drm/scheduler: fix fence ref counting

We leaked dependency fences when processes were beeing killed.

Additional to that grab a reference to the last scheduled fence.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220929180151.139751-1-christian.koenig@amd.com

drivers/gpu/drm/scheduler/sched_entity.c

@@ -207,6 +207,7 @@ static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f,
 	struct drm_sched_job *job = container_of(cb, struct drm_sched_job,
 						 finish_cb);
 
+	dma_fence_put(f);
 	INIT_WORK(&job->work, drm_sched_entity_kill_jobs_work);
 	schedule_work(&job->work);
 }
@@ -234,8 +235,10 @@ static void drm_sched_entity_kill_jobs(struct drm_sched_entity *entity)
 		struct drm_sched_fence *s_fence = job->s_fence;
 
 		/* Wait for all dependencies to avoid data corruptions */
-		while ((f = drm_sched_job_dependency(job, entity)))
+		while ((f = drm_sched_job_dependency(job, entity))) {
 			dma_fence_wait(f, false);
+			dma_fence_put(f);
+		}
 
 		drm_sched_fence_scheduled(s_fence);
 		dma_fence_set_error(&s_fence->finished, -ESRCH);
@@ -250,6 +253,7 @@ static void drm_sched_entity_kill_jobs(struct drm_sched_entity *entity)
 			continue;
 		}
 
+		dma_fence_get(entity->last_scheduled);
 		r = dma_fence_add_callback(entity->last_scheduled,
 					   &job->finish_cb,
 					   drm_sched_entity_kill_jobs_cb);