On Wed, 3 Dec 2025 17:50:34 -0800
Chia-I Wu <[email protected]> wrote:
> 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.
>
> Fixes: d2624d90a0b77 ("drm/panthor: assign unique names to queues")
> Signed-off-by: Chia-I Wu <[email protected]>
Reviewed-by: Boris Brezillon <[email protected]>
> ---
> 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 33b9ef537e359..a8b1347e4da71 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -23,6 +23,7 @@
> #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"
> @@ -923,6 +924,9 @@ 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]);
>
