta_exec);
     }
 
     account_cfs_rq_runtime(cfs_rq, delta_exec);
 }
 
 static void update_curr_fair(struct rq *rq)
 {
     update_curr(cfs_rq_of(&rq->curr->se));
 }
 
 static inline void
 update_stats_wait_start_fair(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     struct sched_statistics *stats;
     struct task_struct *p = NULL;
 
     if (!schedstat_enabled())
         return;
 
     stats = __schedstats_from_se(se);
 
     if (entity_is_task(se))
         p = task_of(se);
 
     __update_stats_wait_start(rq_of(cfs_rq), p, stats);
 }
 
 static inline void
 update_stats_wait_end_fair(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     struct sched_statistics *stats;
     struct task_struct *p = NULL;
 
     if (!schedstat_enabled())
         return;
 
     stats = __schedstats_from_se(se);
 
     /*
      * When the sched_schedstat changes from 0 to 1, some sched se
      * maybe already in the runqueue, the se->statistics.wait_start
      * will be 0.So it will let the delta wrong. We need to avoid this
      * scenario.
      */
     if (unlikely(!schedstat_val(stats->wait_start)))
         return;
 
     if (entity_is_task(se))
         p = task_of(se);
 
     __update_stats_wait_end(rq_of(cfs_rq), p, stats);
 }
 
 static inline void
 update_stats_enqueue_sleeper_fair(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     struct sched_statistics *stats;
     struct task_struct *tsk = NULL;
 
     if (!schedstat_enabled())
         return;
 
     stats = __schedstats_from_se(se);
 
     if (entity_is_task(se))
         tsk = task_of(se);
 
     __update_stats_enqueue_sleeper(rq_of(cfs_rq), tsk, stats);
 }
 
 /*
  * Task is being enqueued - update stats:
  */
 static inline void
 update_stats_enqueue_fair(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
     if (!schedstat_enabled())
         return;
 
     /*
      * Are we enqueueing a waiting task? (for current tasks
      * a dequeue/enqueue event is a NOP)
      */
     if (se != cfs_rq->curr)
         update_stats_wait_start_fair(cfs_rq, se);
 
     if (flags & ENQUEUE_WAKEUP)
         update_stats_enqueue_sleeper_fair(cfs_rq, se);
 }
 
 static inline void
 update_stats_dequeue_fair(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
 
     if (!schedstat_enabled())
         return;
 
     /*
      * Mark the end of the wait period if dequeueing a
      * waiting task:
      */
     if (se != cfs_rq->curr)
         update_stats_wait_end_fair(cfs_rq, se);
 
     if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
         struct task_struct *tsk = task_of(se);
         unsigned int state;
 
         /* XXX racy against TTWU */
         state = READ_ONCE(tsk->__state);
         if (state & TASK_INTERRUPTIBLE)
             __schedstat_set(tsk->stats.sleep_start,
                       rq_clock(rq_of(cfs_rq)));
         if (state & TASK_UNINTERRUPTIBLE)
             __schedstat_set(tsk->stats.block_start,
                       rq_clock(rq_of(cfs_rq)));
     }
 }
 
 /*
  * We are picking a new current task - update its stats:
  */
 static inline void
 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     /*
      * We are starting a new run period:
      */
     se->exec_start = rq_clock_task(rq_of(cfs_rq));
 }
 
 /**************************************************
  * Scheduling class queueing methods:
  */
 
 #ifdef CONFIG_NUMA
 #define NUMA_IMBALANCE_MIN 2
 
 static inline long
 adjust_numa_imbalance(int imbalance, int dst_running, int imb_numa_nr)
 {
     /*
      * Allow a NUMA imbalance if busy CPUs is less than the maximum
      * threshold. Above this threshold, individual tasks may be contending
      * for both memory bandwidth and any shared HT resources.  This is an
      * approximation as the number of running tasks may not be related to
      * the number of busy CPUs due to sched_setaffinity.
      */
     if (dst_running > imb_numa_nr)
         return imbalance;
 
     /*
      * Allow a small imbalance based on a simple pair of communicating
      * tasks that remain local when the destination is lightly loaded.
      */
     if (imbalance <= NUMA_IMBALANCE_MIN)
         return 0;
 
     return imbalance;
 }
 #endif /* CONFIG_NUMA */
 
 #ifdef CONFIG_NUMA_BALANCING
 /*
  * Approximate time to scan a full NUMA task in ms. The task scan period is
  * calculated based on the tasks virtual memory size and
  * numa_balancing_scan_size.
  */
 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
 
 /* Portion of address space to scan in MB */
 unsigned int sysctl_numa_balancing_scan_size = 256;
 
 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
 unsigned int sysctl_numa_balancing_scan_delay = 1000;
 
 struct numa_group {
     refcount_t refcount;
 
     spinlock_t lock; /* nr_tasks, tasks */
     int nr_tasks;
     pid_t gid;
     int active_nodes;
 
     struct rcu_head rcu;
     unsigned long total_faults;
     unsigned long max_faults_cpu;
     /*
      * faults[] array is split into two regions: faults_mem and faults_cpu.
      *
      * Faults_cpu is used to decide whether memory should move
      * towards the CPU. As a consequence, these stats are weighted
      * more by CPU use than by memory faults.
      */
     unsigned long faults[];
 };
 
 /*
  * For functions that can be called in multiple contexts that permit reading
  * ->numa_group (see struct task_struct for locking rules).
  */
 static struct numa_group *deref_task_numa_group(struct task_struct *p)
 {
     return rcu_dereference_check(p->numa_group, p == current ||
         (lockdep_is_held(__rq_lockp(task_rq(p))) && !READ_ONCE(p->on_cpu)));
 }
 
 static struct numa_group *deref_curr_numa_group(struct task_struct *p)
 {
     return rcu_dereference_protected(p->numa_group, p == current);
 }
 
 static inline unsigned long group_faults_priv(struct numa_group *ng);
 static inline unsigned long group_faults_shared(struct numa_group *ng);
 
 static unsigned int task_nr_scan_windows(struct task_struct *p)
 {
     unsigned long rss = 0;
     unsigned long nr_scan_pages;
 
     /*
      * Calculations based on RSS as non-present and empty pages are skipped
      * by the PTE scanner and NUMA hinting faults should be trapped based
      * on resident pages
      */
     nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
     rss = get_mm_rss(p->mm);
     if (!rss)
         rss = nr_scan_pages;
 
     rss = round_up(rss, nr_scan_pages);
     return rss / nr_scan_pages;
 }
 
 /* For sanity's sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
 #define MAX_SCAN_WINDOW 2560
 
 static unsigned int task_scan_min(struct task_struct *p)
 {
     unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
     unsigned int scan, floor;
     unsigned int windows = 1;
 
     if (scan_size < MAX_SCAN_WINDOW)
         windows = MAX_SCAN_WINDOW / scan_size;
     floor = 1000 / windows;
 
     scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
     return max_t(unsigned int, floor, scan);
 }
 
 static unsigned int task_scan_start(struct task_struct *p)
 {
     unsigned long smin = task_scan_min(p);
     unsigned long period = smin;
     struct numa_group *ng;
 
     /* Scale the maximum scan period with the amount of shared memory. */
     rcu_read_lock();
     ng = rcu_dereference(p->numa_group);
     if (ng) {
         unsigned long shared = group_faults_shared(ng);
         unsigned long private = group_faults_priv(ng);
 
         period *= refcount_read(&ng->refcount);
         period *= shared + 1;
         period /= private + shared + 1;
     }
     rcu_read_unlock();
 
     return max(smin, period);
 }
 
 static unsigned int task_scan_max(struct task_struct *p)
 {
     unsigned long smin = task_scan_min(p);
     unsigned long smax;
     struct numa_group *ng;
 
     /* Watch for min being lower than max due to floor calculations */
     smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
 
     /* Scale the maximum scan period with the amount of shared memory. */
     ng = deref_curr_numa_group(p);
     if (ng) {
         unsigned long shared = group_faults_shared(ng);
         unsigned long private = group_faults_priv(ng);
         unsigned long period = smax;
 
         period *= refcount_read(&ng->refcount);
         period *= shared + 1;
         period /= private + shared + 1;
 
         smax = max(smax, period);
     }
 
     return max(smin, smax);
 }
 
 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
 {
     rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
     rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
 }
 
 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
 {
     rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
     rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
 }
 
 /* Shared or private faults. */
 #define NR_NUMA_HINT_FAULT_TYPES 2
 
 /* Memory and CPU locality */
 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
 
 /* Averaged statistics, and temporary buffers. */
 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
 
 pid_t task_numa_group_id(struct task_struct *p)
 {
     struct numa_group *ng;
     pid_t gid = 0;
 
     rcu_read_lock();
     ng = rcu_dereference(p->numa_group);
     if (ng)
         gid = ng->gid;
     rcu_read_unlock();
 
     return gid;
 }
 
 /*
  * The averaged statistics, shared & private, memory & CPU,
  * occupy the first half of the array. The second half of the
  * array is for current counters, which are averaged into the
  * first set by task_numa_placement.
  */
 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
 {
     return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
 }
 
 static inline unsigned long task_faults(struct task_struct *p, int nid)
 {
     if (!p->numa_faults)
         return 0;
 
     return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
         p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
 }
 
 static inline unsigned long group_faults(struct task_struct *p, int nid)
 {
     struct numa_group *ng = deref_task_numa_group(p);
 
     if (!ng)
         return 0;
 
     return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
         ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
 }
 
 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
 {
     return group->faults[task_faults_idx(NUMA_CPU, nid, 0)] +
         group->faults[task_faults_idx(NUMA_CPU, nid, 1)];
 }
 
 static inline unsigned long group_faults_priv(struct numa_group *ng)
 {
     unsigned long faults = 0;
     int node;
 
     for_each_online_node(node) {
         faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
     }
 
     return faults;
 }
 
 static inline unsigned long group_faults_shared(struct numa_group *ng)
 {
     unsigned long faults = 0;
     int node;
 
     for_each_online_node(node) {
         faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
     }
 
     return faults;
 }
 
 /*
  * A node triggering more than 1/3 as many NUMA faults as the maximum is
  * considered part of a numa group's pseudo-interleaving set. Migrations
  * between these nodes are slowed down, to allow things to settle down.
  */
 #define ACTIVE_NODE_FRACTION 3
 
 static bool numa_is_active_node(int nid, struct numa_group *ng)
 {
     return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
 }
 
 /* Handle placement on systems where not all nodes are directly connected. */
 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
                     int lim_dist, bool task)
 {
     unsigned long score = 0;
     int node, max_dist;
 
     /*
      * All nodes are directly connected, and the same distance
      * from each other. No need for fancy placement algorithms.
      */
     if (sched_numa_topology_type == NUMA_DIRECT)
         return 0;
 
     /* sched_max_numa_distance may be changed in parallel. */
     max_dist = READ_ONCE(sched_max_numa_distance);
     /*
      * This code is called for each node, introducing N^2 complexity,
      * which should be ok given the number of nodes rarely exceeds 8.
      */
     for_each_online_node(node) {
         unsigned long faults;
         int dist = node_distance(nid, node);
 
         /*
          * The furthest away nodes in the system are not interesting
          * for placement; nid was already counted.
          */
         if (dist >= max_dist || node == nid)
             continue;
 
         /*
          * On systems with a backplane NUMA topology, compare groups
          * of nodes, and move tasks towards the group with the most
          * memory accesses. When comparing two nodes at distance
          * "hoplimit", only nodes closer by than "hoplimit" are part
          * of each group. Skip other nodes.
          */
         if (sched_numa_topology_type == NUMA_BACKPLANE && dist >= lim_dist)
             continue;
 
         /* Add up the faults from nearby nodes. */
         if (task)
             faults = task_faults(p, node);
         else
             faults = group_faults(p, node);
 
         /*
          * On systems with a glueless mesh NUMA topology, there are
          * no fixed "groups of nodes". Instead, nodes that are not
          * directly connected bounce traffic through intermediate
          * nodes; a numa_group can occupy any set of nodes.
          * The further away a node is, the less the faults count.
          * This seems to result in good task placement.
          */
         if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
             faults *= (max_dist - dist);
             faults /= (max_dist - LOCAL_DISTANCE);
         }
 
         score += faults;
     }
 
     return score;
 }
 
 /*
  * These return the fraction of accesses done by a particular task, or
  * task group, on a particular numa node.  The group weight is given a
  * larger multiplier, in order to group tasks together that are almost
  * evenly spread out between numa nodes.
  */
 static inline unsigned long task_weight(struct task_struct *p, int nid,
                     int dist)
 {
     unsigned long faults, total_faults;
 
     if (!p->numa_faults)
         return 0;
 
     total_faults = p->total_numa_faults;
 
     if (!total_faults)
         return 0;
 
     faults = task_faults(p, nid);
     faults += score_nearby_nodes(p, nid, dist, true);
 
     return 1000 * faults / total_faults;
 }
 
 static inline unsigned long group_weight(struct task_struct *p, int nid,
                      int dist)
 {
     struct numa_group *ng = deref_task_numa_group(p);
     unsigned long faults, total_faults;
 
     if (!ng)
         return 0;
 
     total_faults = ng->total_faults;
 
     if (!total_faults)
         return 0;
 
     faults = group_faults(p, nid);
     faults += score_nearby_nodes(p, nid, dist, false);
 
     return 1000 * faults / total_faults;
 }
 
 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
                 int src_nid, int dst_cpu)
 {
     struct numa_group *ng = deref_curr_numa_group(p);
     int dst_nid = cpu_to_node(dst_cpu);
     int last_cpupid, this_cpupid;
 
     this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
     last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
 
     /*
      * Allow first faults or private faults to migrate immediately early in
      * the lifetime of a task. The magic number 4 is based on waiting for
      * two full passes of the "multi-stage node selection" test that is
      * executed below.
      */
     if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) &&
         (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
         return true;
 
     /*
      * Multi-stage node selection is used in conjunction with a periodic
      * migration fault to build a temporal task<->page relation. By using
      * a two-stage filter we remove short/unlikely relations.
      *
      * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
      * a task's usage of a particular page (n_p) per total usage of this
      * page (n_t) (in a given time-span) to a probability.
      *
      * Our periodic faults will sample this probability and getting the
      * same result twice in a row, given these samples are fully
      * independent, is then given by P(n)^2, provided our sample period
      * is sufficiently short compared to the usage pattern.
      *
      * This quadric squishes small probabilities, making it less likely we
      * act on an unlikely task<->page relation.
      */
     if (!cpupid_pid_unset(last_cpupid) &&
                 cpupid_to_nid(last_cpupid) != dst_nid)
         return false;
 
     /* Always allow migrate on private faults */
     if (cpupid_match_pid(p, last_cpupid))
         return true;
 
     /* A shared fault, but p->numa_group has not been set up yet. */
     if (!ng)
         return true;
 
     /*
      * Destination node is much more heavily used than the source
      * node? Allow migration.
      */
     if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
                     ACTIVE_NODE_FRACTION)
         return true;
 
     /*
      * Distribute memory according to CPU & memory use on each node,
      * with 3/4 hysteresis to avoid unnecessary memory migrations:
      *
      * faults_cpu(dst)   3   faults_cpu(src)
      * --------------- * - > ---------------
      * faults_mem(dst)   4   faults_mem(src)
      */
     return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
            group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
 }
 
 /*
  * 'numa_type' describes the node at the moment of load balancing.
  */
 enum numa_type {
     /* The node has spare capacity that can be used to run more tasks.  */
     node_has_spare = 0,
     /*
      * The node is fully used and the tasks don't compete for more CPU
      * cycles. Nevertheless, some tasks might wait before running.
      */
     node_fully_busy,
     /*
      * The node is overloaded and can't provide expected CPU cycles to all
      * tasks.
      */
     node_overloaded
 };
 
 /* Cached statistics for all CPUs within a node */
 struct numa_stats {
     unsigned long load;
     unsigned long runnable;
     unsigned long util;
     /* Total compute capacity of CPUs on a node */
     unsigned long compute_capacity;
     unsigned int nr_running;
     unsigned int weight;
     enum numa_type node_type;
     int idle_cpu;
 };
 
 static inline bool is_core_idle(int cpu)
 {
 #ifdef CONFIG_SCHED_SMT
     int sibling;
 
     for_each_cpu(sibling, cpu_smt_mask(cpu)) {
         if (cpu == sibling)
             continue;
 
         if (!idle_cpu(sibling))
             return false;
     }
 #endif
 
     return true;
 }
 
 struct task_numa_env {
     struct task_struct *p;
 
     int src_cpu, src_nid;
     int dst_cpu, dst_nid;
     int imb_numa_nr;
 
     struct numa_stats src_stats, dst_stats;
 
     int imbalance_pct;
     int dist;
 
     struct task_struct *best_task;
     long best_imp;
     int best_cpu;
 };
 
 static unsigned long cpu_load(struct rq *rq);
 static unsigned long cpu_runnable(struct rq *rq);
 
 static inline enum
 numa_type numa_classify(unsigned int imbalance_pct,
              struct numa_stats *ns)
 {
     if ((ns->nr_running > ns->weight) &&
         (((ns->compute_capacity * 100) < (ns->util * imbalance_pct)) ||
          ((ns->compute_capacity * imbalance_pct) < (ns->runnable * 100))))
         return node_overloaded;
 
     if ((ns->nr_running < ns->weight) ||
         (((ns->compute_capacity * 100) > (ns->util * imbalance_pct)) &&
          ((ns->compute_capacity * imbalance_pct) > (ns->runnable * 100))))
         return node_has_spare;
 
     return node_fully_busy;
 }
 
 #ifdef CONFIG_SCHED_SMT
 /* Forward declarations of select_idle_sibling helpers */
 static inline bool test_idle_cores(int cpu, bool def);
 static inline int numa_idle_core(int idle_core, int cpu)
 {
     if (!static_branch_likely(&sched_smt_present) ||
         idle_core >= 0 || !test_idle_cores(cpu, false))
         return idle_core;
 
     /*
      * Prefer cores instead of packing HT siblings
      * and triggering future load balancing.
      */
     if (is_core_idle(cpu))
         idle_core = cpu;
 
     return idle_core;
 }
 #else
 static inline int numa_idle_core(int idle_core, int cpu)
 {
     return idle_core;
 }
 #endif
 
 /*
  * Gather all necessary information to make NUMA balancing placement
  * decisions that are compatible with standard load balancer. This
  * borrows code and logic from update_sg_lb_stats but sharing a
  * common implementation is impractical.
  */
 static void update_numa_stats(struct task_numa_env *env,
                   struct numa_stats *ns, int nid,
                   bool find_idle)
 {
     int cpu, idle_core = -1;
 
     memset(ns, 0, sizeof(*ns));
     ns->idle_cpu = -1;
 
     rcu_read_lock();
     for_each_cpu(cpu, cpumask_of_node(nid)) {
         struct rq *rq = cpu_rq(cpu);
 
         ns->load += cpu_load(rq);
         ns->runnable += cpu_runnable(rq);
         ns->util += cpu_util_cfs(cpu);
         ns->nr_running += rq->cfs.h_nr_running;
         ns->compute_capacity += capacity_of(cpu);
 
         if (find_idle && !rq->nr_running && idle_cpu(cpu)) {
             if (READ_ONCE(rq->numa_migrate_on) ||
                 !cpumask_test_cpu(cpu, env->p->cpus_ptr))
                 continue;
 
             if (ns->idle_cpu == -1)
                 ns->idle_cpu = cpu;
 
             idle_core = numa_idle_core(idle_core, cpu);
         }
     }
     rcu_read_unlock();
 
     ns->weight = cpumask_weight(cpumask_of_node(nid));
 
     ns->node_type = numa_classify(env->imbalance_pct, ns);
 
     if (idle_core >= 0)
         ns->idle_cpu = idle_core;
 }
 
 static void task_numa_assign(struct task_numa_env *env,
                  struct task_struct *p, long imp)
 {
     struct rq *rq = cpu_rq(env->dst_cpu);
 
     /* Check if run-queue part of active NUMA balance. */
     if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
         int cpu;
         int start = env->dst_cpu;
 
         /* Find alternative idle CPU. */
         for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start) {
             if (cpu == env->best_cpu || !idle_cpu(cpu) ||
                 !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
                 continue;
             }
 
             env->dst_cpu = cpu;
             rq = cpu_rq(env->dst_cpu);
             if (!xchg(&rq->numa_migrate_on, 1))
                 goto assign;
         }
 
         /* Failed to find an alternative idle CPU */
         return;
     }
 
 assign:
     /*
      * Clear previous best_cpu/rq numa-migrate flag, since task now
      * found a better CPU to move/swap.
      */
     if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
         rq = cpu_rq(env->best_cpu);
         WRITE_ONCE(rq->numa_migrate_on, 0);
     }
 
     if (env->best_task)
         put_task_struct(env->best_task);
     if (p)
         get_task_struct(p);
 
     env->best_task = p;
     env->best_imp = imp;
     env->best_cpu = env->dst_cpu;
 }
 
 static bool load_too_imbalanced(long src_load, long dst_load,
                 struct task_numa_env *env)
 {
     long imb, old_imb;
     long orig_src_load, orig_dst_load;
     long src_capacity, dst_capacity;
 
     /*
      * The load is corrected for the CPU capacity available on each node.
      *
      * src_load        dst_load
      * ------------ vs ---------
      * src_capacity    dst_capacity
      */
     src_capacity = env->src_stats.compute_capacity;
     dst_capacity = env->dst_stats.compute_capacity;
 
     imb = abs(dst_load * src_capacity - src_load * dst_capacity);
 
     orig_src_load = env->src_stats.load;
     orig_dst_load = env->dst_stats.load;
 
     old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
 
     /* Would this change make things worse? */
     return (imb > old_imb);
 }
 
 /*
  * Maximum NUMA importance can be 1998 (2*999);
  * SMALLIMP @ 30 would be close to 1998/64.
  * Used to deter task migration.
  */
 #define SMALLIMP    30
 
 /*
  * This checks if the overall compute and NUMA accesses of the system would
  * be improved if the source tasks was migrated to the target dst_cpu taking
  * into account that it might be best if task running on the dst_cpu should
  * be exchanged with the source task
  */
 static bool task_numa_compare(struct task_numa_env *env,
                   long taskimp, long groupimp, bool maymove)
 {
     struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
     struct rq *dst_rq = cpu_rq(env->dst_cpu);
     long imp = p_ng ? groupimp : taskimp;
     struct task_struct *cur;
     long src_load, dst_load;
     int dist = env->dist;
     long moveimp = imp;
     long load;
     bool stopsearch = false;
 
     if (READ_ONCE(dst_rq->numa_migrate_on))
         return false;
 
     rcu_read_lock();
     cur = rcu_dereference(dst_rq->curr);
     if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
         cur = NULL;
 
     /*
      * Because we have preemption enabled we can get migrated around and
      * end try selecting ourselves (current == env->p) as a swap candidate.
      */
     if (cur == env->p) {
         stopsearch = true;
         goto unlock;
     }
 
     if (!cur) {
         if (maymove && moveimp >= env->best_imp)
             goto assign;
         else
             goto unlock;
     }
 
     /* Skip this swap candidate if cannot move to the source cpu. */
     if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr))
         goto unlock;
 
     /*
      * Skip this swap candidate if it is not moving to its preferred
      * node and the best task is.
      */
     if (env->best_task &&
         env->best_task->numa_preferred_nid == env->src_nid &&
         cur->numa_preferred_nid != env->src_nid) {
         goto unlock;
     }
 
     /*
      * "imp" is the fault differential for the source task between the
      * source and destination node. Calculate the total differential for
      * the source task and potential destination task. The more negative
      * the value is, the more remote accesses that would be expected to
      * be incurred if the tasks were swapped.
      *
      * If dst and source tasks are in the same NUMA group, or not
      * in any group then look only at task weights.
      */
     cur_ng = rcu_dereference(cur->numa_group);
     if (cur_ng == p_ng) {
         /*
          * Do not swap within a group or between tasks that have
          * no group if there is spare capacity. Swapping does
          * not address the load imbalance and helps one task at
          * the cost of punishing another.
          */
         if (env->dst_stats.node_type == node_has_spare)
             goto unlock;
 
         imp = taskimp + task_weight(cur, env->src_nid, dist) -
               task_weight(cur, env->dst_nid, dist);
         /*
          * Add some hysteresis to prevent swapping the
          * tasks within a group over tiny differences.
          */
         if (cur_ng)
             imp -= imp / 16;
     } else {
         /*
          * Compare the group weights. If a task is all by itself
          * (not part of a group), use the task weight instead.
          */
         if (cur_ng && p_ng)
             imp += group_weight(cur, env->src_nid, dist) -
                    group_weight(cur, env->dst_nid, dist);
         else
             imp += task_weight(cur, env->src_nid, dist) -
                    task_weight(cur, env->dst_nid, dist);
     }
 
     /* Discourage picking a task already on its preferred node */
     if (cur->numa_preferred_nid == env->dst_nid)
         imp -= imp / 16;
 
     /*
      * Encourage picking a task that moves to its preferred node.
      * This potentially makes imp larger than it's maximum of
      * 1998 (see SMALLIMP and task_weight for why) but in this
      * case, it does not matter.
      */
     if (cur->numa_preferred_nid == env->src_nid)
         imp += imp / 8;
 
     if (maymove && moveimp > imp && moveimp > env->best_imp) {
         imp = moveimp;
         cur = NULL;
         goto assign;
     }
 
     /*
      * Prefer swapping with a task moving to its preferred node over a
      * task that is not.
      */
     if (env->best_task && cur->numa_preferred_nid == env->src_nid &&
         env->best_task->numa_preferred_nid != env->src_nid) {
         goto assign;
     }
 
     /*
      * If the NUMA importance is less than SMALLIMP,
      * task migration might only result in ping pong
      * of tasks and also hurt performance due to cache
      * misses.
      */
     if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
         goto unlock;
 
     /*
      * In the overloaded case, try and keep the load balanced.
      */
     load = task_h_load(env->p) - task_h_load(cur);
     if (!load)
         goto assign;
 
     dst_load = env->dst_stats.load + load;
     src_load = env->src_stats.load - load;
 
     if (load_too_imbalanced(src_load, dst_load, env))
         goto unlock;
 
 assign:
     /* Evaluate an idle CPU for a task numa move. */
     if (!cur) {
         int cpu = env->dst_stats.idle_cpu;
 
         /* Nothing cached so current CPU went idle since the search. */
         if (cpu < 0)
             cpu = env->dst_cpu;
 
         /*
          * If the CPU is no longer truly idle and the previous best CPU
          * is, keep using it.
          */
         if (!idle_cpu(cpu) && env->best_cpu >= 0 &&
             idle_cpu(env->best_cpu)) {
             cpu = env->best_cpu;
         }
 
         env->dst_cpu = cpu;
     }
 
     task_numa_assign(env, cur, imp);
 
     /*
      * If a move to idle is allowed because there is capacity or load
      * balance improves then stop the search. While a better swap
      * candidate may exist, a search is not free.
      */
     if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu))
         stopsearch = true;
 
     /*
      * If a swap candidate must be identified and the current best task
      * moves its preferred node then stop the search.
      */
     if (!maymove && env->best_task &&
         env->best_task->numa_preferred_nid == env->src_nid) {
         stopsearch = true;
     }
 unlock:
     rcu_read_unlock();
 
     return stopsearch;
 }
 
 static void task_numa_find_cpu(struct task_numa_env *env,
                 long taskimp, long groupimp)
 {
     bool maymove = false;
     int cpu;
 
     /*
      * If dst node has spare capacity, then check if there is an
      * imbalance that would be overruled by the load balancer.
      */
     if (env->dst_stats.node_type == node_has_spare) {
         unsigned int imbalance;
         int src_running, dst_running;
 
         /*
          * Would movement cause an imbalance? Note that if src has
          * more running tasks that the imbalance is ignored as the
          * move improves the imbalance from the perspective of the
          * CPU load balancer.
          * */
         src_running = env->src_stats.nr_running - 1;
         dst_running = env->dst_stats.nr_running + 1;
         imbalance = max(0, dst_running - src_running);
         imbalance = adjust_numa_imbalance(imbalance, dst_running,
                           env->imb_numa_nr);
 
         /* Use idle CPU if there is no imbalance */
         if (!imbalance) {
             maymove = true;
             if (env->dst_stats.idle_cpu >= 0) {
                 env->dst_cpu = env->dst_stats.idle_cpu;
                 task_numa_assign(env, NULL, 0);
                 return;
             }
         }
     } else {
         long src_load, dst_load, load;
         /*
          * If the improvement from just moving env->p direction is better
          * than swapping tasks around, check if a move is possible.
          */
         load = task_h_load(env->p);
         dst_load = env->dst_stats.load + load;
         src_load = env->src_stats.load - load;
         maymove = !load_too_imbalanced(src_load, dst_load, env);
     }
 
     for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
         /* Skip this CPU if the source task cannot migrate */
         if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
             continue;
 
         env->dst_cpu = cpu;
         if (task_numa_compare(env, taskimp, groupimp, maymove))
             break;
     }
 }
 
 static int task_numa_migrate(struct task_struct *p)
 {
     struct task_numa_env env = {
         .p = p,
 
         .src_cpu = task_cpu(p),
         .src_nid = task_node(p),
 
         .imbalance_pct = 112,
 
         .best_task = NULL,
         .best_imp = 0,
         .best_cpu = -1,
     };
     unsigned long taskweight, groupweight;
     struct sched_domain *sd;
     long taskimp, groupimp;
     struct numa_group *ng;
     struct rq *best_rq;
     int nid, ret, dist;
 
     /*
      * Pick the lowest SD_NUMA domain, as that would have the smallest
      * imbalance and would be the first to start moving tasks about.
      *
      * And we want to avoid any moving of tasks about, as that would create
      * random movement of tasks -- counter the numa conditions we're trying
      * to satisfy here.
      */
     rcu_read_lock();
     sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
     if (sd) {
         env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
         env.imb_numa_nr = sd->imb_numa_nr;
     }
     rcu_read_unlock();
 
     /*
      * Cpusets can break the scheduler domain tree into smaller
      * balance domains, some of which do not cross NUMA boundaries.
      * Tasks that are "trapped" in such domains cannot be migrated
      * elsewhere, so there is no point in (re)trying.
      */
     if (unlikely(!sd)) {
         sched_setnuma(p, task_node(p));
         return -EINVAL;
     }
 
     env.dst_nid = p->numa_preferred_nid;
     dist = env.dist = node_distance(env.src_nid, env.dst_nid);
     taskweight = task_weight(p, env.src_nid, dist);
     groupweight = group_weight(p, env.src_nid, dist);
     update_numa_stats(&env, &env.src_stats, env.src_nid, false);
     taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
     groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
     update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
 
     /* Try to find a spot on the preferred nid. */
     task_numa_find_cpu(&env, taskimp, groupimp);
 
     /*
      * Look at other nodes in these cases:
      * - there is no space available on the preferred_nid
      * - the task is part of a numa_group that is interleaved across
      *   multiple NUMA nodes; in order to better consolidate the group,
      *   we need to check other locations.
      */
     ng = deref_curr_numa_group(p);
     if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
         for_each_node_state(nid, N_CPU) {
             if (nid == env.src_nid || nid == p->numa_preferred_nid)
                 continue;
 
             dist = node_distance(env.src_nid, env.dst_nid);
             if (sched_numa_topology_type == NUMA_BACKPLANE &&
                         dist != env.dist) {
                 taskweight = task_weight(p, env.src_nid, dist);
                 groupweight = group_weight(p, env.src_nid, dist);
             }
 
             /* Only consider nodes where both task and groups benefit */
             taskimp = task_weight(p, nid, dist) - taskweight;
             groupimp = group_weight(p, nid, dist) - groupweight;
             if (taskimp < 0 && groupimp < 0)
                 continue;
 
             env.dist = dist;
             env.dst_nid = nid;
             update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
             task_numa_find_cpu(&env, taskimp, groupimp);
         }
     }
 
     /*
      * If the task is part of a workload that spans multiple NUMA nodes,
      * and is migrating into one of the workload's active nodes, remember
      * this node as the task's preferred numa node, so the workload can
      * settle down.
      * A task that migrated to a second choice node will be better off
      * trying for a better one later. Do not set the preferred node here.
      */
     if (ng) {
         if (env.best_cpu == -1)
             nid = env.src_nid;
         else
             nid = cpu_to_node(env.best_cpu);
 
         if (nid != p->numa_preferred_nid)
             sched_setnuma(p, nid);
     }
 
     /* No better CPU than the current one was found. */
     if (env.best_cpu == -1) {
         trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
         return -EAGAIN;
     }
 
     best_rq = cpu_rq(env.best_cpu);
     if (env.best_task == NULL) {
         ret = migrate_task_to(p, env.best_cpu);
         WRITE_ONCE(best_rq->numa_migrate_on, 0);
         if (ret != 0)
             trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
         return ret;
     }
 
     ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
     WRITE_ONCE(best_rq->numa_migrate_on, 0);
 
     if (ret != 0)
         trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
     put_task_struct(env.best_task);
     return ret;
 }
 
 /* Attempt to migrate a task to a CPU on the preferred node. */
 static void numa_migrate_preferred(struct task_struct *p)
 {
     unsigned long interval = HZ;
 
     /* This task has no NUMA fault statistics yet */
     if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults))
         return;
 
     /* Periodically retry migrating the task to the preferred node */
     interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
     p->numa_migrate_retry = jiffies + interval;
 
     /* Success if task is already running on preferred CPU */
     if (task_node(p) == p->numa_preferred_nid)
         return;
 
     /* Otherwise, try migrate to a CPU on the preferred node */
     task_numa_migrate(p);
 }
 
 /*
  * Find out how many nodes the workload is actively running on. Do this by
  * tracking the nodes from which NUMA hinting faults are triggered. This can
  * be different from the set of nodes where the workload's memory is currently
  * located.
  */
 static void numa_group_count_active_nodes(struct numa_group *numa_group)
 {
     unsigned long faults, max_faults = 0;
     int nid, active_nodes = 0;
 
     for_each_node_state(nid, N_CPU) {
         faults = group_faults_cpu(numa_group, nid);
         if (faults > max_faults)
             max_faults = faults;
     }
 
     for_each_node_state(nid, N_CPU) {
         faults = group_faults_cpu(numa_group, nid);
         if (faults * ACTIVE_NODE_FRACTION > max_faults)
             active_nodes++;
     }
 
     numa_group->max_faults_cpu = max_faults;
     numa_group->active_nodes = active_nodes;
 }
 
 /*
  * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
  * increments. The more local the fault statistics are, the higher the scan
  * period will be for the next scan window. If local/(local+remote) ratio is
  * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
  * the scan period will decrease. Aim for 70% local accesses.
  */
 #define NUMA_PERIOD_SLOTS 10
 #define NUMA_PERIOD_THRESHOLD 7
 
 /*
  * Increase the scan period (slow down scanning) if the majority of
  * our memory is already on our local node, or if the majority of
  * the page accesses are shared with other processes.
  * Otherwise, decrease the scan period.
  */
 static void update_task_scan_period(struct task_struct *p,
             unsigned long shared, unsigned long private)
 {
     unsigned int period_slot;
     int lr_ratio, ps_ratio;
     int diff;
 
     unsigned long remote = p->numa_faults_locality[0];
     unsigned long local = p->numa_faults_locality[1];
 
     /*
      * If there were no record hinting faults then either the task is
      * completely idle or all activity is in areas that are not of interest
      * to automatic numa balancing. Related to that, if there were failed
      * migration then it implies we are migrating too quickly or the local
      * node is overloaded. In either case, scan slower
      */
     if (local + shared == 0 || p->numa_faults_locality[2]) {
         p->numa_scan_period = min(p->numa_scan_period_max,
             p->numa_scan_period << 1);
 
         p->mm->numa_next_scan = jiffies +
             msecs_to_jiffies(p->numa_scan_period);
 
         return;
     }
 
     /*
      * Prepare to scale scan period relative to the current period.
      *   == NUMA_PERIOD_THRESHOLD scan period stays the same
      *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
      *   >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
      */
     period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
     lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
     ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
 
     if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
         /*
          * Most memory accesses are local. There is no need to
          * do fast NUMA scanning, since memory is already local.
          */
         int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
         if (!slot)
             slot = 1;
         diff = slot * period_slot;
     } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
         /*
          * Most memory accesses are shared with other tasks.
          * There is no point in continuing fast NUMA scanning,
          * since other tasks may just move the memory elsewhere.
          */
         int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
         if (!slot)
             slot = 1;
         diff = slot * period_slot;
     } else {
         /*
          * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
          * yet they are not on the local NUMA node. Speed up
          * NUMA scanning to get the memory moved over.
          */
         int ratio = max(lr_ratio, ps_ratio);
         diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
     }
 
     p->numa_scan_period = clamp(p->numa_scan_period + diff,
             task_scan_min(p), task_scan_max(p));
     memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
 }
 
 /*
  * Get the fraction of time the task has been running since the last
  * NUMA placement cycle. The scheduler keeps similar statistics, but
  * decays those on a 32ms period, which is orders of magnitude off
  * from the dozens-of-seconds NUMA balancing period. Use the scheduler
  * stats only if the task is so new there are no NUMA statistics yet.
  */
 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
 {
     u64 runtime, delta, now;
     /* Use the start of this time slice to avoid calculations. */
     now = p->se.exec_start;
     runtime = p->se.sum_exec_runtime;
 
     if (p->last_task_numa_placement) {
         delta = runtime - p->last_sum_exec_runtime;
         *period = now - p->last_task_numa_placement;
 
         /* Avoid time going backwards, prevent potential divide error: */
         if (unlikely((s64)*period < 0))
             *period = 0;
     } else {
         delta = p->se.avg.load_sum;
         *period = LOAD_AVG_MAX;
     }
 
     p->last_sum_exec_runtime = runtime;
     p->last_task_numa_placement = now;
 
     return delta;
 }
 
 /*
  * Determine the preferred nid for a task in a numa_group. This needs to
  * be done in a way that produces consistent results with group_weight,
  * otherwise workloads might not converge.
  */
 static int preferred_group_nid(struct task_struct *p, int nid)
 {
     nodemask_t nodes;
     int dist;
 
     /* Direct connections between all NUMA nodes. */
     if (sched_numa_topology_type == NUMA_DIRECT)
         return nid;
 
