From d8a36f8418034bacef0b5b73c0822f41646d77ba Mon Sep 17 00:00:00 2001 From: =?utf8?q?Christian=20K=C3=B6nig?= Date: Fri, 29 Mar 2019 19:30:23 +0100 Subject: [PATCH] drm/amdgpu: fix old fence check in amdgpu_fence_emit MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit [ 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: Christian König Reviewed-by: Chunming Zhou Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c index 7056925..869ff62 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c @@ -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; -- 2.7.4