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drm/scheduler: Fix hang when sched_entity released

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[ Upstream commit c61cdbdbffc169dc7f1e6fe94dfffaf574fe672a ]

Problem: If scheduler is already stopped by the time sched_entity
is released and entity's job_queue not empty I encountred
a hang in drm_sched_entity_flush. This is because drm_sched_entity_is_idle
never becomes false.

Fix: In drm_sched_fini detach all sched_entities from the
scheduler's run queues. This will satisfy drm_sched_entity_is_idle.
Also wakeup all those processes stuck in sched_entity flushing
as the scheduler main thread which wakes them up is stopped by now.

v2:
Reverse order of drm_sched_rq_remove_entity and marking
s_entity as stopped to prevent reinserion back to rq due
to race.

v3:
Drop drm_sched_rq_remove_entity, only modify entity->stopped
and check for it in drm_sched_entity_is_idle

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210512142648.666476-14-andrey.grodzovsky@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Andrey Grodzovsky 2021-05-12 10:26:45 -04:00 committed by Greg Kroah-Hartman
parent 73ac001f06
commit 5ed8c298b2
2 changed files with 26 additions and 1 deletions
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3
drivers/gpu/drm/scheduler/sched_entity.c
View File

@ -113,7 +113,8 @@ 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_count(&entity->job_queue) == 0)
spsc_queue_count(&entity->job_queue) == 0 ||
entity->stopped)
return true;
return false;

24
drivers/gpu/drm/scheduler/sched_main.c
View File

@ -887,9 +887,33 @@ EXPORT_SYMBOL(drm_sched_init);
*/
void drm_sched_fini(struct drm_gpu_scheduler *sched)
{
struct drm_sched_entity *s_entity;
int i;
if (sched->thread)
kthread_stop(sched->thread);
for (i = DRM_SCHED_PRIORITY_COUNT - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
struct drm_sched_rq *rq = &sched->sched_rq[i];
if (!rq)
continue;
spin_lock(&rq->lock);
list_for_each_entry(s_entity, &rq->entities, list)
/*
* Prevents reinsertion and marks job_queue as idle,
* it will removed from rq in drm_sched_entity_fini
* eventually
*/
s_entity->stopped = true;
spin_unlock(&rq->lock);
}
/* Wakeup everyone stuck in drm_sched_entity_flush for this scheduler */
wake_up_all(&sched->job_scheduled);
/* Confirm no work left behind accessing device structures */
cancel_delayed_work_sync(&sched->work_tdr);