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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Deadline Scheduling Class (SCHED_DEADLINE)
  *
  * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
  *
  * Tasks that periodically executes their instances for less than their
  * runtime won't miss any of their deadlines.
  * Tasks that are not periodic or sporadic or that tries to execute more
  * than their reserved bandwidth will be slowed down (and may potentially
  * miss some of their deadlines), and won't affect any other task.
  *
  * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
  *                    Juri Lelli <juri.lelli@gmail.com>,
  *                    Michael Trimarchi <michael@amarulasolutions.com>,
  *                    Fabio Checconi <fchecconi@gmail.com>
  */
 
 /*
  * Default limits for DL period; on the top end we guard against small util
  * tasks still getting ridiculously long effective runtimes, on the bottom end we
  * guard against timer DoS.
  */
 static unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */
 static unsigned int sysctl_sched_dl_period_min = 100;     /* 100 us */
 #ifdef CONFIG_SYSCTL
 static struct ctl_table sched_dl_sysctls[] = {
     {
         .procname       = "sched_deadline_period_max_us",
         .data           = &sysctl_sched_dl_period_max,
         .maxlen         = sizeof(unsigned int),
         .mode           = 0644,
         .proc_handler   = proc_douintvec_minmax,
         .extra1         = (void *)&sysctl_sched_dl_period_min,
     },
     {
         .procname       = "sched_deadline_period_min_us",
         .data           = &sysctl_sched_dl_period_min,
         .maxlen         = sizeof(unsigned int),
         .mode           = 0644,
         .proc_handler   = proc_douintvec_minmax,
         .extra2         = (void *)&sysctl_sched_dl_period_max,
     },
     {}
 };
 
 static int __init sched_dl_sysctl_init(void)
 {
     register_sysctl_init("kernel", sched_dl_sysctls);
     return 0;
 }
 late_initcall(sched_dl_sysctl_init);
 #endif
 
 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
 {
     return container_of(dl_se, struct task_struct, dl);
 }
 
 static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
 {
     return container_of(dl_rq, struct rq, dl);
 }
 
 static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
 {
     struct task_struct *p = dl_task_of(dl_se);
     struct rq *rq = task_rq(p);
 
     return &rq->dl;
 }
 
 static inline int on_dl_rq(struct sched_dl_entity *dl_se)
 {
     return !RB_EMPTY_NODE(&dl_se->rb_node);
 }
 
 #ifdef CONFIG_RT_MUTEXES
 static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
 {
     return dl_se->pi_se;
 }
 
 static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
 {
     return pi_of(dl_se) != dl_se;
 }
 #else
 static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
 {
     return dl_se;
 }
 
 static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
 {
     return false;
 }
 #endif
 
 #ifdef CONFIG_SMP
 static inline struct dl_bw *dl_bw_of(int i)
 {
     RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
              "sched RCU must be held");
     return &cpu_rq(i)->rd->dl_bw;
 }
 
 static inline int dl_bw_cpus(int i)
 {
     struct root_domain *rd = cpu_rq(i)->rd;
     int cpus;
 
     RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
              "sched RCU must be held");
 
     if (cpumask_subset(rd->span, cpu_active_mask))
         return cpumask_weight(rd->span);
 
     cpus = 0;
 
     for_each_cpu_and(i, rd->span, cpu_active_mask)
         cpus++;
 
     return cpus;
 }
 
 static inline unsigned long __dl_bw_capacity(int i)
 {
     struct root_domain *rd = cpu_rq(i)->rd;
     unsigned long cap = 0;
 
     RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
              "sched RCU must be held");
 
     for_each_cpu_and(i, rd->span, cpu_active_mask)
         cap += capacity_orig_of(i);
 
     return cap;
 }
 
 /*
  * XXX Fix: If 'rq->rd == def_root_domain' perform AC against capacity
  * of the CPU the task is running on rather rd's \Sum CPU capacity.
  */
 static inline unsigned long dl_bw_capacity(int i)
 {
     if (!static_branch_unlikely(&sched_asym_cpucapacity) &&
         capacity_orig_of(i) == SCHED_CAPACITY_SCALE) {
         return dl_bw_cpus(i) << SCHED_CAPACITY_SHIFT;
     } else {
         return __dl_bw_capacity(i);
     }
 }
 
 static inline bool dl_bw_visited(int cpu, u64 gen)
 {
     struct root_domain *rd = cpu_rq(cpu)->rd;
 
     if (rd->visit_gen == gen)
         return true;
 
     rd->visit_gen = gen;
     return false;
 }
 
 static inline
 void __dl_update(struct dl_bw *dl_b, s64 bw)
 {
     struct root_domain *rd = container_of(dl_b, struct root_domain, dl_bw);
     int i;
 
     RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
              "sched RCU must be held");
     for_each_cpu_and(i, rd->span, cpu_active_mask) {
         struct rq *rq = cpu_rq(i);
 
         rq->dl.extra_bw += bw;
     }
 }
 #else
 static inline struct dl_bw *dl_bw_of(int i)
 {
     return &cpu_rq(i)->dl.dl_bw;
 }
 
 static inline int dl_bw_cpus(int i)
 {
     return 1;
 }
 
 static inline unsigned long dl_bw_capacity(int i)
 {
     return SCHED_CAPACITY_SCALE;
 }
 
 static inline bool dl_bw_visited(int cpu, u64 gen)
 {
     return false;
 }
 
 static inline
 void __dl_update(struct dl_bw *dl_b, s64 bw)
 {
     struct dl_rq *dl = container_of(dl_b, struct dl_rq, dl_bw);
 
     dl->extra_bw += bw;
 }
 #endif
 
 static inline
 void __dl_sub(struct dl_bw *dl_b, u64 tsk_bw, int cpus)
 {
     dl_b->total_bw -= tsk_bw;
     __dl_update(dl_b, (s32)tsk_bw / cpus);
 }
 
 static inline
 void __dl_add(struct dl_bw *dl_b, u64 tsk_bw, int cpus)
 {
     dl_b->total_bw += tsk_bw;
     __dl_update(dl_b, -((s32)tsk_bw / cpus));
 }
 
 static inline bool
 __dl_overflow(struct dl_bw *dl_b, unsigned long cap, u64 old_bw, u64 new_bw)
 {
     return dl_b->bw != -1 &&
            cap_scale(dl_b->bw, cap) < dl_b->total_bw - old_bw + new_bw;
 }
 
 static inline
 void __add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 {
     u64 old = dl_rq->running_bw;
 
     lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
     dl_rq->running_bw += dl_bw;
     SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
     SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
     /* kick cpufreq (see the comment in kernel/sched/sched.h). */
     cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
 }
 
 static inline
 void __sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 {
     u64 old = dl_rq->running_bw;
 
     lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
     dl_rq->running_bw -= dl_bw;
     SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */
     if (dl_rq->running_bw > old)
         dl_rq->running_bw = 0;
     /* kick cpufreq (see the comment in kernel/sched/sched.h). */
     cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
 }
 
 static inline
 void __add_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
 {
     u64 old = dl_rq->this_bw;
 
     lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
     dl_rq->this_bw += dl_bw;
     SCHED_WARN_ON(dl_rq->this_bw < old); /* overflow */
 }
 
 static inline
 void __sub_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
 {
     u64 old = dl_rq->this_bw;
 
     lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
     dl_rq->this_bw -= dl_bw;
     SCHED_WARN_ON(dl_rq->this_bw > old); /* underflow */
     if (dl_rq->this_bw > old)
         dl_rq->this_bw = 0;
     SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
 }
 
 static inline
 void add_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     if (!dl_entity_is_special(dl_se))
         __add_rq_bw(dl_se->dl_bw, dl_rq);
 }
 
 static inline
 void sub_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     if (!dl_entity_is_special(dl_se))
         __sub_rq_bw(dl_se->dl_bw, dl_rq);
 }
 
 static inline
 void add_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     if (!dl_entity_is_special(dl_se))
         __add_running_bw(dl_se->dl_bw, dl_rq);
 }
 
 static inline
 void sub_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     if (!dl_entity_is_special(dl_se))
         __sub_running_bw(dl_se->dl_bw, dl_rq);
 }
 
 static void dl_change_utilization(struct task_struct *p, u64 new_bw)
 {
     struct rq *rq;
 
     BUG_ON(p->dl.flags & SCHED_FLAG_SUGOV);
 
     if (task_on_rq_queued(p))
         return;
 
     rq = task_rq(p);
     if (p->dl.dl_non_contending) {
         sub_running_bw(&p->dl, &rq->dl);
         p->dl.dl_non_contending = 0;
         /*
          * If the timer handler is currently running and the
          * timer cannot be canceled, inactive_task_timer()
          * will see that dl_not_contending is not set, and
          * will not touch the rq's active utilization,
          * so we are still safe.
          */
         if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
             put_task_struct(p);
     }
     __sub_rq_bw(p->dl.dl_bw, &rq->dl);
     __add_rq_bw(new_bw, &rq->dl);
 }
 
 /*
  * The utilization of a task cannot be immediately removed from
  * the rq active utilization (running_bw) when the task blocks.
  * Instead, we have to wait for the so called "0-lag time".
  *
  * If a task blocks before the "0-lag time", a timer (the inactive
  * timer) is armed, and running_bw is decreased when the timer
  * fires.
  *
  * If the task wakes up again before the inactive timer fires,
  * the timer is canceled, whereas if the task wakes up after the
  * inactive timer fired (and running_bw has been decreased) the
  * task's utilization has to be added to running_bw again.
  * A flag in the deadline scheduling entity (dl_non_contending)
  * is used to avoid race conditions between the inactive timer handler
  * and task wakeups.
  *
  * The following diagram shows how running_bw is updated. A task is
  * "ACTIVE" when its utilization contributes to running_bw; an
  * "ACTIVE contending" task is in the TASK_RUNNING state, while an
  * "ACTIVE non contending" task is a blocked task for which the "0-lag time"
  * has not passed yet. An "INACTIVE" task is a task for which the "0-lag"
  * time already passed, which does not contribute to running_bw anymore.
  *                              +------------------+
  *             wakeup           |    ACTIVE        |
  *          +------------------>+   contending     |
  *          | add_running_bw    |                  |
  *          |                   +----+------+------+
  *          |                        |      ^
  *          |                dequeue |      |
  * +--------+-------+                |      |
  * |                |   t >= 0-lag   |      | wakeup
  * |    INACTIVE    |<---------------+      |
  * |                | sub_running_bw |      |
  * +--------+-------+                |      |
  *          ^                        |      |
  *          |              t < 0-lag |      |
  *          |                        |      |
  *          |                        V      |
  *          |                   +----+------+------+
  *          | sub_running_bw    |    ACTIVE        |
  *          +-------------------+                  |
  *            inactive timer    |  non contending  |
  *            fired             +------------------+
  *
  * The task_non_contending() function is invoked when a task
  * blocks, and checks if the 0-lag time already passed or
  * not (in the first case, it directly updates running_bw;
  * in the second case, it arms the inactive timer).
  *
  * The task_contending() function is invoked when a task wakes
  * up, and checks if the task is still in the "ACTIVE non contending"
  * state or not (in the second case, it updates running_bw).
  */
 static void task_non_contending(struct task_struct *p)
 {
     struct sched_dl_entity *dl_se = &p->dl;
     struct hrtimer *timer = &dl_se->inactive_timer;
     struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
     struct rq *rq = rq_of_dl_rq(dl_rq);
     s64 zerolag_time;
 
