drm/amdgpu: fence wait old rcu slot

since the rcu slot was initialized to be num_hw_submission,
if command submission doesn't use scheduler, this limitation
will be invalid like uvd test.

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 4303b44..d81f1f4 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -121,7 +121,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct fence **f)
 {
        struct amdgpu_device *adev = ring->adev;
        struct amdgpu_fence *fence;
-       struct fence **ptr;
+       struct fence *old, **ptr;
        uint32_t seq;
 
        fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);
@@ -141,7 +141,11 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct fence **f)
        /* This function can't be called concurrently anyway, otherwise
         * emitting the fence would mess up the hardware ring buffer.
         */
-       BUG_ON(rcu_dereference_protected(*ptr, 1));
+       old = rcu_dereference_protected(*ptr, 1);
+       if (old && !fence_is_signaled(old)) {
+               DRM_INFO("rcu slot is busy\n");
+               fence_wait(old, false);
+       }
 
        rcu_assign_pointer(*ptr, fence_get(&fence->base));