Lin I explicitly pointed out that you should *not* send it to stable@vger.kernel.org.

Greg and other stable maintainers please ignore this mail, the bug fix is going upstream through the normal DRM channels.

Regards, Christian.

On 17.07.25 10:34, Lin.Cao wrote:

When application A submits jobs and application B submits a job with a dependency on A's fence, the normal flow wakes up the scheduler after processing each job. However, the optimization in drm_sched_entity_add_dependency_cb() uses a callback that only clears dependencies without waking up the scheduler.

When application A is killed before its jobs can run, the callback gets triggered but only clears the dependency without waking up the scheduler, causing the scheduler to enter sleep state and application B to hang.

Remove the optimization by deleting drm_sched_entity_clear_dep() and its usage, ensuring the scheduler is always woken up when dependencies are cleared.

Fixes: 777dbd458c89 ("drm/amdgpu: drop a dummy wakeup scheduler") Cc: stable@vger.kernel.org # v4.6+

Signed-off-by: Lin.Cao lincao12@amd.com Reviewed-by: Christian König christian.koenig@amd.com

---

drivers/gpu/drm/scheduler/sched_entity.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index e671aa241720..ac678de7fe5e 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -355,17 +355,6 @@ void drm_sched_entity_destroy(struct drm_sched_entity *entity) } EXPORT_SYMBOL(drm_sched_entity_destroy); -/* drm_sched_entity_clear_dep - callback to clear the entities dependency */ -static void drm_sched_entity_clear_dep(struct dma_fence *f,

• 		       struct dma_fence_cb *cb)
  

-{

• struct drm_sched_entity *entity =

• container_of(cb, struct drm_sched_entity, cb);
  

• entity->dependency = NULL;
• dma_fence_put(f);

-}

/*

• drm_sched_entity_wakeup - callback to clear the entity's dependency and
• wake up the scheduler

@@ -376,7 +365,8 @@ static void drm_sched_entity_wakeup(struct dma_fence *f, struct drm_sched_entity *entity = container_of(cb, struct drm_sched_entity, cb);

• drm_sched_entity_clear_dep(f, cb);

• entity->dependency = NULL;
• dma_fence_put(f); drm_sched_wakeup(entity->rq->sched);

} @@ -429,13 +419,6 @@ static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity) fence = dma_fence_get(&s_fence->scheduled); dma_fence_put(entity->dependency); entity->dependency = fence;

• if (!dma_fence_add_callback(fence, &entity->cb,
  

• 			    drm_sched_entity_clear_dep))
  

• 	return true;
  

• /* Ignore it when it is already scheduled */
  

• dma_fence_put(fence);
  

• return false;
  

  }

if (!dma_fence_add_callback(entity->dependency, &entity->cb,