     /*
      * If this is a non-deadline task that has been boosted,
      * do nothing
      */
     if (dl_se->dl_runtime == 0)
         return;
 
     if (dl_entity_is_special(dl_se))
         return;
 
     WARN_ON(dl_se->dl_non_contending);
 
     zerolag_time = dl_se->deadline -
          div64_long((dl_se->runtime * dl_se->dl_period),
             dl_se->dl_runtime);
 
     /*
      * Using relative times instead of the absolute "0-lag time"
      * allows to simplify the code
      */
     zerolag_time -= rq_clock(rq);
 
     /*
      * If the "0-lag time" already passed, decrease the active
      * utilization now, instead of starting a timer
      */
     if ((zerolag_time < 0) || hrtimer_active(&dl_se->inactive_timer)) {
         if (dl_task(p))
             sub_running_bw(dl_se, dl_rq);
         if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
             struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
 
             if (READ_ONCE(p->__state) == TASK_DEAD)
                 sub_rq_bw(&p->dl, &rq->dl);
             raw_spin_lock(&dl_b->lock);
             __dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
             __dl_clear_params(p);
             raw_spin_unlock(&dl_b->lock);
         }
 
         return;
     }
 
     dl_se->dl_non_contending = 1;
     get_task_struct(p);
     hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL_HARD);
 }
 
 static void task_contending(struct sched_dl_entity *dl_se, int flags)
 {
     struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 
     /*
      * If this is a non-deadline task that has been boosted,
      * do nothing
      */
     if (dl_se->dl_runtime == 0)
         return;
 
     if (flags & ENQUEUE_MIGRATED)
         add_rq_bw(dl_se, dl_rq);
 
     if (dl_se->dl_non_contending) {
         dl_se->dl_non_contending = 0;
         /*
          * If the timer handler is currently running and the
          * timer cannot be canceled, inactive_task_timer()
          * will see that dl_not_contending is not set, and
          * will not touch the rq's active utilization,
          * so we are still safe.
          */
         if (hrtimer_try_to_cancel(&dl_se->inactive_timer) == 1)
             put_task_struct(dl_task_of(dl_se));
     } else {
         /*
          * Since "dl_non_contending" is not set, the
          * task's utilization has already been removed from
          * active utilization (either when the task blocked,
          * when the "inactive timer" fired).
          * So, add it back.
          */
         add_running_bw(dl_se, dl_rq);
     }
 }
 
 static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
 {
     struct sched_dl_entity *dl_se = &p->dl;
 
     return rb_first_cached(&dl_rq->root) == &dl_se->rb_node;
 }
 
 static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq);
 
 void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
 {
     raw_spin_lock_init(&dl_b->dl_runtime_lock);
     dl_b->dl_period = period;
     dl_b->dl_runtime = runtime;
 }
 
 void init_dl_bw(struct dl_bw *dl_b)
 {
     raw_spin_lock_init(&dl_b->lock);
     if (global_rt_runtime() == RUNTIME_INF)
         dl_b->bw = -1;
     else
         dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
     dl_b->total_bw = 0;
 }
 
 void init_dl_rq(struct dl_rq *dl_rq)
 {
     dl_rq->root = RB_ROOT_CACHED;
 
 #ifdef CONFIG_SMP
     /* zero means no -deadline tasks */
     dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
 
     dl_rq->dl_nr_migratory = 0;
     dl_rq->overloaded = 0;
     dl_rq->pushable_dl_tasks_root = RB_ROOT_CACHED;
 #else
     init_dl_bw(&dl_rq->dl_bw);
 #endif
 
     dl_rq->running_bw = 0;
     dl_rq->this_bw = 0;
     init_dl_rq_bw_ratio(dl_rq);
 }
 
 #ifdef CONFIG_SMP
 
 static inline int dl_overloaded(struct rq *rq)
 {
     return atomic_read(&rq->rd->dlo_count);
 }
 
 static inline void dl_set_overload(struct rq *rq)
 {
     if (!rq->online)
         return;
 
     cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
     /*
      * Must be visible before the overload count is
      * set (as in sched_rt.c).
      *
      * Matched by the barrier in pull_dl_task().
      */
     smp_wmb();
     atomic_inc(&rq->rd->dlo_count);
 }
 
 static inline void dl_clear_overload(struct rq *rq)
 {
     if (!rq->online)
         return;
 
     atomic_dec(&rq->rd->dlo_count);
     cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
 }
 
 static void update_dl_migration(struct dl_rq *dl_rq)
 {
     if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) {
         if (!dl_rq->overloaded) {
             dl_set_overload(rq_of_dl_rq(dl_rq));
             dl_rq->overloaded = 1;
         }
     } else if (dl_rq->overloaded) {
         dl_clear_overload(rq_of_dl_rq(dl_rq));
         dl_rq->overloaded = 0;
     }
 }
 
 static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     struct task_struct *p = dl_task_of(dl_se);
 
     if (p->nr_cpus_allowed > 1)
         dl_rq->dl_nr_migratory++;
 
     update_dl_migration(dl_rq);
 }
 
 static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     struct task_struct *p = dl_task_of(dl_se);
 
     if (p->nr_cpus_allowed > 1)
         dl_rq->dl_nr_migratory--;
 
     update_dl_migration(dl_rq);
 }
 
 #define __node_2_pdl(node) \
     rb_entry((node), struct task_struct, pushable_dl_tasks)
 
 static inline bool __pushable_less(struct rb_node *a, const struct rb_node *b)
 {
     return dl_entity_preempt(&__node_2_pdl(a)->dl, &__node_2_pdl(b)->dl);
 }
 
 /*
  * The list of pushable -deadline task is not a plist, like in
  * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
  */
 static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 {
     struct rb_node *leftmost;
 
     BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
 
     leftmost = rb_add_cached(&p->pushable_dl_tasks,
                  &rq->dl.pushable_dl_tasks_root,
                  __pushable_less);
     if (leftmost)
         rq->dl.earliest_dl.next = p->dl.deadline;
 }
 
 static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 {
     struct dl_rq *dl_rq = &rq->dl;
     struct rb_root_cached *root = &dl_rq->pushable_dl_tasks_root;
     struct rb_node *leftmost;
 
     if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
         return;
 
     leftmost = rb_erase_cached(&p->pushable_dl_tasks, root);
     if (leftmost)
         dl_rq->earliest_dl.next = __node_2_pdl(leftmost)->dl.deadline;
 
     RB_CLEAR_NODE(&p->pushable_dl_tasks);
 }
 
 static inline int has_pushable_dl_tasks(struct rq *rq)
 {
     return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root);
 }
 
 static int push_dl_task(struct rq *rq);
 
 static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
 {
     return rq->online && dl_task(prev);
 }
 
 static DEFINE_PER_CPU(struct callback_head, dl_push_head);
 static DEFINE_PER_CPU(struct callback_head, dl_pull_head);
 
 static void push_dl_tasks(struct rq *);
 static void pull_dl_task(struct rq *);
 
 static inline void deadline_queue_push_tasks(struct rq *rq)
 {
     if (!has_pushable_dl_tasks(rq))
         return;
 
     queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
 }
 
 static inline void deadline_queue_pull_task(struct rq *rq)
 {
     queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
 }
 
 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
 
 static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p)
 {
     struct rq *later_rq = NULL;
     struct dl_bw *dl_b;
 
     later_rq = find_lock_later_rq(p, rq);
     if (!later_rq) {
         int cpu;
 
         /*
          * If we cannot preempt any rq, fall back to pick any
          * online CPU:
          */
         cpu = cpumask_any_and(cpu_active_mask, p->cpus_ptr);
         if (cpu >= nr_cpu_ids) {
             /*
              * Failed to find any suitable CPU.
              * The task will never come back!
              */
             BUG_ON(dl_bandwidth_enabled());
 
             /*
              * If admission control is disabled we
              * try a little harder to let the task
              * run.
              */
             cpu = cpumask_any(cpu_active_mask);
         }
         later_rq = cpu_rq(cpu);
         double_lock_balance(rq, later_rq);
     }
 
     if (p->dl.dl_non_contending || p->dl.dl_throttled) {
         /*
          * Inactive timer is armed (or callback is running, but
          * waiting for us to release rq locks). In any case, when it
          * will fire (or continue), it will see running_bw of this
          * task migrated to later_rq (and correctly handle it).
          */
         sub_running_bw(&p->dl, &rq->dl);
         sub_rq_bw(&p->dl, &rq->dl);
 
         add_rq_bw(&p->dl, &later_rq->dl);
         add_running_bw(&p->dl, &later_rq->dl);
     } else {
         sub_rq_bw(&p->dl, &rq->dl);
         add_rq_bw(&p->dl, &later_rq->dl);
     }
 
     /*
      * And we finally need to fixup root_domain(s) bandwidth accounting,
      * since p is still hanging out in the old (now moved to default) root
      * domain.
      */
     dl_b = &rq->rd->dl_bw;
     raw_spin_lock(&dl_b->lock);
     __dl_sub(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
     raw_spin_unlock(&dl_b->lock);
 
     dl_b = &later_rq->rd->dl_bw;
     raw_spin_lock(&dl_b->lock);
     __dl_add(dl_b, p->dl.dl_bw, cpumask_weight(later_rq->rd->span));
     raw_spin_unlock(&dl_b->lock);
 
     set_task_cpu(p, later_rq->cpu);
     double_unlock_balance(later_rq, rq);
 
     return later_rq;
 }
 
 #else
 
 static inline
 void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 {
 }
 
 static inline
 void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 {
 }
 
 static inline
 void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
 }
 
 static inline
 void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
 }
 
 static inline void deadline_queue_push_tasks(struct rq *rq)
 {
 }
 
 static inline void deadline_queue_pull_task(struct rq *rq)
 {
 }
 #endif /* CONFIG_SMP */
 
 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, int flags);
 
 /*
  * We are being explicitly informed that a new instance is starting,
  * and this means that:
  *  - the absolute deadline of the entity has to be placed at
  *    current time + relative deadline;
  *  - the runtime of the entity has to be set to the maximum value.
  *
  * The capability of specifying such event is useful whenever a -deadline
  * entity wants to (try to!) synchronize its behaviour with the scheduler's
  * one, and to (try to!) reconcile itself with its own scheduling
  * parameters.
  */
 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 {
     struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
     struct rq *rq = rq_of_dl_rq(dl_rq);
 
     WARN_ON(is_dl_boosted(dl_se));
     WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
 
     /*
      * We are racing with the deadline timer. So, do nothing because
      * the deadline timer handler will take care of properly recharging
      * the runtime and postponing the deadline
      */
     if (dl_se->dl_throttled)
         return;
 
     /*
      * We use the regular wall clock time to set deadlines in the
      * future; in fact, we must consider execution overheads (time
      * spent on hardirq context, etc.).
      */
     dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
     dl_se->runtime = dl_se->dl_runtime;
 }
 
