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 // SPDX-License-Identifier: GPL-2.0-or-later
 /* sched.c - SPU scheduler.
  *
  * Copyright (C) IBM 2005
  * Author: Mark Nutter <mnutter@us.ibm.com>
  *
  * 2006-03-31   NUMA domains added.
  */
 
 #undef DEBUG
 
 #include <linux/errno.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/loadavg.h>
 #include <linux/sched/rt.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/completion.h>
 #include <linux/vmalloc.h>
 #include <linux/smp.h>
 #include <linux/stddef.h>
 #include <linux/unistd.h>
 #include <linux/numa.h>
 #include <linux/mutex.h>
 #include <linux/notifier.h>
 #include <linux/kthread.h>
 #include <linux/pid_namespace.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 
 #include <asm/io.h>
 #include <asm/mmu_context.h>
 #include <asm/spu.h>
 #include <asm/spu_csa.h>
 #include <asm/spu_priv1.h>
 #include "spufs.h"
 #define CREATE_TRACE_POINTS
 #include "sputrace.h"
 
 struct spu_prio_array {
     DECLARE_BITMAP(bitmap, MAX_PRIO);
     struct list_head runq[MAX_PRIO];
     spinlock_t runq_lock;
     int nr_waiting;
 };
 
 static unsigned long spu_avenrun[3];
 static struct spu_prio_array *spu_prio;
 static struct task_struct *spusched_task;
 static struct timer_list spusched_timer;
 static struct timer_list spuloadavg_timer;
 
 /*
  * Priority of a normal, non-rt, non-niced'd process (aka nice level 0).
  */
 #define NORMAL_PRIO     120
 
 /*
  * Frequency of the spu scheduler tick.  By default we do one SPU scheduler
  * tick for every 10 CPU scheduler ticks.
  */
 #define SPUSCHED_TICK       (10)
 
 /*
  * These are the 'tuning knobs' of the scheduler:
  *
  * Minimum timeslice is 5 msecs (or 1 spu scheduler tick, whichever is
  * larger), default timeslice is 100 msecs, maximum timeslice is 800 msecs.
  */
 #define MIN_SPU_TIMESLICE   max(5 * HZ / (1000 * SPUSCHED_TICK), 1)
 #define DEF_SPU_TIMESLICE   (100 * HZ / (1000 * SPUSCHED_TICK))
 
 #define SCALE_PRIO(x, prio) \
     max(x * (MAX_PRIO - prio) / (NICE_WIDTH / 2), MIN_SPU_TIMESLICE)
 
 /*
  * scale user-nice values [ -20 ... 0 ... 19 ] to time slice values:
  * [800ms ... 100ms ... 5ms]
  *
  * The higher a thread's priority, the bigger timeslices
  * it gets during one round of execution. But even the lowest
  * priority thread gets MIN_TIMESLICE worth of execution time.
  */
 void spu_set_timeslice(struct spu_context *ctx)
 {
     if (ctx->prio < NORMAL_PRIO)
         ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE * 4, ctx->prio);
     else
         ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE, ctx->prio);
 }
 
 /*
  * Update scheduling information from the owning thread.
  */
 void __spu_update_sched_info(struct spu_context *ctx)
 {
     /*
      * assert that the context is not on the runqueue, so it is safe
      * to change its scheduling parameters.
      */
     BUG_ON(!list_empty(&ctx->rq));
 
     /*
      * 32-Bit assignments are atomic on powerpc, and we don't care about
      * memory ordering here because retrieving the controlling thread is
      * per definition racy.
      */
     ctx->tid = current->pid;
 
     /*
      * We do our own priority calculations, so we normally want
      * ->static_prio to start with. Unfortunately this field
      * contains junk for threads with a realtime scheduling
      * policy so we have to look at ->prio in this case.
      */
     if (rt_prio(current->prio))
         ctx->prio = current->prio;
     else
         ctx->prio = current->static_prio;
     ctx->policy = current->policy;
 
     /*
      * TO DO: the context may be loaded, so we may need to activate
      * it again on a different node. But it shouldn't hurt anything
      * to update its parameters, because we know that the scheduler
      * is not actively looking at this field, since it is not on the
      * runqueue. The context will be rescheduled on the proper node
      * if it is timesliced or preempted.
      */
     cpumask_copy(&ctx->cpus_allowed, current->cpus_ptr);
 
     /* Save the current cpu id for spu interrupt routing. */
     ctx->last_ran = raw_smp_processor_id();
 }
 
 void spu_update_sched_info(struct spu_context *ctx)
 {
     int node;
 
     if (ctx->state == SPU_STATE_RUNNABLE) {
         node = ctx->spu->node;
 
