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>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 4303b447efe8..d81f1f4883a6 100644
--- 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));