[PATCH v2] drm/amdgpu: Fix the dead lock issue.

[Christian König]

Am 10.09.2018 um 11:34 schrieb Emily Deng:
> It will ramdomly have the dead lock issue when test TDR:
> 1. amdgpu_device_handle_vram_lost gets the lock shadow_list_lock
> 2. amdgpu_bo_create locked the bo's resv lock
> 3. amdgpu_bo_create_shadow is waiting for the shadow_list_lock
> 4. amdgpu_device_recover_vram_from_shadow is waiting for the bo's resv
> lock.
>
> v2:
>     Make a local copy of the list
>
> Signed-off-by: Emily Deng <Emily.Deng at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 12 +++++++++++-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_object.h |  1 +
>   2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index acfc63e..2b9f597 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -3006,6 +3006,9 @@ static int amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
>   	long r = 1;
>   	int i = 0;
>   	long tmo;
> +	struct list_head local_shadow_list;
> +
> +	INIT_LIST_HEAD(&local_shadow_list);
>   
>   	if (amdgpu_sriov_runtime(adev))
>   		tmo = msecs_to_jiffies(8000);
> @@ -3013,8 +3016,15 @@ static int amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
>   		tmo = msecs_to_jiffies(100);
>   
>   	DRM_INFO("recover vram bo from shadow start\n");
> +
>   	mutex_lock(&adev->shadow_list_lock);
>   	list_for_each_entry_safe(bo, tmp, &adev->shadow_list, shadow_list) {
> +		amdgpu_bo_ref(bo);
> +		list_add_tail(&bo->copy_shadow_list, &local_shadow_list);
> +	}

Please don't add an extra copy_shadow_list field to amdgpu_bo.

Instead just use bo->shadow list for this. When you hold a reference to 
the BO it should not be removed from the shadow list.

Additional to that you can just use list_splice_init() to move the whole 
shadow list to your local list.

Christian.

> +	mutex_unlock(&adev->shadow_list_lock);
> +
> +	list_for_each_entry_safe(bo, tmp, &local_shadow_list, copy_shadow_list) {
>   		next = NULL;
>   		amdgpu_device_recover_vram_from_shadow(adev, ring, bo, &next);
>   		if (fence) {
> @@ -3033,8 +3043,8 @@ static int amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
>   
>   		dma_fence_put(fence);
>   		fence = next;
> +		amdgpu_bo_unref(&bo);
>   	}
> -	mutex_unlock(&adev->shadow_list_lock);
>   
>   	if (fence) {
>   		r = dma_fence_wait_timeout(fence, false, tmo);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
> index 907fdf4..cfee16c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
> @@ -103,6 +103,7 @@ struct amdgpu_bo {
>   		struct list_head	mn_list;
>   		struct list_head	shadow_list;
>   	};
> +        struct list_head                copy_shadow_list;
>   
>   	struct kgd_mem                  *kfd_bo;
>   };