         /*
          * Take list_mutex to sync with find_victim().
          */
         mutex_lock(&cbe_spu_info[node].list_mutex);
         __spu_update_sched_info(ctx);
         mutex_unlock(&cbe_spu_info[node].list_mutex);
     } else {
         __spu_update_sched_info(ctx);
     }
 }
 
 static int __node_allowed(struct spu_context *ctx, int node)
 {
     if (nr_cpus_node(node)) {
         const struct cpumask *mask = cpumask_of_node(node);
 
         if (cpumask_intersects(mask, &ctx->cpus_allowed))
             return 1;
     }
 
     return 0;
 }
 
 static int node_allowed(struct spu_context *ctx, int node)
 {
     int rval;
 
     spin_lock(&spu_prio->runq_lock);
     rval = __node_allowed(ctx, node);
     spin_unlock(&spu_prio->runq_lock);
 
     return rval;
 }
 
 void do_notify_spus_active(void)
 {
     int node;
 
     /*
      * Wake up the active spu_contexts.
      */
     for_each_online_node(node) {
         struct spu *spu;
 
         mutex_lock(&cbe_spu_info[node].list_mutex);
         list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
             if (spu->alloc_state != SPU_FREE) {
                 struct spu_context *ctx = spu->ctx;
                 set_bit(SPU_SCHED_NOTIFY_ACTIVE,
                     &ctx->sched_flags);
                 mb();
                 wake_up_all(&ctx->stop_wq);
             }
         }
         mutex_unlock(&cbe_spu_info[node].list_mutex);
     }
 }
 
 /**
  * spu_bind_context - bind spu context to physical spu
  * @spu:    physical spu to bind to
  * @ctx:    context to bind
  */
 static void spu_bind_context(struct spu *spu, struct spu_context *ctx)
 {
     spu_context_trace(spu_bind_context__enter, ctx, spu);
 
     spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
 
     if (ctx->flags & SPU_CREATE_NOSCHED)
         atomic_inc(&cbe_spu_info[spu->node].reserved_spus);
 
     ctx->stats.slb_flt_base = spu->stats.slb_flt;
     ctx->stats.class2_intr_base = spu->stats.class2_intr;
 
     spu_associate_mm(spu, ctx->owner);
 
     spin_lock_irq(&spu->register_lock);
     spu->ctx = ctx;
     spu->flags = 0;
     ctx->spu = spu;
     ctx->ops = &spu_hw_ops;
     spu->pid = current->pid;
     spu->tgid = current->tgid;
     spu->ibox_callback = spufs_ibox_callback;
     spu->wbox_callback = spufs_wbox_callback;
     spu->stop_callback = spufs_stop_callback;
     spu->mfc_callback = spufs_mfc_callback;
     spin_unlock_irq(&spu->register_lock);
 
     spu_unmap_mappings(ctx);
 
     spu_switch_log_notify(spu, ctx, SWITCH_LOG_START, 0);
     spu_restore(&ctx->csa, spu);
     spu->timestamp = jiffies;
     ctx->state = SPU_STATE_RUNNABLE;
 
     spuctx_switch_state(ctx, SPU_UTIL_USER);
 }
 
 /*
  * Must be used with the list_mutex held.
  */
 static inline int sched_spu(struct spu *spu)
 {
     BUG_ON(!mutex_is_locked(&cbe_spu_info[spu->node].list_mutex));
 
     return (!spu->ctx || !(spu->ctx->flags & SPU_CREATE_NOSCHED));
 }
 
 static void aff_merge_remaining_ctxs(struct spu_gang *gang)
 {
     struct spu_context *ctx;
 
     list_for_each_entry(ctx, &gang->aff_list_head, aff_list) {
         if (list_empty(&ctx->aff_list))
             list_add(&ctx->aff_list, &gang->aff_list_head);
     }
     gang->aff_flags |= AFF_MERGED;
 }
 
 static void aff_set_offsets(struct spu_gang *gang)
 {
     struct spu_context *ctx;
     int offset;
 
     offset = -1;
     list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
                                 aff_list) {
         if (&ctx->aff_list == &gang->aff_list_head)
             break;
         ctx->aff_offset = offset--;
     }
 
     offset = 0;
     list_for_each_entry(ctx, gang->aff_ref_ctx->aff_list.prev, aff_list) {
         if (&ctx->aff_list == &gang->aff_list_head)
             break;
         ctx->aff_offset = offset++;
     }
 
     gang->aff_flags |= AFF_OFFSETS_SET;
 }
 
 static struct spu *aff_ref_location(struct spu_context *ctx, int mem_aff,
          int group_size, int lowest_offset)
 {
     struct spu *spu;
     int node, n;
 
