[POWERPC] spu sched: make addition to stop_wq and runque atomic vs wakeup

Addition to stop_wq needs to happen before adding to the runqeueue and
under the same lock so that we don't have a race window for a lost
wake up in the spu scheduler.

Signed-off-by: Luke Browning <lukebrowning@us.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>

1 files changed, 16 insertions, 22 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 876828cc95a2..91030b8abdca 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -236,44 +236,40 @@ static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
  * spu_add_to_rq - add a context to the runqueue
  * @ctx:       context to add
  */
-static void spu_add_to_rq(struct spu_context *ctx)
+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);
+        int prio = ctx->prio;
+
+        list_add_tail(&ctx->rq, &spu_prio->runq[prio]);
+        set_bit(prio, spu_prio->bitmap);
 }
 
-static void __spu_del_from_rq(struct spu_context *ctx, int prio)
+static void __spu_del_from_rq(struct spu_context *ctx)
 {
+        int prio = ctx->prio;
+
         if (!list_empty(&ctx->rq))
                 list_del_init(&ctx->rq);
         if (list_empty(&spu_prio->runq[prio]))
-                clear_bit(ctx->prio, spu_prio->bitmap);
-}
-
-/**
- * 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);
-        __spu_del_from_rq(ctx, ctx->prio);
-        spin_unlock(&spu_prio->runq_lock);
+                clear_bit(prio, spu_prio->bitmap);
 }
 
 static void spu_prio_wait(struct spu_context *ctx)
 {
         DEFINE_WAIT(wait);
 
+        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);
 }
@@ -300,7 +296,7 @@ static void spu_reschedule(struct spu *spu)
                 BUG_ON(list_empty(rq));
 
                 ctx = list_entry(rq->next, struct spu_context, rq);
-                __spu_del_from_rq(ctx, best);
+                __spu_del_from_rq(ctx);
                 wake_up(&ctx->stop_wq);
         }
         spin_unlock(&spu_prio->runq_lock);
@@ -427,9 +423,7 @@ int spu_activate(struct spu_context *ctx, unsigned long flags)
                         return 0;
                 }
 
-                spu_add_to_rq(ctx);
                 spu_prio_wait(ctx);
-                spu_del_from_rq(ctx);
         } while (!signal_pending(current));
 
         return -ERESTARTSYS;