From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
Without the locking amdgpu currently can race
amdgpu_ctx_set_entity_priority() and drm_sched_job_arm(), leading to the
latter accesing potentially inconsitent entity->sched_list and
entity->num_sched_list pair.
The comment on drm_sched_entity_modify_sched() however says:
"""
* Note that this must be called under the same common lock for @entity as
* drm_sched_job_arm() and drm_sched_entity_push_job(), or the driver needs to
* guarantee through some other means that this is never called while new jobs
* can be pushed to @entity.
"""
It is unclear if that is referring to this race or something else.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
Fixes: b37aced31eb0 ("drm/scheduler: implement a function to modify sched list")
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Luben Tuikov <ltuikov89@xxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v5.7+
---
drivers/gpu/drm/scheduler/sched_entity.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index 58c8161289fe..ae8be30472cd 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -133,8 +133,10 @@ void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
{
WARN_ON(!num_sched_list || !sched_list);
+ spin_lock(&entity->rq_lock);
entity->sched_list = sched_list;
entity->num_sched_list = num_sched_list;
+ spin_unlock(&entity->rq_lock);
}
EXPORT_SYMBOL(drm_sched_entity_modify_sched);
--
2.46.0
