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authorChristoph Hellwig <hch@lst.de>2007-06-04 23:26:51 +1000
committerPaul Mackerras <paulus@samba.org>2007-06-07 11:44:39 +1000
commitbb5db29aa0379f0f3ef857a3a3715f17261c611b (patch)
tree7de8b9a16f8a78fb99ac10e1f8d64664b5472aa3 /arch/powerpc/platforms/cell/spufs/sched.c
parent47d3a5faa3f72186f769ed9579c630afb8433f2b (diff)
[POWERPC] spufs scheduler: Fix wakeup races
Fix the race between checking for contexts on the runqueue and actually waking them in spu_deactive and spu_yield. The guts of spu_reschedule are split into a new helper called grab_runnable_context which shows if there is a runnable thread below a specified priority and if yes removes if from the runqueue and uses it. This function is used by the new __spu_deactivate hepler shared by preemption and spu_yield to grab a new context before deactivating a specified priority and if yes removes if from the runqueue and uses it. This function is used by the new __spu_deactivate hepler shared by preemption and spu_yield to grab a new context before deactivating the old one. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com> Signed-off-by: Jeremy Kerr <jk@ozlabs.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/platforms/cell/spufs/sched.c')
-rw-r--r--arch/powerpc/platforms/cell/spufs/sched.c159
1 files changed, 77 insertions, 82 deletions
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index b6ecb30e7d58..68fcdc4515ab 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -93,43 +93,6 @@ void spu_stop_tick(struct spu_context *ctx)
}
}
-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
@@ -273,34 +236,6 @@ static void spu_prio_wait(struct spu_context *ctx)
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 list_head *rq = &spu_prio->runq[best];
- struct spu_context *ctx;
-
- BUG_ON(list_empty(rq));
-
- ctx = list_entry(rq->next, struct spu_context, rq);
- __spu_del_from_rq(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;
@@ -429,6 +364,51 @@ int spu_activate(struct spu_context *ctx, unsigned long flags)
}
/**
+ * 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)
+{
+ struct spu_context *ctx = NULL;
+ int best;
+
+ spin_lock(&spu_prio->runq_lock);
+ best = sched_find_first_bit(spu_prio->bitmap);
+ if (best < prio) {
+ struct list_head *rq = &spu_prio->runq[best];
+
+ BUG_ON(list_empty(rq));
+
+ ctx = list_entry(rq->next, struct spu_context, rq);
+ __spu_del_from_rq(ctx);
+ }
+ 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);
+ if (new || force) {
+ spu_unbind_context(spu, ctx);
+ spu_free(spu);
+ if (new)
+ wake_up(&new->stop_wq);
+ }
+
+ }
+
+ return new != NULL;
+}
+
+/**
* spu_deactivate - unbind a context from it's physical spu
* @ctx: spu context to unbind
*
@@ -437,12 +417,7 @@ int spu_activate(struct spu_context *ctx, unsigned long flags)
*/
void spu_deactivate(struct spu_context *ctx)
{
- struct spu *spu = ctx->spu;
-
- if (spu) {
- spu_unbind_context(spu, ctx);
- spu_reschedule(spu);
- }
+ __spu_deactivate(ctx, 1, MAX_PRIO);
}
/**
@@ -455,18 +430,38 @@ void spu_deactivate(struct spu_context *ctx)
*/
void spu_yield(struct spu_context *ctx)
{
- struct spu *spu;
+ mutex_lock(&ctx->state_mutex);
+ __spu_deactivate(ctx, 0, MAX_PRIO);
+ mutex_unlock(&ctx->state_mutex);
+}
- 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);
+void spu_sched_tick(struct work_struct *work)
+{
+ struct spu_context *ctx =
+ container_of(work, struct spu_context, sched_work.work);
+ int preempted;
+
+ /*
+ * 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);
+ preempted = __spu_deactivate(ctx, 0, ctx->prio + 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);
}
}

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