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Commit d8a36f84 authored by Christian König's avatar Christian König Committed by Greg Kroah-Hartman
Browse files

drm/amdgpu: fix old fence check in amdgpu_fence_emit 



[ Upstream commit 3d2aca8c8620346abdba96c6300d2c0b90a1d0cc ]

We don't hold a reference to the old fence, so it can go away
any time we are waiting for it to signal.

Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
Reviewed-by: default avatarChunming Zhou <david1.zhou@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent e107bc69

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

+17 −7
Original line number Diff line number Diff line
@@ -136,8 +136,9 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f, 
{

	struct amdgpu_device *adev = ring->adev;

	struct amdgpu_fence *fence;

	struct dma_fence *old, **ptr;

	struct dma_fence __rcu **ptr;

	uint32_t seq;

	int r;



	fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);

	if (fence == NULL)
@@ -153,15 +154,24 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f, 
			       seq, flags | AMDGPU_FENCE_FLAG_INT);



	ptr = &ring->fence_drv.fences[seq & ring->fence_drv.num_fences_mask];

	if (unlikely(rcu_dereference_protected(*ptr, 1))) {

		struct dma_fence *old;



		rcu_read_lock();

		old = dma_fence_get_rcu_safe(ptr);

		rcu_read_unlock();



		if (old) {

			r = dma_fence_wait(old, false);

			dma_fence_put(old);

			if (r)

				return r;

		}

	}



	/* This function can't be called concurrently anyway, otherwise

	 * emitting the fence would mess up the hardware ring buffer.

	 */

	old = rcu_dereference_protected(*ptr, 1);

	if (old && !dma_fence_is_signaled(old)) {

		DRM_INFO("rcu slot is busy\n");

		dma_fence_wait(old, false);

	}



	rcu_assign_pointer(*ptr, dma_fence_get(&fence->base));



	*f = &fence->base;