[POWERPC] spufs: use cancel_rearming_delayed_workqueue when stopping spu contexts

The scheduler workqueue may rearm itself and deadlock when we try to stop
it.  Put a flag in place to avoid skip the work if we're tearing down
the context.

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

2 files changed, 23 insertions, 4 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index c9561582ce2a..003e330fc76f 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -71,14 +71,25 @@ static inline int node_allowed(int node)
 
 void spu_start_tick(struct spu_context *ctx)
 {
-        if (ctx->policy == SCHED_RR)
+        if (ctx->policy == SCHED_RR) {
+                /*
+                 * Make sure the exiting bit is cleared.
+                 */
+                clear_bit(SPU_SCHED_EXITING, &ctx->sched_flags);
                 queue_delayed_work(spu_sched_wq, &ctx->sched_work, SPU_TIMESLICE);
+        }
 }
 
 void spu_stop_tick(struct spu_context *ctx)
 {
-        if (ctx->policy == SCHED_RR)
+        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);
                 cancel_delayed_work(&ctx->sched_work);
+        }
 }
 
 void spu_sched_tick(struct work_struct *work)
@@ -88,6 +99,14 @@ void spu_sched_tick(struct work_struct *work)
         struct spu *spu;
         int rearm = 1;
 
+        /*
+         * 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) {
@@ -377,7 +396,7 @@ static struct spu *find_victim(struct spu_context *ctx)
  * @ctx:        spu context to schedule
  * @flags:      flags (currently ignored)
  *
- * Tries to find a free spu to run @ctx.  If no free spu is availble
+ * 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.
  */
diff --git a/arch/powerpc/platforms/cell/spufs/spufs.h b/arch/powerpc/platforms/cell/spufs/spufs.h
index 5c4e47d69d79..f418378abdff 100644
--- a/arch/powerpc/platforms/cell/spufs/spufs.h
+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -41,7 +41,7 @@ struct spu_gang;
 
 /* ctx->sched_flags */
 enum {
-        SPU_SCHED_WAKE = 0, /* currently unused */
+        SPU_SCHED_EXITING = 0,
 };
 
 struct spu_context {