     /*
      * TODO: A better algorithm could be used to find a good spu to be
      *       used as reference location for the ctxs chain.
      */
     node = cpu_to_node(raw_smp_processor_id());
     for (n = 0; n < MAX_NUMNODES; n++, node++) {
         /*
          * "available_spus" counts how many spus are not potentially
          * going to be used by other affinity gangs whose reference
          * context is already in place. Although this code seeks to
          * avoid having affinity gangs with a summed amount of
          * contexts bigger than the amount of spus in the node,
          * this may happen sporadically. In this case, available_spus
          * becomes negative, which is harmless.
          */
         int available_spus;
 
         node = (node < MAX_NUMNODES) ? node : 0;
         if (!node_allowed(ctx, node))
             continue;
 
         available_spus = 0;
         mutex_lock(&cbe_spu_info[node].list_mutex);
         list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
             if (spu->ctx && spu->ctx->gang && !spu->ctx->aff_offset
                     && spu->ctx->gang->aff_ref_spu)
                 available_spus -= spu->ctx->gang->contexts;
             available_spus++;
         }
         if (available_spus < ctx->gang->contexts) {
             mutex_unlock(&cbe_spu_info[node].list_mutex);
             continue;
         }
 
         list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
             if ((!mem_aff || spu->has_mem_affinity) &&
                             sched_spu(spu)) {
                 mutex_unlock(&cbe_spu_info[node].list_mutex);
                 return spu;
             }
         }
         mutex_unlock(&cbe_spu_info[node].list_mutex);
     }
     return NULL;
 }
 
 static void aff_set_ref_point_location(struct spu_gang *gang)
 {
     int mem_aff, gs, lowest_offset;
     struct spu_context *tmp, *ctx;
 
     mem_aff = gang->aff_ref_ctx->flags & SPU_CREATE_AFFINITY_MEM;
     lowest_offset = 0;
     gs = 0;
 
     list_for_each_entry(tmp, &gang->aff_list_head, aff_list)
         gs++;
 
     list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
                                 aff_list) {
         if (&ctx->aff_list == &gang->aff_list_head)
             break;
         lowest_offset = ctx->aff_offset;
     }
 
     gang->aff_ref_spu = aff_ref_location(gang->aff_ref_ctx, mem_aff, gs,
                             lowest_offset);
 }
 
 static struct spu *ctx_location(struct spu *ref, int offset, int node)
 {
     struct spu *spu;
 
     spu = NULL;
     if (offset >= 0) {
         list_for_each_entry(spu, ref->aff_list.prev, aff_list) {
             BUG_ON(spu->node != node);
             if (offset == 0)
                 break;
             if (sched_spu(spu))
                 offset--;
         }
     } else {
         list_for_each_entry_reverse(spu, ref->aff_list.next, aff_list) {
             BUG_ON(spu->node != node);
             if (offset == 0)
                 break;
             if (sched_spu(spu))
                 offset++;
         }
     }
 
     return spu;
 }
 
 /*
  * affinity_check is called each time a context is going to be scheduled.
  * It returns the spu ptr on which the context must run.
  */
 static int has_affinity(struct spu_context *ctx)
 {
     struct spu_gang *gang = ctx->gang;
 
     if (list_empty(&ctx->aff_list))
         return 0;
 
     if (atomic_read(&ctx->gang->aff_sched_count) == 0)
         ctx->gang->aff_ref_spu = NULL;
 
     if (!gang->aff_ref_spu) {
         if (!(gang->aff_flags & AFF_MERGED))
             aff_merge_remaining_ctxs(gang);
         if (!(gang->aff_flags & AFF_OFFSETS_SET))
             aff_set_offsets(gang);
         aff_set_ref_point_location(gang);
     }
 
     return gang->aff_ref_spu != NULL;
 }
 
 /**
  * spu_unbind_context - unbind spu context from physical spu
  * @spu:    physical spu to unbind from
  * @ctx:    context to unbind
  */
 static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
 {
     u32 status;
 
     spu_context_trace(spu_unbind_context__enter, ctx, spu);
 
     spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
 
     if (spu->ctx->flags & SPU_CREATE_NOSCHED)
         atomic_dec(&cbe_spu_info[spu->node].reserved_spus);
 
     if (ctx->gang)
         /*
          * If ctx->gang->aff_sched_count is positive, SPU affinity is
          * being considered in this gang. Using atomic_dec_if_positive
          * allow us to skip an explicit check for affinity in this gang
          */
         atomic_dec_if_positive(&ctx->gang->aff_sched_count);
 
