[POWERPC] spufs: don't yield CPU in spu_yield

[linux-2.6/zen-sources.git] / arch / powerpc / platforms / cell / spufs / 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/smp_lock.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/numa.h>
#include <linux/mutex.h>
#include <linux/notifier.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 SPU_TIMESLICE   (HZ)

struct spu_prio_array {
        DECLARE_BITMAP(bitmap, MAX_PRIO);
        struct list_head runq[MAX_PRIO];
        spinlock_t runq_lock;
        struct list_head active_list[MAX_NUMNODES];
        struct mutex active_mutex[MAX_NUMNODES];
};

static struct spu_prio_array *spu_prio;
static struct workqueue_struct *spu_sched_wq;

static inline int node_allowed(int node)
{
        cpumask_t mask;

        if (!nr_cpus_node(node))
                return 0;
        mask = node_to_cpumask(node);
        if (!cpus_intersects(mask, current->cpus_allowed))
                return 0;
        return 1;
}

void spu_start_tick(struct spu_context *ctx)
{
        if (ctx->policy == SCHED_RR)
                queue_delayed_work(spu_sched_wq, &ctx->sched_work, SPU_TIMESLICE);
}

void spu_stop_tick(struct spu_context *ctx)
{
        if (ctx->policy == SCHED_RR)
                cancel_delayed_work(&ctx->sched_work);
}

void spu_sched_tick(struct work_struct *work)
{
        struct spu_context *ctx =
                container_of(work, struct spu_context, sched_work.work);
        struct spu *spu;
        int rearm = 1;

        mutex_lock(&ctx->state_mutex);
        spu = ctx->spu;
        if (spu) {
                int best = sched_find_first_bit(spu_prio->bitmap);
                if (best <= ctx->prio) {
                        spu_deactivate(ctx);
                        rearm = 0;
                }
        }
        mutex_unlock(&ctx->state_mutex);

        if (rearm)
                spu_start_tick(ctx);
}

/**
 * spu_add_to_active_list - add spu to active list
 * @spu:        spu to add to the active list
 */
static void spu_add_to_active_list(struct spu *spu)
{
        mutex_lock(&spu_prio->active_mutex[spu->node]);
        list_add_tail(&spu->list, &spu_prio->active_list[spu->node]);
        mutex_unlock(&spu_prio->active_mutex[spu->node]);
}

/**
 * spu_remove_from_active_list - remove spu from active list
 * @spu:       spu to remove from the active list
 */
static void spu_remove_from_active_list(struct spu *spu)
{
        int node = spu->node;

        mutex_lock(&spu_prio->active_mutex[node]);
        list_del_init(&spu->list);
        mutex_unlock(&spu_prio->active_mutex[node]);
}

static BLOCKING_NOTIFIER_HEAD(spu_switch_notifier);

static void spu_switch_notify(struct spu *spu, struct spu_context *ctx)
{
        blocking_notifier_call_chain(&spu_switch_notifier,
                            ctx ? ctx->object_id : 0, spu);
}

int spu_switch_event_register(struct notifier_block * n)
{
        return blocking_notifier_chain_register(&spu_switch_notifier, n);
}

int spu_switch_event_unregister(struct notifier_block * n)
{
        return blocking_notifier_chain_unregister(&spu_switch_notifier, n);
}

/**
 * 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)
{
        pr_debug("%s: pid=%d SPU=%d NODE=%d\n", __FUNCTION__, current->pid,
                 spu->number, spu->node);
        spu->ctx = ctx;
        spu->flags = 0;
        ctx->spu = spu;
        ctx->ops = &spu_hw_ops;
        spu->pid = current->pid;
        spu_associate_mm(spu, ctx->owner);
        spu->ibox_callback = spufs_ibox_callback;
        spu->wbox_callback = spufs_wbox_callback;
        spu->stop_callback = spufs_stop_callback;
        spu->mfc_callback = spufs_mfc_callback;
        spu->dma_callback = spufs_dma_callback;
        mb();
        spu_unmap_mappings(ctx);
        spu_restore(&ctx->csa, spu);
        spu->timestamp = jiffies;
        spu_cpu_affinity_set(spu, raw_smp_processor_id());
        spu_switch_notify(spu, ctx);
        spu_add_to_active_list(spu);
        ctx->state = SPU_STATE_RUNNABLE;
}

