linux-kernel - [PATCH v3] drm/sched: Add warning for removing hack in drm_sched

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20251023123429.139848-2-phasta@kernel.org>
Date: Thu, 23 Oct 2025 14:34:30 +0200
From: Philipp Stanner <phasta@...nel.org>
To: Matthew Brost <matthew.brost@...el.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Philipp Stanner <phasta@...nel.org>,
	Christian König <ckoenig.leichtzumerken@...il.com>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
Cc: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org
Subject: [PATCH v3] drm/sched: Add warning for removing hack in drm_sched_fini()

The assembled developers agreed at the X.Org Developers Conference 2025
that the hack added for amdgpu in drm_sched_fini() shall be removed. It
shouldn't be needed by amdgpu anymore.

As it's unclear whether all drivers really follow the life time rule of
entities having to be torn down before their scheduler, it is reasonable
to warn for a while before removing the hack.

Add a warning in drm_sched_fini() that fires if an entity is still
active.

Signed-off-by: Philipp Stanner <phasta@...nel.org>
---
Changes in v3:
  - Add a READ_ONCE() + comment to make the warning slightly less
    horrible.

Changes in v2:
  - Fix broken brackets.
---
 drivers/gpu/drm/scheduler/sched_main.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 46119aacb809..31039b08c7b9 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -1419,7 +1419,7 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
 		struct drm_sched_rq *rq = sched->sched_rq[i];
 
 		spin_lock(&rq->lock);
-		list_for_each_entry(s_entity, &rq->entities, list)
+		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()
@@ -1440,8 +1440,15 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
 			 * 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);
 		kfree(sched->sched_rq[i]);
 	}
-- 
2.49.0