     spu_unmap_mappings(ctx);
     spu_save(&ctx->csa, spu);
     spu_switch_log_notify(spu, ctx, SWITCH_LOG_STOP, 0);
 
     spin_lock_irq(&spu->register_lock);
     spu->timestamp = jiffies;
     ctx->state = SPU_STATE_SAVED;
     spu->ibox_callback = NULL;
     spu->wbox_callback = NULL;
     spu->stop_callback = NULL;
     spu->mfc_callback = NULL;
     spu->pid = 0;
     spu->tgid = 0;
     ctx->ops = &spu_backing_ops;
     spu->flags = 0;
     spu->ctx = NULL;
     spin_unlock_irq(&spu->register_lock);
 
     spu_associate_mm(spu, NULL);
 
     ctx->stats.slb_flt +=
         (spu->stats.slb_flt - ctx->stats.slb_flt_base);
     ctx->stats.class2_intr +=
         (spu->stats.class2_intr - ctx->stats.class2_intr_base);
 
     /* This maps the underlying spu state to idle */
     spuctx_switch_state(ctx, SPU_UTIL_IDLE_LOADED);
     ctx->spu = NULL;
 
     if (spu_stopped(ctx, &status))
         wake_up_all(&ctx->stop_wq);
 }
 
 /**
  * spu_add_to_rq - add a context to the runqueue
  * @ctx:       context to add
  */
 static void __spu_add_to_rq(struct spu_context *ctx)
 {
     /*
      * Unfortunately this code path can be called from multiple threads
      * on behalf of a single context due to the way the problem state
      * mmap support works.
      *
      * Fortunately we need to wake up all these threads at the same time
      * and can simply skip the runqueue addition for every but the first
      * thread getting into this codepath.
      *
      * It's still quite hacky, and long-term we should proxy all other
      * threads through the owner thread so that spu_run is in control
      * of all the scheduling activity for a given context.
      */
     if (list_empty(&ctx->rq)) {
         list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);
         set_bit(ctx->prio, spu_prio->bitmap);
         if (!spu_prio->nr_waiting++)
             mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
     }
 }
 
 static void spu_add_to_rq(struct spu_context *ctx)
 {
     spin_lock(&spu_prio->runq_lock);
     __spu_add_to_rq(ctx);
     spin_unlock(&spu_prio->runq_lock);
 }
 
 static void __spu_del_from_rq(struct spu_context *ctx)
 {
     int prio = ctx->prio;
 
     if (!list_empty(&ctx->rq)) {
         if (!--spu_prio->nr_waiting)
             del_timer(&spusched_timer);
         list_del_init(&ctx->rq);
 
         if (list_empty(&spu_prio->runq[prio]))
             clear_bit(prio, spu_prio->bitmap);
     }
 }
 
 void spu_del_from_rq(struct spu_context *ctx)
 {
     spin_lock(&spu_prio->runq_lock);
     __spu_del_from_rq(ctx);
     spin_unlock(&spu_prio->runq_lock);
 }
 
 static void spu_prio_wait(struct spu_context *ctx)
 {
     DEFINE_WAIT(wait);
 
     /*
      * The caller must explicitly wait for a context to be loaded
      * if the nosched flag is set.  If NOSCHED is not set, the caller
      * queues the context and waits for an spu event or error.
      */
     BUG_ON(!(ctx->flags & SPU_CREATE_NOSCHED));
 
     spin_lock(&spu_prio->runq_lock);
     prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
     if (!signal_pending(current)) {
         __spu_add_to_rq(ctx);
         spin_unlock(&spu_prio->runq_lock);
         mutex_unlock(&ctx->state_mutex);
         schedule();
         mutex_lock(&ctx->state_mutex);
         spin_lock(&spu_prio->runq_lock);
         __spu_del_from_rq(ctx);
     }
     spin_unlock(&spu_prio->runq_lock);
     __set_current_state(TASK_RUNNING);
     remove_wait_queue(&ctx->stop_wq, &wait);
 }
 
 static struct spu *spu_get_idle(struct spu_context *ctx)
 {
     struct spu *spu, *aff_ref_spu;
     int node, n;
 
     spu_context_nospu_trace(spu_get_idle__enter, ctx);
 
     if (ctx->gang) {
         mutex_lock(&ctx->gang->aff_mutex);
         if (has_affinity(ctx)) {
             aff_ref_spu = ctx->gang->aff_ref_spu;
             atomic_inc(&ctx->gang->aff_sched_count);
             mutex_unlock(&ctx->gang->aff_mutex);
             node = aff_ref_spu->node;
 
