[PATCH] drm/scheduler: use job count instead of peek

From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: andrey.grodzovsky@amd.com, dri-devel@lists.freedesktop.org,
	Monk.Liu@amd.com, Emily.Deng@amd.com
Subject: [PATCH] drm/scheduler: use job count instead of peek
Date: Fri,  9 Aug 2019 17:31:09 +0200	[thread overview]
Message-ID: <20190809153109.79228-1-christian.koenig@amd.com> (raw)

The spsc_queue_peek function is accessing queue->head which belongs to
the consumer thread and shouldn't be accessed by the producer

This is fixing a rare race condition when destroying entities.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/scheduler/sched_entity.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index 35ddbec1375a..671c90f34ede 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -95,7 +95,7 @@ static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
 	rmb(); /* for list_empty to work without lock */
 
 	if (list_empty(&entity->list) ||
-	    spsc_queue_peek(&entity->job_queue) == NULL)
+	    spsc_queue_count(&entity->job_queue) == 0)
 		return true;
 
 	return false;
@@ -281,7 +281,7 @@ void drm_sched_entity_fini(struct drm_sched_entity *entity)
 	/* Consumption of existing IBs wasn't completed. Forcefully
 	 * remove them here.
 	 */
-	if (spsc_queue_peek(&entity->job_queue)) {
+	if (spsc_queue_count(&entity->job_queue)) {
 		if (sched) {
 			/* Park the kernel for a moment to make sure it isn't processing
 			 * our enity.
-- 
2.17.1

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