Re: [PATCH] drm/sched: Drain all entities in DRM sched run job worker

["Christian König" <christian.koenig@amd.com>]

Am 24.01.24 um 22:08 schrieb Matthew Brost:
> All entities must be drained in the DRM scheduler run job worker to
> avoid the following case. An entity found that is ready, no job found
> ready on entity, and run job worker goes idle with other entities + jobs
> ready. Draining all ready entities (i.e. loop over all ready entities)
> in the run job worker ensures all job that are ready will be scheduled.

That doesn't make sense. drm_sched_select_entity() only returns entities 
which are "ready", e.g. have a job to run.

If that's not the case any more then you have broken something else.

Regards,
Christian.

>
> Cc: Thorsten Leemhuis <regressions@leemhuis.info>
> Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
> Closes: https://lore.kernel.org/all/CABXGCsM2VLs489CH-vF-1539-s3in37=bwuOWtoeeE+q26zE+Q@mail.gmail.com/
> Reported-and-tested-by: Mario Limonciello <mario.limonciello@amd.com>
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3124
> Link: https://lore.kernel.org/all/20240123021155.2775-1-mario.limonciello@amd.com/
> Reported-by: Vlastimil Babka <vbabka@suse.cz>
> Closes: https://lore.kernel.org/dri-devel/05ddb2da-b182-4791-8ef7-82179fd159a8@amd.com/T/#m0c31d4d1b9ae9995bb880974c4f1dbaddc33a48a
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/scheduler/sched_main.c | 15 +++++++--------
>   1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 550492a7a031..85f082396d42 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -1178,21 +1178,20 @@ static void drm_sched_run_job_work(struct work_struct *w)
>   	struct drm_sched_entity *entity;
>   	struct dma_fence *fence;
>   	struct drm_sched_fence *s_fence;
> -	struct drm_sched_job *sched_job;
> +	struct drm_sched_job *sched_job = NULL;
>   	int r;
>   
>   	if (READ_ONCE(sched->pause_submit))
>   		return;
>   
> -	entity = drm_sched_select_entity(sched);
> +	/* Find entity with a ready job */
> +	while (!sched_job && (entity = drm_sched_select_entity(sched))) {
> +		sched_job = drm_sched_entity_pop_job(entity);
> +		if (!sched_job)
> +			complete_all(&entity->entity_idle);
> +	}
>   	if (!entity)
> -		return;
> -
> -	sched_job = drm_sched_entity_pop_job(entity);
> -	if (!sched_job) {
> -		complete_all(&entity->entity_idle);
>   		return;	/* No more work */
> -	}
>   
>   	s_fence = sched_job->s_fence;
>