[PATCH] drm/scheduler: add NULL pointer check for run queue (v2)

[PATCH] drm/scheduler: add NULL pointer check for run queue (v2)

[Junwei Zhang]

To check rq pointer before adding entity into it.
That avoids NULL pointer access in some case.

v2: move the check to caller

Suggested-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>
---
 drivers/gpu/drm/scheduler/gpu_scheduler.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c b/drivers/gpu/drm/scheduler/gpu_scheduler.c
index 16bf446..dac71e3 100644
--- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
+++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
@@ -547,6 +547,11 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job,
 	if (first) {
 		/* Add the entity to the run queue */
 		spin_lock(&entity->rq_lock);
+		if (!entity->rq) {
+			DRM_ERROR("Trying to push to a killed entity\n");
+			spin_unlock(&entity->rq_lock);
+			return;
+		}
 		drm_sched_rq_add_entity(entity->rq, entity);
 		spin_unlock(&entity->rq_lock);
 		drm_sched_wakeup(sched);
-- 
1.9.1

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Re: [PATCH] drm/scheduler: add NULL pointer check for run queue (v2)

[Christian König]

Am 16.07.2018 um 11:23 schrieb Junwei Zhang:
> To check rq pointer before adding entity into it.
> That avoids NULL pointer access in some case.
>
> v2: move the check to caller
>
> Suggested-by: Christian König <christian.koenig@amd.com>
> Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
>   drivers/gpu/drm/scheduler/gpu_scheduler.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> index 16bf446..dac71e3 100644
> --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> @@ -547,6 +547,11 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job,
>   	if (first) {
>   		/* Add the entity to the run queue */
>   		spin_lock(&entity->rq_lock);
> +		if (!entity->rq) {
> +			DRM_ERROR("Trying to push to a killed entity\n");
> +			spin_unlock(&entity->rq_lock);
> +			return;
> +		}
>   		drm_sched_rq_add_entity(entity->rq, entity);
>   		spin_unlock(&entity->rq_lock);
>   		drm_sched_wakeup(sched);

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Re: [PATCH] drm/scheduler: add NULL pointer check for run queue (v2)

[Michel Dänzer]

On 2018-07-16 11:23 AM, Junwei Zhang wrote:
> To check rq pointer before adding entity into it.
> That avoids NULL pointer access in some case.
> 
> v2: move the check to caller
> 
> Suggested-by: Christian König <christian.koenig@amd.com>
> Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>
> ---
>  drivers/gpu/drm/scheduler/gpu_scheduler.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> index 16bf446..dac71e3 100644
> --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> @@ -547,6 +547,11 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job,
>  	if (first) {
>  		/* Add the entity to the run queue */
>  		spin_lock(&entity->rq_lock);
> +		if (!entity->rq) {
> +			DRM_ERROR("Trying to push to a killed entity\n");

This could result in spamming dmesg with this error message. I suggest

		if (WARN_ON_ONCE(!entity->rq)) {

instead, no DRM_ERROR. That will produce a single warning with a backtrace.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer
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Re: [PATCH] drm/scheduler: add NULL pointer check for run queue (v2)

[Zhang, Jerry (Junwei)]

On 07/16/2018 05:54 PM, Michel Dänzer wrote:
> On 2018-07-16 11:23 AM, Junwei Zhang wrote:
>> To check rq pointer before adding entity into it.
>> That avoids NULL pointer access in some case.
>>
>> v2: move the check to caller
>>
>> Suggested-by: Christian König <christian.koenig@amd.com>
>> Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>
>> ---
>>   drivers/gpu/drm/scheduler/gpu_scheduler.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c b/drivers/gpu/drm/scheduler/gpu_scheduler.c
>> index 16bf446..dac71e3 100644
>> --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
>> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
>> @@ -547,6 +547,11 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job,
>>   	if (first) {
>>   		/* Add the entity to the run queue */
>>   		spin_lock(&entity->rq_lock);
>> +		if (!entity->rq) {
>> +			DRM_ERROR("Trying to push to a killed entity\n");
>
> This could result in spamming dmesg with this error message. I suggest

Thanks for your comments.
Actually it will cause App or GPU hang, as the job is unexpected to push to a non-existing entity run queue.
Now we're trying to predict that before kernel panic or BUG_ON.

Regards,
Jerry

>
> 		if (WARN_ON_ONCE(!entity->rq)) {
>
> instead, no DRM_ERROR. That will produce a single warning with a backtrace.
>
>
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