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

["Zhang, Jerry (Junwei)" <Jerry.Zhang-5C7GfCeVMHo@public.gmane.org>]

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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