/**
 * 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)
{
        pr_debug("%s: unbind pid=%d SPU=%d NODE=%d\n", __FUNCTION__,
                 spu->pid, spu->number, spu->node);

        spu_remove_from_active_list(spu);
        spu_switch_notify(spu, NULL);
        spu_unmap_mappings(ctx);
        spu_save(&ctx->csa, spu);
        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->dma_callback = NULL;
        spu_associate_mm(spu, NULL);
        spu->pid = 0;
        ctx->ops = &spu_backing_ops;
        ctx->spu = NULL;
        spu->flags = 0;
        spu->ctx = NULL;
}

/**
 * spu_add_to_rq - add a context to the runqueue
 * @ctx:       context to add
 */
static void spu_add_to_rq(struct spu_context *ctx)
{
        spin_lock(&spu_prio->runq_lock);
        list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);
        set_bit(ctx->prio, spu_prio->bitmap);
        spin_unlock(&spu_prio->runq_lock);
}

/**
 * spu_del_from_rq - remove a context from the runqueue
 * @ctx:       context to remove
 */
static void spu_del_from_rq(struct spu_context *ctx)
{
        spin_lock(&spu_prio->runq_lock);
        list_del_init(&ctx->rq);
        if (list_empty(&spu_prio->runq[ctx->prio]))
                clear_bit(ctx->prio, spu_prio->bitmap);
        spin_unlock(&spu_prio->runq_lock);
}

/**
 * spu_grab_context - remove one context from the runqueue
 * @prio:      priority of the context to be removed
 *
 * This function removes one context from the runqueue for priority @prio.
 * If there is more than one context with the given priority the first
 * task on the runqueue will be taken.
 *
 * Returns the spu_context it just removed.
 *
 * Must be called with spu_prio->runq_lock held.
 */
static struct spu_context *spu_grab_context(int prio)
{
        struct list_head *rq = &spu_prio->runq[prio];

        if (list_empty(rq))
                return NULL;
        return list_entry(rq->next, struct spu_context, rq);
}

static void spu_prio_wait(struct spu_context *ctx)
{
        DEFINE_WAIT(wait);

        prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
        if (!signal_pending(current)) {
                mutex_unlock(&ctx->state_mutex);
                schedule();
                mutex_lock(&ctx->state_mutex);
        }
        __set_current_state(TASK_RUNNING);
        remove_wait_queue(&ctx->stop_wq, &wait);
}

/**
 * spu_reschedule - try to find a runnable context for a spu
 * @spu:       spu available
 *
 * This function is called whenever a spu becomes idle.  It looks for the
 * most suitable runnable spu context and schedules it for execution.
 */
static void spu_reschedule(struct spu *spu)
{
        int best;

        spu_free(spu);

        spin_lock(&spu_prio->runq_lock);
        best = sched_find_first_bit(spu_prio->bitmap);
        if (best < MAX_PRIO) {
                struct spu_context *ctx = spu_grab_context(best);
                if (ctx)
                        wake_up(&ctx->stop_wq);
        }
        spin_unlock(&spu_prio->runq_lock);
}

static struct spu *spu_get_idle(struct spu_context *ctx)
{
        struct spu *spu = NULL;
        int node = cpu_to_node(raw_smp_processor_id());
        int n;

        for (n = 0; n < MAX_NUMNODES; n++, node++) {
                node = (node < MAX_NUMNODES) ? node : 0;
                if (!node_allowed(node))
                        continue;
                spu = spu_alloc_node(node);
                if (spu)
                        break;
        }
        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;