 /*
  * Pure Earliest Deadline First (EDF) scheduling does not deal with the
  * possibility of a entity lasting more than what it declared, and thus
  * exhausting its runtime.
  *
  * Here we are interested in making runtime overrun possible, but we do
  * not want a entity which is misbehaving to affect the scheduling of all
  * other entities.
  * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
  * is used, in order to confine each entity within its own bandwidth.
  *
  * This function deals exactly with that, and ensures that when the runtime
  * of a entity is replenished, its deadline is also postponed. That ensures
  * the overrunning entity can't interfere with other entity in the system and
  * can't make them miss their deadlines. Reasons why this kind of overruns
  * could happen are, typically, a entity voluntarily trying to overcome its
  * runtime, or it just underestimated it during sched_setattr().
  */
 static void replenish_dl_entity(struct sched_dl_entity *dl_se)
 {
     struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
     struct rq *rq = rq_of_dl_rq(dl_rq);
 
     BUG_ON(pi_of(dl_se)->dl_runtime <= 0);
 
     /*
      * This could be the case for a !-dl task that is boosted.
      * Just go with full inherited parameters.
      */
     if (dl_se->dl_deadline == 0) {
         dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
         dl_se->runtime = pi_of(dl_se)->dl_runtime;
     }
 
     if (dl_se->dl_yielded && dl_se->runtime > 0)
         dl_se->runtime = 0;
 
     /*
      * We keep moving the deadline away until we get some
      * available runtime for the entity. This ensures correct
      * handling of situations where the runtime overrun is
      * arbitrary large.
      */
     while (dl_se->runtime <= 0) {
         dl_se->deadline += pi_of(dl_se)->dl_period;
         dl_se->runtime += pi_of(dl_se)->dl_runtime;
     }
 
     /*
      * At this point, the deadline really should be "in
      * the future" with respect to rq->clock. If it's
      * not, we are, for some reason, lagging too much!
      * Anyway, after having warn userspace abut that,
      * we still try to keep the things running by
      * resetting the deadline and the budget of the
      * entity.
      */
     if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
         printk_deferred_once("sched: DL replenish lagged too much\n");
         dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
         dl_se->runtime = pi_of(dl_se)->dl_runtime;
     }
 
     if (dl_se->dl_yielded)
         dl_se->dl_yielded = 0;
     if (dl_se->dl_throttled)
         dl_se->dl_throttled = 0;
 }
 
 /*
  * Here we check if --at time t-- an entity (which is probably being
  * [re]activated or, in general, enqueued) can use its remaining runtime
  * and its current deadline _without_ exceeding the bandwidth it is
  * assigned (function returns true if it can't). We are in fact applying
  * one of the CBS rules: when a task wakes up, if the residual runtime
  * over residual deadline fits within the allocated bandwidth, then we
  * can keep the current (absolute) deadline and residual budget without
  * disrupting the schedulability of the system. Otherwise, we should
  * refill the runtime and set the deadline a period in the future,
  * because keeping the current (absolute) deadline of the task would
  * result in breaking guarantees promised to other tasks (refer to
  * Documentation/scheduler/sched-deadline.rst for more information).
  *
  * This function returns true if:
  *
  *   runtime / (deadline - t) > dl_runtime / dl_deadline ,
  *
  * IOW we can't recycle current parameters.
  *
  * Notice that the bandwidth check is done against the deadline. For
  * task with deadline equal to period this is the same of using
  * dl_period instead of dl_deadline in the equation above.
  */
 static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
 {
     u64 left, right;
 
     /*
      * left and right are the two sides of the equation above,
      * after a bit of shuffling to use multiplications instead
      * of divisions.
      *
      * Note that none of the time values involved in the two
      * multiplications are absolute: dl_deadline and dl_runtime
      * are the relative deadline and the maximum runtime of each
      * instance, runtime is the runtime left for the last instance
      * and (deadline - t), since t is rq->clock, is the time left
      * to the (absolute) deadline. Even if overflowing the u64 type
      * is very unlikely to occur in both cases, here we scale down
      * as we want to avoid that risk at all. Scaling down by 10
      * means that we reduce granularity to 1us. We are fine with it,
      * since this is only a true/false check and, anyway, thinking
      * of anything below microseconds resolution is actually fiction
      * (but still we want to give the user that illusion >;).
      */
     left = (pi_of(dl_se)->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
     right = ((dl_se->deadline - t) >> DL_SCALE) *
         (pi_of(dl_se)->dl_runtime >> DL_SCALE);
 
     return dl_time_before(right, left);
 }
 
 /*
  * Revised wakeup rule [1]: For self-suspending tasks, rather then
  * re-initializing task's runtime and deadline, the revised wakeup
  * rule adjusts the task's runtime to avoid the task to overrun its
  * density.
  *
  * Reasoning: a task may overrun the density if:
  *    runtime / (deadline - t) > dl_runtime / dl_deadline
  *
  * Therefore, runtime can be adjusted to:
  *     runtime = (dl_runtime / dl_deadline) * (deadline - t)
  *
  * In such way that runtime will be equal to the maximum density
  * the task can use without breaking any rule.
  *
  * [1] Luca Abeni, Giuseppe Lipari, and Juri Lelli. 2015. Constant
  * bandwidth server revisited. SIGBED Rev. 11, 4 (January 2015), 19-24.
  */
 static void
 update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq)
 {
     u64 laxity = dl_se->deadline - rq_clock(rq);
 
     /*
      * If the task has deadline < period, and the deadline is in the past,
      * it should already be throttled before this check.
      *
      * See update_dl_entity() comments for further details.
      */
     WARN_ON(dl_time_before(dl_se->deadline, rq_clock(rq)));
 
     dl_se->runtime = (dl_se->dl_density * laxity) >> BW_SHIFT;
 }
 
 /*
  * Regarding the deadline, a task with implicit deadline has a relative
  * deadline == relative period. A task with constrained deadline has a
  * relative deadline <= relative period.
  *
  * We support constrained deadline tasks. However, there are some restrictions
  * applied only for tasks which do not have an implicit deadline. See
  * update_dl_entity() to know more about such restrictions.
  *
  * The dl_is_implicit() returns true if the task has an implicit deadline.
  */
 static inline bool dl_is_implicit(struct sched_dl_entity *dl_se)
 {
     return dl_se->dl_deadline == dl_se->dl_period;
 }
 
 /*
  * When a deadline entity is placed in the runqueue, its runtime and deadline
  * might need to be updated. This is done by a CBS wake up rule. There are two
  * different rules: 1) the original CBS; and 2) the Revisited CBS.
  *
  * When the task is starting a new period, the Original CBS is used. In this
  * case, the runtime is replenished and a new absolute deadline is set.
  *
  * When a task is queued before the begin of the next period, using the
  * remaining runtime and deadline could make the entity to overflow, see
  * dl_entity_overflow() to find more about runtime overflow. When such case
  * is detected, the runtime and deadline need to be updated.
  *
  * If the task has an implicit deadline, i.e., deadline == period, the Original
  * CBS is applied. the runtime is replenished and a new absolute deadline is
  * set, as in the previous cases.
  *
  * However, the Original CBS does not work properly for tasks with
  * deadline < period, which are said to have a constrained deadline. By
  * applying the Original CBS, a constrained deadline task would be able to run
  * runtime/deadline in a period. With deadline < period, the task would
  * overrun the runtime/period allowed bandwidth, breaking the admission test.
  *
  * In order to prevent this misbehave, the Revisited CBS is used for
  * constrained deadline tasks when a runtime overflow is detected. In the
  * Revisited CBS, rather than replenishing & setting a new absolute deadline,
  * the remaining runtime of the task is reduced to avoid runtime overflow.
  * Please refer to the comments update_dl_revised_wakeup() function to find
  * more about the Revised CBS rule.
  */
 static void update_dl_entity(struct sched_dl_entity *dl_se)
 {
     struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
     struct rq *rq = rq_of_dl_rq(dl_rq);
 
     if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
         dl_entity_overflow(dl_se, rq_clock(rq))) {
 
         if (unlikely(!dl_is_implicit(dl_se) &&
                  !dl_time_before(dl_se->deadline, rq_clock(rq)) &&
                  !is_dl_boosted(dl_se))) {
             update_dl_revised_wakeup(dl_se, rq);
             return;
         }
 
         dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
         dl_se->runtime = pi_of(dl_se)->dl_runtime;
     }
 }
 
 static inline u64 dl_next_period(struct sched_dl_entity *dl_se)
 {
     return dl_se->deadline - dl_se->dl_deadline + dl_se->dl_period;
 }
 
 /*
  * If the entity depleted all its runtime, and if we want it to sleep
  * while waiting for some new execution time to become available, we
  * set the bandwidth replenishment timer to the replenishment instant
  * and try to activate it.
  *
  * Notice that it is important for the caller to know if the timer
  * actually started or not (i.e., the replenishment instant is in
  * the future or in the past).
  */
 static int start_dl_timer(struct task_struct *p)
 {
     struct sched_dl_entity *dl_se = &p->dl;
     struct hrtimer *timer = &dl_se->dl_timer;
     struct rq *rq = task_rq(p);
     ktime_t now, act;
     s64 delta;
 
     lockdep_assert_rq_held(rq);
 
     /*
      * We want the timer to fire at the deadline, but considering
      * that it is actually coming from rq->clock and not from
      * hrtimer's time base reading.
      */
     act = ns_to_ktime(dl_next_period(dl_se));
     now = hrtimer_cb_get_time(timer);
     delta = ktime_to_ns(now) - rq_clock(rq);
     act = ktime_add_ns(act, delta);
 
     /*
      * If the expiry time already passed, e.g., because the value
      * chosen as the deadline is too small, don't even try to
      * start the timer in the past!
      */
     if (ktime_us_delta(act, now) < 0)
         return 0;
 
     /*
      * !enqueued will guarantee another callback; even if one is already in
      * progress. This ensures a balanced {get,put}_task_struct().
      *
      * The race against __run_timer() clearing the enqueued state is
      * harmless because we're holding task_rq()->lock, therefore the timer
      * expiring after we've done the check will wait on its task_rq_lock()
      * and observe our state.
      */
     if (!hrtimer_is_queued(timer)) {
         get_task_struct(p);
         hrtimer_start(timer, act, HRTIMER_MODE_ABS_HARD);
     }
 
     return 1;
 }
 
 /*
  * This is the bandwidth enforcement timer callback. If here, we know
  * a task is not on its dl_rq, since the fact that the timer was running
  * means the task is throttled and needs a runtime replenishment.
  *
  * However, what we actually do depends on the fact the task is active,
  * (it is on its rq) or has been removed from there by a call to
  * dequeue_task_dl(). In the former case we must issue the runtime
  * replenishment and add the task back to the dl_rq; in the latter, we just
  * do nothing but clearing dl_throttled, so that runtime and deadline
  * updating (and the queueing back to dl_rq) will be done by the
  * next call to enqueue_task_dl().
  */
 static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 {
     struct sched_dl_entity *dl_se = container_of(timer,
                              struct sched_dl_entity,
                              dl_timer);
     struct task_struct *p = dl_task_of(dl_se);
     struct rq_flags rf;
     struct rq *rq;
 
     rq = task_rq_lock(p, &rf);
 
     /*
      * The task might have changed its scheduling policy to something
      * different than SCHED_DEADLINE (through switched_from_dl()).
      */
     if (!dl_task(p))
         goto unlock;
 