     /*
      * On a system with glueless mesh NUMA topology, group_weight
      * scores nodes according to the number of NUMA hinting faults on
      * both the node itself, and on nearby nodes.
      */
     if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
         unsigned long score, max_score = 0;
         int node, max_node = nid;
 
         dist = sched_max_numa_distance;
 
         for_each_node_state(node, N_CPU) {
             score = group_weight(p, node, dist);
             if (score > max_score) {
                 max_score = score;
                 max_node = node;
             }
         }
         return max_node;
     }
 
     /*
      * Finding the preferred nid in a system with NUMA backplane
      * interconnect topology is more involved. The goal is to locate
      * tasks from numa_groups near each other in the system, and
      * untangle workloads from different sides of the system. This requires
      * searching down the hierarchy of node groups, recursively searching
      * inside the highest scoring group of nodes. The nodemask tricks
      * keep the complexity of the search down.
      */
     nodes = node_states[N_CPU];
     for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
         unsigned long max_faults = 0;
         nodemask_t max_group = NODE_MASK_NONE;
         int a, b;
 
         /* Are there nodes at this distance from each other? */
         if (!find_numa_distance(dist))
             continue;
 
         for_each_node_mask(a, nodes) {
             unsigned long faults = 0;
             nodemask_t this_group;
             nodes_clear(this_group);
 
             /* Sum group's NUMA faults; includes a==b case. */
             for_each_node_mask(b, nodes) {
                 if (node_distance(a, b) < dist) {
                     faults += group_faults(p, b);
                     node_set(b, this_group);
                     node_clear(b, nodes);
                 }
             }
 
             /* Remember the top group. */
             if (faults > max_faults) {
                 max_faults = faults;
                 max_group = this_group;
                 /*
                  * subtle: at the smallest distance there is
                  * just one node left in each "group", the
                  * winner is the preferred nid.
                  */
                 nid = a;
             }
         }
         /* Next round, evaluate the nodes within max_group. */
         if (!max_faults)
             break;
         nodes = max_group;
     }
     return nid;
 }
 
 static void task_numa_placement(struct task_struct *p)
 {
     int seq, nid, max_nid = NUMA_NO_NODE;
     unsigned long max_faults = 0;
     unsigned long fault_types[2] = { 0, 0 };
     unsigned long total_faults;
     u64 runtime, period;
     spinlock_t *group_lock = NULL;
     struct numa_group *ng;
 
     /*
      * The p->mm->numa_scan_seq field gets updated without
      * exclusive access. Use READ_ONCE() here to ensure
      * that the field is read in a single access:
      */
     seq = READ_ONCE(p->mm->numa_scan_seq);
     if (p->numa_scan_seq == seq)
         return;
     p->numa_scan_seq = seq;
     p->numa_scan_period_max = task_scan_max(p);
 
     total_faults = p->numa_faults_locality[0] +
                p->numa_faults_locality[1];
     runtime = numa_get_avg_runtime(p, &period);
 
     /* If the task is part of a group prevent parallel updates to group stats */
     ng = deref_curr_numa_group(p);
     if (ng) {
         group_lock = &ng->lock;
         spin_lock_irq(group_lock);
     }
 
     /* Find the node with the highest number of faults */
     for_each_online_node(nid) {
         /* Keep track of the offsets in numa_faults array */
         int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
         unsigned long faults = 0, group_faults = 0;
         int priv;
 
         for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
             long diff, f_diff, f_weight;
 
             mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
             membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
             cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
             cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
 
             /* Decay existing window, copy faults since last scan */
             diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
             fault_types[priv] += p->numa_faults[membuf_idx];
             p->numa_faults[membuf_idx] = 0;
 
             /*
              * Normalize the faults_from, so all tasks in a group
              * count according to CPU use, instead of by the raw
              * number of faults. Tasks with little runtime have
              * little over-all impact on throughput, and thus their
              * faults are less important.
              */
             f_weight = div64_u64(runtime << 16, period + 1);
             f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
                    (total_faults + 1);
             f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
             p->numa_faults[cpubuf_idx] = 0;
 
             p->numa_faults[mem_idx] += diff;
             p->numa_faults[cpu_idx] += f_diff;
             faults += p->numa_faults[mem_idx];
             p->total_numa_faults += diff;
             if (ng) {
                 /*
                  * safe because we can only change our own group
                  *
                  * mem_idx represents the offset for a given
                  * nid and priv in a specific region because it
                  * is at the beginning of the numa_faults array.
                  */
                 ng->faults[mem_idx] += diff;
                 ng->faults[cpu_idx] += f_diff;
                 ng->total_faults += diff;
                 group_faults += ng->faults[mem_idx];
             }
         }
 
         if (!ng) {
             if (faults > max_faults) {
                 max_faults = faults;
                 max_nid = nid;
             }
         } else if (group_faults > max_faults) {
             max_faults = group_faults;
             max_nid = nid;
         }
     }
 
     /* Cannot migrate task to CPU-less node */
     if (max_nid != NUMA_NO_NODE && !node_state(max_nid, N_CPU)) {
         int near_nid = max_nid;
         int distance, near_distance = INT_MAX;
 
         for_each_node_state(nid, N_CPU) {
             distance = node_distance(max_nid, nid);
             if (distance < near_distance) {
                 near_nid = nid;
                 near_distance = distance;
             }
         }
         max_nid = near_nid;
     }
 
     if (ng) {
         numa_group_count_active_nodes(ng);
         spin_unlock_irq(group_lock);
         max_nid = preferred_group_nid(p, max_nid);
     }
 
     if (max_faults) {
         /* Set the new preferred node */
         if (max_nid != p->numa_preferred_nid)
             sched_setnuma(p, max_nid);
     }
 
     update_task_scan_period(p, fault_types[0], fault_types[1]);
 }
 
 static inline int get_numa_group(struct numa_group *grp)
 {
     return refcount_inc_not_zero(&grp->refcount);
 }
 
 static inline void put_numa_group(struct numa_group *grp)
 {
     if (refcount_dec_and_test(&grp->refcount))
         kfree_rcu(grp, rcu);
 }
 
 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
             int *priv)
 {
     struct numa_group *grp, *my_grp;
     struct task_struct *tsk;
     bool join = false;
     int cpu = cpupid_to_cpu(cpupid);
     int i;
 
     if (unlikely(!deref_curr_numa_group(p))) {
         unsigned int size = sizeof(struct numa_group) +
                     NR_NUMA_HINT_FAULT_STATS *
                     nr_node_ids * sizeof(unsigned long);
 
         grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
         if (!grp)
             return;
 
         refcount_set(&grp->refcount, 1);
         grp->active_nodes = 1;
         grp->max_faults_cpu = 0;
         spin_lock_init(&grp->lock);
         grp->gid = p->pid;
 
         for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
             grp->faults[i] = p->numa_faults[i];
 
         grp->total_faults = p->total_numa_faults;
 
         grp->nr_tasks++;
         rcu_assign_pointer(p->numa_group, grp);
     }
 
     rcu_read_lock();
     tsk = READ_ONCE(cpu_rq(cpu)->curr);
 
     if (!cpupid_match_pid(tsk, cpupid))
         goto no_join;
 
     grp = rcu_dereference(tsk->numa_group);
     if (!grp)
         goto no_join;
 
     my_grp = deref_curr_numa_group(p);
     if (grp == my_grp)
         goto no_join;
 
     /*
      * Only join the other group if its bigger; if we're the bigger group,
      * the other task will join us.
      */
     if (my_grp->nr_tasks > grp->nr_tasks)
         goto no_join;
 
     /*
      * Tie-break on the grp address.
      */
     if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
         goto no_join;
 
     /* Always join threads in the same process. */
     if (tsk->mm == current->mm)
         join = true;
 
     /* Simple filter to avoid false positives due to PID collisions */
     if (flags & TNF_SHARED)
         join = true;
 
     /* Update priv based on whether false sharing was detected */
     *priv = !join;
 
     if (join && !get_numa_group(grp))
         goto no_join;
 
     rcu_read_unlock();
 
     if (!join)
         return;
 
     BUG_ON(irqs_disabled());
     double_lock_irq(&my_grp->lock, &grp->lock);
 
     for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
         my_grp->faults[i] -= p->numa_faults[i];
         grp->faults[i] += p->numa_faults[i];
     }
     my_grp->total_faults -= p->total_numa_faults;
     grp->total_faults += p->total_numa_faults;
 
     my_grp->nr_tasks--;
     grp->nr_tasks++;
 
     spin_unlock(&my_grp->lock);
     spin_unlock_irq(&grp->lock);
 
     rcu_assign_pointer(p->numa_group, grp);
 
     put_numa_group(my_grp);
     return;
 
 no_join:
     rcu_read_unlock();
     return;
 }
 
 /*
  * Get rid of NUMA statistics associated with a task (either current or dead).
  * If @final is set, the task is dead and has reached refcount zero, so we can
  * safely free all relevant data structures. Otherwise, there might be
  * concurrent reads from places like load balancing and procfs, and we should
  * reset the data back to default state without freeing ->numa_faults.
  */
 void task_numa_free(struct task_struct *p, bool final)
 {
     /* safe: p either is current or is being freed by current */
     struct numa_group *grp = rcu_dereference_raw(p->numa_group);
     unsigned long *numa_faults = p->numa_faults;
     unsigned long flags;
     int i;
 
     if (!numa_faults)
         return;
 
     if (grp) {
         spin_lock_irqsave(&grp->lock, flags);
         for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
             grp->faults[i] -= p->numa_faults[i];
         grp->total_faults -= p->total_numa_faults;
 
         grp->nr_tasks--;
         spin_unlock_irqrestore(&grp->lock, flags);
         RCU_INIT_POINTER(p->numa_group, NULL);
         put_numa_group(grp);
     }
 
     if (final) {
         p->numa_faults = NULL;
         kfree(numa_faults);
     } else {
         p->total_numa_faults = 0;
         for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
             numa_faults[i] = 0;
     }
 }
 
 /*
  * Got a PROT_NONE fault for a page on @node.
  */
 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
 {
     struct task_struct *p = current;
     bool migrated = flags & TNF_MIGRATED;
     int cpu_node = task_node(current);
     int local = !!(flags & TNF_FAULT_LOCAL);
     struct numa_group *ng;
     int priv;
 
     if (!static_branch_likely(&sched_numa_balancing))
         return;
 
     /* for example, ksmd faulting in a user's mm */
     if (!p->mm)
         return;
 
     /* Allocate buffer to track faults on a per-node basis */
     if (unlikely(!p->numa_faults)) {
         int size = sizeof(*p->numa_faults) *
                NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
 
         p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
         if (!p->numa_faults)
             return;
 
         p->total_numa_faults = 0;
         memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
     }
 
     /*
      * First accesses are treated as private, otherwise consider accesses
      * to be private if the accessing pid has not changed
      */
     if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
         priv = 1;
     } else {
         priv = cpupid_match_pid(p, last_cpupid);
         if (!priv && !(flags & TNF_NO_GROUP))
             task_numa_group(p, last_cpupid, flags, &priv);
     }
 
     /*
      * If a workload spans multiple NUMA nodes, a shared fault that
      * occurs wholly within the set of nodes that the workload is
      * actively using should be counted as local. This allows the
      * scan rate to slow down when a workload has settled down.
      */
     ng = deref_curr_numa_group(p);
     if (!priv && !local && ng && ng->active_nodes > 1 &&
                 numa_is_active_node(cpu_node, ng) &&
                 numa_is_active_node(mem_node, ng))
         local = 1;
 
     /*
      * Retry to migrate task to preferred node periodically, in case it
      * previously failed, or the scheduler moved us.
      */
     if (time_after(jiffies, p->numa_migrate_retry)) {
         task_numa_placement(p);
         numa_migrate_preferred(p);
     }
 
     if (migrated)
         p->numa_pages_migrated += pages;
     if (flags & TNF_MIGRATE_FAIL)
         p->numa_faults_locality[2] += pages;
 
     p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
     p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
     p->numa_faults_locality[local] += pages;
 }
 
 static void reset_ptenuma_scan(struct task_struct *p)
 {
     /*
      * We only did a read acquisition of the mmap sem, so
      * p->mm->numa_scan_seq is written to without exclusive access
      * and the update is not guaranteed to be atomic. That's not
      * much of an issue though, since this is just used for
      * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
      * expensive, to avoid any form of compiler optimizations:
      */
     WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
     p->mm->numa_scan_offset = 0;
 }
 
 /*
  * The expensive part of numa migration is done from task_work context.
  * Triggered from task_tick_numa().
  */
 static void task_numa_work(struct callback_head *work)
 {
     unsigned long migrate, next_scan, now = jiffies;
     struct task_struct *p = current;
     struct mm_struct *mm = p->mm;
     u64 runtime = p->se.sum_exec_runtime;
     struct vm_area_struct *vma;
     unsigned long start, end;
     unsigned long nr_pte_updates = 0;
     long pages, virtpages;
 
     SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
 
     work->next = work;
     /*
      * Who cares about NUMA placement when they're dying.
      *
      * NOTE: make sure not to dereference p->mm before this check,
      * exit_task_work() happens _after_ exit_mm() so we could be called
      * without p->mm even though we still had it when we enqueued this
      * work.
      */
     if (p->flags & PF_EXITING)
         return;
 
     if (!mm->numa_next_scan) {
         mm->numa_next_scan = now +
             msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
     }
 
     /*
      * Enforce maximal scan/migration frequency..
      */
     migrate = mm->numa_next_scan;
     if (time_before(now, migrate))
         return;
 
     if (p->numa_scan_period == 0) {
         p->numa_scan_period_max = task_scan_max(p);
         p->numa_scan_period = task_scan_start(p);
     }
 
     next_scan = now + msecs_to_jiffies(p->numa_scan_period);
     if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
         return;
 
     /*
      * Delay this task enough that another task of this mm will likely win
      * the next time around.
      */
     p->node_stamp += 2 * TICK_NSEC;
 
     start = mm->numa_scan_offset;
     pages = sysctl_numa_balancing_scan_size;
     pages <<= 20 - PAGE_SHIFT; /* MB in pages */
     virtpages = pages * 8;     /* Scan up to this much virtual space */
     if (!pages)
         return;
 
 
     if (!mmap_read_trylock(mm))
         return;
     vma = find_vma(mm, start);
     if (!vma) {
         reset_ptenuma_scan(p);
         start = 0;
         vma = mm->mmap;
     }
     for (; vma; vma = vma->vm_next) {
         if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
             is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
             continue;
         }
 
         /*
          * Shared library pages mapped by multiple processes are not
          * migrated as it is expected they are cache replicated. Avoid
          * hinting faults in read-only file-backed mappings or the vdso
          * as migrating the pages will be of marginal benefit.
          */
         if (!vma->vm_mm ||
             (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
             continue;
 
         /*
          * Skip inaccessible VMAs to avoid any confusion between
          * PROT_NONE and NUMA hinting ptes
          */
         if (!vma_is_accessible(vma))
             continue;
 
         do {
             start = max(start, vma->vm_start);
             end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
             end = min(end, vma->vm_end);
             nr_pte_updates = change_prot_numa(vma, start, end);
 
             /*
              * Try to scan sysctl_numa_balancing_size worth of
              * hpages that have at least one present PTE that
              * is not already pte-numa. If the VMA contains
              * areas that are unused or already full of prot_numa
              * PTEs, scan up to virtpages, to skip through those
              * areas faster.
              */
             if (nr_pte_updates)
                 pages -= (end - start) >> PAGE_SHIFT;
             virtpages -= (end - start) >> PAGE_SHIFT;
 
             start = end;
             if (pages <= 0 || virtpages <= 0)
                 goto out;
 
             cond_resched();
         } while (end != vma->vm_end);
     }
 
 out:
     /*
      * It is possible to reach the end of the VMA list but the last few
      * VMAs are not guaranteed to the vma_migratable. If they are not, we
      * would find the !migratable VMA on the next scan but not reset the
      * scanner to the start so check it now.
      */
     if (vma)
         mm->numa_scan_offset = start;
     else
         reset_ptenuma_scan(p);
     mmap_read_unlock(mm);
 
     /*
      * Make sure tasks use at least 32x as much time to run other code
      * than they used here, to limit NUMA PTE scanning overhead to 3% max.
      * Usually update_task_scan_period slows down scanning enough; on an
      * overloaded system we need to limit overhead on a per task basis.
      */
     if (unlikely(p->se.sum_exec_runtime != runtime)) {
         u64 diff = p->se.sum_exec_runtime - runtime;
         p->node_stamp += 32 * diff;
     }
 }
 
 void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
 {
     int mm_users = 0;
     struct mm_struct *mm = p->mm;
 
     if (mm) {
         mm_users = atomic_read(&mm->mm_users);
         if (mm_users == 1) {
             mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
             mm->numa_scan_seq = 0;
         }
     }
     p->node_stamp           = 0;
     p->numa_scan_seq        = mm ? mm->numa_scan_seq : 0;
     p->numa_scan_period     = sysctl_numa_balancing_scan_delay;
     p->numa_migrate_retry       = 0;
     /* Protect against double add, see task_tick_numa and task_numa_work */
     p->numa_work.next       = &p->numa_work;
     p->numa_faults          = NULL;
     p->numa_pages_migrated      = 0;
     p->total_numa_faults        = 0;
     RCU_INIT_POINTER(p->numa_group, NULL);
     p->last_task_numa_placement = 0;
     p->last_sum_exec_runtime    = 0;
 
     init_task_work(&p->numa_work, task_numa_work);
 
     /* New address space, reset the preferred nid */
     if (!(clone_flags & CLONE_VM)) {
         p->numa_preferred_nid = NUMA_NO_NODE;
         return;
     }
 
     /*
      * New thread, keep existing numa_preferred_nid which should be copied
      * already by arch_dup_task_struct but stagger when scans start.
      */
     if (mm) {
         unsigned int delay;
 
         delay = min_t(unsigned int, task_scan_max(current),
             current->numa_scan_period * mm_users * NSEC_PER_MSEC);
         delay += 2 * TICK_NSEC;
         p->node_stamp = delay;
     }
 }
 
 /*
  * Drive the periodic memory faults..
  */
 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
 {
     struct callback_head *work = &curr->numa_work;
     u64 period, now;
 
     /*
      * We don't care about NUMA placement if we don't have memory.
      */
     if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
         return;
 
     /*
      * Using runtime rather than walltime has the dual advantage that
      * we (mostly) drive the selection from busy threads and that the
      * task needs to have done some actual work before we bother with
      * NUMA placement.
      */
     now = curr->se.sum_exec_runtime;
     period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
 
     if (now > curr->node_stamp + period) {
         if (!curr->node_stamp)
             curr->numa_scan_period = task_scan_start(curr);
         curr->node_stamp += period;
 
         if (!time_before(jiffies, curr->mm->numa_next_scan))
             task_work_add(curr, work, TWA_RESUME);
     }
 }
 
 static void update_scan_period(struct task_struct *p, int new_cpu)
 {
     int src_nid = cpu_to_node(task_cpu(p));
     int dst_nid = cpu_to_node(new_cpu);
 
     if (!static_branch_likely(&sched_numa_balancing))
         return;
 
     if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
         return;
 
     if (src_nid == dst_nid)
         return;
 
     /*
      * Allow resets if faults have been trapped before one scan
      * has completed. This is most likely due to a new task that
      * is pulled cross-node due to wakeups or load balancing.
      */
     if (p->numa_scan_seq) {
         /*
          * Avoid scan adjustments if moving to the preferred
          * node or if the task was not previously running on
          * the preferred node.
          */
         if (dst_nid == p->numa_preferred_nid ||
             (p->numa_preferred_nid != NUMA_NO_NODE &&
             src_nid != p->numa_preferred_nid))
             return;
     }
 
     p->numa_scan_period = task_scan_start(p);
 }
 
 #else
 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
 {
 }
 
 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
 {
 }
 
 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
 {
 }
 
 static inline void update_scan_period(struct task_struct *p, int new_cpu)
 {
 }
 
 #endif /* CONFIG_NUMA_BALANCING */
 
 static void
 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     update_load_add(&cfs_rq->load, se->load.weight);
 #ifdef CONFIG_SMP
     if (entity_is_task(se)) {
         struct rq *rq = rq_of(cfs_rq);
 
         account_numa_enqueue(rq, task_of(se));
         list_add(&se->group_node, &rq->cfs_tasks);
     }
 #endif
     cfs_rq->nr_running++;
     if (se_is_idle(se))
         cfs_rq->idle_nr_running++;
 }
 
 static void
 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     update_load_sub(&cfs_rq->load, se->load.weight);
 #ifdef CONFIG_SMP
     if (entity_is_task(se)) {
         account_numa_dequeue(rq_of(cfs_rq), task_of(se));
         list_del_init(&se->group_node);
     }
 #endif
     cfs_rq->nr_running--;
     if (se_is_idle(se))
         cfs_rq->idle_nr_running--;
 }
 
 /*
  * Signed add and clamp on underflow.
  *
  * Explicitly do a load-store to ensure the intermediate value never hits
  * memory. This allows lockless observations without ever seeing the negative
  * values.
  */
 #define add_positive(_ptr, _val) do {                           \
     typeof(_ptr) ptr = (_ptr);                              \
     typeof(_val) val = (_val);                              \
     typeof(*ptr) res, var = READ_ONCE(*ptr);                \
                                 \
     res = var + val;                                        \
                                 \
     if (val < 0 && res > var)                               \
         res = 0;                                        \
                                 \
     WRITE_ONCE(*ptr, res);                                  \
 } while (0)
 
 /*
  * Unsigned subtract and clamp on underflow.
  *
  * Explicitly do a load-store to ensure the intermediate value never hits
  * memory. This allows lockless observations without ever seeing the negative
  * values.
  */
 #define sub_positive(_ptr, _val) do {               \
     typeof(_ptr) ptr = (_ptr);              \
     typeof(*ptr) val = (_val);              \
     typeof(*ptr) res, var = READ_ONCE(*ptr);        \
     res = var - val;                    \
     if (res > var)                      \
         res = 0;                    \
     WRITE_ONCE(*ptr, res);                  \
 } while (0)
 
 /*
  * Remove and clamp on negative, from a local variable.
  *
  * A variant of sub_positive(), which does not use explicit load-store
  * and is thus optimized for local variable updates.
  */
 #define lsub_positive(_ptr, _val) do {              \
     typeof(_ptr) ptr = (_ptr);              \
     *ptr -= min_t(typeof(*ptr), *ptr, _val);        \
 } while (0)
 
 #ifdef CONFIG_SMP
 static inline void
 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     cfs_rq->avg.load_avg += se->avg.load_avg;
     cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
 }
 
 static inline void
 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
     sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
     /* See update_cfs_rq_load_avg() */
     cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
                       cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
 }
 #else
 static inline void
 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
 static inline void
 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
 #endif
 
 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
                 unsigned long weight)
 {
     if (se->on_rq) {
         /* commit outstanding execution time */
         if (cfs_rq->curr == se)
             update_curr(cfs_rq);
         update_load_sub(&cfs_rq->load, se->load.weight);
     }
     dequeue_load_avg(cfs_rq, se);
 
     update_load_set(&se->load, weight);
 
 #ifdef CONFIG_SMP
     do {
         u32 divider = get_pelt_divider(&se->avg);
 
         se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
     } while (0);
 #endif
 
     enqueue_load_avg(cfs_rq, se);
     if (se->on_rq)
         update_load_add(&cfs_rq->load, se->load.weight);
 
 }
 
 void reweight_task(struct task_struct *p, int prio)
 {
     struct sched_entity *se = &p->se;
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
     struct load_weight *load = &se->load;
     unsigned long weight = scale_load(sched_prio_to_weight[prio]);
 
     reweight_entity(cfs_rq, se, weight);
     load->inv_weight = sched_prio_to_wmult[prio];
 }
 
 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 #ifdef CONFIG_SMP
 /*
  * All this does is approximate the hierarchical proportion which includes that
  * global sum we all love to hate.
  *
  * That is, the weight of a group entity, is the proportional share of the
  * group weight based on the group runqueue weights. That is:
  *
  *                     tg->weight * grq->load.weight
  *   ge->load.weight = -----------------------------               (1)
  *                       \Sum grq->load.weight
  *
  * Now, because computing that sum is prohibitively expensive to compute (been
  * there, done that) we approximate it with this average stuff. The average
  * moves slower and therefore the approximation is cheaper and more stable.
  *
  * So instead of the above, we substitute:
  *
  *   grq->load.weight -> grq->avg.load_avg                         (2)
  *
  * which yields the following:
  *
  *                     tg->weight * grq->avg.load_avg
  *   ge->load.weight = ------------------------------              (3)
  *                             tg->load_avg
  *
  * Where: tg->load_avg ~= \Sum grq->avg.load_avg
  *
  * That is shares_avg, and it is right (given the approximation (2)).
  *
  * The problem with it is that because the average is slow -- it was designed
  * to be exactly that of course -- this leads to transients in boundary
  * conditions. In specific, the case where the group was idle and we start the
  * one task. It takes time for our CPU's grq->avg.load_avg to build up,
  * yielding bad latency etc..
  *
  * Now, in that special case (1) reduces to:
  *
  *                     tg->weight * grq->load.weight
  *   ge->load.weight = ----------------------------- = tg->weight   (4)
  *                         grp->load.weight
  *
  * That is, the sum collapses because all other CPUs are idle; the UP scenario.
  *
  * So what we do is modify our approximation (3) to approach (4) in the (near)
  * UP case, like:
  *
  *   ge->load.weight =
  *
  *              tg->weight * grq->load.weight
  *     ---------------------------------------------------         (5)
  *     tg->load_avg - grq->avg.load_avg + grq->load.weight
  *
  * But because grq->load.weight can drop to 0, resulting in a divide by zero,
  * we need to use grq->avg.load_avg as its lower bound, which then gives:
  *
  *
  *                     tg->weight * grq->load.weight
  *   ge->load.weight = -----------------------------           (6)
  *                             tg_load_avg'
  *
  * Where:
  *
  *   tg_load_avg' = tg->load_avg - grq->avg.load_avg +
  *                  max(grq->load.weight, grq->avg.load_avg)
  *
  * And that is shares_weight and is icky. In the (near) UP case it approaches
  * (4) while in the normal case it approaches (3). It consistently
  * overestimates the ge->load.weight and therefore:
  *
  *   \Sum ge->load.weight >= tg->weight
  *
  * hence icky!
  */
 static long calc_group_shares(struct cfs_rq *cfs_rq)
 {
     long tg_weight, tg_shares, load, shares;
     struct task_group *tg = cfs_rq->tg;
 
     tg_shares = READ_ONCE(tg->shares);
 
     load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
 
     tg_weight = atomic_long_read(&tg->load_avg);
 
     /* Ensure tg_weight >= load */
     tg_weight -= cfs_rq->tg_load_avg_contrib;
     tg_weight += load;
 
     shares = (tg_shares * load);
     if (tg_weight)
         shares /= tg_weight;
 
     /*
      * MIN_SHARES has to be unscaled here to support per-CPU partitioning
      * of a group with small tg->shares value. It is a floor value which is
      * assigned as a minimum load.weight to the sched_entity representing
      * the group on a CPU.
      *
      * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
      * on an 8-core system with 8 tasks each runnable on one CPU shares has
      * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
      * case no task is runnable on a CPU MIN_SHARES=2 should be returned
      * instead of 0.
      */
     return clamp_t(long, shares, MIN_SHARES, tg_shares);
 }
 #endif /* CONFIG_SMP */
 
 /*
  * Recomputes the group entity based on the current state of its group
  * runqueue.
  */
 static void update_cfs_group(struct sched_entity *se)
 {
     struct cfs_rq *gcfs_rq = group_cfs_rq(se);
     long shares;
 
     if (!gcfs_rq)
         return;
 
     if (throttled_hierarchy(gcfs_rq))
         return;
 
 #ifndef CONFIG_SMP
     shares = READ_ONCE(gcfs_rq->tg->shares);
 
     if (likely(se->load.weight == shares))
         return;
 #else
     shares   = calc_group_shares(gcfs_rq);
 #endif
 
     reweight_entity(cfs_rq_of(se), se, shares);
 }
 
 #else /* CONFIG_FAIR_GROUP_SCHED */
 static inline void update_cfs_group(struct sched_entity *se)
 {
 }
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
 {
     struct rq *rq = rq_of(cfs_rq);
 
     if (&rq->cfs == cfs_rq) {
         /*
          * There are a few boundary cases this might miss but it should
          * get called often enough that that should (hopefully) not be
          * a real problem.
          *
          * It will not get called when we go idle, because the idle
          * thread is a different class (!fair), nor will the utilization
          * number include things like RT tasks.
          *
          * As is, the util number is not freq-invariant (we'd have to
          * implement arch_scale_freq_capacity() for that).
          *
          * See cpu_util_cfs().
          */
         cpufreq_update_util(rq, flags);
     }
 }
 
 #ifdef CONFIG_SMP
 static inline bool load_avg_is_decayed(struct sched_avg *sa)
 {
     if (sa->load_sum)
         return false;
 
     if (sa->util_sum)
         return false;
 
     if (sa->runnable_sum)
         return false;
 
     /*
      * _avg must be null when _sum are null because _avg = _sum / divider
      * Make sure that rounding and/or propagation of PELT values never
      * break this.
      */
     SCHED_WARN_ON(sa->load_avg ||
               sa->util_avg ||
               sa->runnable_avg);
 
     return true;
 }
 
 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
 {
     return u64_u32_load_copy(cfs_rq->avg.last_update_time,
                  cfs_rq->last_update_time_copy);
 }
 #ifdef CONFIG_FAIR_GROUP_SCHED
 /*
  * Because list_add_leaf_cfs_rq always places a child cfs_rq on the list
  * immediately before a parent cfs_rq, and cfs_rqs are removed from the list
  * bottom-up, we only have to test whether the cfs_rq before us on the list
  * is our child.
  * If cfs_rq is not on the list, test whether a child needs its to be added to
  * connect a branch to the tree  * (see list_add_leaf_cfs_rq() for details).
  */
 static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq)
 {
     struct cfs_rq *prev_cfs_rq;
     struct list_head *prev;
 
     if (cfs_rq->on_list) {
         prev = cfs_rq->leaf_cfs_rq_list.prev;
     } else {
         struct rq *rq = rq_of(cfs_rq);
 
         prev = rq->tmp_alone_branch;
     }
 
     prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list);
 
     return (prev_cfs_rq->tg->parent == cfs_rq->tg);
 }
 
 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
 {
     if (cfs_rq->load.weight)
         return false;
 
     if (!load_avg_is_decayed(&cfs_rq->avg))
         return false;
 
     if (child_cfs_rq_on_list(cfs_rq))
         return false;
 
     return true;
 }
 
 /**
  * update_tg_load_avg - update the tg's load avg
  * @cfs_rq: the cfs_rq whose avg changed
  *
  * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
  * However, because tg->load_avg is a global value there are performance
  * considerations.
  *
  * In order to avoid having to look at the other cfs_rq's, we use a
  * differential update where we store the last value we propagated. This in
  * turn allows skipping updates if the differential is 'small'.
  *
  * Updating tg's load_avg is necessary before update_cfs_share().
  */
 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
 {
     long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
 
     /*
      * No need to update load_avg for root_task_group as it is not used.
      */
     if (cfs_rq->tg == &root_task_group)
         return;
 
     if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
         atomic_long_add(delta, &cfs_rq->tg->load_avg);
         cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
     }
 }
 
 /*
  * Called within set_task_rq() right before setting a task's CPU. The
  * caller only guarantees p->pi_lock is held; no other assumptions,
  * including the state of rq->lock, should be made.
  */
 void set_task_rq_fair(struct sched_entity *se,
               struct cfs_rq *prev, struct cfs_rq *next)
 {
     u64 p_last_update_time;
     u64 n_last_update_time;
 
     if (!sched_feat(ATTACH_AGE_LOAD))
         return;
 
     /*
      * We are supposed to update the task to "current" time, then its up to
      * date and ready to go to new CPU/cfs_rq. But we have difficulty in
      * getting what current time is, so simply throw away the out-of-date
      * time. This will result in the wakee task is less decayed, but giving
      * the wakee more load sounds not bad.
      */
     if (!(se->avg.last_update_time && prev))
         return;
 
     p_last_update_time = cfs_rq_last_update_time(prev);
     n_last_update_time = cfs_rq_last_update_time(next);
 
     __update_load_avg_blocked_se(p_last_update_time, se);
     se->avg.last_update_time = n_last_update_time;
 }
 
 /*
  * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
  * propagate its contribution. The key to this propagation is the invariant
  * that for each group:
  *
  *   ge->avg == grq->avg                        (1)
  *
  * _IFF_ we look at the pure running and runnable sums. Because they
  * represent the very same entity, just at different points in the hierarchy.
  *
  * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
  * and simply copies the running/runnable sum over (but still wrong, because
  * the group entity and group rq do not have their PELT windows aligned).
  *
  * However, update_tg_cfs_load() is more complex. So we have:
  *
  *   ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg      (2)
  *
  * And since, like util, the runnable part should be directly transferable,
  * the following would _appear_ to be the straight forward approach:
  *
  *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg   (3)
  *
  * And per (1) we have:
  *
  *   ge->avg.runnable_avg == grq->avg.runnable_avg
  *
  * Which gives:
  *
  *                      ge->load.weight * grq->avg.load_avg
  *   ge->avg.load_avg = -----------------------------------     (4)
  *                               grq->load.weight
  *
  * Except that is wrong!
  *
  * Because while for entities historical weight is not important and we
  * really only care about our future and therefore can consider a pure
  * runnable sum, runqueues can NOT do this.
  *
  * We specifically want runqueues to have a load_avg that includes
  * historical weights. Those represent the blocked load, the load we expect
  * to (shortly) return to us. This only works by keeping the weights as
  * integral part of the sum. We therefore cannot decompose as per (3).
  *
  * Another reason this doesn't work is that runnable isn't a 0-sum entity.
  * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
  * rq itself is runnable anywhere between 2/3 and 1 depending on how the
  * runnable section of these tasks overlap (or not). If they were to perfectly
  * align the rq as a whole would be runnable 2/3 of the time. If however we
  * always have at least 1 runnable task, the rq as a whole is always runnable.
  *
  * So we'll have to approximate.. :/
  *
  * Given the constraint:
  *
  *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
  *
  * We can construct a rule that adds runnable to a rq by assuming minimal
  * overlap.
  *
  * On removal, we'll assume each task is equally runnable; which yields:
  *
  *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
  *
  * XXX: only do this for the part of runnable > running ?
  *
  */
 static inline void
 update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
 {
     long delta_sum, delta_avg = gcfs_rq->avg.util_avg - se->avg.util_avg;
     u32 new_sum, divider;
 
     /* Nothing to update */
     if (!delta_avg)
         return;
 
     /*
      * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
      * See ___update_load_avg() for details.
      */
     divider = get_pelt_divider(&cfs_rq->avg);
 
 
     /* Set new sched_entity's utilization */
     se->avg.util_avg = gcfs_rq->avg.util_avg;
     new_sum = se->avg.util_avg * divider;
     delta_sum = (long)new_sum - (long)se->avg.util_sum;
     se->avg.util_sum = new_sum;
 
     /* Update parent cfs_rq utilization */
     add_positive(&cfs_rq->avg.util_avg, delta_avg);
     add_positive(&cfs_rq->avg.util_sum, delta_sum);
 
     /* See update_cfs_rq_load_avg() */
     cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
                       cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
 }
 
 static inline void
 update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
 {
     long delta_sum, delta_avg = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
     u32 new_sum, divider;
 
     /* Nothing to update */
     if (!delta_avg)
         return;
 
     /*
      * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
      * See ___update_load_avg() for details.
      */
     divider = get_pelt_divider(&cfs_rq->avg);
 
     /* Set new sched_entity's runnable */
     se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
     new_sum = se->avg.runnable_avg * divider;
     delta_sum = (long)new_sum - (long)se->avg.runnable_sum;
     se->avg.runnable_sum = new_sum;
 
     /* Update parent cfs_rq runnable */
     add_positive(&cfs_rq->avg.runnable_avg, delta_avg);
     add_positive(&cfs_rq->avg.runnable_sum, delta_sum);
     /* See update_cfs_rq_load_avg() */
     cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
                           cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
 }
 
 static inline void
 update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
 {
     long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
     unsigned long load_avg;
     u64 load_sum = 0;
     s64 delta_sum;
     u32 divider;
 
     if (!runnable_sum)
         return;
 
     gcfs_rq->prop_runnable_sum = 0;
 
     /*
      * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
      * See ___update_load_avg() for details.
      */
     divider = get_pelt_divider(&cfs_rq->avg);
 
     if (runnable_sum >= 0) {
         /*
          * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
          * the CPU is saturated running == runnable.
          */
         runnable_sum += se->avg.load_sum;
         runnable_sum = min_t(long, runnable_sum, divider);
     } else {
         /*
          * Estimate the new unweighted runnable_sum of the gcfs_rq by
          * assuming all tasks are equally runnable.
          */
         if (scale_load_down(gcfs_rq->load.weight)) {
             load_sum = div_u64(gcfs_rq->avg.load_sum,
                 scale_load_down(gcfs_rq->load.weight));
         }
 
         /* But make sure to not inflate se's runnable */
         runnable_sum = min(se->avg.load_sum, load_sum);
     }
 
     /*
      * runnable_sum can't be lower than running_sum
      * Rescale running sum to be in the same range as runnable sum
      * running_sum is in [0 : LOAD_AVG_MAX <<  SCHED_CAPACITY_SHIFT]
      * runnable_sum is in [0 : LOAD_AVG_MAX]
      */
     running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
     runnable_sum = max(runnable_sum, running_sum);
 
     load_sum = se_weight(se) * runnable_sum;
     load_avg = div_u64(load_sum, divider);
 
     delta_avg = load_avg - se->avg.load_avg;
     if (!delta_avg)
         return;
 
     delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
 
     se->avg.load_sum = runnable_sum;
     se->avg.load_avg = load_avg;
     add_positive(&cfs_rq->avg.load_avg, delta_avg);
     add_positive(&cfs_rq->avg.load_sum, delta_sum);
     /* See update_cfs_rq_load_avg() */
     cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
                       cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
 }
 
 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
 {
     cfs_rq->propagate = 1;
     cfs_rq->prop_runnable_sum += runnable_sum;
 }
 
