On 2021-02-26 3:04 a.m., Christian König wrote:
Am 25.02.21 um 22:37 schrieb Andrey Grodzovsky:
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@xxxxxxx>
---
drivers/gpu/drm/scheduler/sched_entity.c | 3 ++-
drivers/gpu/drm/scheduler/sched_main.c | 23 +++++++++++++++++++++++
2 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/scheduler/sched_entity.c
b/drivers/gpu/drm/scheduler/sched_entity.c
index 92d965b629c6..68b10813129a 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -116,7 +116,8 @@ 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;
diff --git a/drivers/gpu/drm/scheduler/sched_main.c
b/drivers/gpu/drm/scheduler/sched_main.c
index 908b0b56032d..b50fab472734 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -897,9 +897,32 @@ EXPORT_SYMBOL(drm_sched_init);
*/
void drm_sched_fini(struct drm_gpu_scheduler *sched)
{
+ int i;
+ struct drm_sched_entity *s_entity;
Please declare i last and have an empty line between declaration and
code.
With that nit pick fixed the patch is Reviewed-by: Christian König
<christian.koenig@xxxxxxx>. Going to push it to drm-misc-next.
Christian.
Done. Since you are pushing attaching the patch here.
Andrey
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);
>From 7f0a1f4ee6d5fa24b50fee199e5d7ea316d2f08e Mon Sep 17 00:00:00 2001
From: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
Date: Fri, 12 Feb 2021 01:45:51 -0500
Subject: drm/scheduler: Fix hang when sched_entity released
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
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@xxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/gpu/drm/scheduler/sched_entity.c | 3 ++-
drivers/gpu/drm/scheduler/sched_main.c | 24 ++++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index 92d965b629c6..68b10813129a 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -116,7 +116,8 @@ 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;
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 908b0b56032d..ba087354d0a8 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -897,9 +897,33 @@ 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);
--
2.25.1
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