Am 17.05.2018 um 05:05 schrieb Emily Deng:
To free the fence from the amdgpu_fence_slab, need twice call_rcu, to avoid
the amdgpu_fence_slab_fini call kmem_cache_destroy(amdgpu_fence_slab) before
kmem_cache_free(amdgpu_fence_slab, fence), add rcu_barrier after 
drm_sched_entity_fini.

The kmem_cache_free(amdgpu_fence_slab, fence)'s call trace as below:
1.drm_sched_entity_fini ->
drm_sched_entity_cleanup ->
dma_fence_put(entity->last_scheduled) ->
drm_sched_fence_release_finished ->
drm_sched_fence_release_scheduled ->
call_rcu(&fence->finished.rcu, drm_sched_fence_free)

2.drm_sched_fence_free ->
dma_fence_put(fence->parent) ->
amdgpu_fence_release ->
call_rcu(&f->rcu, amdgpu_fence_free) ->
kmem_cache_free(amdgpu_fence_slab, fence);

Change-Id: I8dcadd3372f97e72461bf46b41cc26d90f09b8df
Signed-off-by: Emily Deng <emily.d...@amd.com>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index cc3b067..07b2e10 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -134,6 +134,7 @@ static void amdgpu_ttm_global_fini(struct amdgpu_device 
*adev)
        if (adev->mman.mem_global_referenced) {
                drm_sched_entity_fini(adev->mman.entity.sched,
                                      &adev->mman.entity);
+               rcu_barrier();

Good catch, but why don't you put the barrier() before the kmem_cache_destroy()?

That looks like it would make more sense.

Christian.

                mutex_destroy(&adev->mman.gtt_window_lock);
                drm_global_item_unref(&adev->mman.bo_global_ref.ref);
                drm_global_item_unref(&adev->mman.mem_global_ref);

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