 /* Update task and its cfs_rq load average */
 static inline int propagate_entity_load_avg(struct sched_entity *se)
 {
     struct cfs_rq *cfs_rq, *gcfs_rq;
 
     if (entity_is_task(se))
         return 0;
 
     gcfs_rq = group_cfs_rq(se);
     if (!gcfs_rq->propagate)
         return 0;
 
     gcfs_rq->propagate = 0;
 
     cfs_rq = cfs_rq_of(se);
 
     add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
 
     update_tg_cfs_util(cfs_rq, se, gcfs_rq);
     update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
     update_tg_cfs_load(cfs_rq, se, gcfs_rq);
 
     trace_pelt_cfs_tp(cfs_rq);
     trace_pelt_se_tp(se);
 
     return 1;
 }
 
 /*
  * Check if we need to update the load and the utilization of a blocked
  * group_entity:
  */
 static inline bool skip_blocked_update(struct sched_entity *se)
 {
     struct cfs_rq *gcfs_rq = group_cfs_rq(se);
 
     /*
      * If sched_entity still have not zero load or utilization, we have to
      * decay it:
      */
     if (se->avg.load_avg || se->avg.util_avg)
         return false;
 
     /*
      * If there is a pending propagation, we have to update the load and
      * the utilization of the sched_entity:
      */
     if (gcfs_rq->propagate)
         return false;
 
     /*
      * Otherwise, the load and the utilization of the sched_entity is
      * already zero and there is no pending propagation, so it will be a
      * waste of time to try to decay it:
      */
     return true;
 }
 
 #else /* CONFIG_FAIR_GROUP_SCHED */
 
 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) {}
 
 static inline int propagate_entity_load_avg(struct sched_entity *se)
 {
     return 0;
 }
 
 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
 
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 #ifdef CONFIG_NO_HZ_COMMON
 static inline void migrate_se_pelt_lag(struct sched_entity *se)
 {
     u64 throttled = 0, now, lut;
     struct cfs_rq *cfs_rq;
     struct rq *rq;
     bool is_idle;
 
     if (load_avg_is_decayed(&se->avg))
         return;
 
     cfs_rq = cfs_rq_of(se);
     rq = rq_of(cfs_rq);
 
     rcu_read_lock();
     is_idle = is_idle_task(rcu_dereference(rq->curr));
     rcu_read_unlock();
 
     /*
      * The lag estimation comes with a cost we don't want to pay all the
      * time. Hence, limiting to the case where the source CPU is idle and
      * we know we are at the greatest risk to have an outdated clock.
      */
     if (!is_idle)
         return;
 
     /*
      * Estimated "now" is: last_update_time + cfs_idle_lag + rq_idle_lag, where:
      *
      *   last_update_time (the cfs_rq's last_update_time)
      *  = cfs_rq_clock_pelt()@cfs_rq_idle
      *      = rq_clock_pelt()@cfs_rq_idle
      *        - cfs->throttled_clock_pelt_time@cfs_rq_idle
      *
      *   cfs_idle_lag (delta between rq's update and cfs_rq's update)
      *      = rq_clock_pelt()@rq_idle - rq_clock_pelt()@cfs_rq_idle
      *
      *   rq_idle_lag (delta between now and rq's update)
      *      = sched_clock_cpu() - rq_clock()@rq_idle
      *
      * We can then write:
      *
      *    now = rq_clock_pelt()@rq_idle - cfs->throttled_clock_pelt_time +
      *          sched_clock_cpu() - rq_clock()@rq_idle
      * Where:
      *      rq_clock_pelt()@rq_idle is rq->clock_pelt_idle
      *      rq_clock()@rq_idle      is rq->clock_idle
      *      cfs->throttled_clock_pelt_time@cfs_rq_idle
      *                              is cfs_rq->throttled_pelt_idle
      */
 
 #ifdef CONFIG_CFS_BANDWIDTH
     throttled = u64_u32_load(cfs_rq->throttled_pelt_idle);
     /* The clock has been stopped for throttling */
     if (throttled == U64_MAX)
         return;
 #endif
     now = u64_u32_load(rq->clock_pelt_idle);
     /*
      * Paired with _update_idle_rq_clock_pelt(). It ensures at the worst case
      * is observed the old clock_pelt_idle value and the new clock_idle,
      * which lead to an underestimation. The opposite would lead to an
      * overestimation.
      */
     smp_rmb();
     lut = cfs_rq_last_update_time(cfs_rq);
 
     now -= throttled;
     if (now < lut)
         /*
          * cfs_rq->avg.last_update_time is more recent than our
          * estimation, let's use it.
          */
         now = lut;
     else
         now += sched_clock_cpu(cpu_of(rq)) - u64_u32_load(rq->clock_idle);
 
     __update_load_avg_blocked_se(now, se);
 }
 #else
 static void migrate_se_pelt_lag(struct sched_entity *se) {}
 #endif
 
 /**
  * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
  * @now: current time, as per cfs_rq_clock_pelt()
  * @cfs_rq: cfs_rq to update
  *
  * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
  * avg. The immediate corollary is that all (fair) tasks must be attached, see
  * post_init_entity_util_avg().
  *
  * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
  *
  * Return: true if the load decayed or we removed load.
  *
  * Since both these conditions indicate a changed cfs_rq->avg.load we should
  * call update_tg_load_avg() when this function returns true.
  */
 static inline int
 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 {
     unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
     struct sched_avg *sa = &cfs_rq->avg;
     int decayed = 0;
 
     if (cfs_rq->removed.nr) {
         unsigned long r;
         u32 divider = get_pelt_divider(&cfs_rq->avg);
 
         raw_spin_lock(&cfs_rq->removed.lock);
         swap(cfs_rq->removed.util_avg, removed_util);
         swap(cfs_rq->removed.load_avg, removed_load);
         swap(cfs_rq->removed.runnable_avg, removed_runnable);
         cfs_rq->removed.nr = 0;
         raw_spin_unlock(&cfs_rq->removed.lock);
 
         r = removed_load;
         sub_positive(&sa->load_avg, r);
         sub_positive(&sa->load_sum, r * divider);
         /* See sa->util_sum below */
         sa->load_sum = max_t(u32, sa->load_sum, sa->load_avg * PELT_MIN_DIVIDER);
 
         r = removed_util;
         sub_positive(&sa->util_avg, r);
         sub_positive(&sa->util_sum, r * divider);
         /*
          * Because of rounding, se->util_sum might ends up being +1 more than
          * cfs->util_sum. Although this is not a problem by itself, detaching
          * a lot of tasks with the rounding problem between 2 updates of
          * util_avg (~1ms) can make cfs->util_sum becoming null whereas
          * cfs_util_avg is not.
          * Check that util_sum is still above its lower bound for the new
          * util_avg. Given that period_contrib might have moved since the last
          * sync, we are only sure that util_sum must be above or equal to
          *    util_avg * minimum possible divider
          */
         sa->util_sum = max_t(u32, sa->util_sum, sa->util_avg * PELT_MIN_DIVIDER);
 
         r = removed_runnable;
         sub_positive(&sa->runnable_avg, r);
         sub_positive(&sa->runnable_sum, r * divider);
         /* See sa->util_sum above */
         sa->runnable_sum = max_t(u32, sa->runnable_sum,
                           sa->runnable_avg * PELT_MIN_DIVIDER);
 
         /*
          * removed_runnable is the unweighted version of removed_load so we
          * can use it to estimate removed_load_sum.
          */
         add_tg_cfs_propagate(cfs_rq,
             -(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);
 
         decayed = 1;
     }
 
     decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
     u64_u32_store_copy(sa->last_update_time,
                cfs_rq->last_update_time_copy,
                sa->last_update_time);
     return decayed;
 }
 
 /**
  * attach_entity_load_avg - attach this entity to its cfs_rq load avg
  * @cfs_rq: cfs_rq to attach to
  * @se: sched_entity to attach
  *
  * Must call update_cfs_rq_load_avg() before this, since we rely on
  * cfs_rq->avg.last_update_time being current.
  */
 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     /*
      * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
      * See ___update_load_avg() for details.
      */
     u32 divider = get_pelt_divider(&cfs_rq->avg);
 
     /*
      * When we attach the @se to the @cfs_rq, we must align the decay
      * window because without that, really weird and wonderful things can
      * happen.
      *
      * XXX illustrate
      */
     se->avg.last_update_time = cfs_rq->avg.last_update_time;
     se->avg.period_contrib = cfs_rq->avg.period_contrib;
 
     /*
      * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
      * period_contrib. This isn't strictly correct, but since we're
      * entirely outside of the PELT hierarchy, nobody cares if we truncate
      * _sum a little.
      */
     se->avg.util_sum = se->avg.util_avg * divider;
 
     se->avg.runnable_sum = se->avg.runnable_avg * divider;
 
     se->avg.load_sum = se->avg.load_avg * divider;
     if (se_weight(se) < se->avg.load_sum)
         se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se));
     else
         se->avg.load_sum = 1;
 
     enqueue_load_avg(cfs_rq, se);
     cfs_rq->avg.util_avg += se->avg.util_avg;
     cfs_rq->avg.util_sum += se->avg.util_sum;
     cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
     cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
 
     add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
 
     cfs_rq_util_change(cfs_rq, 0);
 
     trace_pelt_cfs_tp(cfs_rq);
 }
 
 /**
  * detach_entity_load_avg - detach this entity from its cfs_rq load avg
  * @cfs_rq: cfs_rq to detach from
  * @se: sched_entity to detach
  *
  * Must call update_cfs_rq_load_avg() before this, since we rely on
  * cfs_rq->avg.last_update_time being current.
  */
 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     dequeue_load_avg(cfs_rq, se);
     sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
     sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
     /* See update_cfs_rq_load_avg() */
     cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
                       cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
 
     sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
     sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum);
     /* See update_cfs_rq_load_avg() */
     cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
                           cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
 
     add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
 
     cfs_rq_util_change(cfs_rq, 0);
 
     trace_pelt_cfs_tp(cfs_rq);
 }
 
 /*
  * Optional action to be done while updating the load average
  */
 #define UPDATE_TG   0x1
 #define SKIP_AGE_LOAD   0x2
 #define DO_ATTACH   0x4
 
 /* Update task and its cfs_rq load average */
 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
     u64 now = cfs_rq_clock_pelt(cfs_rq);
     int decayed;
 
     /*
      * Track task load average for carrying it to new CPU after migrated, and
      * track group sched_entity load average for task_h_load calc in migration
      */
     if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
         __update_load_avg_se(now, cfs_rq, se);
 
     decayed  = update_cfs_rq_load_avg(now, cfs_rq);
     decayed |= propagate_entity_load_avg(se);
 
     if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
 
         /*
          * DO_ATTACH means we're here from enqueue_entity().
          * !last_update_time means we've passed through
          * migrate_task_rq_fair() indicating we migrated.
          *
          * IOW we're enqueueing a task on a new CPU.
          */
         attach_entity_load_avg(cfs_rq, se);
         update_tg_load_avg(cfs_rq);
 
     } else if (decayed) {
         cfs_rq_util_change(cfs_rq, 0);
 
         if (flags & UPDATE_TG)
             update_tg_load_avg(cfs_rq);
     }
 }
 
 /*
  * Synchronize entity load avg of dequeued entity without locking
  * the previous rq.
  */
 static void sync_entity_load_avg(struct sched_entity *se)
 {
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
     u64 last_update_time;
 
     last_update_time = cfs_rq_last_update_time(cfs_rq);
     __update_load_avg_blocked_se(last_update_time, se);
 }
 
 /*
  * Task first catches up with cfs_rq, and then subtract
  * itself from the cfs_rq (task must be off the queue now).
  */
 static void remove_entity_load_avg(struct sched_entity *se)
 {
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
     unsigned long flags;
 
     /*
      * tasks cannot exit without having gone through wake_up_new_task() ->
      * post_init_entity_util_avg() which will have added things to the
      * cfs_rq, so we can remove unconditionally.
      */
 
     sync_entity_load_avg(se);
 
     raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
     ++cfs_rq->removed.nr;
     cfs_rq->removed.util_avg    += se->avg.util_avg;
     cfs_rq->removed.load_avg    += se->avg.load_avg;
     cfs_rq->removed.runnable_avg    += se->avg.runnable_avg;
     raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
 }
 
 static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
 {
     return cfs_rq->avg.runnable_avg;
 }
 
 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
 {
     return cfs_rq->avg.load_avg;
 }
 
 static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
 
 static inline unsigned long task_util(struct task_struct *p)
 {
     return READ_ONCE(p->se.avg.util_avg);
 }
 
 static inline unsigned long _task_util_est(struct task_struct *p)
 {
     struct util_est ue = READ_ONCE(p->se.avg.util_est);
 
     return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
 }
 
 static inline unsigned long task_util_est(struct task_struct *p)
 {
     return max(task_util(p), _task_util_est(p));
 }
 
 #ifdef CONFIG_UCLAMP_TASK
 static inline unsigned long uclamp_task_util(struct task_struct *p)
 {
     return clamp(task_util_est(p),
              uclamp_eff_value(p, UCLAMP_MIN),
              uclamp_eff_value(p, UCLAMP_MAX));
 }
 #else
 static inline unsigned long uclamp_task_util(struct task_struct *p)
 {
     return task_util_est(p);
 }
 #endif
 
 static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
                     struct task_struct *p)
 {
     unsigned int enqueued;
 
     if (!sched_feat(UTIL_EST))
         return;
 
     /* Update root cfs_rq's estimated utilization */
     enqueued  = cfs_rq->avg.util_est.enqueued;
     enqueued += _task_util_est(p);
     WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
 
     trace_sched_util_est_cfs_tp(cfs_rq);
 }
 
 static inline void util_est_dequeue(struct cfs_rq *cfs_rq,
                     struct task_struct *p)
 {
     unsigned int enqueued;
 
     if (!sched_feat(UTIL_EST))
         return;
 
     /* Update root cfs_rq's estimated utilization */
     enqueued  = cfs_rq->avg.util_est.enqueued;
     enqueued -= min_t(unsigned int, enqueued, _task_util_est(p));
     WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
 
     trace_sched_util_est_cfs_tp(cfs_rq);
 }
 
 #define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100)
 
 /*
  * Check if a (signed) value is within a specified (unsigned) margin,
  * based on the observation that:
  *
  *     abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
  *
  * NOTE: this only works when value + margin < INT_MAX.
  */
 static inline bool within_margin(int value, int margin)
 {
     return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
 }
 
 static inline void util_est_update(struct cfs_rq *cfs_rq,
                    struct task_struct *p,
                    bool task_sleep)
 {
     long last_ewma_diff, last_enqueued_diff;
     struct util_est ue;
 
     if (!sched_feat(UTIL_EST))
         return;
 
     /*
      * Skip update of task's estimated utilization when the task has not
      * yet completed an activation, e.g. being migrated.
      */
     if (!task_sleep)
         return;
 
     /*
      * If the PELT values haven't changed since enqueue time,
      * skip the util_est update.
      */
     ue = p->se.avg.util_est;
     if (ue.enqueued & UTIL_AVG_UNCHANGED)
         return;
 
     last_enqueued_diff = ue.enqueued;
 
     /*
      * Reset EWMA on utilization increases, the moving average is used only
      * to smooth utilization decreases.
      */
     ue.enqueued = task_util(p);
     if (sched_feat(UTIL_EST_FASTUP)) {
         if (ue.ewma < ue.enqueued) {
             ue.ewma = ue.enqueued;
             goto done;
         }
     }
 
     /*
      * Skip update of task's estimated utilization when its members are
      * already ~1% close to its last activation value.
      */
     last_ewma_diff = ue.enqueued - ue.ewma;
     last_enqueued_diff -= ue.enqueued;
     if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) {
         if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN))
             goto done;
 
         return;
     }
 
     /*
      * To avoid overestimation of actual task utilization, skip updates if
      * we cannot grant there is idle time in this CPU.
      */
     if (task_util(p) > capacity_orig_of(cpu_of(rq_of(cfs_rq))))
         return;
 
     /*
      * Update Task's estimated utilization
      *
      * When *p completes an activation we can consolidate another sample
      * of the task size. This is done by storing the current PELT value
      * as ue.enqueued and by using this value to update the Exponential
      * Weighted Moving Average (EWMA):
      *
      *  ewma(t) = w *  task_util(p) + (1-w) * ewma(t-1)
      *          = w *  task_util(p) +         ewma(t-1)  - w * ewma(t-1)
      *          = w * (task_util(p) -         ewma(t-1)) +     ewma(t-1)
      *          = w * (      last_ewma_diff            ) +     ewma(t-1)
      *          = w * (last_ewma_diff  +  ewma(t-1) / w)
      *
      * Where 'w' is the weight of new samples, which is configured to be
      * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
      */
     ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
     ue.ewma  += last_ewma_diff;
     ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
 done:
     ue.enqueued |= UTIL_AVG_UNCHANGED;
     WRITE_ONCE(p->se.avg.util_est, ue);
 
     trace_sched_util_est_se_tp(&p->se);
 }
 
 static inline int task_fits_capacity(struct task_struct *p,
                      unsigned long capacity)
 {
     return fits_capacity(uclamp_task_util(p), capacity);
 }
 
 static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
 {
     if (!static_branch_unlikely(&sched_asym_cpucapacity))
         return;
 
     if (!p || p->nr_cpus_allowed == 1) {
         rq->misfit_task_load = 0;
         return;
     }
 
     if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
         rq->misfit_task_load = 0;
         return;
     }
 
     /*
      * Make sure that misfit_task_load will not be null even if
      * task_h_load() returns 0.
      */
     rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1);
 }
 
 #else /* CONFIG_SMP */
 
 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
 {
     return true;
 }
 
 #define UPDATE_TG   0x0
 #define SKIP_AGE_LOAD   0x0
 #define DO_ATTACH   0x0
 
 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
 {
     cfs_rq_util_change(cfs_rq, 0);
 }
 
 static inline void remove_entity_load_avg(struct sched_entity *se) {}
 
 static inline void
 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
 static inline void
 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
 
 static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
 {
     return 0;
 }
 
 static inline void
 util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
 
 static inline void
 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
 
 static inline void
 util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p,
         bool task_sleep) {}
 static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
 
 #endif /* CONFIG_SMP */
 
 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 #ifdef CONFIG_SCHED_DEBUG
     s64 d = se->vruntime - cfs_rq->min_vruntime;
 
     if (d < 0)
         d = -d;
 
     if (d > 3*sysctl_sched_latency)
         schedstat_inc(cfs_rq->nr_spread_over);
 #endif
 }
 
 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
     u64 vruntime = cfs_rq->min_vruntime;
 
     /*
      * The 'current' period is already promised to the current tasks,
      * however the extra weight of the new task will slow them down a
      * little, place the new task so that it fits in the slot that
      * stays open at the end.
      */
     if (initial && sched_feat(START_DEBIT))
         vruntime += sched_vslice(cfs_rq, se);
 
     /* sleeps up to a single latency don't count. */
     if (!initial) {
         unsigned long thresh;
 
         if (se_is_idle(se))
             thresh = sysctl_sched_min_granularity;
         else
             thresh = sysctl_sched_latency;
 
         /*
          * Halve their sleep time's effect, to allow
          * for a gentler effect of sleepers:
          */
         if (sched_feat(GENTLE_FAIR_SLEEPERS))
             thresh >>= 1;
 
         vruntime -= thresh;
     }
 
     /* ensure we never gain time by being placed backwards. */
     se->vruntime = max_vruntime(se->vruntime, vruntime);
 }
 
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
 
 static inline bool cfs_bandwidth_used(void);
 
 /*
  * MIGRATION
  *
  *  dequeue
  *    update_curr()
  *      update_min_vruntime()
  *    vruntime -= min_vruntime
  *
  *  enqueue
  *    update_curr()
  *      update_min_vruntime()
  *    vruntime += min_vruntime
  *
  * this way the vruntime transition between RQs is done when both
  * min_vruntime are up-to-date.
  *
  * WAKEUP (remote)
  *
  *  ->migrate_task_rq_fair() (p->state == TASK_WAKING)
  *    vruntime -= min_vruntime
  *
  *  enqueue
  *    update_curr()
  *      update_min_vruntime()
  *    vruntime += min_vruntime
  *
  * this way we don't have the most up-to-date min_vruntime on the originating
  * CPU and an up-to-date min_vruntime on the destination CPU.
  */
 
 static void
 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
     bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
     bool curr = cfs_rq->curr == se;
 
     /*
      * If we're the current task, we must renormalise before calling
      * update_curr().
      */
     if (renorm && curr)
         se->vruntime += cfs_rq->min_vruntime;
 
     update_curr(cfs_rq);
 
     /*
      * Otherwise, renormalise after, such that we're placed at the current
      * moment in time, instead of some random moment in the past. Being
      * placed in the past could significantly boost this task to the
      * fairness detriment of existing tasks.
      */
     if (renorm && !curr)
         se->vruntime += cfs_rq->min_vruntime;
 
     /*
      * When enqueuing a sched_entity, we must:
      *   - Update loads to have both entity and cfs_rq synced with now.
      *   - Add its load to cfs_rq->runnable_avg
      *   - For group_entity, update its weight to reflect the new share of
      *     its group cfs_rq
      *   - Add its new weight to cfs_rq->load.weight
      */
     update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
     se_update_runnable(se);
     update_cfs_group(se);
     account_entity_enqueue(cfs_rq, se);
 
     if (flags & ENQUEUE_WAKEUP)
         place_entity(cfs_rq, se, 0);
 
     check_schedstat_required();
     update_stats_enqueue_fair(cfs_rq, se, flags);
     check_spread(cfs_rq, se);
     if (!curr)
         __enqueue_entity(cfs_rq, se);
     se->on_rq = 1;
 
     if (cfs_rq->nr_running == 1) {
         check_enqueue_throttle(cfs_rq);
         if (!throttled_hierarchy(cfs_rq))
             list_add_leaf_cfs_rq(cfs_rq);
     }
 }
 
 static void __clear_buddies_last(struct sched_entity *se)
 {
     for_each_sched_entity(se) {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
         if (cfs_rq->last != se)
             break;
 
         cfs_rq->last = NULL;
     }
 }
 
 static void __clear_buddies_next(struct sched_entity *se)
 {
     for_each_sched_entity(se) {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
         if (cfs_rq->next != se)
             break;
 
         cfs_rq->next = NULL;
     }
 }
 
 static void __clear_buddies_skip(struct sched_entity *se)
 {
     for_each_sched_entity(se) {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
         if (cfs_rq->skip != se)
             break;
 
         cfs_rq->skip = NULL;
     }
 }
 
 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     if (cfs_rq->last == se)
         __clear_buddies_last(se);
 
     if (cfs_rq->next == se)
         __clear_buddies_next(se);
 
     if (cfs_rq->skip == se)
         __clear_buddies_skip(se);
 }
 
 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
 
 static void
 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
     /*
      * Update run-time statistics of the 'current'.
      */
     update_curr(cfs_rq);
 
     /*
      * When dequeuing a sched_entity, we must:
      *   - Update loads to have both entity and cfs_rq synced with now.
      *   - Subtract its load from the cfs_rq->runnable_avg.
      *   - Subtract its previous weight from cfs_rq->load.weight.
      *   - For group entity, update its weight to reflect the new share
      *     of its group cfs_rq.
      */
     update_load_avg(cfs_rq, se, UPDATE_TG);
     se_update_runnable(se);
 
     update_stats_dequeue_fair(cfs_rq, se, flags);
 
     clear_buddies(cfs_rq, se);
 
     if (se != cfs_rq->curr)
         __dequeue_entity(cfs_rq, se);
     se->on_rq = 0;
     account_entity_dequeue(cfs_rq, se);
 
     /*
      * Normalize after update_curr(); which will also have moved
      * min_vruntime if @se is the one holding it back. But before doing
      * update_min_vruntime() again, which will discount @se's position and
      * can move min_vruntime forward still more.
      */
     if (!(flags & DEQUEUE_SLEEP))
         se->vruntime -= cfs_rq->min_vruntime;
 
     /* return excess runtime on last dequeue */
     return_cfs_rq_runtime(cfs_rq);
 
     update_cfs_group(se);
 
     /*
      * Now advance min_vruntime if @se was the entity holding it back,
      * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
      * put back on, and if we advance min_vruntime, we'll be placed back
      * further than we started -- ie. we'll be penalized.
      */
     if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
         update_min_vruntime(cfs_rq);
 
     if (cfs_rq->nr_running == 0)
         update_idle_cfs_rq_clock_pelt(cfs_rq);
 }
 
 /*
  * Preempt the current task with a newly woken task if needed:
  */
 static void
 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
     unsigned long ideal_runtime, delta_exec;
     struct sched_entity *se;
     s64 delta;
 
     ideal_runtime = sched_slice(cfs_rq, curr);
     delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
     if (delta_exec > ideal_runtime) {
         resched_curr(rq_of(cfs_rq));
         /*
          * The current task ran long enough, ensure it doesn't get
          * re-elected due to buddy favours.
          */
         clear_buddies(cfs_rq, curr);
         return;
     }
 
     /*
      * Ensure that a task that missed wakeup preemption by a
      * narrow margin doesn't have to wait for a full slice.
      * This also mitigates buddy induced latencies under load.
      */
     if (delta_exec < sysctl_sched_min_granularity)
         return;
 
     se = __pick_first_entity(cfs_rq);
     delta = curr->vruntime - se->vruntime;
 
     if (delta < 0)
         return;
 
     if (delta > ideal_runtime)
         resched_curr(rq_of(cfs_rq));
 }
 
 static void
 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
     clear_buddies(cfs_rq, se);
 
     /* 'current' is not kept within the tree. */
     if (se->on_rq) {
         /*
          * Any task has to be enqueued before it get to execute on
          * a CPU. So account for the time it spent waiting on the
          * runqueue.
          */
         update_stats_wait_end_fair(cfs_rq, se);
         __dequeue_entity(cfs_rq, se);
         update_load_avg(cfs_rq, se, UPDATE_TG);
     }
 
     update_stats_curr_start(cfs_rq, se);
     cfs_rq->curr = se;
 
     /*
      * Track our maximum slice length, if the CPU's load is at
      * least twice that of our own weight (i.e. dont track it
      * when there are only lesser-weight tasks around):
      */
     if (schedstat_enabled() &&
         rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
         struct sched_statistics *stats;
 
         stats = __schedstats_from_se(se);
         __schedstat_set(stats->slice_max,
                 max((u64)stats->slice_max,
                     se->sum_exec_runtime - se->prev_sum_exec_runtime));
     }
 
     se->prev_sum_exec_runtime = se->sum_exec_runtime;
 }
 
 static int
 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
 
 /*
  * Pick the next process, keeping these things in mind, in this order:
  * 1) keep things fair between processes/task groups
  * 2) pick the "next" process, since someone really wants that to run
  * 3) pick the "last" process, for cache locality
  * 4) do not run the "skip" process, if something else is available
  */
 static struct sched_entity *
 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
     struct sched_entity *left = __pick_first_entity(cfs_rq);
     struct sched_entity *se;
 
     /*
      * If curr is set we have to see if its left of the leftmost entity
      * still in the tree, provided there was anything in the tree at all.
      */
     if (!left || (curr && entity_before(curr, left)))
         left = curr;
 
     se = left; /* ideally we run the leftmost entity */
 
     /*
      * Avoid running the skip buddy, if running something else can
      * be done without getting too unfair.
      */
     if (cfs_rq->skip && cfs_rq->skip == se) {
         struct sched_entity *second;
 
         if (se == curr) {
             second = __pick_first_entity(cfs_rq);
         } else {
             second = __pick_next_entity(se);
             if (!second || (curr && entity_before(curr, second)))
                 second = curr;
         }
 
         if (second && wakeup_preempt_entity(second, left) < 1)
             se = second;
     }
 
     if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) {
         /*
          * Someone really wants this to run. If it's not unfair, run it.
          */
         se = cfs_rq->next;
     } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) {
         /*
          * Prefer last buddy, try to return the CPU to a preempted task.
          */
         se = cfs_rq->last;
     }
 
     return se;
 }
 
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
 
 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
 {
     /*
      * If still on the runqueue then deactivate_task()
      * was not called and update_curr() has to be done:
      */
     if (prev->on_rq)
         update_curr(cfs_rq);
 
     /* throttle cfs_rqs exceeding runtime */
     check_cfs_rq_runtime(cfs_rq);
 
     check_spread(cfs_rq, prev);
 
     if (prev->on_rq) {
         update_stats_wait_start_fair(cfs_rq, prev);
         /* Put 'current' back into the tree. */
         __enqueue_entity(cfs_rq, prev);
         /* in !on_rq case, update occurred at dequeue */
         update_load_avg(cfs_rq, prev, 0);
     }
     cfs_rq->curr = NULL;
 }
 
 static void
 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 {
     /*
      * Update run-time statistics of the 'current'.
      */
     update_curr(cfs_rq);
 
     /*
      * Ensure that runnable average is periodically updated.
      */
     update_load_avg(cfs_rq, curr, UPDATE_TG);
     update_cfs_group(curr);
 
 #ifdef CONFIG_SCHED_HRTICK
     /*
      * queued ticks are scheduled to match the slice, so don't bother
      * validating it and just reschedule.
      */
     if (queued) {
         resched_curr(rq_of(cfs_rq));
         return;
     }
     /*
      * don't let the period tick interfere with the hrtick preemption
      */
     if (!sched_feat(DOUBLE_TICK) &&
             hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
         return;
 #endif
 
     if (cfs_rq->nr_running > 1)
         check_preempt_tick(cfs_rq, curr);
 }
 
 
 /**************************************************
  * CFS bandwidth control machinery
  */
 
 #ifdef CONFIG_CFS_BANDWIDTH
 
 #ifdef CONFIG_JUMP_LABEL
 static struct static_key __cfs_bandwidth_used;
 
 static inline bool cfs_bandwidth_used(void)
 {
     return static_key_false(&__cfs_bandwidth_used);
 }
 
 void cfs_bandwidth_usage_inc(void)
 {
     static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
 }
 
 void cfs_bandwidth_usage_dec(void)
 {
     static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
 }
 #else /* CONFIG_JUMP_LABEL */
 static bool cfs_bandwidth_used(void)
 {
     return true;
 }
 
 void cfs_bandwidth_usage_inc(void) {}
 void cfs_bandwidth_usage_dec(void) {}
 #endif /* CONFIG_JUMP_LABEL */
 
 /*
  * default period for cfs group bandwidth.
  * default: 0.1s, units: nanoseconds
  */
 static inline u64 default_cfs_period(void)
 {
     return 100000000ULL;
 }
 
 static inline u64 sched_cfs_bandwidth_slice(void)
 {
     return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
 }
 
 /*
  * Replenish runtime according to assigned quota. We use sched_clock_cpu
  * directly instead of rq->clock to avoid adding additional synchronization
  * around rq->lock.
  *
  * requires cfs_b->lock
  */
 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
 {
     s64 runtime;
 
     if (unlikely(cfs_b->quota == RUNTIME_INF))
         return;
 
     cfs_b->runtime += cfs_b->quota;
     runtime = cfs_b->runtime_snap - cfs_b->runtime;
     if (runtime > 0) {
         cfs_b->burst_time += runtime;
         cfs_b->nr_burst++;
     }
 
     cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
     cfs_b->runtime_snap = cfs_b->runtime;
 }
 
 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
 {
     return &tg->cfs_bandwidth;
 }
 
 /* returns 0 on failure to allocate runtime */
 static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
                    struct cfs_rq *cfs_rq, u64 target_runtime)
 {
     u64 min_amount, amount = 0;
 
     lockdep_assert_held(&cfs_b->lock);
 
     /* note: this is a positive sum as runtime_remaining <= 0 */
     min_amount = target_runtime - cfs_rq->runtime_remaining;
 
     if (cfs_b->quota == RUNTIME_INF)
         amount = min_amount;
     else {
         start_cfs_bandwidth(cfs_b);
 
         if (cfs_b->runtime > 0) {
             amount = min(cfs_b->runtime, min_amount);
             cfs_b->runtime -= amount;
             cfs_b->idle = 0;
         }
     }
 
     cfs_rq->runtime_remaining += amount;
 
     return cfs_rq->runtime_remaining > 0;
 }
 
 /* returns 0 on failure to allocate runtime */
 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
     struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
     int ret;
 
     raw_spin_lock(&cfs_b->lock);
     ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
     raw_spin_unlock(&cfs_b->lock);
 
     return ret;
 }
 
 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
 {
     /* dock delta_exec before expiring quota (as it could span periods) */
     cfs_rq->runtime_remaining -= delta_exec;
 
     if (likely(cfs_rq->runtime_remaining > 0))
         return;
 
     if (cfs_rq->throttled)
         return;
     /*
      * if we're unable to extend our runtime we resched so that the active
      * hierarchy can be throttled
      */
     if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
         resched_curr(rq_of(cfs_rq));
 }
 
 static __always_inline
 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
 {
     if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
         return;
 
     __account_cfs_rq_runtime(cfs_rq, delta_exec);
 }
 
 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
 {
     return cfs_bandwidth_used() && cfs_rq->throttled;
 }
 
 /* check whether cfs_rq, or any parent, is throttled */
 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
 {
     return cfs_bandwidth_used() && cfs_rq->throttle_count;
 }
 
 /*
  * Ensure that neither of the group entities corresponding to src_cpu or
  * dest_cpu are members of a throttled hierarchy when performing group
  * load-balance operations.
  */
 static inline int throttled_lb_pair(struct task_group *tg,
                     int src_cpu, int dest_cpu)
 {
     struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
 
     src_cfs_rq = tg->cfs_rq[src_cpu];
     dest_cfs_rq = tg->cfs_rq[dest_cpu];
 
     return throttled_hierarchy(src_cfs_rq) ||
            throttled_hierarchy(dest_cfs_rq);
 }
 
 static int tg_unthrottle_up(struct task_group *tg, void *data)
 {
     struct rq *rq = data;
     struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
     cfs_rq->throttle_count--;
     if (!cfs_rq->throttle_count) {
         cfs_rq->throttled_clock_pelt_time += rq_clock_pelt(rq) -
                          cfs_rq->throttled_clock_pelt;
 
         /* Add cfs_rq with load or one or more already running entities to the list */
         if (!cfs_rq_is_decayed(cfs_rq))
             list_add_leaf_cfs_rq(cfs_rq);
     }
 
     return 0;
 }
 
 static int tg_throttle_down(struct task_group *tg, void *data)
 {
     struct rq *rq = data;
     struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
     /* group is entering throttled state, stop time */
     if (!cfs_rq->throttle_count) {
         cfs_rq->throttled_clock_pelt = rq_clock_pelt(rq);
         list_del_leaf_cfs_rq(cfs_rq);
     }
     cfs_rq->throttle_count++;
 
     return 0;
 }
 
 static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
 {
     struct rq *rq = rq_of(cfs_rq);
     struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
     struct sched_entity *se;
     long task_delta, idle_task_delta, dequeue = 1;
 
     raw_spin_lock(&cfs_b->lock);
     /* This will start the period timer if necessary */
     if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
         /*
          * We have raced with bandwidth becoming available, and if we
          * actually throttled the timer might not unthrottle us for an
          * entire period. We additionally needed to make sure that any
          * subsequent check_cfs_rq_runtime calls agree not to throttle
          * us, as we may commit to do cfs put_prev+pick_next, so we ask
          * for 1ns of runtime rather than just check cfs_b.
          */
         dequeue = 0;
     } else {
         list_add_tail_rcu(&cfs_rq->throttled_list,
                   &cfs_b->throttled_cfs_rq);
     }
     raw_spin_unlock(&cfs_b->lock);
 
     if (!dequeue)
         return false;  /* Throttle no longer required. */
 
     se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
 
     /* freeze hierarchy runnable averages while throttled */
     rcu_read_lock();
     walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
     rcu_read_unlock();
 
     task_delta = cfs_rq->h_nr_running;
     idle_task_delta = cfs_rq->idle_h_nr_running;
     for_each_sched_entity(se) {
         struct cfs_rq *qcfs_rq = cfs_rq_of(se);
         /* throttled entity or throttle-on-deactivate */
         if (!se->on_rq)
             goto done;
 
         dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
 
         if (cfs_rq_is_idle(group_cfs_rq(se)))
             idle_task_delta = cfs_rq->h_nr_running;
 
         qcfs_rq->h_nr_running -= task_delta;
         qcfs_rq->idle_h_nr_running -= idle_task_delta;
 
         if (qcfs_rq->load.weight) {
             /* Avoid re-evaluating load for this entity: */
             se = parent_entity(se);
             break;
         }
     }
 
     for_each_sched_entity(se) {
         struct cfs_rq *qcfs_rq = cfs_rq_of(se);
         /* throttled entity or throttle-on-deactivate */
         if (!se->on_rq)
             goto done;
 
         update_load_avg(qcfs_rq, se, 0);
         se_update_runnable(se);
 
         if (cfs_rq_is_idle(group_cfs_rq(se)))
             idle_task_delta = cfs_rq->h_nr_running;
 
         qcfs_rq->h_nr_running -= task_delta;
         qcfs_rq->idle_h_nr_running -= idle_task_delta;
     }
 
     /* At this point se is NULL and we are at root level*/
     sub_nr_running(rq, task_delta);
 
 done:
     /*
      * Note: distribution will already see us throttled via the
      * throttled-list.  rq->lock protects completion.
      */
     cfs_rq->throttled = 1;
     cfs_rq->throttled_clock = rq_clock(rq);
     return true;
 }
 
 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 {
     struct rq *rq = rq_of(cfs_rq);
     struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
     struct sched_entity *se;
     long task_delta, idle_task_delta;
 
     se = cfs_rq->tg->se[cpu_of(rq)];
 
     cfs_rq->throttled = 0;
 
     update_rq_clock(rq);
 
     raw_spin_lock(&cfs_b->lock);
     cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
     list_del_rcu(&cfs_rq->throttled_list);
     raw_spin_unlock(&cfs_b->lock);
 
     /* update hierarchical throttle state */
     walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
 
     if (!cfs_rq->load.weight) {
         if (!cfs_rq->on_list)
             return;
         /*
          * Nothing to run but something to decay (on_list)?
          * Complete the branch.
          */
         for_each_sched_entity(se) {
             if (list_add_leaf_cfs_rq(cfs_rq_of(se)))
                 break;
         }
         goto unthrottle_throttle;
     }
 
     task_delta = cfs_rq->h_nr_running;
     idle_task_delta = cfs_rq->idle_h_nr_running;
     for_each_sched_entity(se) {
         struct cfs_rq *qcfs_rq = cfs_rq_of(se);
 
         if (se->on_rq)
             break;
         enqueue_entity(qcfs_rq, se, ENQUEUE_WAKEUP);
 
         if (cfs_rq_is_idle(group_cfs_rq(se)))
             idle_task_delta = cfs_rq->h_nr_running;
 
         qcfs_rq->h_nr_running += task_delta;
         qcfs_rq->idle_h_nr_running += idle_task_delta;
 
         /* end evaluation on encountering a throttled cfs_rq */
         if (cfs_rq_throttled(qcfs_rq))
             goto unthrottle_throttle;
     }
 
     for_each_sched_entity(se) {
         struct cfs_rq *qcfs_rq = cfs_rq_of(se);
 
         update_load_avg(qcfs_rq, se, UPDATE_TG);
         se_update_runnable(se);
 
         if (cfs_rq_is_idle(group_cfs_rq(se)))
             idle_task_delta = cfs_rq->h_nr_running;
 
         qcfs_rq->h_nr_running += task_delta;
         qcfs_rq->idle_h_nr_running += idle_task_delta;
 
         /* end evaluation on encountering a throttled cfs_rq */
         if (cfs_rq_throttled(qcfs_rq))
             goto unthrottle_throttle;
     }
 
     /* At this point se is NULL and we are at root level*/
     add_nr_running(rq, task_delta);
 
 unthrottle_throttle:
     assert_list_leaf_cfs_rq(rq);
 
     /* Determine whether we need to wake up potentially idle CPU: */
     if (rq->curr == rq->idle && rq->cfs.nr_running)
         resched_curr(rq);
 }
 
 static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
 {
     struct cfs_rq *cfs_rq;
     u64 runtime, remaining = 1;
 
     rcu_read_lock();
     list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
                 throttled_list) {
         struct rq *rq = rq_of(cfs_rq);
         struct rq_flags rf;
 
         rq_lock_irqsave(rq, &rf);
         if (!cfs_rq_throttled(cfs_rq))
             goto next;
 
         /* By the above check, this should never be true */
         SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
 
         raw_spin_lock(&cfs_b->lock);
         runtime = -cfs_rq->runtime_remaining + 1;
         if (runtime > cfs_b->runtime)
             runtime = cfs_b->runtime;
         cfs_b->runtime -= runtime;
         remaining = cfs_b->runtime;
         raw_spin_unlock(&cfs_b->lock);
 
         cfs_rq->runtime_remaining += runtime;
 
         /* we check whether we're throttled above */
         if (cfs_rq->runtime_remaining > 0)
             unthrottle_cfs_rq(cfs_rq);
 
 next:
         rq_unlock_irqrestore(rq, &rf);
 
         if (!remaining)
             break;
     }
     rcu_read_unlock();
 }
 
 /*
  * Responsible for refilling a task_group's bandwidth and unthrottling its
  * cfs_rqs as appropriate. If there has been no activity within the last
  * period the timer is deactivated until scheduling resumes; cfs_b->idle is
  * used to track this state.
  */
 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
 {
     int throttled;
 
     /* no need to continue the timer with no bandwidth constraint */
     if (cfs_b->quota == RUNTIME_INF)
         goto out_deactivate;
 
     throttled = !list_empty(&cfs_b->throttled_cfs_rq);
     cfs_b->nr_periods += overrun;
 
     /* Refill extra burst quota even if cfs_b->idle */
     __refill_cfs_bandwidth_runtime(cfs_b);
 
     /*
      * idle depends on !throttled (for the case of a large deficit), and if
      * we're going inactive then everything else can be deferred
      */
     if (cfs_b->idle && !throttled)
         goto out_deactivate;
 
     if (!throttled) {
         /* mark as potentially idle for the upcoming period */
         cfs_b->idle = 1;
         return 0;
     }
 
     /* account preceding periods in which throttling occurred */
     cfs_b->nr_throttled += overrun;
 
     /*
      * This check is repeated as we release cfs_b->lock while we unthrottle.
      */
     while (throttled && cfs_b->runtime > 0) {
         raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
         /* we can't nest cfs_b->lock while distributing bandwidth */
         distribute_cfs_runtime(cfs_b);
         raw_spin_lock_irqsave(&cfs_b->lock, flags);
 
         throttled = !list_empty(&cfs_b->throttled_cfs_rq);
     }
 
     /*
      * While we are ensured activity in the period following an
      * unthrottle, this also covers the case in which the new bandwidth is
      * insufficient to cover the existing bandwidth deficit.  (Forcing the
      * timer to remain active while there are any throttled entities.)
      */
     cfs_b->idle = 0;
 
     return 0;
 
 out_deactivate:
     return 1;
 }
 
 /* a cfs_rq won't donate quota below this amount */
 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
 /* minimum remaining period time to redistribute slack quota */
 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
 /* how long we wait to gather additional slack before distributing */
 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
 
 /*
  * Are we near the end of the current quota period?
  *
  * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
  * hrtimer base being cleared by hrtimer_start. In the case of
  * migrate_hrtimers, base is never cleared, so we are fine.
  */
 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
 {
     struct hrtimer *refresh_timer = &cfs_b->period_timer;
     s64 remaining;
 
     /* if the call-back is running a quota refresh is already occurring */
     if (hrtimer_callback_running(refresh_timer))
         return 1;
 
     /* is a quota refresh about to occur? */
     remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
     if (remaining < (s64)min_expire)
         return 1;
 
     return 0;
 }
 
 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
 {
     u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
 
     /* if there's a quota refresh soon don't bother with slack */
     if (runtime_refresh_within(cfs_b, min_left))
         return;
 
     /* don't push forwards an existing deferred unthrottle */
     if (cfs_b->slack_started)
         return;
     cfs_b->slack_started = true;
 
     hrtimer_start(&cfs_b->slack_timer,
             ns_to_ktime(cfs_bandwidth_slack_period),
             HRTIMER_MODE_REL);
 }
 
 /* we know any runtime found here is valid as update_curr() precedes return */
 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
     struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
     s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
 
     if (slack_runtime <= 0)
         return;
 
     raw_spin_lock(&cfs_b->lock);
     if (cfs_b->quota != RUNTIME_INF) {
         cfs_b->runtime += slack_runtime;
 
         /* we are under rq->lock, defer unthrottling using a timer */
         if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
             !list_empty(&cfs_b->throttled_cfs_rq))
             start_cfs_slack_bandwidth(cfs_b);
     }
     raw_spin_unlock(&cfs_b->lock);
 
     /* even if it's not valid for return we don't want to try again */
     cfs_rq->runtime_remaining -= slack_runtime;
 }
 
 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
     if (!cfs_bandwidth_used())
         return;
 
     if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
         return;
 
     __return_cfs_rq_runtime(cfs_rq);
 }
 
 /*
  * This is done with a timer (instead of inline with bandwidth return) since
  * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
  */
 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
 {
     u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
     unsigned long flags;
 
     /* confirm we're still not at a refresh boundary */
     raw_spin_lock_irqsave(&cfs_b->lock, flags);
     cfs_b->slack_started = false;
 
     if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
         raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
         return;
     }
 
     if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
         runtime = cfs_b->runtime;
 
     raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
 
     if (!runtime)
         return;
 
     distribute_cfs_runtime(cfs_b);
 }
 
 /*
  * When a group wakes up we want to make sure that its quota is not already
  * expired/exceeded, otherwise it may be allowed to steal additional ticks of
  * runtime as update_curr() throttling can not trigger until it's on-rq.
  */
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
 {
     if (!cfs_bandwidth_used())
         return;
 
     /* an active group must be handled by the update_curr()->put() path */
     if (!cfs_rq->runtime_enabled || cfs_rq->curr)
         return;
 
     /* ensure the group is not already throttled */
     if (cfs_rq_throttled(cfs_rq))
         return;
 
     /* update runtime allocation */
     account_cfs_rq_runtime(cfs_rq, 0);
     if (cfs_rq->runtime_remaining <= 0)
         throttle_cfs_rq(cfs_rq);
 }
 
 static void sync_throttle(struct task_group *tg, int cpu)
 {
     struct cfs_rq *pcfs_rq, *cfs_rq;
 
     if (!cfs_bandwidth_used())
         return;
 
     if (!tg->parent)
         return;
 
     cfs_rq = tg->cfs_rq[cpu];
     pcfs_rq = tg->parent->cfs_rq[cpu];
 
     cfs_rq->throttle_count = pcfs_rq->throttle_count;
     cfs_rq->throttled_clock_pelt = rq_clock_pelt(cpu_rq(cpu));
 }
 
 /* conditionally throttle active cfs_rq's from put_prev_entity() */
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
     if (!cfs_bandwidth_used())
         return false;
 
     if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
         return false;
 
     /*
      * it's possible for a throttled entity to be forced into a running
      * state (e.g. set_curr_task), in this case we're finished.
      */
     if (cfs_rq_throttled(cfs_rq))
         return true;
 
     return throttle_cfs_rq(cfs_rq);
 }
 
 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
 {
     struct cfs_bandwidth *cfs_b =
         container_of(timer, struct cfs_bandwidth, slack_timer);
 
     do_sched_cfs_slack_timer(cfs_b);
 
     return HRTIMER_NORESTART;
 }
 
 extern const u64 max_cfs_quota_period;
 
 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
 {
     struct cfs_bandwidth *cfs_b =
         container_of(timer, struct cfs_bandwidth, period_timer);
     unsigned long flags;
     int overrun;
     int idle = 0;
     int count = 0;
 
     raw_spin_lock_irqsave(&cfs_b->lock, flags);
     for (;;) {
         overrun = hrtimer_forward_now(timer, cfs_b->period);
         if (!overrun)
             break;
 
         idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
 
         if (++count > 3) {
             u64 new, old = ktime_to_ns(cfs_b->period);
 
             /*
              * Grow period by a factor of 2 to avoid losing precision.
              * Precision loss in the quota/period ratio can cause __cfs_schedulable
              * to fail.
              */
             new = old * 2;
             if (new < max_cfs_quota_period) {
                 cfs_b->period = ns_to_ktime(new);
                 cfs_b->quota *= 2;
                 cfs_b->burst *= 2;
 
                 pr_warn_ratelimited(
     "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
                     smp_processor_id(),
                     div_u64(new, NSEC_PER_USEC),
                     div_u64(cfs_b->quota, NSEC_PER_USEC));
             } else {
                 pr_warn_ratelimited(
     "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
                     smp_processor_id(),
                     div_u64(old, NSEC_PER_USEC),
                     div_u64(cfs_b->quota, NSEC_PER_USEC));
             }
 
             /* reset count so we don't come right back in here */
             count = 0;
         }
     }
     if (idle)
         cfs_b->period_active = 0;
     raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
 
     return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
 }
 
 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
 {
     raw_spin_lock_init(&cfs_b->lock);
     cfs_b->runtime = 0;
     cfs_b->quota = RUNTIME_INF;
     cfs_b->period = ns_to_ktime(default_cfs_period());
     cfs_b->burst = 0;
 
     INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
     hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
     cfs_b->period_timer.function = sched_cfs_period_timer;
     hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
     cfs_b->slack_timer.function = sched_cfs_slack_timer;
     cfs_b->slack_started = false;
 }
 
 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
     cfs_rq->runtime_enabled = 0;
     INIT_LIST_HEAD(&cfs_rq->throttled_list);
 }
 
 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
 {
     lockdep_assert_held(&cfs_b->lock);
 
     if (cfs_b->period_active)
         return;
 
     cfs_b->period_active = 1;
     hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
     hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
 }
 
 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
 {
     /* init_cfs_bandwidth() was not called */
     if (!cfs_b->throttled_cfs_rq.next)
         return;
 
     hrtimer_cancel(&cfs_b->period_timer);
     hrtimer_cancel(&cfs_b->slack_timer);
 }
 
 /*
  * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
  *
  * The race is harmless, since modifying bandwidth settings of unhooked group
  * bits doesn't do much.
  */
 
 /* cpu online callback */
 static void __maybe_unused update_runtime_enabled(struct rq *rq)
 {
     struct task_group *tg;
 
     lockdep_assert_rq_held(rq);
 
     rcu_read_lock();
     list_for_each_entry_rcu(tg, &task_groups, list) {
         struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
         raw_spin_lock(&cfs_b->lock);
         cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
         raw_spin_unlock(&cfs_b->lock);
     }
     rcu_read_unlock();
 }
 
 /* cpu offline callback */
 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
 {
     struct task_group *tg;
 
     lockdep_assert_rq_held(rq);
 
     rcu_read_lock();
     list_for_each_entry_rcu(tg, &task_groups, list) {
         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
 
         if (!cfs_rq->runtime_enabled)
             continue;
 
         /*
          * clock_task is not advancing so we just need to make sure
          * there's some valid quota amount
          */
         cfs_rq->runtime_remaining = 1;
         /*
          * Offline rq is schedulable till CPU is completely disabled
          * in take_cpu_down(), so we prevent new cfs throttling here.
          */
         cfs_rq->runtime_enabled = 0;
 
         if (cfs_rq_throttled(cfs_rq))
             unthrottle_cfs_rq(cfs_rq);
     }
     rcu_read_unlock();
 }
 
 #else /* CONFIG_CFS_BANDWIDTH */
 
 static inline bool cfs_bandwidth_used(void)
 {
     return false;
 }
 
 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
 static inline void sync_throttle(struct task_group *tg, int cpu) {}
 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
 
 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
 {
     return 0;
 }
 
 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
 {
     return 0;
 }
 
 static inline int throttled_lb_pair(struct task_group *tg,
                     int src_cpu, int dest_cpu)
 {
     return 0;
 }
 
 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
 #endif
 
 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
 {
     return NULL;
 }
 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
 static inline void update_runtime_enabled(struct rq *rq) {}
 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
 
 #endif /* CONFIG_CFS_BANDWIDTH */
 
 /**************************************************
  * CFS operations on tasks:
  */
 
 #ifdef CONFIG_SCHED_HRTICK
 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
 {
     struct sched_entity *se = &p->se;
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
     SCHED_WARN_ON(task_rq(p) != rq);
 
     if (rq->cfs.h_nr_running > 1) {
         u64 slice = sched_slice(cfs_rq, se);
         u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
         s64 delta = slice - ran;
 
         if (delta < 0) {
             if (task_current(rq, p))
                 resched_curr(rq);
             return;
         }
         hrtick_start(rq, delta);
     }
 }
 
 /*
  * called from enqueue/dequeue and updates the hrtick when the
  * current task is from our class and nr_running is low enough
  * to matter.
  */
 static void hrtick_update(struct rq *rq)
 {
     struct task_struct *curr = rq->curr;
 
     if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
         return;
 
     if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
         hrtick_start_fair(rq, curr);
 }
 #else /* !CONFIG_SCHED_HRTICK */
 static inline void
 hrtick_start_fair(struct rq *rq, struct task_struct *p)
 {
 }
 
 static inline void hrtick_update(struct rq *rq)
 {
 }
 #endif
 
 #ifdef CONFIG_SMP
 static inline bool cpu_overutilized(int cpu)
 {
     return !fits_capacity(cpu_util_cfs(cpu), capacity_of(cpu));
 }
 
 static inline void update_overutilized_status(struct rq *rq)
 {
     if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
         WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
         trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED);
     }
 }
 #else
 static inline void update_overutilized_status(struct rq *rq) { }
 #endif
 
 /* Runqueue only has SCHED_IDLE tasks enqueued */
 static int sched_idle_rq(struct rq *rq)
 {
     return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
             rq->nr_running);
 }
 
 /*
  * Returns true if cfs_rq only has SCHED_IDLE entities enqueued. Note the use
  * of idle_nr_running, which does not consider idle descendants of normal
  * entities.
  */
 static bool sched_idle_cfs_rq(struct cfs_rq *cfs_rq)
 {
     return cfs_rq->nr_running &&
         cfs_rq->nr_running == cfs_rq->idle_nr_running;
 }
 
 #ifdef CONFIG_SMP
 static int sched_idle_cpu(int cpu)
 {
     return sched_idle_rq(cpu_rq(cpu));
 }
 #endif
 
 /*
  * The enqueue_task method is called before nr_running is
  * increased. Here we update the fair scheduling stats and
  * then put the task into the rbtree:
  */
 static void
 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 {
     struct cfs_rq *cfs_rq;
     struct sched_entity *se = &p->se;
     int idle_h_nr_running = task_has_idle_policy(p);
     int task_new = !(flags & ENQUEUE_WAKEUP);
 
     /*
      * The code below (indirectly) updates schedutil which looks at
      * the cfs_rq utilization to select a frequency.
      * Let's add the task's estimated utilization to the cfs_rq's
      * estimated utilization, before we update schedutil.
      */
     util_est_enqueue(&rq->cfs, p);
 
     /*
      * If in_iowait is set, the code below may not trigger any cpufreq
      * utilization updates, so do it here explicitly with the IOWAIT flag
      * passed.
      */
     if (p->in_iowait)
         cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
 
     for_each_sched_entity(se) {
         if (se->on_rq)
             break;
         cfs_rq = cfs_rq_of(se);
         enqueue_entity(cfs_rq, se, flags);
 
         cfs_rq->h_nr_running++;
         cfs_rq->idle_h_nr_running += idle_h_nr_running;
 
         if (cfs_rq_is_idle(cfs_rq))
             idle_h_nr_running = 1;
 
         /* end evaluation on encountering a throttled cfs_rq */
         if (cfs_rq_throttled(cfs_rq))
             goto enqueue_throttle;
 
         flags = ENQUEUE_WAKEUP;
     }
 
     for_each_sched_entity(se) {
         cfs_rq = cfs_rq_of(se);
 
         update_load_avg(cfs_rq, se, UPDATE_TG);
         se_update_runnable(se);
         update_cfs_group(se);
 
         cfs_rq->h_nr_running++;
         cfs_rq->idle_h_nr_running += idle_h_nr_running;
 
         if (cfs_rq_is_idle(cfs_rq))
             idle_h_nr_running = 1;
 
         /* end evaluation on encountering a throttled cfs_rq */
         if (cfs_rq_throttled(cfs_rq))
             goto enqueue_throttle;
     }
 
     /* At this point se is NULL and we are at root level*/
     add_nr_running(rq, 1);
 
     /*
      * Since new tasks are assigned an initial util_avg equal to
      * half of the spare capacity of their CPU, tiny tasks have the
      * ability to cross the overutilized threshold, which will
      * result in the load balancer ruining all the task placement
      * done by EAS. As a way to mitigate that effect, do not account
      * for the first enqueue operation of new tasks during the
      * overutilized flag detection.
      *
      * A better way of solving this problem would be to wait for
      * the PELT signals of tasks to converge before taking them
      * into account, but that is not straightforward to implement,
      * and the following generally works well enough in practice.
      */
     if (!task_new)
         update_overutilized_status(rq);
 
 enqueue_throttle:
     assert_list_leaf_cfs_rq(rq);
 
     hrtick_update(rq);
 }
 
 static void set_next_buddy(struct sched_entity *se);
 
 /*
  * The dequeue_task method is called before nr_running is
  * decreased. We remove the task from the rbtree and
  * update the fair scheduling stats:
  */
 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 {
     struct cfs_rq *cfs_rq;
     struct sched_entity *se = &p->se;
     int task_sleep = flags & DEQUEUE_SLEEP;
     int idle_h_nr_running = task_has_idle_policy(p);
     bool was_sched_idle = sched_idle_rq(rq);
 
     util_est_dequeue(&rq->cfs, p);
 
     for_each_sched_entity(se) {
         cfs_rq = cfs_rq_of(se);
         dequeue_entity(cfs_rq, se, flags);
 
         cfs_rq->h_nr_running--;
         cfs_rq->idle_h_nr_running -= idle_h_nr_running;
 
         if (cfs_rq_is_idle(cfs_rq))
             idle_h_nr_running = 1;
 
         /* end evaluation on encountering a throttled cfs_rq */
         if (cfs_rq_throttled(cfs_rq))
             goto dequeue_throttle;
 
         /* Don't dequeue parent if it has other entities besides us */
         if (cfs_rq->load.weight) {
             /* Avoid re-evaluating load for this entity: */
             se = parent_entity(se);
             /*
              * Bias pick_next to pick a task from this cfs_rq, as
              * p is sleeping when it is within its sched_slice.
              */
             if (task_sleep && se && !throttled_hierarchy(cfs_rq))
                 set_next_buddy(se);
             break;
         }
         flags |= DEQUEUE_SLEEP;
     }
 
     for_each_sched_entity(se) {
         cfs_rq = cfs_rq_of(se);
 
         update_load_avg(cfs_rq, se, UPDATE_TG);
         se_update_runnable(se);
         update_cfs_group(se);
 
         cfs_rq->h_nr_running--;
         cfs_rq->idle_h_nr_running -= idle_h_nr_running;
 
         if (cfs_rq_is_idle(cfs_rq))
             idle_h_nr_running = 1;
 
         /* end evaluation on encountering a throttled cfs_rq */
         if (cfs_rq_throttled(cfs_rq))
             goto dequeue_throttle;
 
     }
 
     /* At this point se is NULL and we are at root level*/
     sub_nr_running(rq, 1);
 
     /* balance early to pull high priority tasks */
     if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
         rq->next_balance = jiffies;
 
 dequeue_throttle:
     util_est_update(&rq->cfs, p, task_sleep);
     hrtick_update(rq);
 }
 
 #ifdef CONFIG_SMP
 
 /* Working cpumask for: load_balance, load_balance_newidle. */
 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
 DEFINE_PER_CPU(cpumask_var_t, select_rq_mask);
 
 #ifdef CONFIG_NO_HZ_COMMON
 
 static struct {
     cpumask_var_t idle_cpus_mask;
     atomic_t nr_cpus;
     int has_blocked;        /* Idle CPUS has blocked load */
     int needs_update;       /* Newly idle CPUs need their next_balance collated */
     unsigned long next_balance;     /* in jiffy units */
     unsigned long next_blocked; /* Next update of blocked load in jiffies */
 } nohz ____cacheline_aligned;
 
 #endif /* CONFIG_NO_HZ_COMMON */
 
 static unsigned long cpu_load(struct rq *rq)
 {
     return cfs_rq_load_avg(&rq->cfs);
 }
 
 /*
  * cpu_load_without - compute CPU load without any contributions from *p
  * @cpu: the CPU which load is requested
  * @p: the task which load should be discounted
  *
  * The load of a CPU is defined by the load of tasks currently enqueued on that
  * CPU as well as tasks which are currently sleeping after an execution on that
  * CPU.
  *
  * This method returns the load of the specified CPU by discounting the load of
  * the specified task, whenever the task is currently contributing to the CPU
  * load.
  */
 static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
 {
     struct cfs_rq *cfs_rq;
     unsigned int load;
 
     /* Task has no contribution or is new */
     if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
         return cpu_load(rq);
 
     cfs_rq = &rq->cfs;
     load = READ_ONCE(cfs_rq->avg.load_avg);
 
     /* Discount task's util from CPU's util */
     lsub_positive(&load, task_h_load(p));
 
     return load;
 }
 
 static unsigned long cpu_runnable(struct rq *rq)
 {
     return cfs_rq_runnable_avg(&rq->cfs);
 }
 
 static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
 {
     struct cfs_rq *cfs_rq;
     unsigned int runnable;
 
     /* Task has no contribution or is new */
     if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
         return cpu_runnable(rq);
 
     cfs_rq = &rq->cfs;
     runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
 
     /* Discount task's runnable from CPU's runnable */
     lsub_positive(&runnable, p->se.avg.runnable_avg);
 
     return runnable;
 }
 
 static unsigned long capacity_of(int cpu)
 {
     return cpu_rq(cpu)->cpu_capacity;
 }
 
 static void record_wakee(struct task_struct *p)
 {
     /*
      * Only decay a single time; tasks that have less then 1 wakeup per
      * jiffy will not have built up many flips.
      */
     if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
         current->wakee_flips >>= 1;
         current->wakee_flip_decay_ts = jiffies;
     }
 
     if (current->last_wakee != p) {
         current->last_wakee = p;
         current->wakee_flips++;
     }
 }
 
 /*
  * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
  *
  * A waker of many should wake a different task than the one last awakened
  * at a frequency roughly N times higher than one of its wakees.
  *
  * In order to determine whether we should let the load spread vs consolidating
  * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
  * partner, and a factor of lls_size higher frequency in the other.
  *
  * With both conditions met, we can be relatively sure that the relationship is
  * non-monogamous, with partner count exceeding socket size.
  *
  * Waker/wakee being client/server, worker/dispatcher, interrupt source or
  * whatever is irrelevant, spread criteria is apparent partner count exceeds
  * socket size.
  */
 static int wake_wide(struct task_struct *p)
 {
     unsigned int master = current->wakee_flips;
     unsigned int slave = p->wakee_flips;
     int factor = __this_cpu_read(sd_llc_size);
 
     if (master < slave)
         swap(master, slave);
     if (slave < factor || master < slave * factor)
         return 0;
     return 1;
 }
 
 /*
  * The purpose of wake_affine() is to quickly determine on which CPU we can run
  * soonest. For the purpose of speed we only consider the waking and previous
  * CPU.
  *
  * wake_affine_idle() - only considers 'now', it check if the waking CPU is
  *          cache-affine and is (or will be) idle.
  *
  * wake_affine_weight() - considers the weight to reflect the average
  *            scheduling latency of the CPUs. This seems to work
  *            for the overloaded case.
  */
 static int
 wake_affine_idle(int this_cpu, int prev_cpu, int sync)
 {
     /*
      * If this_cpu is idle, it implies the wakeup is from interrupt
      * context. Only allow the move if cache is shared. Otherwise an
      * interrupt intensive workload could force all tasks onto one
      * node depending on the IO topology or IRQ affinity settings.
      *
      * If the prev_cpu is idle and cache affine then avoid a migration.
      * There is no guarantee that the cache hot data from an interrupt
      * is more important than cache hot data on the prev_cpu and from
      * a cpufreq perspective, it's better to have higher utilisation
      * on one CPU.
      */
     if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
         return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
 
     if (sync && cpu_rq(this_cpu)->nr_running == 1)
         return this_cpu;
 
     if (available_idle_cpu(prev_cpu))
         return prev_cpu;
 
     return nr_cpumask_bits;
 }
 
 static int
 wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
            int this_cpu, int prev_cpu, int sync)
 {
     s64 this_eff_load, prev_eff_load;
     unsigned long task_load;
 
     this_eff_load = cpu_load(cpu_rq(this_cpu));
 
     if (sync) {
         unsigned long current_load = task_h_load(current);
 
         if (current_load > this_eff_load)
             return this_cpu;
 
         this_eff_load -= current_load;
     }
 
     task_load = task_h_load(p);
 
     this_eff_load += task_load;
     if (sched_feat(WA_BIAS))
         this_eff_load *= 100;
     this_eff_load *= capacity_of(prev_cpu);
 
     prev_eff_load = cpu_load(cpu_rq(prev_cpu));
     prev_eff_load -= task_load;
     if (sched_feat(WA_BIAS))
         prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
     prev_eff_load *= capacity_of(this_cpu);
 
     /*
      * If sync, adjust the weight of prev_eff_load such that if
      * prev_eff == this_eff that select_idle_sibling() will consider
      * stacking the wakee on top of the waker if no other CPU is
      * idle.
      */
     if (sync)
         prev_eff_load += 1;
 
     return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
 }
 
 static int wake_affine(struct sched_domain *sd, struct task_struct *p,
                int this_cpu, int prev_cpu, int sync)
 {
     int target = nr_cpumask_bits;
 
     if (sched_feat(WA_IDLE))
         target = wake_affine_idle(this_cpu, prev_cpu, sync);
 
     if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
         target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
 
     schedstat_inc(p->stats.nr_wakeups_affine_attempts);
     if (target == nr_cpumask_bits)
         return prev_cpu;
 
     schedstat_inc(sd->ttwu_move_affine);
     schedstat_inc(p->stats.nr_wakeups_affine);
     return target;
 }
 
 static struct sched_group *
 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);
 
 /*
  * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
  */
 static int
 find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 {
     unsigned long load, min_load = ULONG_MAX;
     unsigned int min_exit_latency = UINT_MAX;
     u64 latest_idle_timestamp = 0;
     int least_loaded_cpu = this_cpu;
     int shallowest_idle_cpu = -1;
     int i;
 
     /* Check if we have any choice: */
     if (group->group_weight == 1)
         return cpumask_first(sched_group_span(group));
 
     /* Traverse only the allowed CPUs */
     for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
         struct rq *rq = cpu_rq(i);
 
         if (!sched_core_cookie_match(rq, p))
             continue;
 
         if (sched_idle_cpu(i))
             return i;
 
         if (available_idle_cpu(i)) {
             struct cpuidle_state *idle = idle_get_state(rq);
             if (idle && idle->exit_latency < min_exit_latency) {
                 /*
                  * We give priority to a CPU whose idle state
                  * has the smallest exit latency irrespective
                  * of any idle timestamp.
                  */
                 min_exit_latency = idle->exit_latency;
                 latest_idle_timestamp = rq->idle_stamp;
                 shallowest_idle_cpu = i;
             } else if ((!idle || idle->exit_latency == min_exit_latency) &&
                    rq->idle_stamp > latest_idle_timestamp) {
                 /*
                  * If equal or no active idle state, then
                  * the most recently idled CPU might have
                  * a warmer cache.
                  */
                 latest_idle_timestamp = rq->idle_stamp;
                 shallowest_idle_cpu = i;
             }
         } else if (shallowest_idle_cpu == -1) {
             load = cpu_load(cpu_rq(i));
             if (load < min_load) {
                 min_load = load;
                 least_loaded_cpu = i;
             }
         }
     }
 
     return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
 }
 
 static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
                   int cpu, int prev_cpu, int sd_flag)
 {
     int new_cpu = cpu;
 
     if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
         return prev_cpu;
 
     /*
      * We need task's util for cpu_util_without, sync it up to
      * prev_cpu's last_update_time.
      */
     if (!(sd_flag & SD_BALANCE_FORK))
         sync_entity_load_avg(&p->se);
 
     while (sd) {
         struct sched_group *group;
         struct sched_domain *tmp;
         int weight;
 
         if (!(sd->flags & sd_flag)) {
             sd = sd->child;
             continue;
         }
 
         group = find_idlest_group(sd, p, cpu);
         if (!group) {
             sd = sd->child;
             continue;
         }
 
         new_cpu = find_idlest_group_cpu(group, p, cpu);
         if (new_cpu == cpu) {
             /* Now try balancing at a lower domain level of 'cpu': */
             sd = sd->child;
             continue;
         }
 
         /* Now try balancing at a lower domain level of 'new_cpu': */
         cpu = new_cpu;
         weight = sd->span_weight;
         sd = NULL;
         for_each_domain(cpu, tmp) {
             if (weight <= tmp->span_weight)
                 break;
             if (tmp->flags & sd_flag)
                 sd = tmp;
         }
     }
 
     return new_cpu;
 }
 
 static inline int __select_idle_cpu(int cpu, struct task_struct *p)
 {
     if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
         sched_cpu_cookie_match(cpu_rq(cpu), p))
         return cpu;
 
     return -1;
 }
 
 #ifdef CONFIG_SCHED_SMT
 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
 EXPORT_SYMBOL_GPL(sched_smt_present);
 
 static inline void set_idle_cores(int cpu, int val)
 {
     struct sched_domain_shared *sds;
 
     sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
     if (sds)
         WRITE_ONCE(sds->has_idle_cores, val);
 }
 
 static inline bool test_idle_cores(int cpu, bool def)
 {
     struct sched_domain_shared *sds;
 
     sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
     if (sds)
         return READ_ONCE(sds->has_idle_cores);
 
     return def;
 }
 
 /*
  * Scans the local SMT mask to see if the entire core is idle, and records this
  * information in sd_llc_shared->has_idle_cores.
  *
  * Since SMT siblings share all cache levels, inspecting this limited remote
  * state should be fairly cheap.
  */
 void __update_idle_core(struct rq *rq)
 {
     int core = cpu_of(rq);
     int cpu;
 
     rcu_read_lock();
     if (test_idle_cores(core, true))
         goto unlock;
 
     for_each_cpu(cpu, cpu_smt_mask(core)) {
         if (cpu == core)
             continue;
 
         if (!available_idle_cpu(cpu))
             goto unlock;
     }
 
     set_idle_cores(core, 1);
 unlock:
     rcu_read_unlock();
 }
 
 /*
  * Scan the entire LLC domain for idle cores; this dynamically switches off if
  * there are no idle cores left in the system; tracked through
  * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
  */
 static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
 {
     bool idle = true;
     int cpu;
 
     if (!static_branch_likely(&sched_smt_present))
         return __select_idle_cpu(core, p);
 
     for_each_cpu(cpu, cpu_smt_mask(core)) {
         if (!available_idle_cpu(cpu)) {
             idle = false;
             if (*idle_cpu == -1) {
                 if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
                     *idle_cpu = cpu;
                     break;
                 }
                 continue;
             }
             break;
         }
         if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
             *idle_cpu = cpu;
     }
 
     if (idle)
         return core;
 
     cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
     return -1;
 }
 
 /*
  * Scan the local SMT mask for idle CPUs.
  */
 static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
     int cpu;
 
     for_each_cpu(cpu, cpu_smt_mask(target)) {
         if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
             !cpumask_test_cpu(cpu, sched_domain_span(sd)))
             continue;
         if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
             return cpu;
     }
 
     return -1;
 }
 
 #else /* CONFIG_SCHED_SMT */
 
 static inline void set_idle_cores(int cpu, int val)
 {
 }
 
 static inline bool test_idle_cores(int cpu, bool def)
 {
     return def;
 }
 
 static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
 {
     return __select_idle_cpu(core, p);
 }
 
 static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
     return -1;
 }
 
 #endif /* CONFIG_SCHED_SMT */
 
 /*
  * Scan the LLC domain for idle CPUs; this is dynamically regulated by
  * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
  * average idle time for this rq (as found in rq->avg_idle).
  */
 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target)
 {
     struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
     int i, cpu, idle_cpu = -1, nr = INT_MAX;
     struct sched_domain_shared *sd_share;
     struct rq *this_rq = this_rq();
     int this = smp_processor_id();
     struct sched_domain *this_sd;
     u64 time = 0;
 
     this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
     if (!this_sd)
         return -1;
 
     cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
 
     if (sched_feat(SIS_PROP) && !has_idle_core) {
         u64 avg_cost, avg_idle, span_avg;
         unsigned long now = jiffies;
 
         /*
          * If we're busy, the assumption that the last idle period
          * predicts the future is flawed; age away the remaining
          * predicted idle time.
          */
         if (unlikely(this_rq->wake_stamp < now)) {
             while (this_rq->wake_stamp < now && this_rq->wake_avg_idle) {
                 this_rq->wake_stamp++;
                 this_rq->wake_avg_idle >>= 1;
             }
         }
 
         avg_idle = this_rq->wake_avg_idle;
         avg_cost = this_sd->avg_scan_cost + 1;
 
         span_avg = sd->span_weight * avg_idle;
         if (span_avg > 4*avg_cost)
             nr = div_u64(span_avg, avg_cost);
         else
             nr = 4;
 
         time = cpu_clock(this);
     }
 
     if (sched_feat(SIS_UTIL)) {
         sd_share = rcu_dereference(per_cpu(sd_llc_shared, target));
         if (sd_share) {
             /* because !--nr is the condition to stop scan */
             nr = READ_ONCE(sd_share->nr_idle_scan) + 1;
             /* overloaded LLC is unlikely to have idle cpu/core */
             if (nr == 1)
                 return -1;
         }
     }
 
     for_each_cpu_wrap(cpu, cpus, target + 1) {
         if (has_idle_core) {
             i = select_idle_core(p, cpu, cpus, &idle_cpu);
             if ((unsigned int)i < nr_cpumask_bits)
                 return i;
 
         } else {
             if (!--nr)
                 return -1;
             idle_cpu = __select_idle_cpu(cpu, p);
             if ((unsigned int)idle_cpu < nr_cpumask_bits)
                 break;
         }
     }
 
     if (has_idle_core)
         set_idle_cores(target, false);
 
     if (sched_feat(SIS_PROP) && !has_idle_core) {
         time = cpu_clock(this) - time;
 
         /*
          * Account for the scan cost of wakeups against the average
          * idle time.
          */
         this_rq->wake_avg_idle -= min(this_rq->wake_avg_idle, time);
 
         update_avg(&this_sd->avg_scan_cost, time);
     }
 
     return idle_cpu;
 }
 
 /*
  * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
  * the task fits. If no CPU is big enough, but there are idle ones, try to
  * maximize capacity.
  */
 static int
 select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 {
     unsigned long task_util, best_cap = 0;
     int cpu, best_cpu = -1;
     struct cpumask *cpus;
 
     cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
     cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
 
     task_util = uclamp_task_util(p);
 
     for_each_cpu_wrap(cpu, cpus, target) {
         unsigned long cpu_cap = capacity_of(cpu);
 
         if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
             continue;
         if (fits_capacity(task_util, cpu_cap))
             return cpu;
 
         if (cpu_cap > best_cap) {
             best_cap = cpu_cap;
             best_cpu = cpu;
         }
     }
 
     return best_cpu;
 }
 
 static inline bool asym_fits_capacity(unsigned long task_util, int cpu)
 {
     if (static_branch_unlikely(&sched_asym_cpucapacity))
         return fits_capacity(task_util, capacity_of(cpu));
 
     return true;
 }
 
 /*
  * Try and locate an idle core/thread in the LLC cache domain.
  */
 static int select_idle_sibling(struct task_struct *p, int prev, int target)
 {
     bool has_idle_core = false;
     struct sched_domain *sd;
     unsigned long task_util;
     int i, recent_used_cpu;
 
     /*
      * On asymmetric system, update task utilization because we will check
      * that the task fits with cpu's capacity.
      */
     if (static_branch_unlikely(&sched_asym_cpucapacity)) {
         sync_entity_load_avg(&p->se);
         task_util = uclamp_task_util(p);
     }
 
     /*
      * per-cpu select_rq_mask usage
      */
     lockdep_assert_irqs_disabled();
 
     if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
         asym_fits_capacity(task_util, target))
         return target;
 
     /*
      * If the previous CPU is cache affine and idle, don't be stupid:
      */
     if (prev != target && cpus_share_cache(prev, target) &&
         (available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
         asym_fits_capacity(task_util, prev))
         return prev;
 
     /*
      * Allow a per-cpu kthread to stack with the wakee if the
      * kworker thread and the tasks previous CPUs are the same.
      * The assumption is that the wakee queued work for the
      * per-cpu kthread that is now complete and the wakeup is
      * essentially a sync wakeup. An obvious example of this
      * pattern is IO completions.
      */
     if (is_per_cpu_kthread(current) &&
         in_task() &&
         prev == smp_processor_id() &&
         this_rq()->nr_running <= 1 &&
         asym_fits_capacity(task_util, prev)) {
         return prev;
     }
 
