From b8ae2640f9acd4f411c9227d2493755d03fe440a Mon Sep 17 00:00:00 2001 From: "Jesse.Zhang" Date: Wed, 24 Sep 2025 16:00:06 +0800 Subject: [PATCH 5277/5403] drm/amdgpu: Fix fence signaling race condition in userqueue MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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) Reviewed-by: Christian König Signed-off-by: Jesse Zhang Signed-off-by: Alex Deucher --- 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 95e91d1dc58a..761bad98da3e 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c @@ -284,7 +284,7 @@ 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); -- 2.54.0