On 24.09.25 11:02, Jesse.Zhang wrote:
> This commit fixes a potential race condition in the userqueue fence
> signaling mechanism by replacing dma_fence_is_signaled_locked() with
> dma_fence_is_signaled().
>
> The issue occurred because:
> 1. dma_fence_is_signaled_locked() should only be used when holding
> the fence's individual lock, not just the fence list lock
> 2. Using the locked variant without the proper fence lock could lead
> to double-signaling scenarios:
> - Hardware completion signals the fence
> - Software path also tries to signal the same fence
>
> By using dma_fence_is_signaled() instead, we properly handle the
> locking hierarchy and avoid the race condition while still maintaining
> the necessary synchronization through the fence_list_lock.
>
> v2: drop the comment (Christian)
>
> Signed-off-by: Jesse Zhang <jesse.zh...@amd.com>
Reviewed-by: Christian König <christian.koe...@amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
> index 59d0abbdfc2f..aab55f38d81f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
> @@ -289,7 +289,7 @@ static int amdgpu_userq_fence_create(struct
> amdgpu_usermode_queue *userq,
>
> /* Check if hardware has already processed the job */
> spin_lock_irqsave(&fence_drv->fence_list_lock, flags);
> - if (!dma_fence_is_signaled_locked(fence))
> + if (!dma_fence_is_signaled(fence))
> list_add_tail(&userq_fence->link, &fence_drv->fences);
> else
> dma_fence_put(fence);
