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.
Signed-off-by: Andrey Grodzovsky andrey.grodzovsky@amd.com --- drivers/gpu/drm/scheduler/sched_main.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index 908b0b5..c6b7947 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -897,9 +897,40 @@ EXPORT_SYMBOL(drm_sched_init); */ void drm_sched_fini(struct drm_gpu_scheduler *sched) { + int i; + struct drm_sched_entity *s_entity; if (sched->thread) kthread_stop(sched->thread);
+ /* Detach all sched_entites from this scheduler once it's stopped */ + 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; + + /* Loop this way because rq->lock is taken in drm_sched_rq_remove_entity */ + spin_lock(&rq->lock); + while ((s_entity = list_first_entry_or_null(&rq->entities, + struct drm_sched_entity, + list))) { + spin_unlock(&rq->lock); + + /* Prevent reinsertion and remove */ + spin_lock(&s_entity->rq_lock); + s_entity->stopped = true; + drm_sched_rq_remove_entity(rq, s_entity); + spin_unlock(&s_entity->rq_lock); + + spin_lock(&rq->lock); + } + 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);