[PATCH 1/2] drm/scheduler: Avoid using wait_event_killable for dying process.

[Christian König]

Am 30.05.2018 um 21:54 schrieb Andrey Grodzovsky:
> Dying process might be blocked from receiving any more signals
> so avoid using it.
>
> Also retire enity->fini_status and just check the SW queue,
> if it's not empty do the fallback cleanup.
>
> Also handle entity->last_scheduled == NULL use case which
> happens when HW ring is already hangged whem a  new entity
> tried to enqeue jobs.
>
> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>

Would be nice to have to split that patch up further, but not sure if 
that is actually doable.

Additional to that a few more nitpicks below.

> ---
>   drivers/gpu/drm/scheduler/gpu_scheduler.c | 47 ++++++++++++++++++++++---------
>   include/drm/gpu_scheduler.h               |  1 -
>   2 files changed, 34 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> index 44d4807..4d038f9 100644
> --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> @@ -135,7 +135,6 @@ int drm_sched_entity_init(struct drm_gpu_scheduler *sched,
>   	entity->rq = rq;
>   	entity->sched = sched;
>   	entity->guilty = guilty;
> -	entity->fini_status = 0;
>   	entity->last_scheduled = NULL;
>   
>   	spin_lock_init(&entity->rq_lock);
> @@ -173,7 +172,8 @@ static bool drm_sched_entity_is_initialized(struct drm_gpu_scheduler *sched,
>   static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
>   {
>   	rmb();
> -	if (spsc_queue_peek(&entity->job_queue) == NULL)
> +
> +	if (entity->rq == NULL || spsc_queue_peek(&entity->job_queue) == NULL)

Usual kernel coding style is more to use "!entity->rq" instead of 
"entity->rq == NULL".

>   		return true;
>   
>   	return false;
> @@ -227,12 +227,16 @@ void drm_sched_entity_do_release(struct drm_gpu_scheduler *sched,
>   	 * The client will not queue more IBs during this fini, consume existing
>   	 * queued IBs or discard them on SIGKILL
>   	*/
> -	if ((current->flags & PF_SIGNALED) && current->exit_code == SIGKILL)
> -		entity->fini_status = -ERESTARTSYS;
> +	if ((current->flags & PF_EXITING))
> +		wait_event_timeout(sched->job_scheduled,
> +				drm_sched_entity_is_idle(entity), msecs_to_jiffies(1000));

Mhm, making the timeout a parameter or at least use a define would be 
nice to have.

Additional to that it might be a good idea to return the remaining 
timeout and use that as parameter for the next call.

E.g. this way when we need to cleanup multiple queues we don't wait for 
1000 ms each, but rather only 1000 ms in total.

>   	else
> -		entity->fini_status = wait_event_killable(sched->job_scheduled,
> -					drm_sched_entity_is_idle(entity));
> -	drm_sched_entity_set_rq(entity, NULL);
> +		wait_event_killable(sched->job_scheduled, drm_sched_entity_is_idle(entity));
> +
> +
> +	/* For killed process disable any more IBs enqueue right now */
> +	if ((current->flags & PF_EXITING) && (current->exit_code == SIGKILL))
> +		drm_sched_entity_set_rq(entity, NULL);
>   }
>   EXPORT_SYMBOL(drm_sched_entity_do_release);
>   
> @@ -247,7 +251,13 @@ EXPORT_SYMBOL(drm_sched_entity_do_release);
>   void drm_sched_entity_cleanup(struct drm_gpu_scheduler *sched,
>   			   struct drm_sched_entity *entity)
>   {
> -	if (entity->fini_status) {
> +
> +	drm_sched_entity_set_rq(entity, NULL);
> +
> +	/* Consumption of existing IBs wasn't completed. Forcefully
> +	 * remove them here.
> +	 */
> +	if (spsc_queue_peek(&entity->job_queue)) {
>   		struct drm_sched_job *job;
>   		int r;
>   
> @@ -267,12 +277,22 @@ void drm_sched_entity_cleanup(struct drm_gpu_scheduler *sched,
>   			struct drm_sched_fence *s_fence = job->s_fence;
>   			drm_sched_fence_scheduled(s_fence);
>   			dma_fence_set_error(&s_fence->finished, -ESRCH);
> -			r = dma_fence_add_callback(entity->last_scheduled, &job->finish_cb,
> -							drm_sched_entity_kill_jobs_cb);
> -			if (r == -ENOENT)
> +
> +			/*
> +			 * When pipe is hanged by older entity, new entity might
> +			 * not even have chance to submit it's first job to HW
> +			 * and so entity->last_scheduled will remain NULL
> +			 */
> +			if (!entity->last_scheduled)
>   				drm_sched_entity_kill_jobs_cb(NULL, &job->finish_cb);
> -			else if (r)
> -				DRM_ERROR("fence add callback failed (%d)\n", r);
> +			else {

Coding style nit pick when one side of an else has { or } the other side 
should have it as well.

> +				r = dma_fence_add_callback(entity->last_scheduled, &job->finish_cb,
> +								drm_sched_entity_kill_jobs_cb);
> +				if (r == -ENOENT)
> +					drm_sched_entity_kill_jobs_cb(NULL, &job->finish_cb);
> +				else if (r)
> +					DRM_ERROR("fence add callback failed (%d)\n", r);
> +			}
>   		}
>   	}
>   
> @@ -713,6 +733,7 @@ static int drm_sched_main(void *param)
>   			continue;
>   
>   		sched_job = drm_sched_entity_pop_job(entity);
> +

Unnecessary blank line added.

Apart from that thanks a lot for taking care of that, that is really 
appreciated.

Thanks,
Christian.

>   		if (!sched_job)
>   			continue;
>   
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index dec6558..d220ac9 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -64,7 +64,6 @@ struct drm_sched_entity {
>   	struct dma_fence		*dependency;
>   	struct dma_fence_cb		cb;
>   	atomic_t			*guilty; /* points to ctx's guilty */
> -	int            fini_status;
>   	struct dma_fence    *last_scheduled;
>   };
>