     /*
      * The task might have been boosted by someone else and might be in the
      * boosting/deboosting path, its not throttled.
      */
     if (is_dl_boosted(dl_se))
         goto unlock;
 
     /*
      * Spurious timer due to start_dl_timer() race; or we already received
      * a replenishment from rt_mutex_setprio().
      */
     if (!dl_se->dl_throttled)
         goto unlock;
 
     sched_clock_tick();
     update_rq_clock(rq);
 
     /*
      * If the throttle happened during sched-out; like:
      *
      *   schedule()
      *     deactivate_task()
      *       dequeue_task_dl()
      *         update_curr_dl()
      *           start_dl_timer()
      *         __dequeue_task_dl()
      *     prev->on_rq = 0;
      *
      * We can be both throttled and !queued. Replenish the counter
      * but do not enqueue -- wait for our wakeup to do that.
      */
     if (!task_on_rq_queued(p)) {
         replenish_dl_entity(dl_se);
         goto unlock;
     }
 
 #ifdef CONFIG_SMP
     if (unlikely(!rq->online)) {
         /*
          * If the runqueue is no longer available, migrate the
          * task elsewhere. This necessarily changes rq.
          */
         lockdep_unpin_lock(__rq_lockp(rq), rf.cookie);
         rq = dl_task_offline_migration(rq, p);
         rf.cookie = lockdep_pin_lock(__rq_lockp(rq));
         update_rq_clock(rq);
 
         /*
          * Now that the task has been migrated to the new RQ and we
          * have that locked, proceed as normal and enqueue the task
          * there.
          */
     }
 #endif
 
     enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
     if (dl_task(rq->curr))
         check_preempt_curr_dl(rq, p, 0);
     else
         resched_curr(rq);
 
 #ifdef CONFIG_SMP
     /*
      * Queueing this task back might have overloaded rq, check if we need
      * to kick someone away.
      */
     if (has_pushable_dl_tasks(rq)) {
         /*
          * Nothing relies on rq->lock after this, so its safe to drop
          * rq->lock.
          */
         rq_unpin_lock(rq, &rf);
         push_dl_task(rq);
         rq_repin_lock(rq, &rf);
     }
 #endif
 
 unlock:
     task_rq_unlock(rq, p, &rf);
 
     /*
      * This can free the task_struct, including this hrtimer, do not touch
      * anything related to that after this.
      */
     put_task_struct(p);
 
     return HRTIMER_NORESTART;
 }
 
 void init_dl_task_timer(struct sched_dl_entity *dl_se)
 {
     struct hrtimer *timer = &dl_se->dl_timer;
 
     hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
     timer->function = dl_task_timer;
 }
 
 /*
  * During the activation, CBS checks if it can reuse the current task's
  * runtime and period. If the deadline of the task is in the past, CBS
  * cannot use the runtime, and so it replenishes the task. This rule
  * works fine for implicit deadline tasks (deadline == period), and the
  * CBS was designed for implicit deadline tasks. However, a task with
  * constrained deadline (deadline < period) might be awakened after the
  * deadline, but before the next period. In this case, replenishing the
  * task would allow it to run for runtime / deadline. As in this case
  * deadline < period, CBS enables a task to run for more than the
  * runtime / period. In a very loaded system, this can cause a domino
  * effect, making other tasks miss their deadlines.
  *
  * To avoid this problem, in the activation of a constrained deadline
  * task after the deadline but before the next period, throttle the
  * task and set the replenishing timer to the begin of the next period,
  * unless it is boosted.
  */
 static inline void dl_check_constrained_dl(struct sched_dl_entity *dl_se)
 {
     struct task_struct *p = dl_task_of(dl_se);
     struct rq *rq = rq_of_dl_rq(dl_rq_of_se(dl_se));
 
     if (dl_time_before(dl_se->deadline, rq_clock(rq)) &&
         dl_time_before(rq_clock(rq), dl_next_period(dl_se))) {
         if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(p)))
             return;
         dl_se->dl_throttled = 1;
         if (dl_se->runtime > 0)
             dl_se->runtime = 0;
     }
 }
 
 static
 int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
 {
     return (dl_se->runtime <= 0);
 }
 
 /*
  * This function implements the GRUB accounting rule:
  * according to the GRUB reclaiming algorithm, the runtime is
  * not decreased as "dq = -dt", but as
  * "dq = -max{u / Umax, (1 - Uinact - Uextra)} dt",
  * where u is the utilization of the task, Umax is the maximum reclaimable
  * utilization, Uinact is the (per-runqueue) inactive utilization, computed
  * as the difference between the "total runqueue utilization" and the
  * runqueue active utilization, and Uextra is the (per runqueue) extra
  * reclaimable utilization.
  * Since rq->dl.running_bw and rq->dl.this_bw contain utilizations
  * multiplied by 2^BW_SHIFT, the result has to be shifted right by
  * BW_SHIFT.
  * Since rq->dl.bw_ratio contains 1 / Umax multiplied by 2^RATIO_SHIFT,
  * dl_bw is multiped by rq->dl.bw_ratio and shifted right by RATIO_SHIFT.
  * Since delta is a 64 bit variable, to have an overflow its value
  * should be larger than 2^(64 - 20 - 8), which is more than 64 seconds.
  * So, overflow is not an issue here.
  */
 static u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
 {
     u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot - Uact */
     u64 u_act;
     u64 u_act_min = (dl_se->dl_bw * rq->dl.bw_ratio) >> RATIO_SHIFT;
 
     /*
      * Instead of computing max{u * bw_ratio, (1 - u_inact - u_extra)},
      * we compare u_inact + rq->dl.extra_bw with
      * 1 - (u * rq->dl.bw_ratio >> RATIO_SHIFT), because
      * u_inact + rq->dl.extra_bw can be larger than
      * 1 * (so, 1 - u_inact - rq->dl.extra_bw would be negative
      * leading to wrong results)
      */
     if (u_inact + rq->dl.extra_bw > BW_UNIT - u_act_min)
         u_act = u_act_min;
     else
         u_act = BW_UNIT - u_inact - rq->dl.extra_bw;
 
     return (delta * u_act) >> BW_SHIFT;
 }
 
 /*
  * Update the current task's runtime statistics (provided it is still
  * a -deadline task and has not been removed from the dl_rq).
  */
 static void update_curr_dl(struct rq *rq)
 {
     struct task_struct *curr = rq->curr;
     struct sched_dl_entity *dl_se = &curr->dl;
     u64 delta_exec, scaled_delta_exec;
     int cpu = cpu_of(rq);
     u64 now;
 
     if (!dl_task(curr) || !on_dl_rq(dl_se))
         return;
 
     /*
      * Consumed budget is computed considering the time as
      * observed by schedulable tasks (excluding time spent
      * in hardirq context, etc.). Deadlines are instead
      * computed using hard walltime. This seems to be the more
      * natural solution, but the full ramifications of this
      * approach need further study.
      */
     now = rq_clock_task(rq);
     delta_exec = now - curr->se.exec_start;
     if (unlikely((s64)delta_exec <= 0)) {
         if (unlikely(dl_se->dl_yielded))
             goto throttle;
         return;
     }
 
     schedstat_set(curr->stats.exec_max,
               max(curr->stats.exec_max, delta_exec));
 
     trace_sched_stat_runtime(curr, delta_exec, 0);
 
     curr->se.sum_exec_runtime += delta_exec;
     account_group_exec_runtime(curr, delta_exec);
 
     curr->se.exec_start = now;
     cgroup_account_cputime(curr, delta_exec);
 
     if (dl_entity_is_special(dl_se))
         return;
 
     /*
      * For tasks that participate in GRUB, we implement GRUB-PA: the
      * spare reclaimed bandwidth is used to clock down frequency.
      *
      * For the others, we still need to scale reservation parameters
      * according to current frequency and CPU maximum capacity.
      */
     if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) {
         scaled_delta_exec = grub_reclaim(delta_exec,
                          rq,
                          &curr->dl);
     } else {
         unsigned long scale_freq = arch_scale_freq_capacity(cpu);
         unsigned long scale_cpu = arch_scale_cpu_capacity(cpu);
 
         scaled_delta_exec = cap_scale(delta_exec, scale_freq);
         scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu);
     }
 
     dl_se->runtime -= scaled_delta_exec;
 
 throttle:
     if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
         dl_se->dl_throttled = 1;
 
         /* If requested, inform the user about runtime overruns. */
         if (dl_runtime_exceeded(dl_se) &&
             (dl_se->flags & SCHED_FLAG_DL_OVERRUN))
             dl_se->dl_overrun = 1;
 
         __dequeue_task_dl(rq, curr, 0);
         if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(curr)))
             enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
 
         if (!is_leftmost(curr, &rq->dl))
             resched_curr(rq);
     }
 
     /*
      * Because -- for now -- we share the rt bandwidth, we need to
      * account our runtime there too, otherwise actual rt tasks
      * would be able to exceed the shared quota.
      *
      * Account to the root rt group for now.
      *
      * The solution we're working towards is having the RT groups scheduled
      * using deadline servers -- however there's a few nasties to figure
      * out before that can happen.
      */
     if (rt_bandwidth_enabled()) {
         struct rt_rq *rt_rq = &rq->rt;
 
         raw_spin_lock(&rt_rq->rt_runtime_lock);
         /*
          * We'll let actual RT tasks worry about the overflow here, we
          * have our own CBS to keep us inline; only account when RT
          * bandwidth is relevant.
          */
         if (sched_rt_bandwidth_account(rt_rq))
             rt_rq->rt_time += delta_exec;
         raw_spin_unlock(&rt_rq->rt_runtime_lock);
     }
 }
 
 static enum hrtimer_restart inactive_task_timer(struct hrtimer *timer)
 {
     struct sched_dl_entity *dl_se = container_of(timer,
                              struct sched_dl_entity,
                              inactive_timer);
     struct task_struct *p = dl_task_of(dl_se);
     struct rq_flags rf;
     struct rq *rq;
 
     rq = task_rq_lock(p, &rf);
 
     sched_clock_tick();
     update_rq_clock(rq);
 
     if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
         struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
 
         if (READ_ONCE(p->__state) == TASK_DEAD && dl_se->dl_non_contending) {
             sub_running_bw(&p->dl, dl_rq_of_se(&p->dl));
             sub_rq_bw(&p->dl, dl_rq_of_se(&p->dl));
             dl_se->dl_non_contending = 0;
         }
 
         raw_spin_lock(&dl_b->lock);
         __dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
         raw_spin_unlock(&dl_b->lock);
         __dl_clear_params(p);
 
         goto unlock;
     }
     if (dl_se->dl_non_contending == 0)
         goto unlock;
 
     sub_running_bw(dl_se, &rq->dl);
     dl_se->dl_non_contending = 0;
 unlock:
     task_rq_unlock(rq, p, &rf);
     put_task_struct(p);
 
     return HRTIMER_NORESTART;
 }
 
 void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se)
 {
     struct hrtimer *timer = &dl_se->inactive_timer;
 
     hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
     timer->function = inactive_task_timer;
 }
 
 #define __node_2_dle(node) \
     rb_entry((node), struct sched_dl_entity, rb_node)
 