     /* Check a recently used CPU as a potential idle candidate: */
     recent_used_cpu = p->recent_used_cpu;
     p->recent_used_cpu = prev;
     if (recent_used_cpu != prev &&
         recent_used_cpu != target &&
         cpus_share_cache(recent_used_cpu, target) &&
         (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
         cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) &&
         asym_fits_capacity(task_util, recent_used_cpu)) {
         return recent_used_cpu;
     }
 
     /*
      * For asymmetric CPU capacity systems, our domain of interest is
      * sd_asym_cpucapacity rather than sd_llc.
      */
     if (static_branch_unlikely(&sched_asym_cpucapacity)) {
         sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
         /*
          * On an asymmetric CPU capacity system where an exclusive
          * cpuset defines a symmetric island (i.e. one unique
          * capacity_orig value through the cpuset), the key will be set
          * but the CPUs within that cpuset will not have a domain with
          * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
          * capacity path.
          */
         if (sd) {
             i = select_idle_capacity(p, sd, target);
             return ((unsigned)i < nr_cpumask_bits) ? i : target;
         }
     }
 
     sd = rcu_dereference(per_cpu(sd_llc, target));
     if (!sd)
         return target;
 
     if (sched_smt_active()) {
         has_idle_core = test_idle_cores(target, false);
 
         if (!has_idle_core && cpus_share_cache(prev, target)) {
             i = select_idle_smt(p, sd, prev);
             if ((unsigned int)i < nr_cpumask_bits)
                 return i;
         }
     }
 
     i = select_idle_cpu(p, sd, has_idle_core, target);
     if ((unsigned)i < nr_cpumask_bits)
         return i;
 
     return target;
 }
 
 /*
  * Predicts what cpu_util(@cpu) would return if @p was removed from @cpu
  * (@dst_cpu = -1) or migrated to @dst_cpu.
  */
 static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
 {
     struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
     unsigned long util = READ_ONCE(cfs_rq->avg.util_avg);
 
     /*
      * If @dst_cpu is -1 or @p migrates from @cpu to @dst_cpu remove its
      * contribution. If @p migrates from another CPU to @cpu add its
      * contribution. In all the other cases @cpu is not impacted by the
      * migration so its util_avg is already correct.
      */
     if (task_cpu(p) == cpu && dst_cpu != cpu)
         lsub_positive(&util, task_util(p));
     else if (task_cpu(p) != cpu && dst_cpu == cpu)
         util += task_util(p);
 
     if (sched_feat(UTIL_EST)) {
         unsigned long util_est;
 
         util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
 
         /*
          * During wake-up @p isn't enqueued yet and doesn't contribute
          * to any cpu_rq(cpu)->cfs.avg.util_est.enqueued.
          * If @dst_cpu == @cpu add it to "simulate" cpu_util after @p
          * has been enqueued.
          *
          * During exec (@dst_cpu = -1) @p is enqueued and does
          * contribute to cpu_rq(cpu)->cfs.util_est.enqueued.
          * Remove it to "simulate" cpu_util without @p's contribution.
          *
          * Despite the task_on_rq_queued(@p) check there is still a
          * small window for a possible race when an exec
          * select_task_rq_fair() races with LB's detach_task().
          *
          *   detach_task()
          *     deactivate_task()
          *       p->on_rq = TASK_ON_RQ_MIGRATING;
          *       -------------------------------- A
          *       dequeue_task()                    \
          *         dequeue_task_fair()              + Race Time
          *           util_est_dequeue()            /
          *       -------------------------------- B
          *
          * The additional check "current == p" is required to further
          * reduce the race window.
          */
         if (dst_cpu == cpu)
             util_est += _task_util_est(p);
         else if (unlikely(task_on_rq_queued(p) || current == p))
             lsub_positive(&util_est, _task_util_est(p));
 
         util = max(util, util_est);
     }
 
     return min(util, capacity_orig_of(cpu));
 }
 
 /*
  * cpu_util_without: compute cpu utilization without any contributions from *p
  * @cpu: the CPU which utilization is requested
  * @p: the task which utilization should be discounted
  *
  * The utilization of a CPU is defined by the utilization of tasks currently
  * enqueued on that CPU as well as tasks which are currently sleeping after an
  * execution on that CPU.
  *
  * This method returns the utilization of the specified CPU by discounting the
  * utilization of the specified task, whenever the task is currently
  * contributing to the CPU utilization.
  */
 static unsigned long cpu_util_without(int cpu, struct task_struct *p)
 {
     /* Task has no contribution or is new */
     if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
         return cpu_util_cfs(cpu);
 
     return cpu_util_next(cpu, p, -1);
 }
 
 /*
  * energy_env - Utilization landscape for energy estimation.
  * @task_busy_time: Utilization contribution by the task for which we test the
  *                  placement. Given by eenv_task_busy_time().
  * @pd_busy_time:   Utilization of the whole perf domain without the task
  *                  contribution. Given by eenv_pd_busy_time().
  * @cpu_cap:        Maximum CPU capacity for the perf domain.
  * @pd_cap:         Entire perf domain capacity. (pd->nr_cpus * cpu_cap).
  */
 struct energy_env {
     unsigned long task_busy_time;
     unsigned long pd_busy_time;
     unsigned long cpu_cap;
     unsigned long pd_cap;
 };
 
 /*
  * Compute the task busy time for compute_energy(). This time cannot be
  * injected directly into effective_cpu_util() because of the IRQ scaling.
  * The latter only makes sense with the most recent CPUs where the task has
  * run.
  */
 static inline void eenv_task_busy_time(struct energy_env *eenv,
                        struct task_struct *p, int prev_cpu)
 {
     unsigned long busy_time, max_cap = arch_scale_cpu_capacity(prev_cpu);
     unsigned long irq = cpu_util_irq(cpu_rq(prev_cpu));
 
     if (unlikely(irq >= max_cap))
         busy_time = max_cap;
     else
         busy_time = scale_irq_capacity(task_util_est(p), irq, max_cap);
 
     eenv->task_busy_time = busy_time;
 }
 
 /*
  * Compute the perf_domain (PD) busy time for compute_energy(). Based on the
  * utilization for each @pd_cpus, it however doesn't take into account
  * clamping since the ratio (utilization / cpu_capacity) is already enough to
  * scale the EM reported power consumption at the (eventually clamped)
  * cpu_capacity.
  *
  * The contribution of the task @p for which we want to estimate the
  * energy cost is removed (by cpu_util_next()) and must be calculated
  * separately (see eenv_task_busy_time). This ensures:
  *
  *   - A stable PD utilization, no matter which CPU of that PD we want to place
  *     the task on.
  *
  *   - A fair comparison between CPUs as the task contribution (task_util())
  *     will always be the same no matter which CPU utilization we rely on
  *     (util_avg or util_est).
  *
  * Set @eenv busy time for the PD that spans @pd_cpus. This busy time can't
  * exceed @eenv->pd_cap.
  */
 static inline void eenv_pd_busy_time(struct energy_env *eenv,
                      struct cpumask *pd_cpus,
                      struct task_struct *p)
 {
     unsigned long busy_time = 0;
     int cpu;
 
     for_each_cpu(cpu, pd_cpus) {
         unsigned long util = cpu_util_next(cpu, p, -1);
 
         busy_time += effective_cpu_util(cpu, util, ENERGY_UTIL, NULL);
     }
 
     eenv->pd_busy_time = min(eenv->pd_cap, busy_time);
 }
 
 /*
  * Compute the maximum utilization for compute_energy() when the task @p
  * is placed on the cpu @dst_cpu.
  *
  * Returns the maximum utilization among @eenv->cpus. This utilization can't
  * exceed @eenv->cpu_cap.
  */
 static inline unsigned long
 eenv_pd_max_util(struct energy_env *eenv, struct cpumask *pd_cpus,
          struct task_struct *p, int dst_cpu)
 {
     unsigned long max_util = 0;
     int cpu;
 
     for_each_cpu(cpu, pd_cpus) {
         struct task_struct *tsk = (cpu == dst_cpu) ? p : NULL;
         unsigned long util = cpu_util_next(cpu, p, dst_cpu);
         unsigned long cpu_util;
 
         /*
          * Performance domain frequency: utilization clamping
          * must be considered since it affects the selection
          * of the performance domain frequency.
          * NOTE: in case RT tasks are running, by default the
          * FREQUENCY_UTIL's utilization can be max OPP.
          */
         cpu_util = effective_cpu_util(cpu, util, FREQUENCY_UTIL, tsk);
         max_util = max(max_util, cpu_util);
     }
 
     return min(max_util, eenv->cpu_cap);
 }
 
 /*
  * compute_energy(): Use the Energy Model to estimate the energy that @pd would
  * consume for a given utilization landscape @eenv. When @dst_cpu < 0, the task
  * contribution is ignored.
  */
 static inline unsigned long
 compute_energy(struct energy_env *eenv, struct perf_domain *pd,
            struct cpumask *pd_cpus, struct task_struct *p, int dst_cpu)
 {
     unsigned long max_util = eenv_pd_max_util(eenv, pd_cpus, p, dst_cpu);
     unsigned long busy_time = eenv->pd_busy_time;
 
     if (dst_cpu >= 0)
         busy_time = min(eenv->pd_cap, busy_time + eenv->task_busy_time);
 
     return em_cpu_energy(pd->em_pd, max_util, busy_time, eenv->cpu_cap);
 }
 
 /*
  * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
  * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
  * spare capacity in each performance domain and uses it as a potential
  * candidate to execute the task. Then, it uses the Energy Model to figure
  * out which of the CPU candidates is the most energy-efficient.
  *
  * The rationale for this heuristic is as follows. In a performance domain,
  * all the most energy efficient CPU candidates (according to the Energy
  * Model) are those for which we'll request a low frequency. When there are
  * several CPUs for which the frequency request will be the same, we don't
  * have enough data to break the tie between them, because the Energy Model
  * only includes active power costs. With this model, if we assume that
  * frequency requests follow utilization (e.g. using schedutil), the CPU with
  * the maximum spare capacity in a performance domain is guaranteed to be among
  * the best candidates of the performance domain.
  *
  * In practice, it could be preferable from an energy standpoint to pack
  * small tasks on a CPU in order to let other CPUs go in deeper idle states,
  * but that could also hurt our chances to go cluster idle, and we have no
  * ways to tell with the current Energy Model if this is actually a good
  * idea or not. So, find_energy_efficient_cpu() basically favors
  * cluster-packing, and spreading inside a cluster. That should at least be
  * a good thing for latency, and this is consistent with the idea that most
  * of the energy savings of EAS come from the asymmetry of the system, and
  * not so much from breaking the tie between identical CPUs. That's also the
  * reason why EAS is enabled in the topology code only for systems where
  * SD_ASYM_CPUCAPACITY is set.
  *
  * NOTE: Forkees are not accepted in the energy-aware wake-up path because
  * they don't have any useful utilization data yet and it's not possible to
  * forecast their impact on energy consumption. Consequently, they will be
  * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
  * to be energy-inefficient in some use-cases. The alternative would be to
  * bias new tasks towards specific types of CPUs first, or to try to infer
  * their util_avg from the parent task, but those heuristics could hurt
  * other use-cases too. So, until someone finds a better way to solve this,
  * let's keep things simple by re-using the existing slow path.
  */
 static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 {
     struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
     unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
     struct root_domain *rd = this_rq()->rd;
     int cpu, best_energy_cpu, target = -1;
     struct sched_domain *sd;
     struct perf_domain *pd;
     struct energy_env eenv;
 
     rcu_read_lock();
     pd = rcu_dereference(rd->pd);
     if (!pd || READ_ONCE(rd->overutilized))
         goto unlock;
 
     /*
      * Energy-aware wake-up happens on the lowest sched_domain starting
      * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
      */
     sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
     while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
         sd = sd->parent;
     if (!sd)
         goto unlock;
 
     target = prev_cpu;
 
     sync_entity_load_avg(&p->se);
     if (!task_util_est(p))
         goto unlock;
 
     eenv_task_busy_time(&eenv, p, prev_cpu);
 
     for (; pd; pd = pd->next) {
         unsigned long cpu_cap, cpu_thermal_cap, util;
         unsigned long cur_delta, max_spare_cap = 0;
         bool compute_prev_delta = false;
         int max_spare_cap_cpu = -1;
         unsigned long base_energy;
 
         cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
 
         if (cpumask_empty(cpus))
             continue;
 
         /* Account thermal pressure for the energy estimation */
         cpu = cpumask_first(cpus);
         cpu_thermal_cap = arch_scale_cpu_capacity(cpu);
         cpu_thermal_cap -= arch_scale_thermal_pressure(cpu);
 
         eenv.cpu_cap = cpu_thermal_cap;
         eenv.pd_cap = 0;
 
         for_each_cpu(cpu, cpus) {
             eenv.pd_cap += cpu_thermal_cap;
 
             if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
                 continue;
 
             if (!cpumask_test_cpu(cpu, p->cpus_ptr))
                 continue;
 
             util = cpu_util_next(cpu, p, cpu);
             cpu_cap = capacity_of(cpu);
 
             /*
              * Skip CPUs that cannot satisfy the capacity request.
              * IOW, placing the task there would make the CPU
              * overutilized. Take uclamp into account to see how
              * much capacity we can get out of the CPU; this is
              * aligned with sched_cpu_util().
              */
             util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
             if (!fits_capacity(util, cpu_cap))
                 continue;
 
             lsub_positive(&cpu_cap, util);
 
             if (cpu == prev_cpu) {
                 /* Always use prev_cpu as a candidate. */
                 compute_prev_delta = true;
             } else if (cpu_cap > max_spare_cap) {
                 /*
                  * Find the CPU with the maximum spare capacity
                  * in the performance domain.
                  */
                 max_spare_cap = cpu_cap;
                 max_spare_cap_cpu = cpu;
             }
         }
 
         if (max_spare_cap_cpu < 0 && !compute_prev_delta)
             continue;
 
         eenv_pd_busy_time(&eenv, cpus, p);
         /* Compute the 'base' energy of the pd, without @p */
         base_energy = compute_energy(&eenv, pd, cpus, p, -1);
 
         /* Evaluate the energy impact of using prev_cpu. */
         if (compute_prev_delta) {
             prev_delta = compute_energy(&eenv, pd, cpus, p,
                             prev_cpu);
             /* CPU utilization has changed */
             if (prev_delta < base_energy)
                 goto unlock;
             prev_delta -= base_energy;
             best_delta = min(best_delta, prev_delta);
         }
 
         /* Evaluate the energy impact of using max_spare_cap_cpu. */
         if (max_spare_cap_cpu >= 0) {
             cur_delta = compute_energy(&eenv, pd, cpus, p,
                            max_spare_cap_cpu);
             /* CPU utilization has changed */
             if (cur_delta < base_energy)
                 goto unlock;
             cur_delta -= base_energy;
             if (cur_delta < best_delta) {
                 best_delta = cur_delta;
                 best_energy_cpu = max_spare_cap_cpu;
             }
         }
     }
     rcu_read_unlock();
 
     if (best_delta < prev_delta)
         target = best_energy_cpu;
 
     return target;
 
 unlock:
     rcu_read_unlock();
 
     return target;
 }
 
 /*
  * select_task_rq_fair: Select target runqueue for the waking task in domains
  * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
  * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
  *
  * Balances load by selecting the idlest CPU in the idlest group, or under
  * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
  *
  * Returns the target CPU number.
  */
 static int
 select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 {
     int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
     struct sched_domain *tmp, *sd = NULL;
     int cpu = smp_processor_id();
     int new_cpu = prev_cpu;
     int want_affine = 0;
     /* SD_flags and WF_flags share the first nibble */
     int sd_flag = wake_flags & 0xF;
 
     /*
      * required for stable ->cpus_allowed
      */
     lockdep_assert_held(&p->pi_lock);
     if (wake_flags & WF_TTWU) {
         record_wakee(p);
 
         if (sched_energy_enabled()) {
             new_cpu = find_energy_efficient_cpu(p, prev_cpu);
             if (new_cpu >= 0)
                 return new_cpu;
             new_cpu = prev_cpu;
         }
 
         want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
     }
 
     rcu_read_lock();
     for_each_domain(cpu, tmp) {
         /*
          * If both 'cpu' and 'prev_cpu' are part of this domain,
          * cpu is a valid SD_WAKE_AFFINE target.
          */
         if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
             cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
             if (cpu != prev_cpu)
                 new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
 
             sd = NULL; /* Prefer wake_affine over balance flags */
             break;
         }
 
         /*
          * Usually only true for WF_EXEC and WF_FORK, as sched_domains
          * usually do not have SD_BALANCE_WAKE set. That means wakeup
          * will usually go to the fast path.
          */
         if (tmp->flags & sd_flag)
             sd = tmp;
         else if (!want_affine)
             break;
     }
 
     if (unlikely(sd)) {
         /* Slow path */
         new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
     } else if (wake_flags & WF_TTWU) { /* XXX always ? */
         /* Fast path */
         new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
     }
     rcu_read_unlock();
 
     return new_cpu;
 }
 
 static void detach_entity_cfs_rq(struct sched_entity *se);
 
 /*
  * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
  * cfs_rq_of(p) references at time of call are still valid and identify the
  * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
  */
 static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
 {
     struct sched_entity *se = &p->se;
 
     /*
      * As blocked tasks retain absolute vruntime the migration needs to
      * deal with this by subtracting the old and adding the new
      * min_vruntime -- the latter is done by enqueue_entity() when placing
      * the task on the new runqueue.
      */
     if (READ_ONCE(p->__state) == TASK_WAKING) {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
         se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
     }
 
     if (p->on_rq == TASK_ON_RQ_MIGRATING) {
         /*
          * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
          * rq->lock and can modify state directly.
          */
         lockdep_assert_rq_held(task_rq(p));
         detach_entity_cfs_rq(se);
 
     } else {
         remove_entity_load_avg(se);
 
         /*
          * Here, the task's PELT values have been updated according to
          * the current rq's clock. But if that clock hasn't been
          * updated in a while, a substantial idle time will be missed,
          * leading to an inflation after wake-up on the new rq.
          *
          * Estimate the missing time from the cfs_rq last_update_time
          * and update sched_avg to improve the PELT continuity after
          * migration.
          */
         migrate_se_pelt_lag(se);
     }
 
     /* Tell new CPU we are migrated */
     se->avg.last_update_time = 0;
 
     /* We have migrated, no longer consider this task hot */
     se->exec_start = 0;
 
     update_scan_period(p, new_cpu);
 }
 
 static void task_dead_fair(struct task_struct *p)
 {
     remove_entity_load_avg(&p->se);
 }
 
 static int
 balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 {
     if (rq->nr_running)
         return 1;
 
     return newidle_balance(rq, rf) != 0;
 }
 #endif /* CONFIG_SMP */
 
 static unsigned long wakeup_gran(struct sched_entity *se)
 {
     unsigned long gran = sysctl_sched_wakeup_granularity;
 
     /*
      * Since its curr running now, convert the gran from real-time
      * to virtual-time in his units.
      *
      * By using 'se' instead of 'curr' we penalize light tasks, so
      * they get preempted easier. That is, if 'se' < 'curr' then
      * the resulting gran will be larger, therefore penalizing the
      * lighter, if otoh 'se' > 'curr' then the resulting gran will
      * be smaller, again penalizing the lighter task.
      *
      * This is especially important for buddies when the leftmost
      * task is higher priority than the buddy.
      */
     return calc_delta_fair(gran, se);
 }
 
 /*
  * Should 'se' preempt 'curr'.
  *
  *             |s1
  *        |s2
  *   |s3
  *         g
  *      |<--->|c
  *
  *  w(c, s1) = -1
  *  w(c, s2) =  0
  *  w(c, s3) =  1
  *
  */
 static int
 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
 {
     s64 gran, vdiff = curr->vruntime - se->vruntime;
 
     if (vdiff <= 0)
         return -1;
 
     gran = wakeup_gran(se);
     if (vdiff > gran)
         return 1;
 
     return 0;
 }
 
 static void set_last_buddy(struct sched_entity *se)
 {
     for_each_sched_entity(se) {
         if (SCHED_WARN_ON(!se->on_rq))
             return;
         if (se_is_idle(se))
             return;
         cfs_rq_of(se)->last = se;
     }
 }
 
 static void set_next_buddy(struct sched_entity *se)
 {
     for_each_sched_entity(se) {
         if (SCHED_WARN_ON(!se->on_rq))
             return;
         if (se_is_idle(se))
             return;
         cfs_rq_of(se)->next = se;
     }
 }
 
 static void set_skip_buddy(struct sched_entity *se)
 {
     for_each_sched_entity(se)
         cfs_rq_of(se)->skip = se;
 }
 
 /*
  * Preempt the current task with a newly woken task if needed:
  */
 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
 {
     struct task_struct *curr = rq->curr;
     struct sched_entity *se = &curr->se, *pse = &p->se;
     struct cfs_rq *cfs_rq = task_cfs_rq(curr);
     int scale = cfs_rq->nr_running >= sched_nr_latency;
     int next_buddy_marked = 0;
     int cse_is_idle, pse_is_idle;
 
     if (unlikely(se == pse))
         return;
 
     /*
      * This is possible from callers such as attach_tasks(), in which we
      * unconditionally check_preempt_curr() after an enqueue (which may have
      * lead to a throttle).  This both saves work and prevents false
      * next-buddy nomination below.
      */
     if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
         return;
 
     if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
         set_next_buddy(pse);
         next_buddy_marked = 1;
     }
 
     /*
      * We can come here with TIF_NEED_RESCHED already set from new task
      * wake up path.
      *
      * Note: this also catches the edge-case of curr being in a throttled
      * group (e.g. via set_curr_task), since update_curr() (in the
      * enqueue of curr) will have resulted in resched being set.  This
      * prevents us from potentially nominating it as a false LAST_BUDDY
      * below.
      */
     if (test_tsk_need_resched(curr))
         return;
 
     /* Idle tasks are by definition preempted by non-idle tasks. */
     if (unlikely(task_has_idle_policy(curr)) &&
         likely(!task_has_idle_policy(p)))
         goto preempt;
 
     /*
      * Batch and idle tasks do not preempt non-idle tasks (their preemption
      * is driven by the tick):
      */
     if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
         return;
 
     find_matching_se(&se, &pse);
     BUG_ON(!pse);
 
     cse_is_idle = se_is_idle(se);
     pse_is_idle = se_is_idle(pse);
 
     /*
      * Preempt an idle group in favor of a non-idle group (and don't preempt
      * in the inverse case).
      */
     if (cse_is_idle && !pse_is_idle)
         goto preempt;
     if (cse_is_idle != pse_is_idle)
         return;
 
     update_curr(cfs_rq_of(se));
     if (wakeup_preempt_entity(se, pse) == 1) {
         /*
          * Bias pick_next to pick the sched entity that is
          * triggering this preemption.
          */
         if (!next_buddy_marked)
             set_next_buddy(pse);
         goto preempt;
     }
 
     return;
 
 preempt:
     resched_curr(rq);
     /*
      * Only set the backward buddy when the current task is still
      * on the rq. This can happen when a wakeup gets interleaved
      * with schedule on the ->pre_schedule() or idle_balance()
      * point, either of which can * drop the rq lock.
      *
      * Also, during early boot the idle thread is in the fair class,
      * for obvious reasons its a bad idea to schedule back to it.
      */
     if (unlikely(!se->on_rq || curr == rq->idle))
         return;
 
     if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
         set_last_buddy(se);
 }
 
 #ifdef CONFIG_SMP
 static struct task_struct *pick_task_fair(struct rq *rq)
 {
     struct sched_entity *se;
     struct cfs_rq *cfs_rq;
 
 again:
     cfs_rq = &rq->cfs;
     if (!cfs_rq->nr_running)
         return NULL;
 
     do {
         struct sched_entity *curr = cfs_rq->curr;
 
         /* When we pick for a remote RQ, we'll not have done put_prev_entity() */
         if (curr) {
             if (curr->on_rq)
                 update_curr(cfs_rq);
             else
                 curr = NULL;
 
             if (unlikely(check_cfs_rq_runtime(cfs_rq)))
                 goto again;
         }
 
         se = pick_next_entity(cfs_rq, curr);
         cfs_rq = group_cfs_rq(se);
     } while (cfs_rq);
 
     return task_of(se);
 }
 #endif
 
 struct task_struct *
 pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 {
     struct cfs_rq *cfs_rq = &rq->cfs;
     struct sched_entity *se;
     struct task_struct *p;
     int new_tasks;
 
 again:
     if (!sched_fair_runnable(rq))
         goto idle;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
     if (!prev || prev->sched_class != &fair_sched_class)
         goto simple;
 
     /*
      * Because of the set_next_buddy() in dequeue_task_fair() it is rather
      * likely that a next task is from the same cgroup as the current.
      *
      * Therefore attempt to avoid putting and setting the entire cgroup
      * hierarchy, only change the part that actually changes.
      */
 
     do {
         struct sched_entity *curr = cfs_rq->curr;
 
         /*
          * Since we got here without doing put_prev_entity() we also
          * have to consider cfs_rq->curr. If it is still a runnable
          * entity, update_curr() will update its vruntime, otherwise
          * forget we've ever seen it.
          */
         if (curr) {
             if (curr->on_rq)
                 update_curr(cfs_rq);
             else
                 curr = NULL;
 
             /*
              * This call to check_cfs_rq_runtime() will do the
              * throttle and dequeue its entity in the parent(s).
              * Therefore the nr_running test will indeed
              * be correct.
              */
             if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
                 cfs_rq = &rq->cfs;
 
                 if (!cfs_rq->nr_running)
                     goto idle;
 
                 goto simple;
             }
         }
 
         se = pick_next_entity(cfs_rq, curr);
         cfs_rq = group_cfs_rq(se);
     } while (cfs_rq);
 
     p = task_of(se);
 
     /*
      * Since we haven't yet done put_prev_entity and if the selected task
      * is a different task than we started out with, try and touch the
      * least amount of cfs_rqs.
      */
     if (prev != p) {
         struct sched_entity *pse = &prev->se;
 
         while (!(cfs_rq = is_same_group(se, pse))) {
             int se_depth = se->depth;
             int pse_depth = pse->depth;
 
             if (se_depth <= pse_depth) {
                 put_prev_entity(cfs_rq_of(pse), pse);
                 pse = parent_entity(pse);
             }
             if (se_depth >= pse_depth) {
                 set_next_entity(cfs_rq_of(se), se);
                 se = parent_entity(se);
             }
         }
 
         put_prev_entity(cfs_rq, pse);
         set_next_entity(cfs_rq, se);
     }
 
     goto done;
 simple:
 #endif
     if (prev)
         put_prev_task(rq, prev);
 
     do {
         se = pick_next_entity(cfs_rq, NULL);
         set_next_entity(cfs_rq, se);
         cfs_rq = group_cfs_rq(se);
     } while (cfs_rq);
 
     p = task_of(se);
 
 done: __maybe_unused;
 #ifdef CONFIG_SMP
     /*
      * Move the next running task to the front of
      * the list, so our cfs_tasks list becomes MRU
      * one.
      */
     list_move(&p->se.group_node, &rq->cfs_tasks);
 #endif
 
     if (hrtick_enabled_fair(rq))
         hrtick_start_fair(rq, p);
 
     update_misfit_status(p, rq);
 
     return p;
 
 idle:
     if (!rf)
         return NULL;
 
     new_tasks = newidle_balance(rq, rf);
 
     /*
      * Because newidle_balance() releases (and re-acquires) rq->lock, it is
      * possible for any higher priority task to appear. In that case we
      * must re-start the pick_next_entity() loop.
      */
     if (new_tasks < 0)
         return RETRY_TASK;
 
     if (new_tasks > 0)
         goto again;
 
     /*
      * rq is about to be idle, check if we need to update the
      * lost_idle_time of clock_pelt
      */
     update_idle_rq_clock_pelt(rq);
 
     return NULL;
 }
 
 static struct task_struct *__pick_next_task_fair(struct rq *rq)
 {
     return pick_next_task_fair(rq, NULL, NULL);
 }
 
 /*
  * Account for a descheduled task:
  */
 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
 {
     struct sched_entity *se = &prev->se;
     struct cfs_rq *cfs_rq;
 
     for_each_sched_entity(se) {
         cfs_rq = cfs_rq_of(se);
         put_prev_entity(cfs_rq, se);
     }
 }
 
 /*
  * sched_yield() is very simple
  *
  * The magic of dealing with the ->skip buddy is in pick_next_entity.
  */
 static void yield_task_fair(struct rq *rq)
 {
     struct task_struct *curr = rq->curr;
     struct cfs_rq *cfs_rq = task_cfs_rq(curr);
     struct sched_entity *se = &curr->se;
 
     /*
      * Are we the only task in the tree?
      */
     if (unlikely(rq->nr_running == 1))
         return;
 
     clear_buddies(cfs_rq, se);
 
     if (curr->policy != SCHED_BATCH) {
         update_rq_clock(rq);
         /*
          * Update run-time statistics of the 'current'.
          */
         update_curr(cfs_rq);
         /*
          * Tell update_rq_clock() that we've just updated,
          * so we don't do microscopic update in schedule()
          * and double the fastpath cost.
          */
         rq_clock_skip_update(rq);
     }
 
     set_skip_buddy(se);
 }
 
 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
 {
     struct sched_entity *se = &p->se;
 
     /* throttled hierarchies are not runnable */
     if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
         return false;
 
     /* Tell the scheduler that we'd really like pse to run next. */
     set_next_buddy(se);
 
     yield_task_fair(rq);
 
     return true;
 }
 
 #ifdef CONFIG_SMP
 /**************************************************
  * Fair scheduling class load-balancing methods.
  *
  * BASICS
  *
  * The purpose of load-balancing is to achieve the same basic fairness the
  * per-CPU scheduler provides, namely provide a proportional amount of compute
  * time to each task. This is expressed in the following equation:
  *
  *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
  *
  * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
  * W_i,0 is defined as:
  *
  *   W_i,0 = \Sum_j w_i,j                                             (2)
  *
  * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
  * is derived from the nice value as per sched_prio_to_weight[].
  *
  * The weight average is an exponential decay average of the instantaneous
  * weight:
  *
  *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
  *
  * C_i is the compute capacity of CPU i, typically it is the
  * fraction of 'recent' time available for SCHED_OTHER task execution. But it
  * can also include other factors [XXX].
  *
  * To achieve this balance we define a measure of imbalance which follows
  * directly from (1):
  *
  *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
  *
  * We them move tasks around to minimize the imbalance. In the continuous
  * function space it is obvious this converges, in the discrete case we get
  * a few fun cases generally called infeasible weight scenarios.
  *
  * [XXX expand on:
  *     - infeasible weights;
  *     - local vs global optima in the discrete case. ]
  *
  *
  * SCHED DOMAINS
  *
  * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
  * for all i,j solution, we create a tree of CPUs that follows the hardware
  * topology where each level pairs two lower groups (or better). This results
  * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
  * tree to only the first of the previous level and we decrease the frequency
  * of load-balance at each level inv. proportional to the number of CPUs in
  * the groups.
  *
  * This yields:
  *
  *     log_2 n     1     n
  *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
  *     i = 0      2^i   2^i
  *                               `- size of each group
  *         |         |     `- number of CPUs doing load-balance
  *         |         `- freq
  *         `- sum over all levels
  *
  * Coupled with a limit on how many tasks we can migrate every balance pass,
  * this makes (5) the runtime complexity of the balancer.
  *
  * An important property here is that each CPU is still (indirectly) connected
  * to every other CPU in at most O(log n) steps:
  *
  * The adjacency matrix of the resulting graph is given by:
  *
  *             log_2 n
  *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
  *             k = 0
  *
  * And you'll find that:
  *
  *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
  *
  * Showing there's indeed a path between every CPU in at most O(log n) steps.
  * The task movement gives a factor of O(m), giving a convergence complexity
  * of:
  *
  *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
  *
  *
  * WORK CONSERVING
  *
  * In order to avoid CPUs going idle while there's still work to do, new idle
  * balancing is more aggressive and has the newly idle CPU iterate up the domain
  * tree itself instead of relying on other CPUs to bring it work.
  *
  * This adds some complexity to both (5) and (8) but it reduces the total idle
  * time.
  *
  * [XXX more?]
  *
  *
  * CGROUPS
  *
  * Cgroups make a horror show out of (2), instead of a simple sum we get:
  *
  *                                s_k,i
  *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
  *                                 S_k
  *
  * Where
  *
  *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
  *
  * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
  *
  * The big problem is S_k, its a global sum needed to compute a local (W_i)
  * property.
  *
  * [XXX write more on how we solve this.. _after_ merging pjt's patches that
  *      rewrite all of this once again.]
  */
 
 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
 
 enum fbq_type { regular, remote, all };
 
 /*
  * 'group_type' describes the group of CPUs at the moment of load balancing.
  *
  * The enum is ordered by pulling priority, with the group with lowest priority
  * first so the group_type can simply be compared when selecting the busiest
  * group. See update_sd_pick_busiest().
  */
 enum group_type {
     /* The group has spare capacity that can be used to run more tasks.  */
     group_has_spare = 0,
     /*
      * The group is fully used and the tasks don't compete for more CPU
      * cycles. Nevertheless, some tasks might wait before running.
      */
     group_fully_busy,
     /*
      * One task doesn't fit with CPU's capacity and must be migrated to a
      * more powerful CPU.
      */
     group_misfit_task,
     /*
      * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
      * and the task should be migrated to it instead of running on the
      * current CPU.
      */
     group_asym_packing,
     /*
      * The tasks' affinity constraints previously prevented the scheduler
      * from balancing the load across the system.
      */
     group_imbalanced,
     /*
      * The CPU is overloaded and can't provide expected CPU cycles to all
      * tasks.
      */
     group_overloaded
 };
 
 enum migration_type {
     migrate_load = 0,
     migrate_util,
     migrate_task,
     migrate_misfit
 };
 
 #define LBF_ALL_PINNED  0x01
 #define LBF_NEED_BREAK  0x02
 #define LBF_DST_PINNED  0x04
 #define LBF_SOME_PINNED 0x08
 #define LBF_ACTIVE_LB   0x10
 
 struct lb_env {
     struct sched_domain *sd;
 
     struct rq       *src_rq;
     int         src_cpu;
 
     int         dst_cpu;
     struct rq       *dst_rq;
 
     struct cpumask      *dst_grpmask;
     int         new_dst_cpu;
     enum cpu_idle_type  idle;
     long            imbalance;
     /* The set of CPUs under consideration for load-balancing */
     struct cpumask      *cpus;
 
     unsigned int        flags;
 
     unsigned int        loop;
     unsigned int        loop_break;
     unsigned int        loop_max;
 
     enum fbq_type       fbq_type;
     enum migration_type migration_type;
     struct list_head    tasks;
 };
 
 /*
  * Is this task likely cache-hot:
  */
 static int task_hot(struct task_struct *p, struct lb_env *env)
 {
     s64 delta;
 
     lockdep_assert_rq_held(env->src_rq);
 
     if (p->sched_class != &fair_sched_class)
         return 0;
 
     if (unlikely(task_has_idle_policy(p)))
         return 0;
 
     /* SMT siblings share cache */
     if (env->sd->flags & SD_SHARE_CPUCAPACITY)
         return 0;
 
     /*
      * Buddy candidates are cache hot:
      */
     if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
             (&p->se == cfs_rq_of(&p->se)->next ||
              &p->se == cfs_rq_of(&p->se)->last))
         return 1;
 
     if (sysctl_sched_migration_cost == -1)
         return 1;
 
     /*
      * Don't migrate task if the task's cookie does not match
      * with the destination CPU's core cookie.
      */
     if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p))
         return 1;
 
     if (sysctl_sched_migration_cost == 0)
         return 0;
 
     delta = rq_clock_task(env->src_rq) - p->se.exec_start;
 
     return delta < (s64)sysctl_sched_migration_cost;
 }
 
 #ifdef CONFIG_NUMA_BALANCING
 /*
  * Returns 1, if task migration degrades locality
  * Returns 0, if task migration improves locality i.e migration preferred.
  * Returns -1, if task migration is not affected by locality.
  */
 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
 {
     struct numa_group *numa_group = rcu_dereference(p->numa_group);
     unsigned long src_weight, dst_weight;
     int src_nid, dst_nid, dist;
 
     if (!static_branch_likely(&sched_numa_balancing))
         return -1;
 
     if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
         return -1;
 
     src_nid = cpu_to_node(env->src_cpu);
     dst_nid = cpu_to_node(env->dst_cpu);
 
     if (src_nid == dst_nid)
         return -1;
 
     /* Migrating away from the preferred node is always bad. */
     if (src_nid == p->numa_preferred_nid) {
         if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
             return 1;
         else
             return -1;
     }
 
     /* Encourage migration to the preferred node. */
     if (dst_nid == p->numa_preferred_nid)
         return 0;
 
     /* Leaving a core idle is often worse than degrading locality. */
     if (env->idle == CPU_IDLE)
         return -1;
 
     dist = node_distance(src_nid, dst_nid);
     if (numa_group) {
         src_weight = group_weight(p, src_nid, dist);
         dst_weight = group_weight(p, dst_nid, dist);
     } else {
         src_weight = task_weight(p, src_nid, dist);
         dst_weight = task_weight(p, dst_nid, dist);
     }
 
     return dst_weight < src_weight;
 }
 
 #else
 static inline int migrate_degrades_locality(struct task_struct *p,
                          struct lb_env *env)
 {
     return -1;
 }
 #endif
 
 /*
  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
  */
 static
 int can_migrate_task(struct task_struct *p, struct lb_env *env)
 {
     int tsk_cache_hot;
 
     lockdep_assert_rq_held(env->src_rq);
 
     /*
      * We do not migrate tasks that are:
      * 1) throttled_lb_pair, or
      * 2) cannot be migrated to this CPU due to cpus_ptr, or
      * 3) running (obviously), or
      * 4) are cache-hot on their current CPU.
      */
     if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
         return 0;
 
     /* Disregard pcpu kthreads; they are where they need to be. */
     if (kthread_is_per_cpu(p))
         return 0;
 
     if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
         int cpu;
 
         schedstat_inc(p->stats.nr_failed_migrations_affine);
 
         env->flags |= LBF_SOME_PINNED;
 
