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

[zhoucm1]

On 2018年09月11日 11:23, Deng, Emily wrote:
>> -----Original Message-----
>> From: Zhou, David(ChunMing)
>> Sent: Tuesday, September 11, 2018 11:03 AM
>> To: Deng, Emily <Emily.Deng at amd.com>; amd-gfx at lists.freedesktop.org
>> Subject: Re: [PATCH] drm/amdgpu: Fix the dead lock issue.
>>
>>
>>
>> On 2018年09月11日 10:51, 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);
>> local_shadow_list is a local variable, I think it doesn't need lock at all, no one
>> change it. Otherwise looks good to me.
> The bo->shadow_list which now is in local_shadow_list maybe destroy in case that it already in amdgpu_bo_destroy, then it will
> change local_shadow_list, so need lock the shadow_list_lock.
Ah, sorry for noise, I forget you don't reference these BOs.

Thanks,
David Zhou
> Best wishes
> Emily Deng
>> Thanks,
>> David Zhou
>>> -	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);
>>> +
>>> +		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)