             mutex_lock(&cbe_spu_info[node].list_mutex);
             spu = ctx_location(aff_ref_spu, ctx->aff_offset, node);
             if (spu && spu->alloc_state == SPU_FREE)
                 goto found;
             mutex_unlock(&cbe_spu_info[node].list_mutex);
 
             atomic_dec(&ctx->gang->aff_sched_count);
             goto not_found;
         }
         mutex_unlock(&ctx->gang->aff_mutex);
     }
     node = cpu_to_node(raw_smp_processor_id());
     for (n = 0; n < MAX_NUMNODES; n++, node++) {
         node = (node < MAX_NUMNODES) ? node : 0;
         if (!node_allowed(ctx, node))
             continue;
 
         mutex_lock(&cbe_spu_info[node].list_mutex);
         list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
             if (spu->alloc_state == SPU_FREE)
                 goto found;
         }
         mutex_unlock(&cbe_spu_info[node].list_mutex);
     }
 
  not_found:
     spu_context_nospu_trace(spu_get_idle__not_found, ctx);
     return NULL;
 
  found:
     spu->alloc_state = SPU_USED;
     mutex_unlock(&cbe_spu_info[node].list_mutex);
     spu_context_trace(spu_get_idle__found, ctx, spu);
     spu_init_channels(spu);
     return spu;
 }
 
 /**
  * find_victim - find a lower priority context to preempt
  * @ctx:    candidate context for running
  *
  * Returns the freed physical spu to run the new context on.
  */
 static struct spu *find_victim(struct spu_context *ctx)
 {
     struct spu_context *victim = NULL;
     struct spu *spu;
     int node, n;
 
     spu_context_nospu_trace(spu_find_victim__enter, ctx);
 
     /*
      * Look for a possible preemption candidate on the local node first.
      * If there is no candidate look at the other nodes.  This isn't
      * exactly fair, but so far the whole spu scheduler tries to keep
      * a strong node affinity.  We might want to fine-tune this in
      * the future.
      */
  restart:
     node = cpu_to_node(raw_smp_processor_id());
     for (n = 0; n < MAX_NUMNODES; n++, node++) {
         node = (node < MAX_NUMNODES) ? node : 0;
         if (!node_allowed(ctx, node))
             continue;
 
         mutex_lock(&cbe_spu_info[node].list_mutex);
         list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
             struct spu_context *tmp = spu->ctx;
 
             if (tmp && tmp->prio > ctx->prio &&
                 !(tmp->flags & SPU_CREATE_NOSCHED) &&
                 (!victim || tmp->prio > victim->prio)) {
                 victim = spu->ctx;
             }
         }
         if (victim)
             get_spu_context(victim);
         mutex_unlock(&cbe_spu_info[node].list_mutex);
 
         if (victim) {
             /*
              * This nests ctx->state_mutex, but we always lock
              * higher priority contexts before lower priority
              * ones, so this is safe until we introduce
              * priority inheritance schemes.
              *
              * XXX if the highest priority context is locked,
              * this can loop a long time.  Might be better to
              * look at another context or give up after X retries.
              */
             if (!mutex_trylock(&victim->state_mutex)) {
                 put_spu_context(victim);
                 victim = NULL;
                 goto restart;
             }
 
             spu = victim->spu;
             if (!spu || victim->prio <= ctx->prio) {
                 /*
                  * This race can happen because we've dropped
                  * the active list mutex.  Not a problem, just
                  * restart the search.
                  */
                 mutex_unlock(&victim->state_mutex);
                 put_spu_context(victim);
                 victim = NULL;
                 goto restart;
             }
 
             spu_context_trace(__spu_deactivate__unload, ctx, spu);
 
             mutex_lock(&cbe_spu_info[node].list_mutex);
             cbe_spu_info[node].nr_active--;
             spu_unbind_context(spu, victim);
             mutex_unlock(&cbe_spu_info[node].list_mutex);
 
             victim->stats.invol_ctx_switch++;
             spu->stats.invol_ctx_switch++;
             if (test_bit(SPU_SCHED_SPU_RUN, &victim->sched_flags))
                 spu_add_to_rq(victim);
 
             mutex_unlock(&victim->state_mutex);
             put_spu_context(victim);
 
             return spu;
         }
     }
 
     return NULL;
 }
 
 static void __spu_schedule(struct spu *spu, struct spu_context *ctx)
 {
     int node = spu->node;
     int success = 0;
 
     spu_set_timeslice(ctx);
 
