[PATCH 6.18 460/752] drm/panthor: fix for dma-fence safe access rules

Sasha Levin
2026-02-28T17:54:35Z

From: Chia-I Wu <olvaffe@gmail.com>

[ Upstream commit efe24898485c5c831e629d9c6fb9350c35cb576f ]

Commit 506aa8b02a8d6 ("dma-fence: Add safe access helpers and document
the rules") details the dma-fence safe access rules. The most common
culprit is that drm_sched_fence_get_timeline_name may race with
group_free_queue.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Cc: stable@vger.kernel.org # v6.17+
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251204174545.399059-1-olvaffe@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/panthor/panthor_sched.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index c7dd98936bd6b..6930053009d5c 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -22,6 +22,7 @@
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
+#include <linux/rcupdate.h>

#include "panthor_devfreq.h"
#include "panthor_device.h"
@@ -926,6 +927,9 @@ static void group_release_work(struct work_struct *work)
release_work);
u32 i;

+ /* dma-fences may still be accessing group->queues under rcu lock. */
+ synchronize_rcu();
+
for (i = 0; i < group->queue_count; i++)
group_free_queue(group, group->queues[i]);

--
2.51.0