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

[Deng, Emily]

>-----Original Message-----
>From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
>zhoucm1
>Sent: Tuesday, September 11, 2018 11:28 AM
>To: Deng, Emily <Emily.Deng at amd.com>; Zhou, David(ChunMing)
><David1.Zhou 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 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.
Yes, I don't reference these Bos, as I found even reference these Bos, it still couldn't avoid the case that another process is already
in amdgpu_bo_destroy.
>
>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)
>
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