         /*
          * Remember if this task can be migrated to any other CPU in
          * our sched_group. We may want to revisit it if we couldn't
          * meet load balance goals by pulling other tasks on src_cpu.
          *
          * Avoid computing new_dst_cpu
          * - for NEWLY_IDLE
          * - if we have already computed one in current iteration
          * - if it's an active balance
          */
         if (env->idle == CPU_NEWLY_IDLE ||
             env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB))
             return 0;
 
         /* Prevent to re-select dst_cpu via env's CPUs: */
         for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
             if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
                 env->flags |= LBF_DST_PINNED;
                 env->new_dst_cpu = cpu;
                 break;
             }
         }
 
         return 0;
     }
 
     /* Record that we found at least one task that could run on dst_cpu */
     env->flags &= ~LBF_ALL_PINNED;
 
     if (task_running(env->src_rq, p)) {
         schedstat_inc(p->stats.nr_failed_migrations_running);
         return 0;
     }
 
     /*
      * Aggressive migration if:
      * 1) active balance
      * 2) destination numa is preferred
      * 3) task is cache cold, or
      * 4) too many balance attempts have failed.
      */
     if (env->flags & LBF_ACTIVE_LB)
         return 1;
 
     tsk_cache_hot = migrate_degrades_locality(p, env);
     if (tsk_cache_hot == -1)
         tsk_cache_hot = task_hot(p, env);
 
     if (tsk_cache_hot <= 0 ||
         env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
         if (tsk_cache_hot == 1) {
             schedstat_inc(env->sd->lb_hot_gained[env->idle]);
             schedstat_inc(p->stats.nr_forced_migrations);
         }
         return 1;
     }
 
     schedstat_inc(p->stats.nr_failed_migrations_hot);
     return 0;
 }
 
 /*
  * detach_task() -- detach the task for the migration specified in env
  */
 static void detach_task(struct task_struct *p, struct lb_env *env)
 {
     lockdep_assert_rq_held(env->src_rq);
 
     deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
     set_task_cpu(p, env->dst_cpu);
 }
 
 /*
  * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
  * part of active balancing operations within "domain".
  *
  * Returns a task if successful and NULL otherwise.
  */
 static struct task_struct *detach_one_task(struct lb_env *env)
 {
     struct task_struct *p;
 
     lockdep_assert_rq_held(env->src_rq);
 
     list_for_each_entry_reverse(p,
             &env->src_rq->cfs_tasks, se.group_node) {
         if (!can_migrate_task(p, env))
             continue;
 
         detach_task(p, env);
 
         /*
          * Right now, this is only the second place where
          * lb_gained[env->idle] is updated (other is detach_tasks)
          * so we can safely collect stats here rather than
          * inside detach_tasks().
          */
         schedstat_inc(env->sd->lb_gained[env->idle]);
         return p;
     }
     return NULL;
 }
 
 static const unsigned int sched_nr_migrate_break = 32;
 
 /*
  * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
  * busiest_rq, as part of a balancing operation within domain "sd".
  *
  * Returns number of detached tasks if successful and 0 otherwise.
  */
 static int detach_tasks(struct lb_env *env)
 {
     struct list_head *tasks = &env->src_rq->cfs_tasks;
     unsigned long util, load;
     struct task_struct *p;
     int detached = 0;
 
     lockdep_assert_rq_held(env->src_rq);
 
     /*
      * Source run queue has been emptied by another CPU, clear
      * LBF_ALL_PINNED flag as we will not test any task.
      */
     if (env->src_rq->nr_running <= 1) {
         env->flags &= ~LBF_ALL_PINNED;
         return 0;
     }
 
     if (env->imbalance <= 0)
         return 0;
 
     while (!list_empty(tasks)) {
         /*
          * We don't want to steal all, otherwise we may be treated likewise,
          * which could at worst lead to a livelock crash.
          */
         if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
             break;
 
         p = list_last_entry(tasks, struct task_struct, se.group_node);
 
         env->loop++;
         /* We've more or less seen every task there is, call it quits */
         if (env->loop > env->loop_max)
             break;
 
         /* take a breather every nr_migrate tasks */
         if (env->loop > env->loop_break) {
             env->loop_break += sched_nr_migrate_break;
             env->flags |= LBF_NEED_BREAK;
             break;
         }
 
         if (!can_migrate_task(p, env))
             goto next;
 
         switch (env->migration_type) {
         case migrate_load:
             /*
              * Depending of the number of CPUs and tasks and the
              * cgroup hierarchy, task_h_load() can return a null
              * value. Make sure that env->imbalance decreases
              * otherwise detach_tasks() will stop only after
              * detaching up to loop_max tasks.
              */
             load = max_t(unsigned long, task_h_load(p), 1);
 
             if (sched_feat(LB_MIN) &&
                 load < 16 && !env->sd->nr_balance_failed)
                 goto next;
 
             /*
              * Make sure that we don't migrate too much load.
              * Nevertheless, let relax the constraint if
              * scheduler fails to find a good waiting task to
              * migrate.
              */
             if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance)
                 goto next;
 
             env->imbalance -= load;
             break;
 
         case migrate_util:
             util = task_util_est(p);
 
             if (util > env->imbalance)
                 goto next;
 
             env->imbalance -= util;
             break;
 
         case migrate_task:
             env->imbalance--;
             break;
 
         case migrate_misfit:
             /* This is not a misfit task */
             if (task_fits_capacity(p, capacity_of(env->src_cpu)))
                 goto next;
 
             env->imbalance = 0;
             break;
         }
 
         detach_task(p, env);
         list_add(&p->se.group_node, &env->tasks);
 
         detached++;
 
 #ifdef CONFIG_PREEMPTION
         /*
          * NEWIDLE balancing is a source of latency, so preemptible
          * kernels will stop after the first task is detached to minimize
          * the critical section.
          */
         if (env->idle == CPU_NEWLY_IDLE)
             break;
 #endif
 
         /*
          * We only want to steal up to the prescribed amount of
          * load/util/tasks.
          */
         if (env->imbalance <= 0)
             break;
 
         continue;
 next:
         list_move(&p->se.group_node, tasks);
     }
 
     /*
      * Right now, this is one of only two places we collect this stat
      * so we can safely collect detach_one_task() stats here rather
      * than inside detach_one_task().
      */
     schedstat_add(env->sd->lb_gained[env->idle], detached);
 
     return detached;
 }
 
 /*
  * attach_task() -- attach the task detached by detach_task() to its new rq.
  */
 static void attach_task(struct rq *rq, struct task_struct *p)
 {
     lockdep_assert_rq_held(rq);
 
     BUG_ON(task_rq(p) != rq);
     activate_task(rq, p, ENQUEUE_NOCLOCK);
     check_preempt_curr(rq, p, 0);
 }
 
 /*
  * attach_one_task() -- attaches the task returned from detach_one_task() to
  * its new rq.
  */
 static void attach_one_task(struct rq *rq, struct task_struct *p)
 {
     struct rq_flags rf;
 
     rq_lock(rq, &rf);
     update_rq_clock(rq);
     attach_task(rq, p);
     rq_unlock(rq, &rf);
 }
 
 /*
  * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
  * new rq.
  */
 static void attach_tasks(struct lb_env *env)
 {
     struct list_head *tasks = &env->tasks;
     struct task_struct *p;
     struct rq_flags rf;
 
     rq_lock(env->dst_rq, &rf);
     update_rq_clock(env->dst_rq);
 
     while (!list_empty(tasks)) {
         p = list_first_entry(tasks, struct task_struct, se.group_node);
         list_del_init(&p->se.group_node);
 
         attach_task(env->dst_rq, p);
     }
 
     rq_unlock(env->dst_rq, &rf);
 }
 
 #ifdef CONFIG_NO_HZ_COMMON
 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
 {
     if (cfs_rq->avg.load_avg)
         return true;
 
     if (cfs_rq->avg.util_avg)
         return true;
 
     return false;
 }
 
 static inline bool others_have_blocked(struct rq *rq)
 {
     if (READ_ONCE(rq->avg_rt.util_avg))
         return true;
 
     if (READ_ONCE(rq->avg_dl.util_avg))
         return true;
 
     if (thermal_load_avg(rq))
         return true;
 
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
     if (READ_ONCE(rq->avg_irq.util_avg))
         return true;
 #endif
 
     return false;
 }
 
 static inline void update_blocked_load_tick(struct rq *rq)
 {
     WRITE_ONCE(rq->last_blocked_load_update_tick, jiffies);
 }
 
 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
 {
     if (!has_blocked)
         rq->has_blocked_load = 0;
 }
 #else
 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
 static inline bool others_have_blocked(struct rq *rq) { return false; }
 static inline void update_blocked_load_tick(struct rq *rq) {}
 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
 #endif
 
 static bool __update_blocked_others(struct rq *rq, bool *done)
 {
     const struct sched_class *curr_class;
     u64 now = rq_clock_pelt(rq);
     unsigned long thermal_pressure;
     bool decayed;
 
     /*
      * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
      * DL and IRQ signals have been updated before updating CFS.
      */
     curr_class = rq->curr->sched_class;
 
     thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
 
     decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
           update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
           update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
           update_irq_load_avg(rq, 0);
 
     if (others_have_blocked(rq))
         *done = false;
 
     return decayed;
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
 static bool __update_blocked_fair(struct rq *rq, bool *done)
 {
     struct cfs_rq *cfs_rq, *pos;
     bool decayed = false;
     int cpu = cpu_of(rq);
 
     /*
      * Iterates the task_group tree in a bottom up fashion, see
      * list_add_leaf_cfs_rq() for details.
      */
     for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
         struct sched_entity *se;
 
         if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
             update_tg_load_avg(cfs_rq);
 
             if (cfs_rq->nr_running == 0)
                 update_idle_cfs_rq_clock_pelt(cfs_rq);
 
             if (cfs_rq == &rq->cfs)
                 decayed = true;
         }
 
         /* Propagate pending load changes to the parent, if any: */
         se = cfs_rq->tg->se[cpu];
         if (se && !skip_blocked_update(se))
             update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
 
         /*
          * There can be a lot of idle CPU cgroups.  Don't let fully
          * decayed cfs_rqs linger on the list.
          */
         if (cfs_rq_is_decayed(cfs_rq))
             list_del_leaf_cfs_rq(cfs_rq);
 
         /* Don't need periodic decay once load/util_avg are null */
         if (cfs_rq_has_blocked(cfs_rq))
             *done = false;
     }
 
     return decayed;
 }
 
 /*
  * Compute the hierarchical load factor for cfs_rq and all its ascendants.
  * This needs to be done in a top-down fashion because the load of a child
  * group is a fraction of its parents load.
  */
 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
 {
     struct rq *rq = rq_of(cfs_rq);
     struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
     unsigned long now = jiffies;
     unsigned long load;
 
     if (cfs_rq->last_h_load_update == now)
         return;
 
     WRITE_ONCE(cfs_rq->h_load_next, NULL);
     for_each_sched_entity(se) {
         cfs_rq = cfs_rq_of(se);
         WRITE_ONCE(cfs_rq->h_load_next, se);
         if (cfs_rq->last_h_load_update == now)
             break;
     }
 
     if (!se) {
         cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
         cfs_rq->last_h_load_update = now;
     }
 
     while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
         load = cfs_rq->h_load;
         load = div64_ul(load * se->avg.load_avg,
             cfs_rq_load_avg(cfs_rq) + 1);
         cfs_rq = group_cfs_rq(se);
         cfs_rq->h_load = load;
         cfs_rq->last_h_load_update = now;
     }
 }
 
 static unsigned long task_h_load(struct task_struct *p)
 {
     struct cfs_rq *cfs_rq = task_cfs_rq(p);
 
     update_cfs_rq_h_load(cfs_rq);
     return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
             cfs_rq_load_avg(cfs_rq) + 1);
 }
 #else
 static bool __update_blocked_fair(struct rq *rq, bool *done)
 {
     struct cfs_rq *cfs_rq = &rq->cfs;
     bool decayed;
 
     decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
     if (cfs_rq_has_blocked(cfs_rq))
         *done = false;
 
     return decayed;
 }
 
 static unsigned long task_h_load(struct task_struct *p)
 {
     return p->se.avg.load_avg;
 }
 #endif
 
 static void update_blocked_averages(int cpu)
 {
     bool decayed = false, done = true;
     struct rq *rq = cpu_rq(cpu);
     struct rq_flags rf;
 
     rq_lock_irqsave(rq, &rf);
     update_blocked_load_tick(rq);
     update_rq_clock(rq);
 
     decayed |= __update_blocked_others(rq, &done);
     decayed |= __update_blocked_fair(rq, &done);
 
     update_blocked_load_status(rq, !done);
     if (decayed)
         cpufreq_update_util(rq, 0);
     rq_unlock_irqrestore(rq, &rf);
 }
 
 /********** Helpers for find_busiest_group ************************/
 
 /*
  * sg_lb_stats - stats of a sched_group required for load_balancing
  */
 struct sg_lb_stats {
     unsigned long avg_load; /*Avg load across the CPUs of the group */
     unsigned long group_load; /* Total load over the CPUs of the group */
     unsigned long group_capacity;
     unsigned long group_util; /* Total utilization over the CPUs of the group */
     unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
     unsigned int sum_nr_running; /* Nr of tasks running in the group */
     unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
     unsigned int idle_cpus;
     unsigned int group_weight;
     enum group_type group_type;
     unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
     unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
 #ifdef CONFIG_NUMA_BALANCING
     unsigned int nr_numa_running;
     unsigned int nr_preferred_running;
 #endif
 };
 
 /*
  * sd_lb_stats - Structure to store the statistics of a sched_domain
  *       during load balancing.
  */
 struct sd_lb_stats {
     struct sched_group *busiest;    /* Busiest group in this sd */
     struct sched_group *local;  /* Local group in this sd */
     unsigned long total_load;   /* Total load of all groups in sd */
     unsigned long total_capacity;   /* Total capacity of all groups in sd */
     unsigned long avg_load; /* Average load across all groups in sd */
     unsigned int prefer_sibling; /* tasks should go to sibling first */
 
     struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
     struct sg_lb_stats local_stat;  /* Statistics of the local group */
 };
 
 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
 {
     /*
      * Skimp on the clearing to avoid duplicate work. We can avoid clearing
      * local_stat because update_sg_lb_stats() does a full clear/assignment.
      * We must however set busiest_stat::group_type and
      * busiest_stat::idle_cpus to the worst busiest group because
      * update_sd_pick_busiest() reads these before assignment.
      */
     *sds = (struct sd_lb_stats){
         .busiest = NULL,
         .local = NULL,
         .total_load = 0UL,
         .total_capacity = 0UL,
         .busiest_stat = {
             .idle_cpus = UINT_MAX,
             .group_type = group_has_spare,
         },
     };
 }
 
 static unsigned long scale_rt_capacity(int cpu)
 {
     struct rq *rq = cpu_rq(cpu);
     unsigned long max = arch_scale_cpu_capacity(cpu);
     unsigned long used, free;
     unsigned long irq;
 
     irq = cpu_util_irq(rq);
 
     if (unlikely(irq >= max))
         return 1;
 
     /*
      * avg_rt.util_avg and avg_dl.util_avg track binary signals
      * (running and not running) with weights 0 and 1024 respectively.
      * avg_thermal.load_avg tracks thermal pressure and the weighted
      * average uses the actual delta max capacity(load).
      */
     used = READ_ONCE(rq->avg_rt.util_avg);
     used += READ_ONCE(rq->avg_dl.util_avg);
     used += thermal_load_avg(rq);
 
     if (unlikely(used >= max))
         return 1;
 
     free = max - used;
 
     return scale_irq_capacity(free, irq, max);
 }
 
 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 {
     unsigned long capacity = scale_rt_capacity(cpu);
     struct sched_group *sdg = sd->groups;
 
     cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
 
     if (!capacity)
         capacity = 1;
 
     cpu_rq(cpu)->cpu_capacity = capacity;
     trace_sched_cpu_capacity_tp(cpu_rq(cpu));
 
     sdg->sgc->capacity = capacity;
     sdg->sgc->min_capacity = capacity;
     sdg->sgc->max_capacity = capacity;
 }
 
 void update_group_capacity(struct sched_domain *sd, int cpu)
 {
     struct sched_domain *child = sd->child;
     struct sched_group *group, *sdg = sd->groups;
     unsigned long capacity, min_capacity, max_capacity;
     unsigned long interval;
 
     interval = msecs_to_jiffies(sd->balance_interval);
     interval = clamp(interval, 1UL, max_load_balance_interval);
     sdg->sgc->next_update = jiffies + interval;
 
     if (!child) {
         update_cpu_capacity(sd, cpu);
         return;
     }
 
     capacity = 0;
     min_capacity = ULONG_MAX;
     max_capacity = 0;
 
     if (child->flags & SD_OVERLAP) {
         /*
          * SD_OVERLAP domains cannot assume that child groups
          * span the current group.
          */
 
         for_each_cpu(cpu, sched_group_span(sdg)) {
             unsigned long cpu_cap = capacity_of(cpu);
 
             capacity += cpu_cap;
             min_capacity = min(cpu_cap, min_capacity);
             max_capacity = max(cpu_cap, max_capacity);
         }
     } else  {
         /*
          * !SD_OVERLAP domains can assume that child groups
          * span the current group.
          */
 
         group = child->groups;
         do {
             struct sched_group_capacity *sgc = group->sgc;
 
             capacity += sgc->capacity;
             min_capacity = min(sgc->min_capacity, min_capacity);
             max_capacity = max(sgc->max_capacity, max_capacity);
             group = group->next;
         } while (group != child->groups);
     }
 
     sdg->sgc->capacity = capacity;
     sdg->sgc->min_capacity = min_capacity;
     sdg->sgc->max_capacity = max_capacity;
 }
 
 /*
  * Check whether the capacity of the rq has been noticeably reduced by side
  * activity. The imbalance_pct is used for the threshold.
  * Return true is the capacity is reduced
  */
 static inline int
 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
 {
     return ((rq->cpu_capacity * sd->imbalance_pct) <
                 (rq->cpu_capacity_orig * 100));
 }
 
 /*
  * Check whether a rq has a misfit task and if it looks like we can actually
  * help that task: we can migrate the task to a CPU of higher capacity, or
  * the task's current CPU is heavily pressured.
  */
 static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
 {
     return rq->misfit_task_load &&
         (rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
          check_cpu_capacity(rq, sd));
 }
 
 /*
  * Group imbalance indicates (and tries to solve) the problem where balancing
  * groups is inadequate due to ->cpus_ptr constraints.
  *
  * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
  * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
  * Something like:
  *
  *  { 0 1 2 3 } { 4 5 6 7 }
  *          *     * * *
  *
  * If we were to balance group-wise we'd place two tasks in the first group and
  * two tasks in the second group. Clearly this is undesired as it will overload
  * cpu 3 and leave one of the CPUs in the second group unused.
  *
  * The current solution to this issue is detecting the skew in the first group
  * by noticing the lower domain failed to reach balance and had difficulty
  * moving tasks due to affinity constraints.
  *
  * When this is so detected; this group becomes a candidate for busiest; see
  * update_sd_pick_busiest(). And calculate_imbalance() and
  * find_busiest_group() avoid some of the usual balance conditions to allow it
  * to create an effective group imbalance.
  *
  * This is a somewhat tricky proposition since the next run might not find the
  * group imbalance and decide the groups need to be balanced again. A most
  * subtle and fragile situation.
  */
 
 static inline int sg_imbalanced(struct sched_group *group)
 {
     return group->sgc->imbalance;
 }
 
 /*
  * group_has_capacity returns true if the group has spare capacity that could
  * be used by some tasks.
  * We consider that a group has spare capacity if the number of task is
  * smaller than the number of CPUs or if the utilization is lower than the
  * available capacity for CFS tasks.
  * For the latter, we use a threshold to stabilize the state, to take into
  * account the variance of the tasks' load and to return true if the available
  * capacity in meaningful for the load balancer.
  * As an example, an available capacity of 1% can appear but it doesn't make
  * any benefit for the load balance.
  */
 static inline bool
 group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
 {
     if (sgs->sum_nr_running < sgs->group_weight)
         return true;
 
     if ((sgs->group_capacity * imbalance_pct) <
             (sgs->group_runnable * 100))
         return false;
 
     if ((sgs->group_capacity * 100) >
             (sgs->group_util * imbalance_pct))
         return true;
 
     return false;
 }
 
 /*
  *  group_is_overloaded returns true if the group has more tasks than it can
  *  handle.
  *  group_is_overloaded is not equals to !group_has_capacity because a group
  *  with the exact right number of tasks, has no more spare capacity but is not
  *  overloaded so both group_has_capacity and group_is_overloaded return
  *  false.
  */
 static inline bool
 group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
 {
     if (sgs->sum_nr_running <= sgs->group_weight)
         return false;
 
     if ((sgs->group_capacity * 100) <
             (sgs->group_util * imbalance_pct))
         return true;
 
     if ((sgs->group_capacity * imbalance_pct) <
             (sgs->group_runnable * 100))
         return true;
 
     return false;
 }
 
 static inline enum
 group_type group_classify(unsigned int imbalance_pct,
               struct sched_group *group,
               struct sg_lb_stats *sgs)
 {
     if (group_is_overloaded(imbalance_pct, sgs))
         return group_overloaded;
 
     if (sg_imbalanced(group))
         return group_imbalanced;
 
     if (sgs->group_asym_packing)
         return group_asym_packing;
 
     if (sgs->group_misfit_task_load)
         return group_misfit_task;
 
     if (!group_has_capacity(imbalance_pct, sgs))
         return group_fully_busy;
 
     return group_has_spare;
 }
 
 /**
  * asym_smt_can_pull_tasks - Check whether the load balancing CPU can pull tasks
  * @dst_cpu:    Destination CPU of the load balancing
  * @sds:    Load-balancing data with statistics of the local group
  * @sgs:    Load-balancing statistics of the candidate busiest group
  * @sg:     The candidate busiest group
  *
  * Check the state of the SMT siblings of both @sds::local and @sg and decide
  * if @dst_cpu can pull tasks.
  *
  * If @dst_cpu does not have SMT siblings, it can pull tasks if two or more of
  * the SMT siblings of @sg are busy. If only one CPU in @sg is busy, pull tasks
  * only if @dst_cpu has higher priority.
  *
  * If both @dst_cpu and @sg have SMT siblings, and @sg has exactly one more
  * busy CPU than @sds::local, let @dst_cpu pull tasks if it has higher priority.
  * Bigger imbalances in the number of busy CPUs will be dealt with in
  * update_sd_pick_busiest().
  *
  * If @sg does not have SMT siblings, only pull tasks if all of the SMT siblings
  * of @dst_cpu are idle and @sg has lower priority.
  *
  * Return: true if @dst_cpu can pull tasks, false otherwise.
  */
 static bool asym_smt_can_pull_tasks(int dst_cpu, struct sd_lb_stats *sds,
                     struct sg_lb_stats *sgs,
                     struct sched_group *sg)
 {
 #ifdef CONFIG_SCHED_SMT
     bool local_is_smt, sg_is_smt;
     int sg_busy_cpus;
 
     local_is_smt = sds->local->flags & SD_SHARE_CPUCAPACITY;
     sg_is_smt = sg->flags & SD_SHARE_CPUCAPACITY;
 
     sg_busy_cpus = sgs->group_weight - sgs->idle_cpus;
 
     if (!local_is_smt) {
         /*
          * If we are here, @dst_cpu is idle and does not have SMT
          * siblings. Pull tasks if candidate group has two or more
          * busy CPUs.
          */
         if (sg_busy_cpus >= 2) /* implies sg_is_smt */
             return true;
 
         /*
          * @dst_cpu does not have SMT siblings. @sg may have SMT
          * siblings and only one is busy. In such case, @dst_cpu
          * can help if it has higher priority and is idle (i.e.,
          * it has no running tasks).
          */
         return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu);
     }
 
     /* @dst_cpu has SMT siblings. */
 
     if (sg_is_smt) {
         int local_busy_cpus = sds->local->group_weight -
                       sds->local_stat.idle_cpus;
         int busy_cpus_delta = sg_busy_cpus - local_busy_cpus;
 
         if (busy_cpus_delta == 1)
             return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu);
 
         return false;
     }
 
     /*
      * @sg does not have SMT siblings. Ensure that @sds::local does not end
      * up with more than one busy SMT sibling and only pull tasks if there
      * are not busy CPUs (i.e., no CPU has running tasks).
      */
     if (!sds->local_stat.sum_nr_running)
         return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu);
 
     return false;
 #else
     /* Always return false so that callers deal with non-SMT cases. */
     return false;
 #endif
 }
 
 static inline bool
 sched_asym(struct lb_env *env, struct sd_lb_stats *sds,  struct sg_lb_stats *sgs,
        struct sched_group *group)
 {
     /* Only do SMT checks if either local or candidate have SMT siblings */
     if ((sds->local->flags & SD_SHARE_CPUCAPACITY) ||
         (group->flags & SD_SHARE_CPUCAPACITY))
         return asym_smt_can_pull_tasks(env->dst_cpu, sds, sgs, group);
 
     return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
 }
 
 static inline bool
 sched_reduced_capacity(struct rq *rq, struct sched_domain *sd)
 {
     /*
      * When there is more than 1 task, the group_overloaded case already
      * takes care of cpu with reduced capacity
      */
     if (rq->cfs.h_nr_running != 1)
         return false;
 
     return check_cpu_capacity(rq, sd);
 }
 
 /**
  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
  * @env: The load balancing environment.
  * @sds: Load-balancing data with statistics of the local group.
  * @group: sched_group whose statistics are to be updated.
  * @sgs: variable to hold the statistics for this group.
  * @sg_status: Holds flag indicating the status of the sched_group
  */
 static inline void update_sg_lb_stats(struct lb_env *env,
                       struct sd_lb_stats *sds,
                       struct sched_group *group,
                       struct sg_lb_stats *sgs,
                       int *sg_status)
 {
     int i, nr_running, local_group;
 
     memset(sgs, 0, sizeof(*sgs));
 
     local_group = group == sds->local;
 
     for_each_cpu_and(i, sched_group_span(group), env->cpus) {
         struct rq *rq = cpu_rq(i);
         unsigned long load = cpu_load(rq);
 
         sgs->group_load += load;
         sgs->group_util += cpu_util_cfs(i);
         sgs->group_runnable += cpu_runnable(rq);
         sgs->sum_h_nr_running += rq->cfs.h_nr_running;
 
         nr_running = rq->nr_running;
         sgs->sum_nr_running += nr_running;
 
         if (nr_running > 1)
             *sg_status |= SG_OVERLOAD;
 
         if (cpu_overutilized(i))
             *sg_status |= SG_OVERUTILIZED;
 
 #ifdef CONFIG_NUMA_BALANCING
         sgs->nr_numa_running += rq->nr_numa_running;
         sgs->nr_preferred_running += rq->nr_preferred_running;
 #endif
         /*
          * No need to call idle_cpu() if nr_running is not 0
          */
         if (!nr_running && idle_cpu(i)) {
             sgs->idle_cpus++;
             /* Idle cpu can't have misfit task */
             continue;
         }
 
         if (local_group)
             continue;
 
         if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
             /* Check for a misfit task on the cpu */
             if (sgs->group_misfit_task_load < rq->misfit_task_load) {
                 sgs->group_misfit_task_load = rq->misfit_task_load;
                 *sg_status |= SG_OVERLOAD;
             }
         } else if ((env->idle != CPU_NOT_IDLE) &&
                sched_reduced_capacity(rq, env->sd)) {
             /* Check for a task running on a CPU with reduced capacity */
             if (sgs->group_misfit_task_load < load)
                 sgs->group_misfit_task_load = load;
         }
     }
 
     sgs->group_capacity = group->sgc->capacity;
 
     sgs->group_weight = group->group_weight;
 
     /* Check if dst CPU is idle and preferred to this group */
     if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
         env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
         sched_asym(env, sds, sgs, group)) {
         sgs->group_asym_packing = 1;
     }
 
     sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
 
     /* Computing avg_load makes sense only when group is overloaded */
     if (sgs->group_type == group_overloaded)
         sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
                 sgs->group_capacity;
 }
 
 /**
  * update_sd_pick_busiest - return 1 on busiest group
  * @env: The load balancing environment.
  * @sds: sched_domain statistics
  * @sg: sched_group candidate to be checked for being the busiest
  * @sgs: sched_group statistics
  *
  * Determine if @sg is a busier group than the previously selected
  * busiest group.
  *
  * Return: %true if @sg is a busier group than the previously selected
  * busiest group. %false otherwise.
  */
 static bool update_sd_pick_busiest(struct lb_env *env,
                    struct sd_lb_stats *sds,
                    struct sched_group *sg,
                    struct sg_lb_stats *sgs)
 {
     struct sg_lb_stats *busiest = &sds->busiest_stat;
 
     /* Make sure that there is at least one task to pull */
     if (!sgs->sum_h_nr_running)
         return false;
 
     /*
      * Don't try to pull misfit tasks we can't help.
      * We can use max_capacity here as reduction in capacity on some
      * CPUs in the group should either be possible to resolve
      * internally or be covered by avg_load imbalance (eventually).
      */
     if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
         (sgs->group_type == group_misfit_task) &&
         (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
          sds->local_stat.group_type != group_has_spare))
         return false;
 
     if (sgs->group_type > busiest->group_type)
         return true;
 
     if (sgs->group_type < busiest->group_type)
         return false;
 
     /*
      * The candidate and the current busiest group are the same type of
      * group. Let check which one is the busiest according to the type.
      */
 
     switch (sgs->group_type) {
     case group_overloaded:
         /* Select the overloaded group with highest avg_load. */
         if (sgs->avg_load <= busiest->avg_load)
             return false;
         break;
 
     case group_imbalanced:
         /*
          * Select the 1st imbalanced group as we don't have any way to
          * choose one more than another.
          */
         return false;
 
     case group_asym_packing:
         /* Prefer to move from lowest priority CPU's work */
         if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
             return false;
         break;
 
     case group_misfit_task:
         /*
          * If we have more than one misfit sg go with the biggest
          * misfit.
          */
         if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
             return false;
         break;
 
     case group_fully_busy:
         /*
          * Select the fully busy group with highest avg_load. In
          * theory, there is no need to pull task from such kind of
          * group because tasks have all compute capacity that they need
          * but we can still improve the overall throughput by reducing
          * contention when accessing shared HW resources.
          *
          * XXX for now avg_load is not computed and always 0 so we
          * select the 1st one.
          */
         if (sgs->avg_load <= busiest->avg_load)
             return false;
         break;
 
     case group_has_spare:
         /*
          * Select not overloaded group with lowest number of idle cpus
          * and highest number of running tasks. We could also compare
          * the spare capacity which is more stable but it can end up
          * that the group has less spare capacity but finally more idle
          * CPUs which means less opportunity to pull tasks.
          */
         if (sgs->idle_cpus > busiest->idle_cpus)
             return false;
         else if ((sgs->idle_cpus == busiest->idle_cpus) &&
              (sgs->sum_nr_running <= busiest->sum_nr_running))
             return false;
 
         break;
     }
 
     /*
      * Candidate sg has no more than one task per CPU and has higher
      * per-CPU capacity. Migrating tasks to less capable CPUs may harm
      * throughput. Maximize throughput, power/energy consequences are not
      * considered.
      */
     if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
         (sgs->group_type <= group_fully_busy) &&
         (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
         return false;
 
     return true;
 }
 
 #ifdef CONFIG_NUMA_BALANCING
 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
 {
     if (sgs->sum_h_nr_running > sgs->nr_numa_running)
         return regular;
     if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
         return remote;
     return all;
 }
 
 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
 {
     if (rq->nr_running > rq->nr_numa_running)
         return regular;
     if (rq->nr_running > rq->nr_preferred_running)
         return remote;
     return all;
 }
 #else
 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
 {
     return all;
 }
 
 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
 {
     return regular;
 }
 #endif /* CONFIG_NUMA_BALANCING */
 
 
 struct sg_lb_stats;
 
 /*
  * task_running_on_cpu - return 1 if @p is running on @cpu.
  */
 
 static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
 {
     /* Task has no contribution or is new */
     if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
         return 0;
 
     if (task_on_rq_queued(p))
         return 1;
 
     return 0;
 }
 
 /**
  * idle_cpu_without - would a given CPU be idle without p ?
  * @cpu: the processor on which idleness is tested.
  * @p: task which should be ignored.
  *
  * Return: 1 if the CPU would be idle. 0 otherwise.
  */
 static int idle_cpu_without(int cpu, struct task_struct *p)
 {
     struct rq *rq = cpu_rq(cpu);
 
     if (rq->curr != rq->idle && rq->curr != p)
         return 0;
 
     /*
      * rq->nr_running can't be used but an updated version without the
      * impact of p on cpu must be used instead. The updated nr_running
      * be computed and tested before calling idle_cpu_without().
      */
 
 #ifdef CONFIG_SMP
     if (rq->ttwu_pending)
         return 0;
 #endif
 
     return 1;
 }
 
 /*
  * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
  * @sd: The sched_domain level to look for idlest group.
  * @group: sched_group whose statistics are to be updated.
  * @sgs: variable to hold the statistics for this group.
  * @p: The task for which we look for the idlest group/CPU.
  */
 static inline void update_sg_wakeup_stats(struct sched_domain *sd,
                       struct sched_group *group,
                       struct sg_lb_stats *sgs,
                       struct task_struct *p)
 {
     int i, nr_running;
 
     memset(sgs, 0, sizeof(*sgs));
 
     for_each_cpu(i, sched_group_span(group)) {
         struct rq *rq = cpu_rq(i);
         unsigned int local;
 
         sgs->group_load += cpu_load_without(rq, p);
         sgs->group_util += cpu_util_without(i, p);
         sgs->group_runnable += cpu_runnable_without(rq, p);
         local = task_running_on_cpu(i, p);
         sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
 
         nr_running = rq->nr_running - local;
         sgs->sum_nr_running += nr_running;
 
         /*
          * No need to call idle_cpu_without() if nr_running is not 0
          */
         if (!nr_running && idle_cpu_without(i, p))
             sgs->idle_cpus++;
 
     }
 
     /* Check if task fits in the group */
     if (sd->flags & SD_ASYM_CPUCAPACITY &&
         !task_fits_capacity(p, group->sgc->max_capacity)) {
         sgs->group_misfit_task_load = 1;
     }
 
     sgs->group_capacity = group->sgc->capacity;
 
     sgs->group_weight = group->group_weight;
 
     sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
 
     /*
      * Computing avg_load makes sense only when group is fully busy or
      * overloaded
      */
     if (sgs->group_type == group_fully_busy ||
         sgs->group_type == group_overloaded)
         sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
                 sgs->group_capacity;
 }
 
 static bool update_pick_idlest(struct sched_group *idlest,
                    struct sg_lb_stats *idlest_sgs,
                    struct sched_group *group,
                    struct sg_lb_stats *sgs)
 {
     if (sgs->group_type < idlest_sgs->group_type)
         return true;
 
     if (sgs->group_type > idlest_sgs->group_type)
         return false;
 
     /*
      * The candidate and the current idlest group are the same type of
      * group. Let check which one is the idlest according to the type.
      */
 
     switch (sgs->group_type) {
     case group_overloaded:
     case group_fully_busy:
         /* Select the group with lowest avg_load. */
         if (idlest_sgs->avg_load <= sgs->avg_load)
             return false;
         break;
 
     case group_imbalanced:
     case group_asym_packing:
         /* Those types are not used in the slow wakeup path */
         return false;
 
     case group_misfit_task:
         /* Select group with the highest max capacity */
         if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
             return false;
         break;
 
     case group_has_spare:
         /* Select group with most idle CPUs */
         if (idlest_sgs->idle_cpus > sgs->idle_cpus)
             return false;
 
         /* Select group with lowest group_util */
         if (idlest_sgs->idle_cpus == sgs->idle_cpus &&
             idlest_sgs->group_util <= sgs->group_util)
             return false;
 
         break;
     }
 
     return true;
 }
 
 /*
  * find_idlest_group() finds and returns the least busy CPU group within the
  * domain.
  *
  * Assumes p is allowed on at least one CPU in sd.
  */
 static struct sched_group *
 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
 {
     struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
     struct sg_lb_stats local_sgs, tmp_sgs;
     struct sg_lb_stats *sgs;
     unsigned long imbalance;
     struct sg_lb_stats idlest_sgs = {
             .avg_load = UINT_MAX,
             .group_type = group_overloaded,
     };
 
     do {
         int local_group;
 
         /* Skip over this group if it has no CPUs allowed */
         if (!cpumask_intersects(sched_group_span(group),
                     p->cpus_ptr))
             continue;
 
         /* Skip over this group if no cookie matched */
         if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group))
             continue;
 
         local_group = cpumask_test_cpu(this_cpu,
                            sched_group_span(group));
 
         if (local_group) {
             sgs = &local_sgs;
             local = group;
         } else {
             sgs = &tmp_sgs;
         }
 
         update_sg_wakeup_stats(sd, group, sgs, p);
 
         if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
             idlest = group;
             idlest_sgs = *sgs;
         }
 
     } while (group = group->next, group != sd->groups);
 
 
     /* There is no idlest group to push tasks to */
     if (!idlest)
         return NULL;
 
     /* The local group has been skipped because of CPU affinity */
     if (!local)
         return idlest;
 
     /*
      * If the local group is idler than the selected idlest group
      * don't try and push the task.
      */
     if (local_sgs.group_type < idlest_sgs.group_type)
         return NULL;
 
     /*
      * If the local group is busier than the selected idlest group
      * try and push the task.
      */
     if (local_sgs.group_type > idlest_sgs.group_type)
         return idlest;
 
     switch (local_sgs.group_type) {
     case group_overloaded:
     case group_fully_busy:
 
         /* Calculate allowed imbalance based on load */
         imbalance = scale_load_down(NICE_0_LOAD) *
                 (sd->imbalance_pct-100) / 100;
 
         /*
          * When comparing groups across NUMA domains, it's possible for
          * the local domain to be very lightly loaded relative to the
          * remote domains but "imbalance" skews the comparison making
          * remote CPUs look much more favourable. When considering
          * cross-domain, add imbalance to the load on the remote node
          * and consider staying local.
          */
 
         if ((sd->flags & SD_NUMA) &&
             ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
             return NULL;
 