 #ifdef CONFIG_SMP
 
 static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
 {
     struct rq *rq = rq_of_dl_rq(dl_rq);
 
     if (dl_rq->earliest_dl.curr == 0 ||
         dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
         if (dl_rq->earliest_dl.curr == 0)
             cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_HIGHER);
         dl_rq->earliest_dl.curr = deadline;
         cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
     }
 }
 
 static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
 {
     struct rq *rq = rq_of_dl_rq(dl_rq);
 
     /*
      * Since we may have removed our earliest (and/or next earliest)
      * task we must recompute them.
      */
     if (!dl_rq->dl_nr_running) {
         dl_rq->earliest_dl.curr = 0;
         dl_rq->earliest_dl.next = 0;
         cpudl_clear(&rq->rd->cpudl, rq->cpu);
         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
     } else {
         struct rb_node *leftmost = rb_first_cached(&dl_rq->root);
         struct sched_dl_entity *entry = __node_2_dle(leftmost);
 
         dl_rq->earliest_dl.curr = entry->deadline;
         cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline);
     }
 }
 
 #else
 
 static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
 static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
 
 #endif /* CONFIG_SMP */
 
 static inline
 void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     int prio = dl_task_of(dl_se)->prio;
     u64 deadline = dl_se->deadline;
 
     WARN_ON(!dl_prio(prio));
     dl_rq->dl_nr_running++;
     add_nr_running(rq_of_dl_rq(dl_rq), 1);
 
     inc_dl_deadline(dl_rq, deadline);
     inc_dl_migration(dl_se, dl_rq);
 }
 
 static inline
 void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
     int prio = dl_task_of(dl_se)->prio;
 
     WARN_ON(!dl_prio(prio));
     WARN_ON(!dl_rq->dl_nr_running);
     dl_rq->dl_nr_running--;
     sub_nr_running(rq_of_dl_rq(dl_rq), 1);
 
     dec_dl_deadline(dl_rq, dl_se->deadline);
     dec_dl_migration(dl_se, dl_rq);
 }
 
 static inline bool __dl_less(struct rb_node *a, const struct rb_node *b)
 {
     return dl_time_before(__node_2_dle(a)->deadline, __node_2_dle(b)->deadline);
 }
 
 static inline struct sched_statistics *
 __schedstats_from_dl_se(struct sched_dl_entity *dl_se)
 {
     return &dl_task_of(dl_se)->stats;
 }
 
 static inline void
 update_stats_wait_start_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
 {
     struct sched_statistics *stats;
 
     if (!schedstat_enabled())
         return;
 
     stats = __schedstats_from_dl_se(dl_se);
     __update_stats_wait_start(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
 }
 
 static inline void
 update_stats_wait_end_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
 {
     struct sched_statistics *stats;
 
     if (!schedstat_enabled())
         return;
 
     stats = __schedstats_from_dl_se(dl_se);
     __update_stats_wait_end(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
 }
 
 static inline void
 update_stats_enqueue_sleeper_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
 {
     struct sched_statistics *stats;
 
     if (!schedstat_enabled())
         return;
 
     stats = __schedstats_from_dl_se(dl_se);
     __update_stats_enqueue_sleeper(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
 }
 
 static inline void
 update_stats_enqueue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se,
             int flags)
 {
     if (!schedstat_enabled())
         return;
 
     if (flags & ENQUEUE_WAKEUP)
         update_stats_enqueue_sleeper_dl(dl_rq, dl_se);
 }
 
 static inline void
 update_stats_dequeue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se,
             int flags)
 {
     struct task_struct *p = dl_task_of(dl_se);
 
     if (!schedstat_enabled())
         return;
 
     if ((flags & DEQUEUE_SLEEP)) {
         unsigned int state;
 
         state = READ_ONCE(p->__state);
         if (state & TASK_INTERRUPTIBLE)
             __schedstat_set(p->stats.sleep_start,
                     rq_clock(rq_of_dl_rq(dl_rq)));
 
         if (state & TASK_UNINTERRUPTIBLE)
             __schedstat_set(p->stats.block_start,
                     rq_clock(rq_of_dl_rq(dl_rq)));
     }
 }
 
 static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
 {
     struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 
     BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
 
     rb_add_cached(&dl_se->rb_node, &dl_rq->root, __dl_less);
 
     inc_dl_tasks(dl_se, dl_rq);
 }
 
 static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
 {
     struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 
     if (RB_EMPTY_NODE(&dl_se->rb_node))
         return;
 
     rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
 
     RB_CLEAR_NODE(&dl_se->rb_node);
 
     dec_dl_tasks(dl_se, dl_rq);
 }
 
 static void
 enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
 {
     BUG_ON(on_dl_rq(dl_se));
 
     update_stats_enqueue_dl(dl_rq_of_se(dl_se), dl_se, flags);
 
     /*
      * If this is a wakeup or a new instance, the scheduling
      * parameters of the task might need updating. Otherwise,
      * we want a replenishment of its runtime.
      */
     if (flags & ENQUEUE_WAKEUP) {
         task_contending(dl_se, flags);
         update_dl_entity(dl_se);
     } else if (flags & ENQUEUE_REPLENISH) {
         replenish_dl_entity(dl_se);
     } else if ((flags & ENQUEUE_RESTORE) &&
           dl_time_before(dl_se->deadline,
                  rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
         setup_new_dl_entity(dl_se);
     }
 
     __enqueue_dl_entity(dl_se);
 }
 
 static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
 {
     __dequeue_dl_entity(dl_se);
 }
 
 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 {
     if (is_dl_boosted(&p->dl)) {
         /*
          * Because of delays in the detection of the overrun of a
          * thread's runtime, it might be the case that a thread
          * goes to sleep in a rt mutex with negative runtime. As
          * a consequence, the thread will be throttled.
          *
          * While waiting for the mutex, this thread can also be
          * boosted via PI, resulting in a thread that is throttled
          * and boosted at the same time.
          *
          * In this case, the boost overrides the throttle.
          */
         if (p->dl.dl_throttled) {
             /*
              * The replenish timer needs to be canceled. No
              * problem if it fires concurrently: boosted threads
              * are ignored in dl_task_timer().
              */
             hrtimer_try_to_cancel(&p->dl.dl_timer);
             p->dl.dl_throttled = 0;
         }
     } else if (!dl_prio(p->normal_prio)) {
         /*
          * Special case in which we have a !SCHED_DEADLINE task that is going
          * to be deboosted, but exceeds its runtime while doing so. No point in
          * replenishing it, as it's going to return back to its original
          * scheduling class after this. If it has been throttled, we need to
          * clear the flag, otherwise the task may wake up as throttled after
          * being boosted again with no means to replenish the runtime and clear
          * the throttle.
          */
         p->dl.dl_throttled = 0;
         if (!(flags & ENQUEUE_REPLENISH))
             printk_deferred_once("sched: DL de-boosted task PID %d: REPLENISH flag missing\n",
                          task_pid_nr(p));
 
         return;
     }
 
     /*
      * Check if a constrained deadline task was activated
      * after the deadline but before the next period.
      * If that is the case, the task will be throttled and
      * the replenishment timer will be set to the next period.
      */
     if (!p->dl.dl_throttled && !dl_is_implicit(&p->dl))
         dl_check_constrained_dl(&p->dl);
 
     if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & ENQUEUE_RESTORE) {
         add_rq_bw(&p->dl, &rq->dl);
         add_running_bw(&p->dl, &rq->dl);
     }
 
     /*
      * If p is throttled, we do not enqueue it. In fact, if it exhausted
      * its budget it needs a replenishment and, since it now is on
      * its rq, the bandwidth timer callback (which clearly has not
      * run yet) will take care of this.
      * However, the active utilization does not depend on the fact
      * that the task is on the runqueue or not (but depends on the
      * task's state - in GRUB parlance, "inactive" vs "active contending").
      * In other words, even if a task is throttled its utilization must
      * be counted in the active utilization; hence, we need to call
      * add_running_bw().
      */
     if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
         if (flags & ENQUEUE_WAKEUP)
             task_contending(&p->dl, flags);
 
         return;
     }
 
     check_schedstat_required();
     update_stats_wait_start_dl(dl_rq_of_se(&p->dl), &p->dl);
 
     enqueue_dl_entity(&p->dl, flags);
 
     if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
         enqueue_pushable_dl_task(rq, p);
 }
 
 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 {
     update_stats_dequeue_dl(&rq->dl, &p->dl, flags);
     dequeue_dl_entity(&p->dl);
     dequeue_pushable_dl_task(rq, p);
 }
 
 static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 {
     update_curr_dl(rq);
     __dequeue_task_dl(rq, p, flags);
 
     if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & DEQUEUE_SAVE) {
         sub_running_bw(&p->dl, &rq->dl);
         sub_rq_bw(&p->dl, &rq->dl);
     }
 
     /*
      * This check allows to start the inactive timer (or to immediately
      * decrease the active utilization, if needed) in two cases:
      * when the task blocks and when it is terminating
      * (p->state == TASK_DEAD). We can handle the two cases in the same
      * way, because from GRUB's point of view the same thing is happening
      * (the task moves from "active contending" to "active non contending"
      * or "inactive")
      */
     if (flags & DEQUEUE_SLEEP)
         task_non_contending(p);
 }
 
 /*
  * Yield task semantic for -deadline tasks is:
  *
  *   get off from the CPU until our next instance, with
  *   a new runtime. This is of little use now, since we
  *   don't have a bandwidth reclaiming mechanism. Anyway,
  *   bandwidth reclaiming is planned for the future, and
  *   yield_task_dl will indicate that some spare budget
  *   is available for other task instances to use it.
  */
 static void yield_task_dl(struct rq *rq)
 {
     /*
      * We make the task go to sleep until its current deadline by
      * forcing its runtime to zero. This way, update_curr_dl() stops
      * it and the bandwidth timer will wake it up and will give it
      * new scheduling parameters (thanks to dl_yielded=1).
      */
     rq->curr->dl.dl_yielded = 1;
 
     update_rq_clock(rq);
     update_curr_dl(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);
 }
 
 #ifdef CONFIG_SMP
 
 static int find_later_rq(struct task_struct *task);
 
 static int
 select_task_rq_dl(struct task_struct *p, int cpu, int flags)
 {
     struct task_struct *curr;
     bool select_rq;
     struct rq *rq;
 
     if (!(flags & WF_TTWU))
         goto out;
 
     rq = cpu_rq(cpu);
 
     rcu_read_lock();
     curr = READ_ONCE(rq->curr); /* unlocked access */
 
     /*
      * If we are dealing with a -deadline task, we must
      * decide where to wake it up.
      * If it has a later deadline and the current task
      * on this rq can't move (provided the waking task
      * can!) we prefer to send it somewhere else. On the
      * other hand, if it has a shorter deadline, we
      * try to make it stay here, it might be important.
      */
     select_rq = unlikely(dl_task(curr)) &&
             (curr->nr_cpus_allowed < 2 ||
              !dl_entity_preempt(&p->dl, &curr->dl)) &&
             p->nr_cpus_allowed > 1;
 
