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

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

[Christian König]

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

[Grodzovsky, Andrey]

Acked-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>

Andrey

On 8/9/19 11:31 AM, Christian König wrote:
> 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.
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RE: [PATCH] drm/scheduler: use job count instead of peek

[Liu, Monk]

Reviewed-by: Monk.liu@amd.com

_____________________________________
Monk Liu|GPU Virtualization Team |AMD


-----Original Message-----
From: Christian König <ckoenig.leichtzumerken@gmail.com> 
Sent: Friday, August 9, 2019 11:31 PM
To: Grodzovsky, Andrey <Andrey.Grodzovsky@amd.com>; dri-devel@lists.freedesktop.org; Liu, Monk <Monk.Liu@amd.com>; Deng, Emily <Emily.Deng@amd.com>
Subject: [PATCH] drm/scheduler: use job count instead of peek

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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