[PATCH] drm/amdgpu: Use dma_resv_lock instead in BO release_notify

[Felix Kuehling]

Am 2021-05-21 um 1:26 a.m. schrieb xinhui pan:
> The reservation object might be locked again by evict/swap after
> individualized. The race is like below.
> cpu 0					cpu 1
> BO release				BO evict or swap
> ttm_bo_individualize_resv {resv = &_resv}
> 					ttm_bo_evict_swapout_allowable
> 						dma_resv_trylock(resv)
> ->release_notify() {BUG_ON(!trylock(resv))}
> 					if (!ttm_bo_get_unless_zero))
> 						dma_resv_unlock(resv)
> Actually this is not a bug if trylock fails. So use dma_resv_lock
> instead.

Please test this with LOCKDEP enabled. I believe the trylock here was
needed to avoid potential deadlocks. Maybe Christian can fill in more
details.

Regards,
  Felix


>
> Signed-off-by: xinhui pan <xinhui.pan at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index 928e8d57cd08..beacb46265f8 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -318,7 +318,7 @@ int amdgpu_amdkfd_remove_fence_on_pt_pd_bos(struct amdgpu_bo *bo)
>  	ef = container_of(dma_fence_get(&info->eviction_fence->base),
>  			struct amdgpu_amdkfd_fence, base);
>  
> -	BUG_ON(!dma_resv_trylock(bo->tbo.base.resv));
> +	dma_resv_lock(bo->tbo.base.resv, NULL);
>  	ret = amdgpu_amdkfd_remove_eviction_fence(bo, ef);
>  	dma_resv_unlock(bo->tbo.base.resv);
>