     /*
      * Take the capacity of the CPU into account to
      * ensure it fits the requirement of the task.
      */
     if (static_branch_unlikely(&sched_asym_cpucapacity))
         select_rq |= !dl_task_fits_capacity(p, cpu);
 
     if (select_rq) {
         int target = find_later_rq(p);
 
         if (target != -1 &&
                 (dl_time_before(p->dl.deadline,
                     cpu_rq(target)->dl.earliest_dl.curr) ||
                 (cpu_rq(target)->dl.dl_nr_running == 0)))
             cpu = target;
     }
     rcu_read_unlock();
 
 out:
     return cpu;
 }
 
 static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused)
 {
     struct rq_flags rf;
     struct rq *rq;
 
     if (READ_ONCE(p->__state) != TASK_WAKING)
         return;
 
     rq = task_rq(p);
     /*
      * Since p->state == TASK_WAKING, set_task_cpu() has been called
      * from try_to_wake_up(). Hence, p->pi_lock is locked, but
      * rq->lock is not... So, lock it
      */
     rq_lock(rq, &rf);
     if (p->dl.dl_non_contending) {
         update_rq_clock(rq);
         sub_running_bw(&p->dl, &rq->dl);
         p->dl.dl_non_contending = 0;
         /*
          * If the timer handler is currently running and the
          * timer cannot be canceled, inactive_task_timer()
          * will see that dl_not_contending is not set, and
          * will not touch the rq's active utilization,
          * so we are still safe.
          */
         if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
             put_task_struct(p);
     }
     sub_rq_bw(&p->dl, &rq->dl);
     rq_unlock(rq, &rf);
 }
 
 static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 {
     /*
      * Current can't be migrated, useless to reschedule,
      * let's hope p can move out.
      */
     if (rq->curr->nr_cpus_allowed == 1 ||
         !cpudl_find(&rq->rd->cpudl, rq->curr, NULL))
         return;
 
     /*
      * p is migratable, so let's not schedule it and
      * see if it is pushed or pulled somewhere else.
      */
     if (p->nr_cpus_allowed != 1 &&
         cpudl_find(&rq->rd->cpudl, p, NULL))
         return;
 
     resched_curr(rq);
 }
 
 static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
 {
     if (!on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) {
         /*
          * 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've
          * not yet started the picking loop.
          */
         rq_unpin_lock(rq, rf);
         pull_dl_task(rq);
         rq_repin_lock(rq, rf);
     }
 
     return sched_stop_runnable(rq) || sched_dl_runnable(rq);
 }
 #endif /* CONFIG_SMP */
 
 /*
  * Only called when both the current and waking task are -deadline
  * tasks.
  */
 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
                   int flags)
 {
     if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
         resched_curr(rq);
         return;
     }
 
 #ifdef CONFIG_SMP
     /*
      * In the unlikely case current and p have the same deadline
      * let us try to decide what's the best thing to do...
      */
     if ((p->dl.deadline == rq->curr->dl.deadline) &&
         !test_tsk_need_resched(rq->curr))
         check_preempt_equal_dl(rq, p);
 #endif /* CONFIG_SMP */
 }
 
 #ifdef CONFIG_SCHED_HRTICK
 static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
 {
     hrtick_start(rq, p->dl.runtime);
 }
 #else /* !CONFIG_SCHED_HRTICK */
 static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
 {
 }
 #endif
 
 static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
 {
     struct sched_dl_entity *dl_se = &p->dl;
     struct dl_rq *dl_rq = &rq->dl;
 
     p->se.exec_start = rq_clock_task(rq);
     if (on_dl_rq(&p->dl))
         update_stats_wait_end_dl(dl_rq, dl_se);
 
     /* You can't push away the running task */
     dequeue_pushable_dl_task(rq, p);
 
     if (!first)
         return;
 
     if (hrtick_enabled_dl(rq))
         start_hrtick_dl(rq, p);
 
     if (rq->curr->sched_class != &dl_sched_class)
         update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
 
     deadline_queue_push_tasks(rq);
 }
 
 static struct sched_dl_entity *pick_next_dl_entity(struct dl_rq *dl_rq)
 {
     struct rb_node *left = rb_first_cached(&dl_rq->root);
 
     if (!left)
         return NULL;
 
     return __node_2_dle(left);
 }
 
 static struct task_struct *pick_task_dl(struct rq *rq)
 {
     struct sched_dl_entity *dl_se;
     struct dl_rq *dl_rq = &rq->dl;
     struct task_struct *p;
 
     if (!sched_dl_runnable(rq))
         return NULL;
 
     dl_se = pick_next_dl_entity(dl_rq);
     BUG_ON(!dl_se);
     p = dl_task_of(dl_se);
 
     return p;
 }
 
 static struct task_struct *pick_next_task_dl(struct rq *rq)
 {
     struct task_struct *p;
 
     p = pick_task_dl(rq);
     if (p)
         set_next_task_dl(rq, p, true);
 
     return p;
 }
 
 static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
 {
     struct sched_dl_entity *dl_se = &p->dl;
     struct dl_rq *dl_rq = &rq->dl;
 
     if (on_dl_rq(&p->dl))
         update_stats_wait_start_dl(dl_rq, dl_se);
 
     update_curr_dl(rq);
 
     update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
     if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
         enqueue_pushable_dl_task(rq, p);
 }
 
 /*
  * 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_dl(struct rq *rq, struct task_struct *p, int queued)
 {
     update_curr_dl(rq);
 
     update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
     /*
      * Even when we have runtime, update_curr_dl() might have resulted in us
      * not being the leftmost task anymore. In that case NEED_RESCHED will
      * be set and schedule() will start a new hrtick for the next task.
      */
     if (hrtick_enabled_dl(rq) && queued && p->dl.runtime > 0 &&
         is_leftmost(p, &rq->dl))
         start_hrtick_dl(rq, p);
 }
 
 static void task_fork_dl(struct task_struct *p)
 {
     /*
      * SCHED_DEADLINE tasks cannot fork and this is achieved through
      * sched_fork()
      */
 }
 
 #ifdef CONFIG_SMP
 
 /* Only try algorithms three times */
 #define DL_MAX_TRIES 3
 
 static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
 {
     if (!task_running(rq, p) &&
         cpumask_test_cpu(cpu, &p->cpus_mask))
         return 1;
     return 0;
 }
 
 /*
  * Return the earliest pushable rq's task, which is suitable to be executed
  * on the CPU, NULL otherwise:
  */
 static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
 {
     struct task_struct *p = NULL;
     struct rb_node *next_node;
 
     if (!has_pushable_dl_tasks(rq))
         return NULL;
 
     next_node = rb_first_cached(&rq->dl.pushable_dl_tasks_root);
 
 next_node:
     if (next_node) {
         p = __node_2_pdl(next_node);
 
         if (pick_dl_task(rq, p, cpu))
             return p;
 
         next_node = rb_next(next_node);
         goto next_node;
     }
 
     return NULL;
 }
 
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
 
 static int find_later_rq(struct task_struct *task)
 {
     struct sched_domain *sd;
     struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
     int this_cpu = smp_processor_id();
     int cpu = task_cpu(task);
 
     /* Make sure the mask is initialized first */
     if (unlikely(!later_mask))
         return -1;
 
     if (task->nr_cpus_allowed == 1)
         return -1;
 
     /*
      * We have to consider system topology and task affinity
      * first, then we can look for a suitable CPU.
      */
     if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
         return -1;
 
     /*
      * If we are here, some targets have been found, including
      * the most suitable which is, among the runqueues where the
      * current tasks have later deadlines than the task's one, the
      * rq with the latest possible one.
      *
      * Now we check how well this matches with task's
      * affinity and system topology.
      *
      * The last CPU where the task run is our first
      * guess, since it is most likely cache-hot there.
      */
     if (cpumask_test_cpu(cpu, later_mask))
         return cpu;
     /*
      * Check if this_cpu is to be skipped (i.e., it is
      * not in the mask) or not.
      */
     if (!cpumask_test_cpu(this_cpu, later_mask))
         this_cpu = -1;
 
     rcu_read_lock();
     for_each_domain(cpu, sd) {
         if (sd->flags & SD_WAKE_AFFINE) {
             int best_cpu;
 
             /*
              * If possible, preempting this_cpu is
              * cheaper than migrating.
              */
             if (this_cpu != -1 &&
                 cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
                 rcu_read_unlock();
                 return this_cpu;
             }
 
             best_cpu = cpumask_any_and_distribute(later_mask,
                                   sched_domain_span(sd));
             /*
              * Last chance: if a CPU being in both later_mask
              * and current sd span is valid, that becomes our
              * choice. Of course, the latest possible CPU is
              * already under consideration through later_mask.
              */
             if (best_cpu < nr_cpu_ids) {
                 rcu_read_unlock();
                 return best_cpu;
             }
         }
     }
     rcu_read_unlock();
 
     /*
      * At this point, all our guesses failed, we just return
      * 'something', and let the caller sort the things out.
      */
     if (this_cpu != -1)
         return this_cpu;
 
     cpu = cpumask_any_distribute(later_mask);
     if (cpu < nr_cpu_ids)
         return cpu;
 
     return -1;
 }
 
 /* Locks the rq it finds */
 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 {
     struct rq *later_rq = NULL;
     int tries;
     int cpu;
 
     for (tries = 0; tries < DL_MAX_TRIES; tries++) {
         cpu = find_later_rq(task);
 
         if ((cpu == -1) || (cpu == rq->cpu))
             break;
 
         later_rq = cpu_rq(cpu);
 
         if (later_rq->dl.dl_nr_running &&
             !dl_time_before(task->dl.deadline,
                     later_rq->dl.earliest_dl.curr)) {
             /*
              * Target rq has tasks of equal or earlier deadline,
              * retrying does not release any lock and is unlikely
              * to yield a different result.
              */
             later_rq = NULL;
             break;
         }
 
         /* Retry if something changed. */
         if (double_lock_balance(rq, later_rq)) {
             if (unlikely(task_rq(task) != rq ||
                      !cpumask_test_cpu(later_rq->cpu, &task->cpus_mask) ||
                      task_running(rq, task) ||
                      !dl_task(task) ||
                      !task_on_rq_queued(task))) {
                 double_unlock_balance(rq, later_rq);
                 later_rq = NULL;
                 break;
             }
         }
 
         /*
          * If the rq we found has no -deadline task, or
          * its earliest one has a later deadline than our
          * task, the rq is a good one.
          */
         if (!later_rq->dl.dl_nr_running ||
             dl_time_before(task->dl.deadline,
                    later_rq->dl.earliest_dl.curr))
             break;
 
         /* Otherwise we try again. */
         double_unlock_balance(rq, later_rq);
         later_rq = NULL;
     }
 
     return later_rq;
 }
 
 static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
 {
     struct task_struct *p;
 
     if (!has_pushable_dl_tasks(rq))
         return NULL;
 
     p = __node_2_pdl(rb_first_cached(&rq->dl.pushable_dl_tasks_root));
 
     BUG_ON(rq->cpu != task_cpu(p));
     BUG_ON(task_current(rq, p));
     BUG_ON(p->nr_cpus_allowed <= 1);
 