         /*
          * If the local group is less loaded than the selected
          * idlest group don't try and push any tasks.
          */
         if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
             return NULL;
 
         if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
             return NULL;
         break;
 
     case group_imbalanced:
     case group_asym_packing:
         /* Those type are not used in the slow wakeup path */
         return NULL;
 
     case group_misfit_task:
         /* Select group with the highest max capacity */
         if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
             return NULL;
         break;
 
     case group_has_spare:
 #ifdef CONFIG_NUMA
         if (sd->flags & SD_NUMA) {
             int imb_numa_nr = sd->imb_numa_nr;
 #ifdef CONFIG_NUMA_BALANCING
             int idlest_cpu;
             /*
              * If there is spare capacity at NUMA, try to select
              * the preferred node
              */
             if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
                 return NULL;
 
             idlest_cpu = cpumask_first(sched_group_span(idlest));
             if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
                 return idlest;
 #endif /* CONFIG_NUMA_BALANCING */
             /*
              * Otherwise, keep the task close to the wakeup source
              * and improve locality if the number of running tasks
              * would remain below threshold where an imbalance is
              * allowed while accounting for the possibility the
              * task is pinned to a subset of CPUs. If there is a
              * real need of migration, periodic load balance will
              * take care of it.
              */
             if (p->nr_cpus_allowed != NR_CPUS) {
                 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
 
                 cpumask_and(cpus, sched_group_span(local), p->cpus_ptr);
                 imb_numa_nr = min(cpumask_weight(cpus), sd->imb_numa_nr);
             }
 
             imbalance = abs(local_sgs.idle_cpus - idlest_sgs.idle_cpus);
             if (!adjust_numa_imbalance(imbalance,
                            local_sgs.sum_nr_running + 1,
                            imb_numa_nr)) {
                 return NULL;
             }
         }
 #endif /* CONFIG_NUMA */
 
         /*
          * Select group with highest number of idle CPUs. We could also
          * compare the utilization which is more stable but it can end
          * up that the group has less spare capacity but finally more
          * idle CPUs which means more opportunity to run task.
          */
         if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
             return NULL;
         break;
     }
 
     return idlest;
 }
 
 static void update_idle_cpu_scan(struct lb_env *env,
                  unsigned long sum_util)
 {
     struct sched_domain_shared *sd_share;
     int llc_weight, pct;
     u64 x, y, tmp;
     /*
      * Update the number of CPUs to scan in LLC domain, which could
      * be used as a hint in select_idle_cpu(). The update of sd_share
      * could be expensive because it is within a shared cache line.
      * So the write of this hint only occurs during periodic load
      * balancing, rather than CPU_NEWLY_IDLE, because the latter
      * can fire way more frequently than the former.
      */
     if (!sched_feat(SIS_UTIL) || env->idle == CPU_NEWLY_IDLE)
         return;
 
     llc_weight = per_cpu(sd_llc_size, env->dst_cpu);
     if (env->sd->span_weight != llc_weight)
         return;
 
     sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu));
     if (!sd_share)
         return;
 
     /*
      * The number of CPUs to search drops as sum_util increases, when
      * sum_util hits 85% or above, the scan stops.
      * The reason to choose 85% as the threshold is because this is the
      * imbalance_pct(117) when a LLC sched group is overloaded.
      *
      * let y = SCHED_CAPACITY_SCALE - p * x^2                       [1]
      * and y'= y / SCHED_CAPACITY_SCALE
      *
      * x is the ratio of sum_util compared to the CPU capacity:
      * x = sum_util / (llc_weight * SCHED_CAPACITY_SCALE)
      * y' is the ratio of CPUs to be scanned in the LLC domain,
      * and the number of CPUs to scan is calculated by:
      *
      * nr_scan = llc_weight * y'                                    [2]
      *
      * When x hits the threshold of overloaded, AKA, when
      * x = 100 / pct, y drops to 0. According to [1],
      * p should be SCHED_CAPACITY_SCALE * pct^2 / 10000
      *
      * Scale x by SCHED_CAPACITY_SCALE:
      * x' = sum_util / llc_weight;                                  [3]
      *
      * and finally [1] becomes:
      * y = SCHED_CAPACITY_SCALE -
      *     x'^2 * pct^2 / (10000 * SCHED_CAPACITY_SCALE)            [4]
      *
      */
     /* equation [3] */
     x = sum_util;
     do_div(x, llc_weight);
 
     /* equation [4] */
     pct = env->sd->imbalance_pct;
     tmp = x * x * pct * pct;
     do_div(tmp, 10000 * SCHED_CAPACITY_SCALE);
     tmp = min_t(long, tmp, SCHED_CAPACITY_SCALE);
     y = SCHED_CAPACITY_SCALE - tmp;
 
     /* equation [2] */
     y *= llc_weight;
     do_div(y, SCHED_CAPACITY_SCALE);
     if ((int)y != sd_share->nr_idle_scan)
         WRITE_ONCE(sd_share->nr_idle_scan, (int)y);
 }
 
 /**
  * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
  * @env: The load balancing environment.
  * @sds: variable to hold the statistics for this sched_domain.
  */
 
 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
 {
     struct sched_domain *child = env->sd->child;
     struct sched_group *sg = env->sd->groups;
     struct sg_lb_stats *local = &sds->local_stat;
     struct sg_lb_stats tmp_sgs;
     unsigned long sum_util = 0;
     int sg_status = 0;
 
     do {
         struct sg_lb_stats *sgs = &tmp_sgs;
         int local_group;
 
         local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
         if (local_group) {
             sds->local = sg;
             sgs = local;
 
             if (env->idle != CPU_NEWLY_IDLE ||
                 time_after_eq(jiffies, sg->sgc->next_update))
                 update_group_capacity(env->sd, env->dst_cpu);
         }
 
         update_sg_lb_stats(env, sds, sg, sgs, &sg_status);
 
         if (local_group)
             goto next_group;
 
 
         if (update_sd_pick_busiest(env, sds, sg, sgs)) {
             sds->busiest = sg;
             sds->busiest_stat = *sgs;
         }
 
 next_group:
         /* Now, start updating sd_lb_stats */
         sds->total_load += sgs->group_load;
         sds->total_capacity += sgs->group_capacity;
 
         sum_util += sgs->group_util;
         sg = sg->next;
     } while (sg != env->sd->groups);
 
     /* Tag domain that child domain prefers tasks go to siblings first */
     sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
 
 
     if (env->sd->flags & SD_NUMA)
         env->fbq_type = fbq_classify_group(&sds->busiest_stat);
 
     if (!env->sd->parent) {
         struct root_domain *rd = env->dst_rq->rd;
 
         /* update overload indicator if we are at root domain */
         WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
 
         /* Update over-utilization (tipping point, U >= 0) indicator */
         WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
         trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED);
     } else if (sg_status & SG_OVERUTILIZED) {
         struct root_domain *rd = env->dst_rq->rd;
 
         WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED);
         trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
     }
 
     update_idle_cpu_scan(env, sum_util);
 }
 
 /**
  * calculate_imbalance - Calculate the amount of imbalance present within the
  *           groups of a given sched_domain during load balance.
  * @env: load balance environment
  * @sds: statistics of the sched_domain whose imbalance is to be calculated.
  */
 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
 {
     struct sg_lb_stats *local, *busiest;
 
     local = &sds->local_stat;
     busiest = &sds->busiest_stat;
 
     if (busiest->group_type == group_misfit_task) {
         if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
             /* Set imbalance to allow misfit tasks to be balanced. */
             env->migration_type = migrate_misfit;
             env->imbalance = 1;
         } else {
             /*
              * Set load imbalance to allow moving task from cpu
              * with reduced capacity.
              */
             env->migration_type = migrate_load;
             env->imbalance = busiest->group_misfit_task_load;
         }
         return;
     }
 
     if (busiest->group_type == group_asym_packing) {
         /*
          * In case of asym capacity, we will try to migrate all load to
          * the preferred CPU.
          */
         env->migration_type = migrate_task;
         env->imbalance = busiest->sum_h_nr_running;
         return;
     }
 
     if (busiest->group_type == group_imbalanced) {
         /*
          * In the group_imb case we cannot rely on group-wide averages
          * to ensure CPU-load equilibrium, try to move any task to fix
          * the imbalance. The next load balance will take care of
          * balancing back the system.
          */
         env->migration_type = migrate_task;
         env->imbalance = 1;
         return;
     }
 
     /*
      * Try to use spare capacity of local group without overloading it or
      * emptying busiest.
      */
     if (local->group_type == group_has_spare) {
         if ((busiest->group_type > group_fully_busy) &&
             !(env->sd->flags & SD_SHARE_PKG_RESOURCES)) {
             /*
              * If busiest is overloaded, try to fill spare
              * capacity. This might end up creating spare capacity
              * in busiest or busiest still being overloaded but
              * there is no simple way to directly compute the
              * amount of load to migrate in order to balance the
              * system.
              */
             env->migration_type = migrate_util;
             env->imbalance = max(local->group_capacity, local->group_util) -
                      local->group_util;
 
             /*
              * In some cases, the group's utilization is max or even
              * higher than capacity because of migrations but the
              * local CPU is (newly) idle. There is at least one
              * waiting task in this overloaded busiest group. Let's
              * try to pull it.
              */
             if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
                 env->migration_type = migrate_task;
                 env->imbalance = 1;
             }
 
             return;
         }
 
         if (busiest->group_weight == 1 || sds->prefer_sibling) {
             unsigned int nr_diff = busiest->sum_nr_running;
             /*
              * When prefer sibling, evenly spread running tasks on
              * groups.
              */
             env->migration_type = migrate_task;
             lsub_positive(&nr_diff, local->sum_nr_running);
             env->imbalance = nr_diff;
         } else {
 
             /*
              * If there is no overload, we just want to even the number of
              * idle cpus.
              */
             env->migration_type = migrate_task;
             env->imbalance = max_t(long, 0,
                            (local->idle_cpus - busiest->idle_cpus));
         }
 
 #ifdef CONFIG_NUMA
         /* Consider allowing a small imbalance between NUMA groups */
         if (env->sd->flags & SD_NUMA) {
             env->imbalance = adjust_numa_imbalance(env->imbalance,
                                    local->sum_nr_running + 1,
                                    env->sd->imb_numa_nr);
         }
 #endif
 
         /* Number of tasks to move to restore balance */
         env->imbalance >>= 1;
 
         return;
     }
 
     /*
      * Local is fully busy but has to take more load to relieve the
      * busiest group
      */
     if (local->group_type < group_overloaded) {
         /*
          * Local will become overloaded so the avg_load metrics are
          * finally needed.
          */
 
         local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
                   local->group_capacity;
 
         /*
          * If the local group is more loaded than the selected
          * busiest group don't try to pull any tasks.
          */
         if (local->avg_load >= busiest->avg_load) {
             env->imbalance = 0;
             return;
         }
 
         sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
                 sds->total_capacity;
     }
 
     /*
      * Both group are or will become overloaded and we're trying to get all
      * the CPUs to the average_load, so we don't want to push ourselves
      * above the average load, nor do we wish to reduce the max loaded CPU
      * below the average load. At the same time, we also don't want to
      * reduce the group load below the group capacity. Thus we look for
      * the minimum possible imbalance.
      */
     env->migration_type = migrate_load;
     env->imbalance = min(
         (busiest->avg_load - sds->avg_load) * busiest->group_capacity,
         (sds->avg_load - local->avg_load) * local->group_capacity
     ) / SCHED_CAPACITY_SCALE;
 }
 
 /******* find_busiest_group() helpers end here *********************/
 
 /*
  * Decision matrix according to the local and busiest group type:
  *
  * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
  * has_spare        nr_idle   balanced   N/A    N/A  balanced   balanced
  * fully_busy       nr_idle   nr_idle    N/A    N/A  balanced   balanced
  * misfit_task      force     N/A        N/A    N/A  N/A        N/A
  * asym_packing     force     force      N/A    N/A  force      force
  * imbalanced       force     force      N/A    N/A  force      force
  * overloaded       force     force      N/A    N/A  force      avg_load
  *
  * N/A :      Not Applicable because already filtered while updating
  *            statistics.
  * balanced : The system is balanced for these 2 groups.
  * force :    Calculate the imbalance as load migration is probably needed.
  * avg_load : Only if imbalance is significant enough.
  * nr_idle :  dst_cpu is not busy and the number of idle CPUs is quite
  *            different in groups.
  */
 
 /**
  * find_busiest_group - Returns the busiest group within the sched_domain
  * if there is an imbalance.
  * @env: The load balancing environment.
  *
  * Also calculates the amount of runnable load which should be moved
  * to restore balance.
  *
  * Return:  - The busiest group if imbalance exists.
  */
 static struct sched_group *find_busiest_group(struct lb_env *env)
 {
     struct sg_lb_stats *local, *busiest;
     struct sd_lb_stats sds;
 
     init_sd_lb_stats(&sds);
 
     /*
      * Compute the various statistics relevant for load balancing at
      * this level.
      */
     update_sd_lb_stats(env, &sds);
 
     if (sched_energy_enabled()) {
         struct root_domain *rd = env->dst_rq->rd;
 
         if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
             goto out_balanced;
     }
 
     local = &sds.local_stat;
     busiest = &sds.busiest_stat;
 
     /* There is no busy sibling group to pull tasks from */
     if (!sds.busiest)
         goto out_balanced;
 
     /* Misfit tasks should be dealt with regardless of the avg load */
     if (busiest->group_type == group_misfit_task)
         goto force_balance;
 
     /* ASYM feature bypasses nice load balance check */
     if (busiest->group_type == group_asym_packing)
         goto force_balance;
 
     /*
      * If the busiest group is imbalanced the below checks don't
      * work because they assume all things are equal, which typically
      * isn't true due to cpus_ptr constraints and the like.
      */
     if (busiest->group_type == group_imbalanced)
         goto force_balance;
 
     /*
      * If the local group is busier than the selected busiest group
      * don't try and pull any tasks.
      */
     if (local->group_type > busiest->group_type)
         goto out_balanced;
 
     /*
      * When groups are overloaded, use the avg_load to ensure fairness
      * between tasks.
      */
     if (local->group_type == group_overloaded) {
         /*
          * If the local group is more loaded than the selected
          * busiest group don't try to pull any tasks.
          */
         if (local->avg_load >= busiest->avg_load)
             goto out_balanced;
 
         /* XXX broken for overlapping NUMA groups */
         sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
                 sds.total_capacity;
 
         /*
          * Don't pull any tasks if this group is already above the
          * domain average load.
          */
         if (local->avg_load >= sds.avg_load)
             goto out_balanced;
 
         /*
          * If the busiest group is more loaded, use imbalance_pct to be
          * conservative.
          */
         if (100 * busiest->avg_load <=
                 env->sd->imbalance_pct * local->avg_load)
             goto out_balanced;
     }
 
     /* Try to move all excess tasks to child's sibling domain */
     if (sds.prefer_sibling && local->group_type == group_has_spare &&
         busiest->sum_nr_running > local->sum_nr_running + 1)
         goto force_balance;
 
     if (busiest->group_type != group_overloaded) {
         if (env->idle == CPU_NOT_IDLE)
             /*
              * If the busiest group is not overloaded (and as a
              * result the local one too) but this CPU is already
              * busy, let another idle CPU try to pull task.
              */
             goto out_balanced;
 
         if (busiest->group_weight > 1 &&
             local->idle_cpus <= (busiest->idle_cpus + 1))
             /*
              * If the busiest group is not overloaded
              * and there is no imbalance between this and busiest
              * group wrt idle CPUs, it is balanced. The imbalance
              * becomes significant if the diff is greater than 1
              * otherwise we might end up to just move the imbalance
              * on another group. Of course this applies only if
              * there is more than 1 CPU per group.
              */
             goto out_balanced;
 
         if (busiest->sum_h_nr_running == 1)
             /*
              * busiest doesn't have any tasks waiting to run
              */
             goto out_balanced;
     }
 
 force_balance:
     /* Looks like there is an imbalance. Compute it */
     calculate_imbalance(env, &sds);
     return env->imbalance ? sds.busiest : NULL;
 
 out_balanced:
     env->imbalance = 0;
     return NULL;
 }
 
 /*
  * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
  */
 static struct rq *find_busiest_queue(struct lb_env *env,
                      struct sched_group *group)
 {
     struct rq *busiest = NULL, *rq;
     unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
     unsigned int busiest_nr = 0;
     int i;
 
     for_each_cpu_and(i, sched_group_span(group), env->cpus) {
         unsigned long capacity, load, util;
         unsigned int nr_running;
         enum fbq_type rt;
 
         rq = cpu_rq(i);
         rt = fbq_classify_rq(rq);
 
         /*
          * We classify groups/runqueues into three groups:
          *  - regular: there are !numa tasks
          *  - remote:  there are numa tasks that run on the 'wrong' node
          *  - all:     there is no distinction
          *
          * In order to avoid migrating ideally placed numa tasks,
          * ignore those when there's better options.
          *
          * If we ignore the actual busiest queue to migrate another
          * task, the next balance pass can still reduce the busiest
          * queue by moving tasks around inside the node.
          *
          * If we cannot move enough load due to this classification
          * the next pass will adjust the group classification and
          * allow migration of more tasks.
          *
          * Both cases only affect the total convergence complexity.
          */
         if (rt > env->fbq_type)
             continue;
 
         nr_running = rq->cfs.h_nr_running;
         if (!nr_running)
             continue;
 
         capacity = capacity_of(i);
 
         /*
          * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
          * eventually lead to active_balancing high->low capacity.
          * Higher per-CPU capacity is considered better than balancing
          * average load.
          */
         if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
             !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
             nr_running == 1)
             continue;
 
         /* Make sure we only pull tasks from a CPU of lower priority */
         if ((env->sd->flags & SD_ASYM_PACKING) &&
             sched_asym_prefer(i, env->dst_cpu) &&
             nr_running == 1)
             continue;
 
         switch (env->migration_type) {
         case migrate_load:
             /*
              * When comparing with load imbalance, use cpu_load()
              * which is not scaled with the CPU capacity.
              */
             load = cpu_load(rq);
 
             if (nr_running == 1 && load > env->imbalance &&
                 !check_cpu_capacity(rq, env->sd))
                 break;
 
             /*
              * For the load comparisons with the other CPUs,
              * consider the cpu_load() scaled with the CPU
              * capacity, so that the load can be moved away
              * from the CPU that is potentially running at a
              * lower capacity.
              *
              * Thus we're looking for max(load_i / capacity_i),
              * crosswise multiplication to rid ourselves of the
              * division works out to:
              * load_i * capacity_j > load_j * capacity_i;
              * where j is our previous maximum.
              */
             if (load * busiest_capacity > busiest_load * capacity) {
                 busiest_load = load;
                 busiest_capacity = capacity;
                 busiest = rq;
             }
             break;
 
         case migrate_util:
             util = cpu_util_cfs(i);
 
             /*
              * Don't try to pull utilization from a CPU with one
              * running task. Whatever its utilization, we will fail
              * detach the task.
              */
             if (nr_running <= 1)
                 continue;
 
             if (busiest_util < util) {
                 busiest_util = util;
                 busiest = rq;
             }
             break;
 
         case migrate_task:
             if (busiest_nr < nr_running) {
                 busiest_nr = nr_running;
                 busiest = rq;
             }
             break;
 
         case migrate_misfit:
             /*
              * For ASYM_CPUCAPACITY domains with misfit tasks we
              * simply seek the "biggest" misfit task.
              */
             if (rq->misfit_task_load > busiest_load) {
                 busiest_load = rq->misfit_task_load;
                 busiest = rq;
             }
 
             break;
 
         }
     }
 
     return busiest;
 }
 
 /*
  * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
  * so long as it is large enough.
  */
 #define MAX_PINNED_INTERVAL 512
 
 static inline bool
 asym_active_balance(struct lb_env *env)
 {
     /*
      * ASYM_PACKING needs to force migrate tasks from busy but
      * lower priority CPUs in order to pack all tasks in the
      * highest priority CPUs.
      */
     return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
            sched_asym_prefer(env->dst_cpu, env->src_cpu);
 }
 
 static inline bool
 imbalanced_active_balance(struct lb_env *env)
 {
     struct sched_domain *sd = env->sd;
 
     /*
      * The imbalanced case includes the case of pinned tasks preventing a fair
      * distribution of the load on the system but also the even distribution of the
      * threads on a system with spare capacity
      */
     if ((env->migration_type == migrate_task) &&
         (sd->nr_balance_failed > sd->cache_nice_tries+2))
         return 1;
 
     return 0;
 }
 
 static int need_active_balance(struct lb_env *env)
 {
     struct sched_domain *sd = env->sd;
 
     if (asym_active_balance(env))
         return 1;
 
     if (imbalanced_active_balance(env))
         return 1;
 
     /*
      * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
      * It's worth migrating the task if the src_cpu's capacity is reduced
      * because of other sched_class or IRQs if more capacity stays
      * available on dst_cpu.
      */
     if ((env->idle != CPU_NOT_IDLE) &&
         (env->src_rq->cfs.h_nr_running == 1)) {
         if ((check_cpu_capacity(env->src_rq, sd)) &&
             (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
             return 1;
     }
 
     if (env->migration_type == migrate_misfit)
         return 1;
 
     return 0;
 }
 
 static int active_load_balance_cpu_stop(void *data);
 
 static int should_we_balance(struct lb_env *env)
 {
     struct sched_group *sg = env->sd->groups;
     int cpu;
 
     /*
      * Ensure the balancing environment is consistent; can happen
      * when the softirq triggers 'during' hotplug.
      */
     if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
         return 0;
 
     /*
      * In the newly idle case, we will allow all the CPUs
      * to do the newly idle load balance.
      *
      * However, we bail out if we already have tasks or a wakeup pending,
      * to optimize wakeup latency.
      */
     if (env->idle == CPU_NEWLY_IDLE) {
         if (env->dst_rq->nr_running > 0 || env->dst_rq->ttwu_pending)
             return 0;
         return 1;
     }
 
     /* Try to find first idle CPU */
     for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
         if (!idle_cpu(cpu))
             continue;
 
         /* Are we the first idle CPU? */
         return cpu == env->dst_cpu;
     }
 
     /* Are we the first CPU of this group ? */
     return group_balance_cpu(sg) == env->dst_cpu;
 }
 
 /*
  * Check this_cpu to ensure it is balanced within domain. Attempt to move
  * tasks if there is an imbalance.
  */
 static int load_balance(int this_cpu, struct rq *this_rq,
             struct sched_domain *sd, enum cpu_idle_type idle,
             int *continue_balancing)
 {
     int ld_moved, cur_ld_moved, active_balance = 0;
     struct sched_domain *sd_parent = sd->parent;
     struct sched_group *group;
     struct rq *busiest;
     struct rq_flags rf;
     struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
 
     struct lb_env env = {
         .sd     = sd,
         .dst_cpu    = this_cpu,
         .dst_rq     = this_rq,
         .dst_grpmask    = sched_group_span(sd->groups),
         .idle       = idle,
         .loop_break = sched_nr_migrate_break,
         .cpus       = cpus,
         .fbq_type   = all,
         .tasks      = LIST_HEAD_INIT(env.tasks),
     };
 
     cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
 
     schedstat_inc(sd->lb_count[idle]);
 
 redo:
     if (!should_we_balance(&env)) {
         *continue_balancing = 0;
         goto out_balanced;
     }
 
     group = find_busiest_group(&env);
     if (!group) {
         schedstat_inc(sd->lb_nobusyg[idle]);
         goto out_balanced;
     }
 
     busiest = find_busiest_queue(&env, group);
     if (!busiest) {
         schedstat_inc(sd->lb_nobusyq[idle]);
         goto out_balanced;
     }
 
     BUG_ON(busiest == env.dst_rq);
 
     schedstat_add(sd->lb_imbalance[idle], env.imbalance);
 
     env.src_cpu = busiest->cpu;
     env.src_rq = busiest;
 
     ld_moved = 0;
     /* Clear this flag as soon as we find a pullable task */
     env.flags |= LBF_ALL_PINNED;
     if (busiest->nr_running > 1) {
         /*
          * Attempt to move tasks. If find_busiest_group has found
          * an imbalance but busiest->nr_running <= 1, the group is
          * still unbalanced. ld_moved simply stays zero, so it is
          * correctly treated as an imbalance.
          */
         env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
 
 more_balance:
         rq_lock_irqsave(busiest, &rf);
         update_rq_clock(busiest);
 
         /*
          * cur_ld_moved - load moved in current iteration
          * ld_moved     - cumulative load moved across iterations
          */
         cur_ld_moved = detach_tasks(&env);
 
         /*
          * We've detached some tasks from busiest_rq. Every
          * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
          * unlock busiest->lock, and we are able to be sure
          * that nobody can manipulate the tasks in parallel.
          * See task_rq_lock() family for the details.
          */
 
         rq_unlock(busiest, &rf);
 
         if (cur_ld_moved) {
             attach_tasks(&env);
             ld_moved += cur_ld_moved;
         }
 
         local_irq_restore(rf.flags);
 
         if (env.flags & LBF_NEED_BREAK) {
             env.flags &= ~LBF_NEED_BREAK;
             goto more_balance;
         }
 
         /*
          * Revisit (affine) tasks on src_cpu that couldn't be moved to
          * us and move them to an alternate dst_cpu in our sched_group
          * where they can run. The upper limit on how many times we
          * iterate on same src_cpu is dependent on number of CPUs in our
          * sched_group.
          *
          * This changes load balance semantics a bit on who can move
          * load to a given_cpu. In addition to the given_cpu itself
          * (or a ilb_cpu acting on its behalf where given_cpu is
          * nohz-idle), we now have balance_cpu in a position to move
          * load to given_cpu. In rare situations, this may cause
          * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
          * _independently_ and at _same_ time to move some load to
          * given_cpu) causing excess load to be moved to given_cpu.
          * This however should not happen so much in practice and
          * moreover subsequent load balance cycles should correct the
          * excess load moved.
          */
         if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
 
             /* Prevent to re-select dst_cpu via env's CPUs */
             __cpumask_clear_cpu(env.dst_cpu, env.cpus);
 
             env.dst_rq   = cpu_rq(env.new_dst_cpu);
             env.dst_cpu  = env.new_dst_cpu;
             env.flags   &= ~LBF_DST_PINNED;
             env.loop     = 0;
             env.loop_break   = sched_nr_migrate_break;
 
             /*
              * Go back to "more_balance" rather than "redo" since we
              * need to continue with same src_cpu.
              */
             goto more_balance;
         }
 
         /*
          * We failed to reach balance because of affinity.
          */
         if (sd_parent) {
             int *group_imbalance = &sd_parent->groups->sgc->imbalance;
 
             if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
                 *group_imbalance = 1;
         }
 
         /* All tasks on this runqueue were pinned by CPU affinity */
         if (unlikely(env.flags & LBF_ALL_PINNED)) {
             __cpumask_clear_cpu(cpu_of(busiest), cpus);
             /*
              * Attempting to continue load balancing at the current
              * sched_domain level only makes sense if there are
              * active CPUs remaining as possible busiest CPUs to
              * pull load from which are not contained within the
              * destination group that is receiving any migrated
              * load.
              */
             if (!cpumask_subset(cpus, env.dst_grpmask)) {
                 env.loop = 0;
                 env.loop_break = sched_nr_migrate_break;
                 goto redo;
             }
             goto out_all_pinned;
         }
     }
 
     if (!ld_moved) {
         schedstat_inc(sd->lb_failed[idle]);
         /*
          * Increment the failure counter only on periodic balance.
          * We do not want newidle balance, which can be very
          * frequent, pollute the failure counter causing
          * excessive cache_hot migrations and active balances.
          */
         if (idle != CPU_NEWLY_IDLE)
             sd->nr_balance_failed++;
 
         if (need_active_balance(&env)) {
             unsigned long flags;
 
             raw_spin_rq_lock_irqsave(busiest, flags);
 
             /*
              * Don't kick the active_load_balance_cpu_stop,
              * if the curr task on busiest CPU can't be
              * moved to this_cpu:
              */
             if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
                 raw_spin_rq_unlock_irqrestore(busiest, flags);
                 goto out_one_pinned;
             }
 
             /* Record that we found at least one task that could run on this_cpu */
             env.flags &= ~LBF_ALL_PINNED;
 
             /*
              * ->active_balance synchronizes accesses to
              * ->active_balance_work.  Once set, it's cleared
              * only after active load balance is finished.
              */
             if (!busiest->active_balance) {
                 busiest->active_balance = 1;
                 busiest->push_cpu = this_cpu;
                 active_balance = 1;
             }
             raw_spin_rq_unlock_irqrestore(busiest, flags);
 
             if (active_balance) {
                 stop_one_cpu_nowait(cpu_of(busiest),
                     active_load_balance_cpu_stop, busiest,
                     &busiest->active_balance_work);
             }
         }
     } else {
         sd->nr_balance_failed = 0;
     }
 
     if (likely(!active_balance) || need_active_balance(&env)) {
         /* We were unbalanced, so reset the balancing interval */
         sd->balance_interval = sd->min_interval;
     }
 
     goto out;
 
 out_balanced:
     /*
      * We reach balance although we may have faced some affinity
      * constraints. Clear the imbalance flag only if other tasks got
      * a chance to move and fix the imbalance.
      */
     if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
         int *group_imbalance = &sd_parent->groups->sgc->imbalance;
 
         if (*group_imbalance)
             *group_imbalance = 0;
     }
 
 out_all_pinned:
     /*
      * We reach balance because all tasks are pinned at this level so
      * we can't migrate them. Let the imbalance flag set so parent level
      * can try to migrate them.
      */
     schedstat_inc(sd->lb_balanced[idle]);
 
     sd->nr_balance_failed = 0;
 
 out_one_pinned:
     ld_moved = 0;
 
     /*
      * newidle_balance() disregards balance intervals, so we could
      * repeatedly reach this code, which would lead to balance_interval
      * skyrocketing in a short amount of time. Skip the balance_interval
      * increase logic to avoid that.
      */
     if (env.idle == CPU_NEWLY_IDLE)
         goto out;
 
     /* tune up the balancing interval */
     if ((env.flags & LBF_ALL_PINNED &&
          sd->balance_interval < MAX_PINNED_INTERVAL) ||
         sd->balance_interval < sd->max_interval)
         sd->balance_interval *= 2;
 out:
     return ld_moved;
 }
 
 static inline unsigned long
 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
 {
     unsigned long interval = sd->balance_interval;
 
     if (cpu_busy)
         interval *= sd->busy_factor;
 
     /* scale ms to jiffies */
     interval = msecs_to_jiffies(interval);
 
     /*
      * Reduce likelihood of busy balancing at higher domains racing with
      * balancing at lower domains by preventing their balancing periods
      * from being multiples of each other.
      */
     if (cpu_busy)
         interval -= 1;
 
     interval = clamp(interval, 1UL, max_load_balance_interval);
 
     return interval;
 }
 
 static inline void
 update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
 {
     unsigned long interval, next;
 
     /* used by idle balance, so cpu_busy = 0 */
     interval = get_sd_balance_interval(sd, 0);
     next = sd->last_balance + interval;
 
     if (time_after(*next_balance, next))
         *next_balance = next;
 }
 
 /*
  * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
  * running tasks off the busiest CPU onto idle CPUs. It requires at
  * least 1 task to be running on each physical CPU where possible, and
  * avoids physical / logical imbalances.
  */
 static int active_load_balance_cpu_stop(void *data)
 {
     struct rq *busiest_rq = data;
     int busiest_cpu = cpu_of(busiest_rq);
     int target_cpu = busiest_rq->push_cpu;
     struct rq *target_rq = cpu_rq(target_cpu);
     struct sched_domain *sd;
     struct task_struct *p = NULL;
     struct rq_flags rf;
 
     rq_lock_irq(busiest_rq, &rf);
     /*
      * Between queueing the stop-work and running it is a hole in which
      * CPUs can become inactive. We should not move tasks from or to
      * inactive CPUs.
      */
     if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
         goto out_unlock;
 
     /* Make sure the requested CPU hasn't gone down in the meantime: */
     if (unlikely(busiest_cpu != smp_processor_id() ||
              !busiest_rq->active_balance))
         goto out_unlock;
 
     /* Is there any task to move? */
     if (busiest_rq->nr_running <= 1)
         goto out_unlock;
 
     /*
      * This condition is "impossible", if it occurs
      * we need to fix it. Originally reported by
      * Bjorn Helgaas on a 128-CPU setup.
      */
     BUG_ON(busiest_rq == target_rq);
 
     /* Search for an sd spanning us and the target CPU. */
     rcu_read_lock();
     for_each_domain(target_cpu, sd) {
         if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
             break;
     }
 
     if (likely(sd)) {
         struct lb_env env = {
             .sd     = sd,
             .dst_cpu    = target_cpu,
             .dst_rq     = target_rq,
             .src_cpu    = busiest_rq->cpu,
             .src_rq     = busiest_rq,
             .idle       = CPU_IDLE,
             .flags      = LBF_ACTIVE_LB,
         };
 
         schedstat_inc(sd->alb_count);
         update_rq_clock(busiest_rq);
 
         p = detach_one_task(&env);
         if (p) {
             schedstat_inc(sd->alb_pushed);
             /* Active balancing done, reset the failure counter. */
             sd->nr_balance_failed = 0;
         } else {
             schedstat_inc(sd->alb_failed);
         }
     }
     rcu_read_unlock();
 out_unlock:
     busiest_rq->active_balance = 0;
     rq_unlock(busiest_rq, &rf);
 
     if (p)
         attach_one_task(target_rq, p);
 
     local_irq_enable();
 
     return 0;
 }
 
 static DEFINE_SPINLOCK(balancing);
 
 /*
  * Scale the max load_balance interval with the number of CPUs in the system.
  * This trades load-balance latency on larger machines for less cross talk.
  */
 void update_max_interval(void)
 {
     max_load_balance_interval = HZ*num_online_cpus()/10;
 }
 
 static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost)
 {
     if (cost > sd->max_newidle_lb_cost) {
         /*
          * Track max cost of a domain to make sure to not delay the
          * next wakeup on the CPU.
          */
         sd->max_newidle_lb_cost = cost;
         sd->last_decay_max_lb_cost = jiffies;
     } else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) {
         /*
          * Decay the newidle max times by ~1% per second to ensure that
          * it is not outdated and the current max cost is actually
          * shorter.
          */
         sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256;
         sd->last_decay_max_lb_cost = jiffies;
 
         return true;
     }
 
     return false;
 }
 
 /*
  * It checks each scheduling domain to see if it is due to be balanced,
  * and initiates a balancing operation if so.
  *
  * Balancing parameters are set up in init_sched_domains.
  */
 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
 {
     int continue_balancing = 1;
     int cpu = rq->cpu;
     int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
     unsigned long interval;
     struct sched_domain *sd;
     /* Earliest time when we have to do rebalance again */
     unsigned long next_balance = jiffies + 60*HZ;
     int update_next_balance = 0;
     int need_serialize, need_decay = 0;
     u64 max_cost = 0;
 
     rcu_read_lock();
     for_each_domain(cpu, sd) {
         /*
          * Decay the newidle max times here because this is a regular
          * visit to all the domains.
          */
         need_decay = update_newidle_cost(sd, 0);
         max_cost += sd->max_newidle_lb_cost;
 
         /*
          * Stop the load balance at this level. There is another
          * CPU in our sched group which is doing load balancing more
          * actively.
          */
         if (!continue_balancing) {
             if (need_decay)
                 continue;
             break;
         }
 
         interval = get_sd_balance_interval(sd, busy);
 
         need_serialize = sd->flags & SD_SERIALIZE;
         if (need_serialize) {
             if (!spin_trylock(&balancing))
                 goto out;
         }
 
         if (time_after_eq(jiffies, sd->last_balance + interval)) {
             if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
                 /*
                  * The LBF_DST_PINNED logic could have changed
                  * env->dst_cpu, so we can't know our idle
                  * state even if we migrated tasks. Update it.
                  */
                 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
                 busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
             }
             sd->last_balance = jiffies;
             interval = get_sd_balance_interval(sd, busy);
         }
         if (need_serialize)
             spin_unlock(&balancing);
 out:
         if (time_after(next_balance, sd->last_balance + interval)) {
             next_balance = sd->last_balance + interval;
             update_next_balance = 1;
         }
     }
     if (need_decay) {
         /*
          * Ensure the rq-wide value also decays but keep it at a
          * reasonable floor to avoid funnies with rq->avg_idle.
          */
         rq->max_idle_balance_cost =
             max((u64)sysctl_sched_migration_cost, max_cost);
     }
     rcu_read_unlock();
 
     /*
      * next_balance will be updated only when there is a need.
      * When the cpu is attached to null domain for ex, it will not be
      * updated.
      */
     if (likely(update_next_balance))
         rq->next_balance = next_balance;
 
 }
 
 static inline int on_null_domain(struct rq *rq)
 {
     return unlikely(!rcu_dereference_sched(rq->sd));
 }
 
 #ifdef CONFIG_NO_HZ_COMMON
 /*
  * idle load balancing details
  * - When one of the busy CPUs notice that there may be an idle rebalancing
  *   needed, they will kick the idle load balancer, which then does idle
  *   load balancing for all the idle CPUs.
  * - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED not set
  *   anywhere yet.
  */
 
 static inline int find_new_ilb(void)
 {
     int ilb;
     const struct cpumask *hk_mask;
 
     hk_mask = housekeeping_cpumask(HK_TYPE_MISC);
 
     for_each_cpu_and(ilb, nohz.idle_cpus_mask, hk_mask) {
 
         if (ilb == smp_processor_id())
             continue;
 
         if (idle_cpu(ilb))
             return ilb;
     }
 
     return nr_cpu_ids;
 }
 
 /*
  * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
  * idle CPU in the HK_TYPE_MISC housekeeping set (if there is one).
  */
 static void kick_ilb(unsigned int flags)
 {
     int ilb_cpu;
 
     /*
      * Increase nohz.next_balance only when if full ilb is triggered but
      * not if we only update stats.
      */
     if (flags & NOHZ_BALANCE_KICK)
         nohz.next_balance = jiffies+1;
 
     ilb_cpu = find_new_ilb();
 
     if (ilb_cpu >= nr_cpu_ids)
         return;
 
     /*
      * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
      * the first flag owns it; cleared by nohz_csd_func().
      */
     flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
     if (flags & NOHZ_KICK_MASK)
         return;
 
     /*
      * This way we generate an IPI on the target CPU which
      * is idle. And the softirq performing nohz idle load balance
      * will be run before returning from the IPI.
      */
     smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
 }
 