     mutex_lock(&cbe_spu_info[node].list_mutex);
     if (spu->ctx == NULL) {
         spu_bind_context(spu, ctx);
         cbe_spu_info[node].nr_active++;
         spu->alloc_state = SPU_USED;
         success = 1;
     }
     mutex_unlock(&cbe_spu_info[node].list_mutex);
 
     if (success)
         wake_up_all(&ctx->run_wq);
     else
         spu_add_to_rq(ctx);
 }
 
 static void spu_schedule(struct spu *spu, struct spu_context *ctx)
 {
     /* not a candidate for interruptible because it's called either
        from the scheduler thread or from spu_deactivate */
     mutex_lock(&ctx->state_mutex);
     if (ctx->state == SPU_STATE_SAVED)
         __spu_schedule(spu, ctx);
     spu_release(ctx);
 }
 
 /**
  * spu_unschedule - remove a context from a spu, and possibly release it.
  * @spu:    The SPU to unschedule from
  * @ctx:    The context currently scheduled on the SPU
  * @free_spu    Whether to free the SPU for other contexts
  *
  * Unbinds the context @ctx from the SPU @spu. If @free_spu is non-zero, the
  * SPU is made available for other contexts (ie, may be returned by
  * spu_get_idle). If this is zero, the caller is expected to schedule another
  * context to this spu.
  *
  * Should be called with ctx->state_mutex held.
  */
 static void spu_unschedule(struct spu *spu, struct spu_context *ctx,
         int free_spu)
 {
     int node = spu->node;
 
     mutex_lock(&cbe_spu_info[node].list_mutex);
     cbe_spu_info[node].nr_active--;
     if (free_spu)
         spu->alloc_state = SPU_FREE;
     spu_unbind_context(spu, ctx);
     ctx->stats.invol_ctx_switch++;
     spu->stats.invol_ctx_switch++;
     mutex_unlock(&cbe_spu_info[node].list_mutex);
 }
 
 /**
  * spu_activate - find a free spu for a context and execute it
  * @ctx:    spu context to schedule
  * @flags:  flags (currently ignored)
  *
  * Tries to find a free spu to run @ctx.  If no free spu is available
  * add the context to the runqueue so it gets woken up once an spu
  * is available.
  */
 int spu_activate(struct spu_context *ctx, unsigned long flags)
 {
     struct spu *spu;
 
     /*
      * If there are multiple threads waiting for a single context
      * only one actually binds the context while the others will
      * only be able to acquire the state_mutex once the context
      * already is in runnable state.
      */
     if (ctx->spu)
         return 0;
 
 spu_activate_top:
     if (signal_pending(current))
         return -ERESTARTSYS;
 
     spu = spu_get_idle(ctx);
     /*
      * If this is a realtime thread we try to get it running by
      * preempting a lower priority thread.
      */
     if (!spu && rt_prio(ctx->prio))
         spu = find_victim(ctx);
     if (spu) {
         unsigned long runcntl;
 
         runcntl = ctx->ops->runcntl_read(ctx);
         __spu_schedule(spu, ctx);
         if (runcntl & SPU_RUNCNTL_RUNNABLE)
             spuctx_switch_state(ctx, SPU_UTIL_USER);
 
         return 0;
     }
 
     if (ctx->flags & SPU_CREATE_NOSCHED) {
         spu_prio_wait(ctx);
         goto spu_activate_top;
     }
 
     spu_add_to_rq(ctx);
 
     return 0;
 }
 
 /**
  * grab_runnable_context - try to find a runnable context
  *
  * Remove the highest priority context on the runqueue and return it
  * to the caller.  Returns %NULL if no runnable context was found.
  */
 static struct spu_context *grab_runnable_context(int prio, int node)
 {
     struct spu_context *ctx;
     int best;
 
     spin_lock(&spu_prio->runq_lock);
     best = find_first_bit(spu_prio->bitmap, prio);
     while (best < prio) {
         struct list_head *rq = &spu_prio->runq[best];
 
         list_for_each_entry(ctx, rq, rq) {
             /* XXX(hch): check for affinity here as well */
             if (__node_allowed(ctx, node)) {
                 __spu_del_from_rq(ctx);
                 goto found;
             }
         }
         best++;
     }
     ctx = NULL;
  found:
     spin_unlock(&spu_prio->runq_lock);
     return ctx;
 }
 
 static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio)
 {
     struct spu *spu = ctx->spu;
     struct spu_context *new = NULL;
 