     BUG_ON(!task_on_rq_queued(p));
     BUG_ON(!dl_task(p));
 
     return p;
 }
 
 /*
  * See if the non running -deadline tasks on this rq
  * can be sent to some other CPU where they can preempt
  * and start executing.
  */
 static int push_dl_task(struct rq *rq)
 {
     struct task_struct *next_task;
     struct rq *later_rq;
     int ret = 0;
 
     if (!rq->dl.overloaded)
         return 0;
 
     next_task = pick_next_pushable_dl_task(rq);
     if (!next_task)
         return 0;
 
 retry:
     /*
      * If next_task preempts rq->curr, and rq->curr
      * can move away, it makes sense to just reschedule
      * without going further in pushing next_task.
      */
     if (dl_task(rq->curr) &&
         dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
         rq->curr->nr_cpus_allowed > 1) {
         resched_curr(rq);
         return 0;
     }
 
     if (is_migration_disabled(next_task))
         return 0;
 
     if (WARN_ON(next_task == rq->curr))
         return 0;
 
     /* We might release rq lock */
     get_task_struct(next_task);
 
     /* Will lock the rq it'll find */
     later_rq = find_lock_later_rq(next_task, rq);
     if (!later_rq) {
         struct task_struct *task;
 
         /*
          * We must check all this again, since
          * find_lock_later_rq releases rq->lock and it is
          * then possible that next_task has migrated.
          */
         task = pick_next_pushable_dl_task(rq);
         if (task == next_task) {
             /*
              * The task is still there. We don't try
              * again, some other CPU will pull it when ready.
              */
             goto out;
         }
 
         if (!task)
             /* No more tasks */
             goto out;
 
         put_task_struct(next_task);
         next_task = task;
         goto retry;
     }
 
     deactivate_task(rq, next_task, 0);
     set_task_cpu(next_task, later_rq->cpu);
     activate_task(later_rq, next_task, 0);
     ret = 1;
 
     resched_curr(later_rq);
 
     double_unlock_balance(rq, later_rq);
 
 out:
     put_task_struct(next_task);
 
     return ret;
 }
 
 static void push_dl_tasks(struct rq *rq)
 {
     /* push_dl_task() will return true if it moved a -deadline task */
     while (push_dl_task(rq))
         ;
 }
 
 static void pull_dl_task(struct rq *this_rq)
 {
     int this_cpu = this_rq->cpu, cpu;
     struct task_struct *p, *push_task;
     bool resched = false;
     struct rq *src_rq;
     u64 dmin = LONG_MAX;
 
     if (likely(!dl_overloaded(this_rq)))
         return;
 
     /*
      * Match the barrier from dl_set_overloaded; this guarantees that if we
      * see overloaded we must also see the dlo_mask bit.
      */
     smp_rmb();
 
     for_each_cpu(cpu, this_rq->rd->dlo_mask) {
         if (this_cpu == cpu)
             continue;
 
         src_rq = cpu_rq(cpu);
 
         /*
          * It looks racy, abd it is! However, as in sched_rt.c,
          * we are fine with this.
          */
         if (this_rq->dl.dl_nr_running &&
             dl_time_before(this_rq->dl.earliest_dl.curr,
                    src_rq->dl.earliest_dl.next))
             continue;
 
         /* Might drop this_rq->lock */
         push_task = NULL;
         double_lock_balance(this_rq, src_rq);
 
         /*
          * If there are no more pullable tasks on the
          * rq, we're done with it.
          */
         if (src_rq->dl.dl_nr_running <= 1)
             goto skip;
 
         p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
 
         /*
          * We found a task to be pulled if:
          *  - it preempts our current (if there's one),
          *  - it will preempt the last one we pulled (if any).
          */
         if (p && dl_time_before(p->dl.deadline, dmin) &&
             (!this_rq->dl.dl_nr_running ||
              dl_time_before(p->dl.deadline,
                     this_rq->dl.earliest_dl.curr))) {
             WARN_ON(p == src_rq->curr);
             WARN_ON(!task_on_rq_queued(p));
 
             /*
              * Then we pull iff p has actually an earlier
              * deadline than the current task of its runqueue.
              */
             if (dl_time_before(p->dl.deadline,
                        src_rq->curr->dl.deadline))
                 goto skip;
 
             if (is_migration_disabled(p)) {
                 push_task = get_push_task(src_rq);
             } else {
                 deactivate_task(src_rq, p, 0);
                 set_task_cpu(p, this_cpu);
                 activate_task(this_rq, p, 0);
                 dmin = p->dl.deadline;
                 resched = true;
             }
 
             /* Is there any other task even earlier? */
         }
 skip:
         double_unlock_balance(this_rq, src_rq);
 
         if (push_task) {
             raw_spin_rq_unlock(this_rq);
             stop_one_cpu_nowait(src_rq->cpu, push_cpu_stop,
                         push_task, &src_rq->push_work);
             raw_spin_rq_lock(this_rq);
         }
     }
 
     if (resched)
         resched_curr(this_rq);
 }
 
 /*
  * Since the task is not running and a reschedule is not going to happen
  * anytime soon on its runqueue, we try pushing it away now.
  */
 static void task_woken_dl(struct rq *rq, struct task_struct *p)
 {
     if (!task_running(rq, p) &&
         !test_tsk_need_resched(rq->curr) &&
         p->nr_cpus_allowed > 1 &&
         dl_task(rq->curr) &&
         (rq->curr->nr_cpus_allowed < 2 ||
          !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
         push_dl_tasks(rq);
     }
 }
 
 static void set_cpus_allowed_dl(struct task_struct *p,
                 const struct cpumask *new_mask,
                 u32 flags)
 {
     struct root_domain *src_rd;
     struct rq *rq;
 
     BUG_ON(!dl_task(p));
 
     rq = task_rq(p);
     src_rd = rq->rd;
     /*
      * Migrating a SCHED_DEADLINE task between exclusive
      * cpusets (different root_domains) entails a bandwidth
      * update. We already made space for us in the destination
      * domain (see cpuset_can_attach()).
      */
     if (!cpumask_intersects(src_rd->span, new_mask)) {
         struct dl_bw *src_dl_b;
 
         src_dl_b = dl_bw_of(cpu_of(rq));
         /*
          * We now free resources of the root_domain we are migrating
          * off. In the worst case, sched_setattr() may temporary fail
          * until we complete the update.
          */
         raw_spin_lock(&src_dl_b->lock);
         __dl_sub(src_dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
         raw_spin_unlock(&src_dl_b->lock);
     }
 
     set_cpus_allowed_common(p, new_mask, flags);
 }
 
 /* Assumes rq->lock is held */
 static void rq_online_dl(struct rq *rq)
 {
     if (rq->dl.overloaded)
         dl_set_overload(rq);
 
     cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
     if (rq->dl.dl_nr_running > 0)
         cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr);
 }
 
 /* Assumes rq->lock is held */
 static void rq_offline_dl(struct rq *rq)
 {
     if (rq->dl.overloaded)
         dl_clear_overload(rq);
 
     cpudl_clear(&rq->rd->cpudl, rq->cpu);
     cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
 }
 
 void __init init_sched_dl_class(void)
 {
     unsigned int i;
 
     for_each_possible_cpu(i)
         zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
                     GFP_KERNEL, cpu_to_node(i));
 }
 
 void dl_add_task_root_domain(struct task_struct *p)
 {
     struct rq_flags rf;
     struct rq *rq;
     struct dl_bw *dl_b;
 
     raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
     if (!dl_task(p)) {
         raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
         return;
     }
 
     rq = __task_rq_lock(p, &rf);
 
     dl_b = &rq->rd->dl_bw;
     raw_spin_lock(&dl_b->lock);
 
     __dl_add(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
 
     raw_spin_unlock(&dl_b->lock);
 
     task_rq_unlock(rq, p, &rf);
 }
 
 void dl_clear_root_domain(struct root_domain *rd)
 {
     unsigned long flags;
 
     raw_spin_lock_irqsave(&rd->dl_bw.lock, flags);
     rd->dl_bw.total_bw = 0;
     raw_spin_unlock_irqrestore(&rd->dl_bw.lock, flags);
 }
 
 #endif /* CONFIG_SMP */
 
 static void switched_from_dl(struct rq *rq, struct task_struct *p)
 {
     /*
      * task_non_contending() can start the "inactive timer" (if the 0-lag
      * time is in the future). If the task switches back to dl before
      * the "inactive timer" fires, it can continue to consume its current
      * runtime using its current deadline. If it stays outside of
      * SCHED_DEADLINE until the 0-lag time passes, inactive_task_timer()
      * will reset the task parameters.
      */
     if (task_on_rq_queued(p) && p->dl.dl_runtime)
         task_non_contending(p);
 
     if (!task_on_rq_queued(p)) {
         /*
          * Inactive timer is armed. However, p is leaving DEADLINE and
          * might migrate away from this rq while continuing to run on
          * some other class. We need to remove its contribution from
          * this rq running_bw now, or sub_rq_bw (below) will complain.
          */
         if (p->dl.dl_non_contending)
             sub_running_bw(&p->dl, &rq->dl);
         sub_rq_bw(&p->dl, &rq->dl);
     }
 
     /*
      * We cannot use inactive_task_timer() to invoke sub_running_bw()
      * at the 0-lag time, because the task could have been migrated
      * while SCHED_OTHER in the meanwhile.
      */
     if (p->dl.dl_non_contending)
         p->dl.dl_non_contending = 0;
 
     /*
      * Since this might be the only -deadline task on the rq,
      * this is the right place to try to pull some other one
      * from an overloaded CPU, if any.
      */
     if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
         return;
 
     deadline_queue_pull_task(rq);
 }
 
 /*
  * When switching to -deadline, we may overload the rq, then
  * we try to push someone off, if possible.
  */
 static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
     if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
         put_task_struct(p);
 
     /* If p is not queued we will update its parameters at next wakeup. */
     if (!task_on_rq_queued(p)) {
         add_rq_bw(&p->dl, &rq->dl);
 
         return;
     }
 
     if (rq->curr != p) {
 #ifdef CONFIG_SMP
         if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
             deadline_queue_push_tasks(rq);
 #endif
         if (dl_task(rq->curr))
             check_preempt_curr_dl(rq, p, 0);
         else
             resched_curr(rq);
     } else {
         update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
     }
 }
 
 /*
  * If the scheduling parameters of a -deadline task changed,
  * a push or pull operation might be needed.
  */
 static void prio_changed_dl(struct rq *rq, struct task_struct *p,
                 int oldprio)
 {
     if (task_on_rq_queued(p) || task_current(rq, p)) {
 #ifdef CONFIG_SMP
         /*
          * This might be too much, but unfortunately
          * we don't have the old deadline value, and
          * we can't argue if the task is increasing
          * or lowering its prio, so...
          */
         if (!rq->dl.overloaded)
             deadline_queue_pull_task(rq);
 
         /*
          * If we now have a earlier deadline task than p,
          * then reschedule, provided p is still on this
          * runqueue.
          */
         if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
             resched_curr(rq);
 #else
         /*
          * Again, we don't know if p has a earlier
          * or later deadline, so let's blindly set a
          * (maybe not needed) rescheduling point.
          */
         resched_curr(rq);
 #endif /* CONFIG_SMP */
     }
 }
 
 DEFINE_SCHED_CLASS(dl) = {
 
     .enqueue_task       = enqueue_task_dl,
     .dequeue_task       = dequeue_task_dl,
     .yield_task     = yield_task_dl,
 