        /*
         * 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 schedule 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(node))
                        continue;

                mutex_lock(&spu_prio->active_mutex[node]);
                list_for_each_entry(spu, &spu_prio->active_list[node], list) {
                        struct spu_context *tmp = spu->ctx;

                        if (tmp->rt_priority < ctx->rt_priority &&
                            (!victim || tmp->rt_priority < victim->rt_priority))
                                victim = spu->ctx;
                }
                mutex_unlock(&spu_prio->active_mutex[node]);

                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.
                         */
                        if (!mutex_trylock(&victim->state_mutex)) {
                                victim = NULL;
                                goto restart;
                        }

                        spu = victim->spu;
                        if (!spu) {
                                /*
                                 * This race can happen because we've dropped
                                 * the active list mutex.  No a problem, just
                                 * restart the search.
                                 */
                                mutex_unlock(&victim->state_mutex);
                                victim = NULL;
                                goto restart;
                        }
                        spu_unbind_context(spu, victim);
                        mutex_unlock(&victim->state_mutex);
                        return spu;
                }
        }

        return NULL;
}

/**
 * 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 availble
 * 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)
{

        if (ctx->spu)
                return 0;

        do {
                struct spu *spu;

                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 && ctx->rt_priority)
                        spu = find_victim(ctx);
                if (spu) {
                        spu_bind_context(spu, ctx);
                        return 0;
                }

                spu_add_to_rq(ctx);
                spu_prio_wait(ctx);
                spu_del_from_rq(ctx);
        } while (!signal_pending(current));

        return -ERESTARTSYS;
}

/**
 * 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)
{
        struct spu *spu = ctx->spu;

        if (spu) {
                spu_unbind_context(spu, ctx);
                spu_reschedule(spu);
        }
}

/**
 * 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)
{
        struct spu *spu;

        if (mutex_trylock(&ctx->state_mutex)) {
                if ((spu = ctx->spu) != NULL) {
                        int best = sched_find_first_bit(spu_prio->bitmap);
                        if (best < MAX_PRIO) {
                                pr_debug("%s: yielding SPU %d NODE %d\n",
                                         __FUNCTION__, spu->number, spu->node);
                                spu_deactivate(ctx);
                        }
                }
                mutex_unlock(&ctx->state_mutex);
        }
}

int __init spu_sched_init(void)
{
        int i;

        spu_sched_wq = create_singlethread_workqueue("spusched");
        if (!spu_sched_wq)
                return 1;

        spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
        if (!spu_prio) {
                printk(KERN_WARNING "%s: Unable to allocate priority queue.\n",
                       __FUNCTION__);
                       destroy_workqueue(spu_sched_wq);
                return 1;
        }
        for (i = 0; i < MAX_PRIO; i++) {
                INIT_LIST_HEAD(&spu_prio->runq[i]);
                __clear_bit(i, spu_prio->bitmap);
        }
        __set_bit(MAX_PRIO, spu_prio->bitmap);
        for (i = 0; i < MAX_NUMNODES; i++) {
                mutex_init(&spu_prio->active_mutex[i]);
                INIT_LIST_HEAD(&spu_prio->active_list[i]);
        }
        spin_lock_init(&spu_prio->runq_lock);
        return 0;
}

void __exit spu_sched_exit(void)
{
        struct spu *spu, *tmp;
        int node;

        for (node = 0; node < MAX_NUMNODES; node++) {
                mutex_lock(&spu_prio->active_mutex[node]);
                list_for_each_entry_safe(spu, tmp, &spu_prio->active_list[node],
                                         list) {
                        list_del_init(&spu->list);
                        spu_free(spu);
                }
                mutex_unlock(&spu_prio->active_mutex[node]);
        }
        kfree(spu_prio);
        destroy_workqueue(spu_sched_wq);
}