[PATCH] drm/amdgpu: add rcu_barrier after entity fini

[Michel Dänzer]

On 2018-05-17 05:05 AM, Emily Deng wrote:
> 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.Deng at 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();
>  		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);
> 

Hmm, this makes me wonder if
https://bugs.freedesktop.org/show_bug.cgi?id=106225 could be related to
something like this as well.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer