Commit b8ae2640 authored by Jesse.Zhang's avatar Jesse.Zhang Committed by Alex Deucher
Browse files

drm/amdgpu: Fix fence signaling race condition in userqueue 



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: default avatarChristian König <christian.koenig@amd.com>
Signed-off-by: default avatarJesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 45da20e0

drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c

+1 −1
Original line number Diff line number Diff line
@@ -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);