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

[Zhang, Jerry (Junwei)]

On 09/11/2018 10:51 AM, Emily Deng wrote:
> 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 | 21 ++++++++++++++++++++-
>   1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 2a21267..8c81404 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -3105,6 +3105,9 @@ 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);
> @@ -3112,8 +3115,19 @@ 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_splice_init(&adev->shadow_list, &local_shadow_list);
> +	mutex_unlock(&adev->shadow_list_lock);
> +
> +
>   	mutex_lock(&adev->shadow_list_lock);
> -	list_for_each_entry_safe(bo, tmp, &adev->shadow_list, shadow_list) {
> +	list_for_each_entry_safe(bo, tmp, &local_shadow_list, shadow_list) {
> +		mutex_unlock(&adev->shadow_list_lock);

We may not to use shadow_list_lock when traverse the local shadow list.

Regards,
Jerry

> +
> +		if (!bo)
> +			continue;
> +
>   		next = NULL;
>   		amdgpu_device_recover_vram_from_shadow(adev, ring, bo, &next);
>   		if (fence) {
> @@ -3132,9 +3146,14 @@ static int amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
>
>   		dma_fence_put(fence);
>   		fence = next;
> +		mutex_lock(&adev->shadow_list_lock);
>   	}
>   	mutex_unlock(&adev->shadow_list_lock);
>
> +	mutex_lock(&adev->shadow_list_lock);
> +	list_splice_init(&local_shadow_list, &adev->shadow_list);
> +	mutex_unlock(&adev->shadow_list_lock);
> +
>   	if (fence) {
>   		r = dma_fence_wait_timeout(fence, false, tmo);
>   		if (r == 0)
>