     if (spu) {
         new = grab_runnable_context(max_prio, spu->node);
         if (new || force) {
             spu_unschedule(spu, ctx, new == NULL);
             if (new) {
                 if (new->flags & SPU_CREATE_NOSCHED)
                     wake_up(&new->stop_wq);
                 else {
                     spu_release(ctx);
                     spu_schedule(spu, new);
                     /* this one can't easily be made
                        interruptible */
                     mutex_lock(&ctx->state_mutex);
                 }
             }
         }
     }
 
     return new != NULL;
 }
 
 /**
  * spu_deactivate - unbind a context from it's physical spu
  * @ctx:    spu context to unbind
  *
  * Unbind @ctx from the physical spu it is running on and schedule
  * the highest priority context to run on the freed physical spu.
  */
 void spu_deactivate(struct spu_context *ctx)
 {
     spu_context_nospu_trace(spu_deactivate__enter, ctx);
     __spu_deactivate(ctx, 1, MAX_PRIO);
 }
 
 /**
  * spu_yield -  yield a physical spu if others are waiting
  * @ctx:    spu context to yield
  *
  * Check if there is a higher priority context waiting and if yes
  * unbind @ctx from the physical spu and schedule the highest
  * priority context to run on the freed physical spu instead.
  */
 void spu_yield(struct spu_context *ctx)
 {
     spu_context_nospu_trace(spu_yield__enter, ctx);
     if (!(ctx->flags & SPU_CREATE_NOSCHED)) {
         mutex_lock(&ctx->state_mutex);
         __spu_deactivate(ctx, 0, MAX_PRIO);
         mutex_unlock(&ctx->state_mutex);
     }
 }
 
 static noinline void spusched_tick(struct spu_context *ctx)
 {
     struct spu_context *new = NULL;
     struct spu *spu = NULL;
 
     if (spu_acquire(ctx))
         BUG();  /* a kernel thread never has signals pending */
 
     if (ctx->state != SPU_STATE_RUNNABLE)
         goto out;
     if (ctx->flags & SPU_CREATE_NOSCHED)
         goto out;
     if (ctx->policy == SCHED_FIFO)
         goto out;
 
     if (--ctx->time_slice && test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
         goto out;
 
     spu = ctx->spu;
 
     spu_context_trace(spusched_tick__preempt, ctx, spu);
 
     new = grab_runnable_context(ctx->prio + 1, spu->node);
     if (new) {
         spu_unschedule(spu, ctx, 0);
         if (test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
             spu_add_to_rq(ctx);
     } else {
         spu_context_nospu_trace(spusched_tick__newslice, ctx);
         if (!ctx->time_slice)
             ctx->time_slice++;
     }
 out:
     spu_release(ctx);
 
     if (new)
         spu_schedule(spu, new);
 }
 
 /**
  * count_active_contexts - count nr of active tasks
  *
  * Return the number of tasks currently running or waiting to run.
  *
  * Note that we don't take runq_lock / list_mutex here.  Reading
  * a single 32bit value is atomic on powerpc, and we don't care
  * about memory ordering issues here.
  */
 static unsigned long count_active_contexts(void)
 {
     int nr_active = 0, node;
 
     for (node = 0; node < MAX_NUMNODES; node++)
         nr_active += cbe_spu_info[node].nr_active;
     nr_active += spu_prio->nr_waiting;
 
     return nr_active;
 }
 
 /**
  * spu_calc_load - update the avenrun load estimates.
  *
  * No locking against reading these values from userspace, as for
  * the CPU loadavg code.
  */
 static void spu_calc_load(void)
 {
     unsigned long active_tasks; /* fixed-point */
 
     active_tasks = count_active_contexts() * FIXED_1;
     spu_avenrun[0] = calc_load(spu_avenrun[0], EXP_1, active_tasks);
     spu_avenrun[1] = calc_load(spu_avenrun[1], EXP_5, active_tasks);
     spu_avenrun[2] = calc_load(spu_avenrun[2], EXP_15, active_tasks);
 }
 
 static void spusched_wake(struct timer_list *unused)
 {
     mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
     wake_up_process(spusched_task);
 }
 
 static void spuloadavg_wake(struct timer_list *unused)
 {
     mod_timer(&spuloadavg_timer, jiffies + LOAD_FREQ);
     spu_calc_load();
 }
 
 static int spusched_thread(void *unused)
 {
     struct spu *spu;
     int node;
 
     while (!kthread_should_stop()) {
         set_current_state(TASK_INTERRUPTIBLE);
         schedule();
         for (node = 0; node < MAX_NUMNODES; node++) {
             struct mutex *mtx = &cbe_spu_info[node].list_mutex;
 
             mutex_lock(mtx);
             list_for_each_entry(spu, &cbe_spu_info[node].spus,
                     cbe_list) {
                 struct spu_context *ctx = spu->ctx;
 