 /*
  * Current decision point for kicking the idle load balancer in the presence
  * of idle CPUs in the system.
  */
 static void nohz_balancer_kick(struct rq *rq)
 {
     unsigned long now = jiffies;
     struct sched_domain_shared *sds;
     struct sched_domain *sd;
     int nr_busy, i, cpu = rq->cpu;
     unsigned int flags = 0;
 
     if (unlikely(rq->idle_balance))
         return;
 
     /*
      * We may be recently in ticked or tickless idle mode. At the first
      * busy tick after returning from idle, we will update the busy stats.
      */
     nohz_balance_exit_idle(rq);
 
     /*
      * None are in tickless mode and hence no need for NOHZ idle load
      * balancing.
      */
     if (likely(!atomic_read(&nohz.nr_cpus)))
         return;
 
     if (READ_ONCE(nohz.has_blocked) &&
         time_after(now, READ_ONCE(nohz.next_blocked)))
         flags = NOHZ_STATS_KICK;
 
     if (time_before(now, nohz.next_balance))
         goto out;
 
     if (rq->nr_running >= 2) {
         flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
         goto out;
     }
 
     rcu_read_lock();
 
     sd = rcu_dereference(rq->sd);
     if (sd) {
         /*
          * If there's a CFS task and the current CPU has reduced
          * capacity; kick the ILB to see if there's a better CPU to run
          * on.
          */
         if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
             flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
             goto unlock;
         }
     }
 
     sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
     if (sd) {
         /*
          * When ASYM_PACKING; see if there's a more preferred CPU
          * currently idle; in which case, kick the ILB to move tasks
          * around.
          */
         for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
             if (sched_asym_prefer(i, cpu)) {
                 flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
                 goto unlock;
             }
         }
     }
 
     sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
     if (sd) {
         /*
          * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
          * to run the misfit task on.
          */
         if (check_misfit_status(rq, sd)) {
             flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
             goto unlock;
         }
 
         /*
          * For asymmetric systems, we do not want to nicely balance
          * cache use, instead we want to embrace asymmetry and only
          * ensure tasks have enough CPU capacity.
          *
          * Skip the LLC logic because it's not relevant in that case.
          */
         goto unlock;
     }
 
     sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
     if (sds) {
         /*
          * If there is an imbalance between LLC domains (IOW we could
          * increase the overall cache use), we need some less-loaded LLC
          * domain to pull some load. Likewise, we may need to spread
          * load within the current LLC domain (e.g. packed SMT cores but
          * other CPUs are idle). We can't really know from here how busy
          * the others are - so just get a nohz balance going if it looks
          * like this LLC domain has tasks we could move.
          */
         nr_busy = atomic_read(&sds->nr_busy_cpus);
         if (nr_busy > 1) {
             flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
             goto unlock;
         }
     }
 unlock:
     rcu_read_unlock();
 out:
     if (READ_ONCE(nohz.needs_update))
         flags |= NOHZ_NEXT_KICK;
 
     if (flags)
         kick_ilb(flags);
 }
 
 static void set_cpu_sd_state_busy(int cpu)
 {
     struct sched_domain *sd;
 
     rcu_read_lock();
     sd = rcu_dereference(per_cpu(sd_llc, cpu));
 
     if (!sd || !sd->nohz_idle)
         goto unlock;
     sd->nohz_idle = 0;
 
     atomic_inc(&sd->shared->nr_busy_cpus);
 unlock:
     rcu_read_unlock();
 }
 
 void nohz_balance_exit_idle(struct rq *rq)
 {
     SCHED_WARN_ON(rq != this_rq());
 
     if (likely(!rq->nohz_tick_stopped))
         return;
 
     rq->nohz_tick_stopped = 0;
     cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
     atomic_dec(&nohz.nr_cpus);
 
     set_cpu_sd_state_busy(rq->cpu);
 }
 
 static void set_cpu_sd_state_idle(int cpu)
 {
     struct sched_domain *sd;
 
     rcu_read_lock();
     sd = rcu_dereference(per_cpu(sd_llc, cpu));
 
     if (!sd || sd->nohz_idle)
         goto unlock;
     sd->nohz_idle = 1;
 
     atomic_dec(&sd->shared->nr_busy_cpus);
 unlock:
     rcu_read_unlock();
 }
 
 /*
  * This routine will record that the CPU is going idle with tick stopped.
  * This info will be used in performing idle load balancing in the future.
  */
 void nohz_balance_enter_idle(int cpu)
 {
     struct rq *rq = cpu_rq(cpu);
 
     SCHED_WARN_ON(cpu != smp_processor_id());
 
     /* If this CPU is going down, then nothing needs to be done: */
     if (!cpu_active(cpu))
         return;
 
     /* Spare idle load balancing on CPUs that don't want to be disturbed: */
     if (!housekeeping_cpu(cpu, HK_TYPE_SCHED))
         return;
 
     /*
      * Can be set safely without rq->lock held
      * If a clear happens, it will have evaluated last additions because
      * rq->lock is held during the check and the clear
      */
     rq->has_blocked_load = 1;
 
     /*
      * The tick is still stopped but load could have been added in the
      * meantime. We set the nohz.has_blocked flag to trig a check of the
      * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
      * of nohz.has_blocked can only happen after checking the new load
      */
     if (rq->nohz_tick_stopped)
         goto out;
 
     /* If we're a completely isolated CPU, we don't play: */
     if (on_null_domain(rq))
         return;
 
     rq->nohz_tick_stopped = 1;
 
     cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
     atomic_inc(&nohz.nr_cpus);
 
     /*
      * Ensures that if nohz_idle_balance() fails to observe our
      * @idle_cpus_mask store, it must observe the @has_blocked
      * and @needs_update stores.
      */
     smp_mb__after_atomic();
 
     set_cpu_sd_state_idle(cpu);
 
     WRITE_ONCE(nohz.needs_update, 1);
 out:
     /*
      * Each time a cpu enter idle, we assume that it has blocked load and
      * enable the periodic update of the load of idle cpus
      */
     WRITE_ONCE(nohz.has_blocked, 1);
 }
 
 static bool update_nohz_stats(struct rq *rq)
 {
     unsigned int cpu = rq->cpu;
 
     if (!rq->has_blocked_load)
         return false;
 
     if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
         return false;
 
     if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
         return true;
 
     update_blocked_averages(cpu);
 
     return rq->has_blocked_load;
 }
 
 /*
  * Internal function that runs load balance for all idle cpus. The load balance
  * can be a simple update of blocked load or a complete load balance with
  * tasks movement depending of flags.
  */
 static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
                    enum cpu_idle_type idle)
 {
     /* Earliest time when we have to do rebalance again */
     unsigned long now = jiffies;
     unsigned long next_balance = now + 60*HZ;
     bool has_blocked_load = false;
     int update_next_balance = 0;
     int this_cpu = this_rq->cpu;
     int balance_cpu;
     struct rq *rq;
 
     SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
 
     /*
      * We assume there will be no idle load after this update and clear
      * the has_blocked flag. If a cpu enters idle in the mean time, it will
      * set the has_blocked flag and trigger another update of idle load.
      * Because a cpu that becomes idle, is added to idle_cpus_mask before
      * setting the flag, we are sure to not clear the state and not
      * check the load of an idle cpu.
      *
      * Same applies to idle_cpus_mask vs needs_update.
      */
     if (flags & NOHZ_STATS_KICK)
         WRITE_ONCE(nohz.has_blocked, 0);
     if (flags & NOHZ_NEXT_KICK)
         WRITE_ONCE(nohz.needs_update, 0);
 
     /*
      * Ensures that if we miss the CPU, we must see the has_blocked
      * store from nohz_balance_enter_idle().
      */
     smp_mb();
 
     /*
      * Start with the next CPU after this_cpu so we will end with this_cpu and let a
      * chance for other idle cpu to pull load.
      */
     for_each_cpu_wrap(balance_cpu,  nohz.idle_cpus_mask, this_cpu+1) {
         if (!idle_cpu(balance_cpu))
             continue;
 
         /*
          * If this CPU gets work to do, stop the load balancing
          * work being done for other CPUs. Next load
          * balancing owner will pick it up.
          */
         if (need_resched()) {
             if (flags & NOHZ_STATS_KICK)
                 has_blocked_load = true;
             if (flags & NOHZ_NEXT_KICK)
                 WRITE_ONCE(nohz.needs_update, 1);
             goto abort;
         }
 
         rq = cpu_rq(balance_cpu);
 
         if (flags & NOHZ_STATS_KICK)
             has_blocked_load |= update_nohz_stats(rq);
 
         /*
          * If time for next balance is due,
          * do the balance.
          */
         if (time_after_eq(jiffies, rq->next_balance)) {
             struct rq_flags rf;
 
             rq_lock_irqsave(rq, &rf);
             update_rq_clock(rq);
             rq_unlock_irqrestore(rq, &rf);
 
             if (flags & NOHZ_BALANCE_KICK)
                 rebalance_domains(rq, CPU_IDLE);
         }
 
         if (time_after(next_balance, rq->next_balance)) {
             next_balance = rq->next_balance;
             update_next_balance = 1;
         }
     }
 
     /*
      * next_balance will be updated only when there is a need.
      * When the CPU is attached to null domain for ex, it will not be
      * updated.
      */
     if (likely(update_next_balance))
         nohz.next_balance = next_balance;
 
     if (flags & NOHZ_STATS_KICK)
         WRITE_ONCE(nohz.next_blocked,
                now + msecs_to_jiffies(LOAD_AVG_PERIOD));
 
 abort:
     /* There is still blocked load, enable periodic update */
     if (has_blocked_load)
         WRITE_ONCE(nohz.has_blocked, 1);
 }
 
 /*
  * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
  * rebalancing for all the cpus for whom scheduler ticks are stopped.
  */
 static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
 {
     unsigned int flags = this_rq->nohz_idle_balance;
 
     if (!flags)
         return false;
 
     this_rq->nohz_idle_balance = 0;
 
     if (idle != CPU_IDLE)
         return false;
 
     _nohz_idle_balance(this_rq, flags, idle);
 
     return true;
 }
 
 /*
  * Check if we need to run the ILB for updating blocked load before entering
  * idle state.
  */
 void nohz_run_idle_balance(int cpu)
 {
     unsigned int flags;
 
     flags = atomic_fetch_andnot(NOHZ_NEWILB_KICK, nohz_flags(cpu));
 
     /*
      * Update the blocked load only if no SCHED_SOFTIRQ is about to happen
      * (ie NOHZ_STATS_KICK set) and will do the same.
      */
     if ((flags == NOHZ_NEWILB_KICK) && !need_resched())
         _nohz_idle_balance(cpu_rq(cpu), NOHZ_STATS_KICK, CPU_IDLE);
 }
 
 static void nohz_newidle_balance(struct rq *this_rq)
 {
     int this_cpu = this_rq->cpu;
 
     /*
      * This CPU doesn't want to be disturbed by scheduler
      * housekeeping
      */
     if (!housekeeping_cpu(this_cpu, HK_TYPE_SCHED))
         return;
 
     /* Will wake up very soon. No time for doing anything else*/
     if (this_rq->avg_idle < sysctl_sched_migration_cost)
         return;
 
     /* Don't need to update blocked load of idle CPUs*/
     if (!READ_ONCE(nohz.has_blocked) ||
         time_before(jiffies, READ_ONCE(nohz.next_blocked)))
         return;
 
     /*
      * Set the need to trigger ILB in order to update blocked load
      * before entering idle state.
      */
     atomic_or(NOHZ_NEWILB_KICK, nohz_flags(this_cpu));
 }
 
 #else /* !CONFIG_NO_HZ_COMMON */
 static inline void nohz_balancer_kick(struct rq *rq) { }
 
 static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
 {
     return false;
 }
 
 static inline void nohz_newidle_balance(struct rq *this_rq) { }
 #endif /* CONFIG_NO_HZ_COMMON */
 
 /*
  * newidle_balance is called by schedule() if this_cpu is about to become
  * idle. Attempts to pull tasks from other CPUs.
  *
  * Returns:
  *   < 0 - we released the lock and there are !fair tasks present
  *     0 - failed, no new tasks
  *   > 0 - success, new (fair) tasks present
  */
 static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
 {
     unsigned long next_balance = jiffies + HZ;
     int this_cpu = this_rq->cpu;
     u64 t0, t1, curr_cost = 0;
     struct sched_domain *sd;
     int pulled_task = 0;
 
     update_misfit_status(NULL, this_rq);
 
     /*
      * There is a task waiting to run. No need to search for one.
      * Return 0; the task will be enqueued when switching to idle.
      */
     if (this_rq->ttwu_pending)
         return 0;
 
     /*
      * We must set idle_stamp _before_ calling idle_balance(), such that we
      * measure the duration of idle_balance() as idle time.
      */
     this_rq->idle_stamp = rq_clock(this_rq);
 
     /*
      * Do not pull tasks towards !active CPUs...
      */
     if (!cpu_active(this_cpu))
         return 0;
 
     /*
      * This is OK, because current is on_cpu, which avoids it being picked
      * for load-balance and preemption/IRQs are still disabled avoiding
      * further scheduler activity on it and we're being very careful to
      * re-start the picking loop.
      */
     rq_unpin_lock(this_rq, rf);
 
     rcu_read_lock();
     sd = rcu_dereference_check_sched_domain(this_rq->sd);
 
     if (!READ_ONCE(this_rq->rd->overload) ||
         (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
 
         if (sd)
             update_next_balance(sd, &next_balance);
         rcu_read_unlock();
 
         goto out;
     }
     rcu_read_unlock();
 
     raw_spin_rq_unlock(this_rq);
 
     t0 = sched_clock_cpu(this_cpu);
     update_blocked_averages(this_cpu);
 
     rcu_read_lock();
     for_each_domain(this_cpu, sd) {
         int continue_balancing = 1;
         u64 domain_cost;
 
         update_next_balance(sd, &next_balance);
 
         if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
             break;
 
         if (sd->flags & SD_BALANCE_NEWIDLE) {
 
             pulled_task = load_balance(this_cpu, this_rq,
                            sd, CPU_NEWLY_IDLE,
                            &continue_balancing);
 
             t1 = sched_clock_cpu(this_cpu);
             domain_cost = t1 - t0;
             update_newidle_cost(sd, domain_cost);
 
             curr_cost += domain_cost;
             t0 = t1;
         }
 
         /*
          * Stop searching for tasks to pull if there are
          * now runnable tasks on this rq.
          */
         if (pulled_task || this_rq->nr_running > 0 ||
             this_rq->ttwu_pending)
             break;
     }
     rcu_read_unlock();
 
     raw_spin_rq_lock(this_rq);
 
     if (curr_cost > this_rq->max_idle_balance_cost)
         this_rq->max_idle_balance_cost = curr_cost;
 
     /*
      * While browsing the domains, we released the rq lock, a task could
      * have been enqueued in the meantime. Since we're not going idle,
      * pretend we pulled a task.
      */
     if (this_rq->cfs.h_nr_running && !pulled_task)
         pulled_task = 1;
 
     /* Is there a task of a high priority class? */
     if (this_rq->nr_running != this_rq->cfs.h_nr_running)
         pulled_task = -1;
 
 out:
     /* Move the next balance forward */
     if (time_after(this_rq->next_balance, next_balance))
         this_rq->next_balance = next_balance;
 
     if (pulled_task)
         this_rq->idle_stamp = 0;
     else
         nohz_newidle_balance(this_rq);
 
     rq_repin_lock(this_rq, rf);
 
     return pulled_task;
 }
 
 /*
  * run_rebalance_domains is triggered when needed from the scheduler tick.
  * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
  */
 static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
 {
     struct rq *this_rq = this_rq();
     enum cpu_idle_type idle = this_rq->idle_balance ?
                         CPU_IDLE : CPU_NOT_IDLE;
 
     /*
      * If this CPU has a pending nohz_balance_kick, then do the
      * balancing on behalf of the other idle CPUs whose ticks are
      * stopped. Do nohz_idle_balance *before* rebalance_domains to
      * give the idle CPUs a chance to load balance. Else we may
      * load balance only within the local sched_domain hierarchy
      * and abort nohz_idle_balance altogether if we pull some load.
      */
     if (nohz_idle_balance(this_rq, idle))
         return;
 
     /* normal load balance */
     update_blocked_averages(this_rq->cpu);
     rebalance_domains(this_rq, idle);
 }
 
 /*
  * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
  */
 void trigger_load_balance(struct rq *rq)
 {
     /*
      * Don't need to rebalance while attached to NULL domain or
      * runqueue CPU is not active
      */
     if (unlikely(on_null_domain(rq) || !cpu_active(cpu_of(rq))))
         return;
 
     if (time_after_eq(jiffies, rq->next_balance))
         raise_softirq(SCHED_SOFTIRQ);
 
     nohz_balancer_kick(rq);
 }
 
 static void rq_online_fair(struct rq *rq)
 {
     update_sysctl();
 
     update_runtime_enabled(rq);
 }
 
 static void rq_offline_fair(struct rq *rq)
 {
     update_sysctl();
 
     /* Ensure any throttled groups are reachable by pick_next_task */
     unthrottle_offline_cfs_rqs(rq);
 }
 
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_SCHED_CORE
 static inline bool
 __entity_slice_used(struct sched_entity *se, int min_nr_tasks)
 {
     u64 slice = sched_slice(cfs_rq_of(se), se);
     u64 rtime = se->sum_exec_runtime - se->prev_sum_exec_runtime;
 
     return (rtime * min_nr_tasks > slice);
 }
 
 #define MIN_NR_TASKS_DURING_FORCEIDLE   2
 static inline void task_tick_core(struct rq *rq, struct task_struct *curr)
 {
     if (!sched_core_enabled(rq))
         return;
 
     /*
      * If runqueue has only one task which used up its slice and
      * if the sibling is forced idle, then trigger schedule to
      * give forced idle task a chance.
      *
      * sched_slice() considers only this active rq and it gets the
      * whole slice. But during force idle, we have siblings acting
      * like a single runqueue and hence we need to consider runnable
      * tasks on this CPU and the forced idle CPU. Ideally, we should
      * go through the forced idle rq, but that would be a perf hit.
      * We can assume that the forced idle CPU has at least
      * MIN_NR_TASKS_DURING_FORCEIDLE - 1 tasks and use that to check
      * if we need to give up the CPU.
      */
     if (rq->core->core_forceidle_count && rq->cfs.nr_running == 1 &&
         __entity_slice_used(&curr->se, MIN_NR_TASKS_DURING_FORCEIDLE))
         resched_curr(rq);
 }
 
 /*
  * se_fi_update - Update the cfs_rq->min_vruntime_fi in a CFS hierarchy if needed.
  */
 static void se_fi_update(struct sched_entity *se, unsigned int fi_seq, bool forceidle)
 {
     for_each_sched_entity(se) {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
         if (forceidle) {
             if (cfs_rq->forceidle_seq == fi_seq)
                 break;
             cfs_rq->forceidle_seq = fi_seq;
         }
 
         cfs_rq->min_vruntime_fi = cfs_rq->min_vruntime;
     }
 }
 
 void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi)
 {
     struct sched_entity *se = &p->se;
 
     if (p->sched_class != &fair_sched_class)
         return;
 
     se_fi_update(se, rq->core->core_forceidle_seq, in_fi);
 }
 
 bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool in_fi)
 {
     struct rq *rq = task_rq(a);
     struct sched_entity *sea = &a->se;
     struct sched_entity *seb = &b->se;
     struct cfs_rq *cfs_rqa;
     struct cfs_rq *cfs_rqb;
     s64 delta;
 
     SCHED_WARN_ON(task_rq(b)->core != rq->core);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
     /*
      * Find an se in the hierarchy for tasks a and b, such that the se's
      * are immediate siblings.
      */
     while (sea->cfs_rq->tg != seb->cfs_rq->tg) {
         int sea_depth = sea->depth;
         int seb_depth = seb->depth;
 
         if (sea_depth >= seb_depth)
             sea = parent_entity(sea);
         if (sea_depth <= seb_depth)
             seb = parent_entity(seb);
     }
 
     se_fi_update(sea, rq->core->core_forceidle_seq, in_fi);
     se_fi_update(seb, rq->core->core_forceidle_seq, in_fi);
 
     cfs_rqa = sea->cfs_rq;
     cfs_rqb = seb->cfs_rq;
 #else
     cfs_rqa = &task_rq(a)->cfs;
     cfs_rqb = &task_rq(b)->cfs;
 #endif
 
     /*
      * Find delta after normalizing se's vruntime with its cfs_rq's
      * min_vruntime_fi, which would have been updated in prior calls
      * to se_fi_update().
      */
     delta = (s64)(sea->vruntime - seb->vruntime) +
         (s64)(cfs_rqb->min_vruntime_fi - cfs_rqa->min_vruntime_fi);
 
     return delta > 0;
 }
 #else
 static inline void task_tick_core(struct rq *rq, struct task_struct *curr) {}
 #endif
 
 /*
  * scheduler tick hitting a task of our scheduling class.
  *
  * NOTE: This function can be called remotely by the tick offload that
  * goes along full dynticks. Therefore no local assumption can be made
  * and everything must be accessed through the @rq and @curr passed in
  * parameters.
  */
 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
 {
     struct cfs_rq *cfs_rq;
     struct sched_entity *se = &curr->se;
 
     for_each_sched_entity(se) {
         cfs_rq = cfs_rq_of(se);
         entity_tick(cfs_rq, se, queued);
     }
 
     if (static_branch_unlikely(&sched_numa_balancing))
         task_tick_numa(rq, curr);
 
     update_misfit_status(curr, rq);
     update_overutilized_status(task_rq(curr));
 
     task_tick_core(rq, curr);
 }
 
 /*
  * called on fork with the child task as argument from the parent's context
  *  - child not yet on the tasklist
  *  - preemption disabled
  */
 static void task_fork_fair(struct task_struct *p)
 {
     struct cfs_rq *cfs_rq;
     struct sched_entity *se = &p->se, *curr;
     struct rq *rq = this_rq();
     struct rq_flags rf;
 
     rq_lock(rq, &rf);
     update_rq_clock(rq);
 
     cfs_rq = task_cfs_rq(current);
     curr = cfs_rq->curr;
     if (curr) {
         update_curr(cfs_rq);
         se->vruntime = curr->vruntime;
     }
     place_entity(cfs_rq, se, 1);
 
     if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
         /*
          * Upon rescheduling, sched_class::put_prev_task() will place
          * 'current' within the tree based on its new key value.
          */
         swap(curr->vruntime, se->vruntime);
         resched_curr(rq);
     }
 
     se->vruntime -= cfs_rq->min_vruntime;
     rq_unlock(rq, &rf);
 }
 
 /*
  * Priority of the task has changed. Check to see if we preempt
  * the current task.
  */
 static void
 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
 {
     if (!task_on_rq_queued(p))
         return;
 
     if (rq->cfs.nr_running == 1)
         return;
 
     /*
      * Reschedule if we are currently running on this runqueue and
      * our priority decreased, or if we are not currently running on
      * this runqueue and our priority is higher than the current's
      */
     if (task_current(rq, p)) {
         if (p->prio > oldprio)
             resched_curr(rq);
     } else
         check_preempt_curr(rq, p, 0);
 }
 
 static inline bool vruntime_normalized(struct task_struct *p)
 {
     struct sched_entity *se = &p->se;
 
     /*
      * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
      * the dequeue_entity(.flags=0) will already have normalized the
      * vruntime.
      */
     if (p->on_rq)
         return true;
 
     /*
      * When !on_rq, vruntime of the task has usually NOT been normalized.
      * But there are some cases where it has already been normalized:
      *
      * - A forked child which is waiting for being woken up by
      *   wake_up_new_task().
      * - A task which has been woken up by try_to_wake_up() and
      *   waiting for actually being woken up by sched_ttwu_pending().
      */
     if (!se->sum_exec_runtime ||
         (READ_ONCE(p->__state) == TASK_WAKING && p->sched_remote_wakeup))
         return true;
 
     return false;
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 /*
  * Propagate the changes of the sched_entity across the tg tree to make it
  * visible to the root
  */
 static void propagate_entity_cfs_rq(struct sched_entity *se)
 {
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
     if (cfs_rq_throttled(cfs_rq))
         return;
 
     if (!throttled_hierarchy(cfs_rq))
         list_add_leaf_cfs_rq(cfs_rq);
 
     /* Start to propagate at parent */
     se = se->parent;
 
     for_each_sched_entity(se) {
         cfs_rq = cfs_rq_of(se);
 
         update_load_avg(cfs_rq, se, UPDATE_TG);
 
         if (cfs_rq_throttled(cfs_rq))
             break;
 
         if (!throttled_hierarchy(cfs_rq))
             list_add_leaf_cfs_rq(cfs_rq);
     }
 }
 #else
 static void propagate_entity_cfs_rq(struct sched_entity *se) { }
 #endif
 
 static void detach_entity_cfs_rq(struct sched_entity *se)
 {
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
     /* Catch up with the cfs_rq and remove our load when we leave */
     update_load_avg(cfs_rq, se, 0);
     detach_entity_load_avg(cfs_rq, se);
     update_tg_load_avg(cfs_rq);
     propagate_entity_cfs_rq(se);
 }
 
 static void attach_entity_cfs_rq(struct sched_entity *se)
 {
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
     /*
      * Since the real-depth could have been changed (only FAIR
      * class maintain depth value), reset depth properly.
      */
     se->depth = se->parent ? se->parent->depth + 1 : 0;
 #endif
 
     /* Synchronize entity with its cfs_rq */
     update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
     attach_entity_load_avg(cfs_rq, se);
     update_tg_load_avg(cfs_rq);
     propagate_entity_cfs_rq(se);
 }
 
 static void detach_task_cfs_rq(struct task_struct *p)
 {
     struct sched_entity *se = &p->se;
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
     if (!vruntime_normalized(p)) {
         /*
          * Fix up our vruntime so that the current sleep doesn't
          * cause 'unlimited' sleep bonus.
          */
         place_entity(cfs_rq, se, 0);
         se->vruntime -= cfs_rq->min_vruntime;
     }
 
     detach_entity_cfs_rq(se);
 }
 
 static void attach_task_cfs_rq(struct task_struct *p)
 {
     struct sched_entity *se = &p->se;
     struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
     attach_entity_cfs_rq(se);
 
     if (!vruntime_normalized(p))
         se->vruntime += cfs_rq->min_vruntime;
 }
 
 static void switched_from_fair(struct rq *rq, struct task_struct *p)
 {
     detach_task_cfs_rq(p);
 }
 
 static void switched_to_fair(struct rq *rq, struct task_struct *p)
 {
     attach_task_cfs_rq(p);
 
     if (task_on_rq_queued(p)) {
         /*
          * We were most likely switched from sched_rt, so
          * kick off the schedule if running, otherwise just see
          * if we can still preempt the current task.
          */
         if (task_current(rq, p))
             resched_curr(rq);
         else
             check_preempt_curr(rq, p, 0);
     }
 }
 
 /* Account for a task changing its policy or group.
  *
  * This routine is mostly called to set cfs_rq->curr field when a task
  * migrates between groups/classes.
  */
 static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
 {
     struct sched_entity *se = &p->se;
 
 #ifdef CONFIG_SMP
     if (task_on_rq_queued(p)) {
         /*
          * Move the next running task to the front of the list, so our
          * cfs_tasks list becomes MRU one.
          */
         list_move(&se->group_node, &rq->cfs_tasks);
     }
 #endif
 
     for_each_sched_entity(se) {
         struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
         set_next_entity(cfs_rq, se);
         /* ensure bandwidth has been allocated on our new cfs_rq */
         account_cfs_rq_runtime(cfs_rq, 0);
     }
 }
 
 void init_cfs_rq(struct cfs_rq *cfs_rq)
 {
     cfs_rq->tasks_timeline = RB_ROOT_CACHED;
     u64_u32_store(cfs_rq->min_vruntime, (u64)(-(1LL << 20)));
 #ifdef CONFIG_SMP
     raw_spin_lock_init(&cfs_rq->removed.lock);
 #endif
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void task_set_group_fair(struct task_struct *p)
 {
     struct sched_entity *se = &p->se;
 
     set_task_rq(p, task_cpu(p));
     se->depth = se->parent ? se->parent->depth + 1 : 0;
 }
 
 static void task_move_group_fair(struct task_struct *p)
 {
     detach_task_cfs_rq(p);
     set_task_rq(p, task_cpu(p));
 
 #ifdef CONFIG_SMP
     /* Tell se's cfs_rq has been changed -- migrated */
     p->se.avg.last_update_time = 0;
 #endif
     attach_task_cfs_rq(p);
 }
 
 static void task_change_group_fair(struct task_struct *p, int type)
 {
     switch (type) {
     case TASK_SET_GROUP:
         task_set_group_fair(p);
         break;
 
     case TASK_MOVE_GROUP:
         task_move_group_fair(p);
         break;
     }
 }
 
 void free_fair_sched_group(struct task_group *tg)
 {
     int i;
 
     for_each_possible_cpu(i) {
         if (tg->cfs_rq)
             kfree(tg->cfs_rq[i]);
         if (tg->se)
             kfree(tg->se[i]);
     }
 
     kfree(tg->cfs_rq);
     kfree(tg->se);
 }
 
 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
 {
     struct sched_entity *se;
     struct cfs_rq *cfs_rq;
     int i;
 
     tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
     if (!tg->cfs_rq)
         goto err;
     tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
     if (!tg->se)
         goto err;
 
     tg->shares = NICE_0_LOAD;
 
     init_cfs_bandwidth(tg_cfs_bandwidth(tg));
 
     for_each_possible_cpu(i) {
         cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
                       GFP_KERNEL, cpu_to_node(i));
         if (!cfs_rq)
             goto err;
 
         se = kzalloc_node(sizeof(struct sched_entity_stats),
                   GFP_KERNEL, cpu_to_node(i));
         if (!se)
             goto err_free_rq;
 
         init_cfs_rq(cfs_rq);
         init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
         init_entity_runnable_average(se);
     }
 
     return 1;
 
 err_free_rq:
     kfree(cfs_rq);
 err:
     return 0;
 }
 
 void online_fair_sched_group(struct task_group *tg)
 {
     struct sched_entity *se;
     struct rq_flags rf;
     struct rq *rq;
     int i;
 
     for_each_possible_cpu(i) {
         rq = cpu_rq(i);
         se = tg->se[i];
         rq_lock_irq(rq, &rf);
         update_rq_clock(rq);
         attach_entity_cfs_rq(se);
         sync_throttle(tg, i);
         rq_unlock_irq(rq, &rf);
     }
 }
 
 void unregister_fair_sched_group(struct task_group *tg)
 {
     unsigned long flags;
     struct rq *rq;
     int cpu;
 
     destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
 
     for_each_possible_cpu(cpu) {
         if (tg->se[cpu])
             remove_entity_load_avg(tg->se[cpu]);
 
         /*
          * Only empty task groups can be destroyed; so we can speculatively
          * check on_list without danger of it being re-added.
          */
         if (!tg->cfs_rq[cpu]->on_list)
             continue;
 
         rq = cpu_rq(cpu);
 
         raw_spin_rq_lock_irqsave(rq, flags);
         list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
         raw_spin_rq_unlock_irqrestore(rq, flags);
     }
 }
 
 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
             struct sched_entity *se, int cpu,
             struct sched_entity *parent)
 {
     struct rq *rq = cpu_rq(cpu);
 
     cfs_rq->tg = tg;
     cfs_rq->rq = rq;
     init_cfs_rq_runtime(cfs_rq);
 
     tg->cfs_rq[cpu] = cfs_rq;
     tg->se[cpu] = se;
 
     /* se could be NULL for root_task_group */
     if (!se)
         return;
 
     if (!parent) {
         se->cfs_rq = &rq->cfs;
         se->depth = 0;
     } else {
         se->cfs_rq = parent->my_q;
         se->depth = parent->depth + 1;
     }
 
     se->my_q = cfs_rq;
     /* guarantee group entities always have weight */
     update_load_set(&se->load, NICE_0_LOAD);
     se->parent = parent;
 }
 
 static DEFINE_MUTEX(shares_mutex);
 
 static int __sched_group_set_shares(struct task_group *tg, unsigned long shares)
 {
     int i;
 
     lockdep_assert_held(&shares_mutex);
 
     /*
      * We can't change the weight of the root cgroup.
      */
     if (!tg->se[0])
         return -EINVAL;
 
     shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
 
     if (tg->shares == shares)
         return 0;
 
     tg->shares = shares;
     for_each_possible_cpu(i) {
         struct rq *rq = cpu_rq(i);
         struct sched_entity *se = tg->se[i];
         struct rq_flags rf;
 
         /* Propagate contribution to hierarchy */
         rq_lock_irqsave(rq, &rf);
         update_rq_clock(rq);
         for_each_sched_entity(se) {
             update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
             update_cfs_group(se);
         }
         rq_unlock_irqrestore(rq, &rf);
     }
 
     return 0;
 }
 
 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
 {
     int ret;
 
     mutex_lock(&shares_mutex);
     if (tg_is_idle(tg))
         ret = -EINVAL;
     else
         ret = __sched_group_set_shares(tg, shares);
     mutex_unlock(&shares_mutex);
 
     return ret;
 }
 
 int sched_group_set_idle(struct task_group *tg, long idle)
 {
     int i;
 
     if (tg == &root_task_group)
         return -EINVAL;
 
     if (idle < 0 || idle > 1)
         return -EINVAL;
 
     mutex_lock(&shares_mutex);
 
     if (tg->idle == idle) {
         mutex_unlock(&shares_mutex);
         return 0;
     }
 
     tg->idle = idle;
 
     for_each_possible_cpu(i) {
         struct rq *rq = cpu_rq(i);
         struct sched_entity *se = tg->se[i];
         struct cfs_rq *parent_cfs_rq, *grp_cfs_rq = tg->cfs_rq[i];
         bool was_idle = cfs_rq_is_idle(grp_cfs_rq);
         long idle_task_delta;
         struct rq_flags rf;
 
         rq_lock_irqsave(rq, &rf);
 
         grp_cfs_rq->idle = idle;
         if (WARN_ON_ONCE(was_idle == cfs_rq_is_idle(grp_cfs_rq)))
             goto next_cpu;
 
         if (se->on_rq) {
             parent_cfs_rq = cfs_rq_of(se);
             if (cfs_rq_is_idle(grp_cfs_rq))
                 parent_cfs_rq->idle_nr_running++;
             else
                 parent_cfs_rq->idle_nr_running--;
         }
 
         idle_task_delta = grp_cfs_rq->h_nr_running -
                   grp_cfs_rq->idle_h_nr_running;
         if (!cfs_rq_is_idle(grp_cfs_rq))
             idle_task_delta *= -1;
 
         for_each_sched_entity(se) {
             struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
             if (!se->on_rq)
                 break;
 
             cfs_rq->idle_h_nr_running += idle_task_delta;
 
             /* Already accounted at parent level and above. */
             if (cfs_rq_is_idle(cfs_rq))
                 break;
         }
 
 next_cpu:
         rq_unlock_irqrestore(rq, &rf);
     }
 
     /* Idle groups have minimum weight. */
     if (tg_is_idle(tg))
         __sched_group_set_shares(tg, scale_load(WEIGHT_IDLEPRIO));
     else
         __sched_group_set_shares(tg, NICE_0_LOAD);
 
     mutex_unlock(&shares_mutex);
     return 0;
 }
 
 #else /* CONFIG_FAIR_GROUP_SCHED */
 
 void free_fair_sched_group(struct task_group *tg) { }
 
 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
 {
     return 1;
 }
 
 void online_fair_sched_group(struct task_group *tg) { }
 
 void unregister_fair_sched_group(struct task_group *tg) { }
 
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 
 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
 {
     struct sched_entity *se = &task->se;
     unsigned int rr_interval = 0;
 
     /*
      * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
      * idle runqueue:
      */
     if (rq->cfs.load.weight)
         rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
 
     return rr_interval;
 }
 
 /*
  * All the scheduling class methods:
  */
 DEFINE_SCHED_CLASS(fair) = {
 
     .enqueue_task       = enqueue_task_fair,
     .dequeue_task       = dequeue_task_fair,
     .yield_task     = yield_task_fair,
     .yield_to_task      = yield_to_task_fair,
 
     .check_preempt_curr = check_preempt_wakeup,
 
     .pick_next_task     = __pick_next_task_fair,
     .put_prev_task      = put_prev_task_fair,
     .set_next_task          = set_next_task_fair,
 
 #ifdef CONFIG_SMP
     .balance        = balance_fair,
     .pick_task      = pick_task_fair,
     .select_task_rq     = select_task_rq_fair,
     .migrate_task_rq    = migrate_task_rq_fair,
 
     .rq_online      = rq_online_fair,
     .rq_offline     = rq_offline_fair,
 
     .task_dead      = task_dead_fair,
     .set_cpus_allowed   = set_cpus_allowed_common,
 #endif
 
     .task_tick      = task_tick_fair,
     .task_fork      = task_fork_fair,
 
     .prio_changed       = prio_changed_fair,
     .switched_from      = switched_from_fair,
     .switched_to        = switched_to_fair,
 
     .get_rr_interval    = get_rr_interval_fair,
 
     .update_curr        = update_curr_fair,
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
     .task_change_group  = task_change_group_fair,
 #endif
 
 #ifdef CONFIG_UCLAMP_TASK
     .uclamp_enabled     = 1,
 #endif
 };
 
 #ifdef CONFIG_SCHED_DEBUG
 void print_cfs_stats(struct seq_file *m, int cpu)
 {
     struct cfs_rq *cfs_rq, *pos;
 
     rcu_read_lock();
     for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
         print_cfs_rq(m, cpu, cfs_rq);
     rcu_read_unlock();
 }
 
 #ifdef CONFIG_NUMA_BALANCING
 void show_numa_stats(struct task_struct *p, struct seq_file *m)
 {
     int node;
     unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
     struct numa_group *ng;
 
     rcu_read_lock();
     ng = rcu_dereference(p->numa_group);
     for_each_online_node(node) {
         if (p->numa_faults) {
             tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
             tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
         }
         if (ng) {
             gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
             gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
         }
         print_numa_stats(m, node, tsf, tpf, gsf, gpf);
     }
     rcu_read_unlock();
 }
 #endif /* CONFIG_NUMA_BALANCING */
 #endif /* CONFIG_SCHED_DEBUG */
 
 __init void init_sched_fair_class(void)
 {
 #ifdef CONFIG_SMP
     open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
 
 #ifdef CONFIG_NO_HZ_COMMON
     nohz.next_balance = jiffies;
     nohz.next_blocked = jiffies;
     zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
 #endif
 #endif /* SMP */
 
 }