linux-kernel - [PATCH 2/2] drm/sched: Use proper locks for drm_sched_job

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Message-ID: <20251030104219.181704-4-phasta@kernel.org>
Date: Thu, 30 Oct 2025 11:42:20 +0100
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>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Boris Brezillon <boris.brezillon@...labora.com>,
	Melissa Wen <mwen@...lia.com>,
	Steven Price <steven.price@....com>
Cc: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH 2/2] drm/sched: Use proper locks for drm_sched_job_init()

drm_sched_job_init() is just racing when checking an entity's runqueue, without
taking the proper spinlock.

Add the lock.

Cc: stable@...r.kernel.org # 6.7+
Fixes: 56e449603f0a ("drm/sched: Convert the GPU scheduler to variable number of run-queues")
Signed-off-by: Philipp Stanner <phasta@...nel.org>
---
 drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 7f938f491b6f..30028054385f 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -799,7 +799,12 @@ int drm_sched_job_init(struct drm_sched_job *job,
 		       u32 credits, void *owner,
 		       uint64_t drm_client_id)
 {
-	if (!entity->rq) {
+	struct drm_sched_rq *rq;
+
+	spin_lock(&entity->lock);
+	rq = entity->rq;
+	spin_unlock(&entity->lock);
+	if (!rq) {
 		/* This will most likely be followed by missing frames
 		 * or worse--a blank screen--leave a trail in the
 		 * logs, so this can be debugged easier.
-- 
2.49.0