                 if (ctx) {
                     get_spu_context(ctx);
                     mutex_unlock(mtx);
                     spusched_tick(ctx);
                     mutex_lock(mtx);
                     put_spu_context(ctx);
                 }
             }
             mutex_unlock(mtx);
         }
     }
 
     return 0;
 }
 
 void spuctx_switch_state(struct spu_context *ctx,
         enum spu_utilization_state new_state)
 {
     unsigned long long curtime;
     signed long long delta;
     struct spu *spu;
     enum spu_utilization_state old_state;
     int node;
 
     curtime = ktime_get_ns();
     delta = curtime - ctx->stats.tstamp;
 
     WARN_ON(!mutex_is_locked(&ctx->state_mutex));
     WARN_ON(delta < 0);
 
     spu = ctx->spu;
     old_state = ctx->stats.util_state;
     ctx->stats.util_state = new_state;
     ctx->stats.tstamp = curtime;
 
     /*
      * Update the physical SPU utilization statistics.
      */
     if (spu) {
         ctx->stats.times[old_state] += delta;
         spu->stats.times[old_state] += delta;
         spu->stats.util_state = new_state;
         spu->stats.tstamp = curtime;
         node = spu->node;
         if (old_state == SPU_UTIL_USER)
             atomic_dec(&cbe_spu_info[node].busy_spus);
         if (new_state == SPU_UTIL_USER)
             atomic_inc(&cbe_spu_info[node].busy_spus);
     }
 }
 
 #ifdef CONFIG_PROC_FS
 static int show_spu_loadavg(struct seq_file *s, void *private)
 {
     int a, b, c;
 
     a = spu_avenrun[0] + (FIXED_1/200);
     b = spu_avenrun[1] + (FIXED_1/200);
     c = spu_avenrun[2] + (FIXED_1/200);
 
     /*
      * Note that last_pid doesn't really make much sense for the
      * SPU loadavg (it even seems very odd on the CPU side...),
      * but we include it here to have a 100% compatible interface.
      */
     seq_printf(s, "%d.%02d %d.%02d %d.%02d %ld/%d %d\n",
         LOAD_INT(a), LOAD_FRAC(a),
         LOAD_INT(b), LOAD_FRAC(b),
         LOAD_INT(c), LOAD_FRAC(c),
         count_active_contexts(),
         atomic_read(&nr_spu_contexts),
         idr_get_cursor(&task_active_pid_ns(current)->idr) - 1);
     return 0;
 }
 #endif
 
 int __init spu_sched_init(void)
 {
     struct proc_dir_entry *entry;
     int err = -ENOMEM, i;
 
     spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
     if (!spu_prio)
         goto out;
 
     for (i = 0; i < MAX_PRIO; i++) {
         INIT_LIST_HEAD(&spu_prio->runq[i]);
         __clear_bit(i, spu_prio->bitmap);
     }
     spin_lock_init(&spu_prio->runq_lock);
 
     timer_setup(&spusched_timer, spusched_wake, 0);
     timer_setup(&spuloadavg_timer, spuloadavg_wake, 0);
 
     spusched_task = kthread_run(spusched_thread, NULL, "spusched");
     if (IS_ERR(spusched_task)) {
         err = PTR_ERR(spusched_task);
         goto out_free_spu_prio;
     }
 
     mod_timer(&spuloadavg_timer, 0);
 
     entry = proc_create_single("spu_loadavg", 0, NULL, show_spu_loadavg);
     if (!entry)
         goto out_stop_kthread;
 
     pr_debug("spusched: tick: %d, min ticks: %d, default ticks: %d\n",
             SPUSCHED_TICK, MIN_SPU_TIMESLICE, DEF_SPU_TIMESLICE);
     return 0;
 
  out_stop_kthread:
     kthread_stop(spusched_task);
  out_free_spu_prio:
     kfree(spu_prio);
  out:
     return err;
 }
 
 void spu_sched_exit(void)
 {
     struct spu *spu;
     int node;
 
     remove_proc_entry("spu_loadavg", NULL);
 
     del_timer_sync(&spusched_timer);
     del_timer_sync(&spuloadavg_timer);
     kthread_stop(spusched_task);
 
     for (node = 0; node < MAX_NUMNODES; node++) {
         mutex_lock(&cbe_spu_info[node].list_mutex);
         list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list)
             if (spu->alloc_state != SPU_FREE)
                 spu->alloc_state = SPU_FREE;
         mutex_unlock(&cbe_spu_info[node].list_mutex);
     }
     kfree(spu_prio);
 }

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