     .check_preempt_curr = check_preempt_curr_dl,
 
     .pick_next_task     = pick_next_task_dl,
     .put_prev_task      = put_prev_task_dl,
     .set_next_task      = set_next_task_dl,
 
 #ifdef CONFIG_SMP
     .balance        = balance_dl,
     .pick_task      = pick_task_dl,
     .select_task_rq     = select_task_rq_dl,
     .migrate_task_rq    = migrate_task_rq_dl,
     .set_cpus_allowed       = set_cpus_allowed_dl,
     .rq_online              = rq_online_dl,
     .rq_offline             = rq_offline_dl,
     .task_woken     = task_woken_dl,
     .find_lock_rq       = find_lock_later_rq,
 #endif
 
     .task_tick      = task_tick_dl,
     .task_fork              = task_fork_dl,
 
     .prio_changed           = prio_changed_dl,
     .switched_from      = switched_from_dl,
     .switched_to        = switched_to_dl,
 
     .update_curr        = update_curr_dl,
 };
 
 /* Used for dl_bw check and update, used under sched_rt_handler()::mutex */
 static u64 dl_generation;
 
 int sched_dl_global_validate(void)
 {
     u64 runtime = global_rt_runtime();
     u64 period = global_rt_period();
     u64 new_bw = to_ratio(period, runtime);
     u64 gen = ++dl_generation;
     struct dl_bw *dl_b;
     int cpu, cpus, ret = 0;
     unsigned long flags;
 
     /*
      * Here we want to check the bandwidth not being set to some
      * value smaller than the currently allocated bandwidth in
      * any of the root_domains.
      */
     for_each_possible_cpu(cpu) {
         rcu_read_lock_sched();
 
         if (dl_bw_visited(cpu, gen))
             goto next;
 
         dl_b = dl_bw_of(cpu);
         cpus = dl_bw_cpus(cpu);
 
         raw_spin_lock_irqsave(&dl_b->lock, flags);
         if (new_bw * cpus < dl_b->total_bw)
             ret = -EBUSY;
         raw_spin_unlock_irqrestore(&dl_b->lock, flags);
 
 next:
         rcu_read_unlock_sched();
 
         if (ret)
             break;
     }
 
     return ret;
 }
 
 static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq)
 {
     if (global_rt_runtime() == RUNTIME_INF) {
         dl_rq->bw_ratio = 1 << RATIO_SHIFT;
         dl_rq->extra_bw = 1 << BW_SHIFT;
     } else {
         dl_rq->bw_ratio = to_ratio(global_rt_runtime(),
               global_rt_period()) >> (BW_SHIFT - RATIO_SHIFT);
         dl_rq->extra_bw = to_ratio(global_rt_period(),
                             global_rt_runtime());
     }
 }
 
 void sched_dl_do_global(void)
 {
     u64 new_bw = -1;
     u64 gen = ++dl_generation;
     struct dl_bw *dl_b;
     int cpu;
     unsigned long flags;
 
     if (global_rt_runtime() != RUNTIME_INF)
         new_bw = to_ratio(global_rt_period(), global_rt_runtime());
 
     for_each_possible_cpu(cpu) {
         rcu_read_lock_sched();
 
         if (dl_bw_visited(cpu, gen)) {
             rcu_read_unlock_sched();
             continue;
         }
 
         dl_b = dl_bw_of(cpu);
 
         raw_spin_lock_irqsave(&dl_b->lock, flags);
         dl_b->bw = new_bw;
         raw_spin_unlock_irqrestore(&dl_b->lock, flags);
 
         rcu_read_unlock_sched();
         init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
     }
 }
 
 /*
  * We must be sure that accepting a new task (or allowing changing the
  * parameters of an existing one) is consistent with the bandwidth
  * constraints. If yes, this function also accordingly updates the currently
  * allocated bandwidth to reflect the new situation.
  *
  * This function is called while holding p's rq->lock.
  */
 int sched_dl_overflow(struct task_struct *p, int policy,
               const struct sched_attr *attr)
 {
     u64 period = attr->sched_period ?: attr->sched_deadline;
     u64 runtime = attr->sched_runtime;
     u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
     int cpus, err = -1, cpu = task_cpu(p);
     struct dl_bw *dl_b = dl_bw_of(cpu);
     unsigned long cap;
 
     if (attr->sched_flags & SCHED_FLAG_SUGOV)
         return 0;
 
     /* !deadline task may carry old deadline bandwidth */
     if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
         return 0;
 
     /*
      * Either if a task, enters, leave, or stays -deadline but changes
      * its parameters, we may need to update accordingly the total
      * allocated bandwidth of the container.
      */
     raw_spin_lock(&dl_b->lock);
     cpus = dl_bw_cpus(cpu);
     cap = dl_bw_capacity(cpu);
 
     if (dl_policy(policy) && !task_has_dl_policy(p) &&
         !__dl_overflow(dl_b, cap, 0, new_bw)) {
         if (hrtimer_active(&p->dl.inactive_timer))
             __dl_sub(dl_b, p->dl.dl_bw, cpus);
         __dl_add(dl_b, new_bw, cpus);
         err = 0;
     } else if (dl_policy(policy) && task_has_dl_policy(p) &&
            !__dl_overflow(dl_b, cap, p->dl.dl_bw, new_bw)) {
         /*
          * XXX this is slightly incorrect: when the task
          * utilization decreases, we should delay the total
          * utilization change until the task's 0-lag point.
          * But this would require to set the task's "inactive
          * timer" when the task is not inactive.
          */
         __dl_sub(dl_b, p->dl.dl_bw, cpus);
         __dl_add(dl_b, new_bw, cpus);
         dl_change_utilization(p, new_bw);
         err = 0;
     } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
         /*
          * Do not decrease the total deadline utilization here,
          * switched_from_dl() will take care to do it at the correct
          * (0-lag) time.
          */
         err = 0;
     }
     raw_spin_unlock(&dl_b->lock);
 
     return err;
 }
 
 /*
  * This function initializes the sched_dl_entity of a newly becoming
  * SCHED_DEADLINE task.
  *
  * Only the static values are considered here, the actual runtime and the
  * absolute deadline will be properly calculated when the task is enqueued
  * for the first time with its new policy.
  */
 void __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
 {
     struct sched_dl_entity *dl_se = &p->dl;
 
     dl_se->dl_runtime = attr->sched_runtime;
     dl_se->dl_deadline = attr->sched_deadline;
     dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
     dl_se->flags = attr->sched_flags & SCHED_DL_FLAGS;
     dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
     dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime);
 }
 
 void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
 {
     struct sched_dl_entity *dl_se = &p->dl;
 
     attr->sched_priority = p->rt_priority;
     attr->sched_runtime = dl_se->dl_runtime;
     attr->sched_deadline = dl_se->dl_deadline;
     attr->sched_period = dl_se->dl_period;
     attr->sched_flags &= ~SCHED_DL_FLAGS;
     attr->sched_flags |= dl_se->flags;
 }
 
 /*
  * This function validates the new parameters of a -deadline task.
  * We ask for the deadline not being zero, and greater or equal
  * than the runtime, as well as the period of being zero or
  * greater than deadline. Furthermore, we have to be sure that
  * user parameters are above the internal resolution of 1us (we
  * check sched_runtime only since it is always the smaller one) and
  * below 2^63 ns (we have to check both sched_deadline and
  * sched_period, as the latter can be zero).
  */
 bool __checkparam_dl(const struct sched_attr *attr)
 {
     u64 period, max, min;
 
     /* special dl tasks don't actually use any parameter */
     if (attr->sched_flags & SCHED_FLAG_SUGOV)
         return true;
 
     /* deadline != 0 */
     if (attr->sched_deadline == 0)
         return false;
 
     /*
      * Since we truncate DL_SCALE bits, make sure we're at least
      * that big.
      */
     if (attr->sched_runtime < (1ULL << DL_SCALE))
         return false;
 
     /*
      * Since we use the MSB for wrap-around and sign issues, make
      * sure it's not set (mind that period can be equal to zero).
      */
     if (attr->sched_deadline & (1ULL << 63) ||
         attr->sched_period & (1ULL << 63))
         return false;
 
     period = attr->sched_period;
     if (!period)
         period = attr->sched_deadline;
 
     /* runtime <= deadline <= period (if period != 0) */
     if (period < attr->sched_deadline ||
         attr->sched_deadline < attr->sched_runtime)
         return false;
 
     max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
     min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
 
     if (period < min || period > max)
         return false;
 
     return true;
 }
 
 /*
  * This function clears the sched_dl_entity static params.
  */
 void __dl_clear_params(struct task_struct *p)
 {
     struct sched_dl_entity *dl_se = &p->dl;
 
     dl_se->dl_runtime       = 0;
     dl_se->dl_deadline      = 0;
     dl_se->dl_period        = 0;
     dl_se->flags            = 0;
     dl_se->dl_bw            = 0;
     dl_se->dl_density       = 0;
 
     dl_se->dl_throttled     = 0;
     dl_se->dl_yielded       = 0;
     dl_se->dl_non_contending    = 0;
     dl_se->dl_overrun       = 0;
 
 #ifdef CONFIG_RT_MUTEXES
     dl_se->pi_se            = dl_se;
 #endif
 }
 
 bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
 {
     struct sched_dl_entity *dl_se = &p->dl;
 
     if (dl_se->dl_runtime != attr->sched_runtime ||
         dl_se->dl_deadline != attr->sched_deadline ||
         dl_se->dl_period != attr->sched_period ||
         dl_se->flags != (attr->sched_flags & SCHED_DL_FLAGS))
         return true;
 
     return false;
 }
 
 #ifdef CONFIG_SMP
 int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
                  const struct cpumask *trial)
 {
     int ret = 1, trial_cpus;
     struct dl_bw *cur_dl_b;
     unsigned long flags;
 
     rcu_read_lock_sched();
     cur_dl_b = dl_bw_of(cpumask_any(cur));
     trial_cpus = cpumask_weight(trial);
 
     raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
     if (cur_dl_b->bw != -1 &&
         cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
         ret = 0;
     raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
     rcu_read_unlock_sched();
 
     return ret;
 }
 
 int dl_cpu_busy(int cpu, struct task_struct *p)
 {
     unsigned long flags, cap;
     struct dl_bw *dl_b;
     bool overflow;
 
     rcu_read_lock_sched();
     dl_b = dl_bw_of(cpu);
     raw_spin_lock_irqsave(&dl_b->lock, flags);
     cap = dl_bw_capacity(cpu);
     overflow = __dl_overflow(dl_b, cap, 0, p ? p->dl.dl_bw : 0);
 
     if (!overflow && p) {
         /*
          * We reserve space for this task in the destination
          * root_domain, as we can't fail after this point.
          * We will free resources in the source root_domain
          * later on (see set_cpus_allowed_dl()).
          */
         __dl_add(dl_b, p->dl.dl_bw, dl_bw_cpus(cpu));
     }
 
     raw_spin_unlock_irqrestore(&dl_b->lock, flags);
     rcu_read_unlock_sched();
 
     return overflow ? -EBUSY : 0;
 }
 #endif
 
 #ifdef CONFIG_SCHED_DEBUG
 void print_dl_stats(struct seq_file *m, int cpu)
 {
     print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
 }
 #endif /* CONFIG_SCHED_DEBUG */