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sched.c

/* sched.c - SPU scheduler.
 *
 * Copyright (C) IBM 2005
 * Author: Mark Nutter <mnutter@us.ibm.com>
 *
 * 2006-03-31     NUMA domains added.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#undef DEBUG

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.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 <linux/marker.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"

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 MAX_USER_PRIO         (MAX_PRIO - MAX_RT_PRIO)
#define SCALE_PRIO(x, prio) \
      max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 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.
       */
      ctx->cpus_allowed = current->cpus_allowed;

      /* 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)) {
            cpumask_t mask = node_to_cpumask(node);

            if (cpus_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.
       *
       * When the awakened processes see their "notify_active" flag is set,
       * they will call spu_switch_notify().
       */
      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;
      spu_switch_notify(spu, ctx);
      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++) {
            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 == 0)
                        available_spus -=
                              (spu->ctx->gang->contexts - 1);
                  else
                        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 *ctx;
      struct spu *tmp;

      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)
            atomic_dec_if_positive(&ctx->gang->aff_sched_count);

      spu_switch_notify(spu, NULL);
      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:    canidate 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 aswell */
                  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;
      CALC_LOAD(spu_avenrun[0], EXP_1, active_tasks);
      CALC_LOAD(spu_avenrun[1], EXP_5, active_tasks);
      CALC_LOAD(spu_avenrun[2], EXP_15, active_tasks);
}

static void spusched_wake(unsigned long data)
{
      mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
      wake_up_process(spusched_task);
}

static void spuloadavg_wake(unsigned long data)
{
      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 timespec ts;
      struct spu *spu;
      enum spu_utilization_state old_state;
      int node;

      ktime_get_ts(&ts);
      curtime = timespec_to_ns(&ts);
      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);
      }
}

#define LOAD_INT(x) ((x) >> FSHIFT)
#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)

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),
            current->nsproxy->pid_ns->last_pid);
      return 0;
}

static int spu_loadavg_open(struct inode *inode, struct file *file)
{
      return single_open(file, show_spu_loadavg, NULL);
}

static const struct file_operations spu_loadavg_fops = {
      .open       = spu_loadavg_open,
      .read       = seq_read,
      .llseek           = seq_lseek,
      .release    = single_release,
};

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);

      setup_timer(&spusched_timer, spusched_wake, 0);
      setup_timer(&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("spu_loadavg", 0, NULL, &spu_loadavg_fops);
      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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