/* 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) {
/*
* Make sure the exiting bit is cleared.
*/
clear_bit(SPU_SCHED_EXITING, &ctx->sched_flags);
mb();
queue_delayed_work(spu_sched_wq, &ctx->sched_work, SPU_TIMESLICE);
}
}
void spu_stop_tick(struct spu_context *ctx)
{
if (ctx->policy == SCHED_RR) {
/*
* While the work can be rearming normally setting this flag
* makes sure it does not rearm itself anymore.
*/
set_bit(SPU_SCHED_EXITING, &ctx->sched_flags);
mb();
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 preempted = 0;
/*
* If this context is being stopped avoid rescheduling from the
* scheduler tick because we would block on the state_mutex.
* The caller will yield the spu later on anyway.
*/
if (test_bit(SPU_SCHED_EXITING, &ctx->sched_flags))
return;
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);
preempted = 1;
}
}
mutex_unlock(&ctx->state_mutex);
if (preempted) {
/*
* We need to break out of the wait loop in spu_run manually
* to ensure this context gets put on the runqueue again
* ASAP.
*/
wake_up(&ctx->stop_wq);
} else
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);
mb();
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);
/*
* We need to break out of the wait loop in spu_run
* manually to ensure this context gets put on the
* runqueue again ASAP.
*/
wake_up(&victim->stop_wq);
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 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)
{
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);
}
