Re: [PATCH] drm/amdgpu: fix fence slab teardown

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Interesting catch, patch is Reviewed-by: Christian König <christian.koenig@xxxxxxx>.

Am 24.10.2016 um 04:34 schrieb zhoucm1:
Acked-by: Chunming Zhou <david1.zhou@xxxxxxx>

On 2016年10月24日 02:31, Grazvydas Ignotas wrote:
To free fences, call_rcu() is used, which calls amdgpu_fence_free()
after a grace period. During teardown, there is no guarantee all
callbacks have finished, so amdgpu_fence_slab may be destroyed before
all fences have been freed. If we are lucky, this results in some slab
warnings, if not, we get a crash in one of rcu threads because callback
is called after amdgpu has already been unloaded.

Fix it with a rcu_barrier().

Fixes: b44135351a3a ("drm/amdgpu: RCU protected amdgpu_fence_release")
Signed-off-by: Grazvydas Ignotas <notasas@xxxxxxxxx>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 3a2e42f..77b34ec 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -68,6 +68,7 @@ int amdgpu_fence_slab_init(void)
    void amdgpu_fence_slab_fini(void)
  {
+    rcu_barrier();
      kmem_cache_destroy(amdgpu_fence_slab);
  }
  /*

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