From: Philipp Stanner <phasta@kernel.org>
Date: Thu, 8 Jan 2026 08:30:20 +0000 (+0100)
Subject: drm/sched: Remove racy hack from drm_sched_fini()
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=4827d6d83f079f7d58d6ec0ed49f85dd2b90837f;p=thirdparty%2Flinux.git

drm/sched: Remove racy hack from drm_sched_fini()

drm_sched_fini() contained a hack to work around a race in amdgpu.
According to AMD, the hack should not be necessary anymore. In case
there should have been undetected users,

commit 975ca62a014c ("drm/sched: Add warning for removing hack in drm_sched_fini()")

had added a warning one release cycle ago.

Thus, it can be derived that the hack can be savely removed by now.

Remove the hack.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20260108083019.63532-2-phasta@kernel.org
---

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index e6ee35406165a..13fa55aed3daa 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -1418,48 +1418,12 @@ static void drm_sched_cancel_remaining_jobs(struct drm_gpu_scheduler *sched)
  */
 void drm_sched_fini(struct drm_gpu_scheduler *sched)
 {
-	struct drm_sched_entity *s_entity;
 	int i;
 
 	drm_sched_wqueue_stop(sched);
 
-	for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
-		struct drm_sched_rq *rq = sched->sched_rq[i];
-
-		spin_lock(&rq->lock);
-		list_for_each_entry(s_entity, &rq->entities, list) {
-			/*
-			 * Prevents reinsertion and marks job_queue as idle,
-			 * it will be removed from the rq in drm_sched_entity_fini()
-			 * eventually
-			 *
-			 * FIXME:
-			 * This lacks the proper spin_lock(&s_entity->lock) and
-			 * is, therefore, a race condition. Most notably, it
-			 * can race with drm_sched_entity_push_job(). The lock
-			 * cannot be taken here, however, because this would
-			 * lead to lock inversion -> deadlock.
-			 *
-			 * The best solution probably is to enforce the life
-			 * time rule of all entities having to be torn down
-			 * before their scheduler. Then, however, locking could
-			 * be dropped alltogether from this function.
-			 *
-			 * For now, this remains a potential race in all
-			 * drivers that keep entities alive for longer than
-			 * the scheduler.
-			 *
-			 * The READ_ONCE() is there to make the lockless read
-			 * (warning about the lockless write below) slightly
-			 * less broken...
-			 */
-			if (!READ_ONCE(s_entity->stopped))
-				dev_warn(sched->dev, "Tearing down scheduler with active entities!\n");
-			s_entity->stopped = true;
-		}
-		spin_unlock(&rq->lock);
+	for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++)
 		kfree(sched->sched_rq[i]);
-	}
 
 	/* Wakeup everyone stuck in drm_sched_entity_flush for this scheduler */
 	wake_up_all(&sched->job_scheduled);