diff mbox series

[2/8] drm/sched: Always wake up correct scheduler in drm_sched_entity_push_job

Message ID 20240909171937.51550-3-tursulin@igalia.com (mailing list archive)
State New, archived
Headers show
Series DRM scheduler fixes, or not, or incorrect kind | expand

Commit Message

Tvrtko Ursulin Sept. 9, 2024, 5:19 p.m. UTC
From: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>

Since drm_sched_entity_modify_sched() can modify the entities run queue,
lets make sure to only dereference the pointer once so both adding and
waking up are guaranteed to be consistent.

Alternative of moving the spin_unlock to after the wake up would for now
be more problematic since the same lock is taken inside
drm_sched_rq_update_fifo().

v2:
 * Improve commit message. (Philipp)
 * Cache the scheduler pointer directly. (Christian)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Fixes: b37aced31eb0 ("drm/scheduler: implement a function to modify sched list")
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Luben Tuikov <ltuikov89@gmail.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Philipp Stanner <pstanner@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.7+
---
 drivers/gpu/drm/scheduler/sched_entity.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Comments

Christian König Sept. 10, 2024, 7:42 a.m. UTC | #1
Am 09.09.24 um 19:19 schrieb Tvrtko Ursulin:
> From: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
>
> Since drm_sched_entity_modify_sched() can modify the entities run queue,
> lets make sure to only dereference the pointer once so both adding and
> waking up are guaranteed to be consistent.
>
> Alternative of moving the spin_unlock to after the wake up would for now
> be more problematic since the same lock is taken inside
> drm_sched_rq_update_fifo().
>
> v2:
>   * Improve commit message. (Philipp)
>   * Cache the scheduler pointer directly. (Christian)
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
> Fixes: b37aced31eb0 ("drm/scheduler: implement a function to modify sched list")
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Luben Tuikov <ltuikov89@gmail.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Philipp Stanner <pstanner@redhat.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: <stable@vger.kernel.org> # v5.7+
> ---
>   drivers/gpu/drm/scheduler/sched_entity.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index ae8be30472cd..76e422548d40 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -599,6 +599,9 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
>   
>   	/* first job wakes up scheduler */
>   	if (first) {
> +		struct drm_gpu_scheduler *sched;
> +		struct drm_sched_rq *rq;
> +
>   		/* Add the entity to the run queue */
>   		spin_lock(&entity->rq_lock);
>   		if (entity->stopped) {
> @@ -608,13 +611,16 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
>   			return;
>   		}
>   
> -		drm_sched_rq_add_entity(entity->rq, entity);
> +		rq = entity->rq;
> +		sched = rq->sched;

The rq variable is now not needed any more except for getting the 
scheduler, isn't it? If yes I would ditch that as well.

Either way Reviewed-by: Christian König <christian.koenig@amd.com> to 
this patch.

Regards,
Christian.

> +
> +		drm_sched_rq_add_entity(rq, entity);
>   		spin_unlock(&entity->rq_lock);
>   
>   		if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
>   			drm_sched_rq_update_fifo(entity, submit_ts);
>   
> -		drm_sched_wakeup(entity->rq->sched, entity);
> +		drm_sched_wakeup(sched, entity);
>   	}
>   }
>   EXPORT_SYMBOL(drm_sched_entity_push_job);
diff mbox series

Patch

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index ae8be30472cd..76e422548d40 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -599,6 +599,9 @@  void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
 
 	/* first job wakes up scheduler */
 	if (first) {
+		struct drm_gpu_scheduler *sched;
+		struct drm_sched_rq *rq;
+
 		/* Add the entity to the run queue */
 		spin_lock(&entity->rq_lock);
 		if (entity->stopped) {
@@ -608,13 +611,16 @@  void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
 			return;
 		}
 
-		drm_sched_rq_add_entity(entity->rq, entity);
+		rq = entity->rq;
+		sched = rq->sched;
+
+		drm_sched_rq_add_entity(rq, entity);
 		spin_unlock(&entity->rq_lock);
 
 		if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
 			drm_sched_rq_update_fifo(entity, submit_ts);
 
-		drm_sched_wakeup(entity->rq->sched, entity);
+		drm_sched_wakeup(sched, entity);
 	}
 }
 EXPORT_SYMBOL(drm_sched_entity_push_job);