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

[Pan, Xinhui]

[AMD Official Use Only]

Oh, sorry for that. I notice the lockdep warning too.
I just think we use trylock elsewhere because we hold the lru_lock mostly.
So I think we can do something like below. Let me verify it later.

@@ -318,7 +318,9 @@ 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);

+       spin_lock(&bo->tbo.bdev->lru_lock);
        BUG_ON(!dma_resv_trylock(bo->tbo.base.resv));
+       spin_unlock(&bo->tbo.bdev->lru_lock);
        ret = amdgpu_amdkfd_remove_eviction_fence(bo, ef);
        dma_resv_unlock(bo->tbo.base.resv);


________________________________________
发件人: Kuehling, Felix <Felix.Kuehling at amd.com>
发送时间: 2021年5月22日 2:24
收件人: Pan, Xinhui; amd-gfx at lists.freedesktop.org
抄送: Deucher, Alexander; Koenig, Christian
主题: Re: [PATCH] drm/amdgpu: Use dma_resv_lock instead in BO release_notify


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);
>