[PATCH] drm/amdgpu: amdgpu_device_recover_vram always failed if only one node in shadow_list

[Koenig, Christian]

Yeah, exactly that's what should happen here.

The value of tmo SHOULD be changed, otherwise we wait tmo jiffies on 
each loop.

Christian.

Am 02.04.19 um 09:29 schrieb Lou, Wentao:
> Hi Christian,
>
> If " tmo = dma_fence_wait_timeout(fence, false, tmo); " was executed inside list_for_each_entry, the value of tmo might be changed.
> But " tmo = dma_fence_wait_timeout(fence, false, tmo); " might be called after exiting the loop of list_for_each_entry.
> It might pass a different value of tmo into dma_fence_wait_timeout.
>
> BR,
> Wentao
>
>
> -----Original Message-----
> From: Christian König <ckoenig.leichtzumerken at gmail.com>
> Sent: Tuesday, April 2, 2019 3:01 PM
> To: Deng, Emily <Emily.Deng at amd.com>; Lou, Wentao <Wentao.Lou at amd.com>; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH] drm/amdgpu: amdgpu_device_recover_vram always failed if only one node in shadow_list
>
> Yeah, agree that is much closer to a correct solution.
>
> But even better would be to correctly update the timeout as well, e.g:
>
> tmo = dma_fence_wait_timeout(fence, false, tmo); dma_fence_put(fence); fence = next; if (tmo == 0)
>       r = -ETIMEDOUT;
>       break
> } else if (tmo < 0) {
>       r = tmo;
>       break;
> }
>
> That we restart the timeout for each wait looks like a rather problematic bug to me as well.
>
> Christian.
>
> Am 02.04.19 um 06:03 schrieb Deng, Emily:
>> Maybe it will be better to add follow check, and change “if (r <= 0 || tmo <= 0) " to "if (r <0 || tmo <= 0)".
>> 	r = dma_fence_wait_timeout(f, false, timeout);
>> 	if (r == 0) {
>> 		r = -ETIMEDOUT;
>> 		break;
>> 	} else if (r < 0) {
>> 		break;
>> 	}
>>
>> Best wishes
>> Emily Deng
>>
>>
>>> -----Original Message-----
>>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
>>> wentalou
>>> Sent: Monday, April 1, 2019 4:59 PM
>>> To: amd-gfx at lists.freedesktop.org
>>> Cc: Lou, Wentao <Wentao.Lou at amd.com>
>>> Subject: [PATCH] drm/amdgpu: amdgpu_device_recover_vram always failed
>>> if only one node in shadow_list
>>>
>>> amdgpu_bo_restore_shadow would assign zero to r if succeeded.
>>> r would remain zero if there is only one node in shadow_list.
>>> current code would always return failure when r <= 0.
>>>
>>> Change-Id: Iae6880e7c78b71fde6a6754c69665c2e312a80a5
>>> Signed-off-by: Wentao Lou <Wentao.Lou at amd.com>
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 6 +++++-
>>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> index c4c61e9..5cf21a4 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> @@ -3171,6 +3171,7 @@ static int amdgpu_device_recover_vram(struct
>>> amdgpu_device *adev)
>>> 	struct dma_fence *fence = NULL, *next = NULL;
>>> 	struct amdgpu_bo *shadow;
>>> 	long r = 1, tmo;
>>> +	bool single_shadow = false;
>>>
>>> 	if (amdgpu_sriov_runtime(adev))
>>> 		tmo = msecs_to_jiffies(8000);
>>> @@ -3194,10 +3195,12 @@ static int amdgpu_device_recover_vram(struct
>>> amdgpu_device *adev)
>>> 			r = dma_fence_wait_timeout(fence, false, tmo);
>>> 			dma_fence_put(fence);
>>> 			fence = next;
>>> +			single_shadow = false;
>>> 			if (r <= 0)
>>> 				break;
>>> 		} else {
>>> 			fence = next;
>>> +			single_shadow = true;
>>> 		}
>>> 	}
>>> 	mutex_unlock(&adev->shadow_list_lock);
>>> @@ -3206,7 +3209,8 @@ static int amdgpu_device_recover_vram(struct
>>> amdgpu_device *adev)
>>> 		tmo = dma_fence_wait_timeout(fence, false, tmo);
>>> 	dma_fence_put(fence);
>>>
>>> -	if (r <= 0 || tmo <= 0) {
>>> +	/* r would be zero even if amdgpu_bo_restore_shadow succeeded when
>>> single shadow in list */
>>> +	if (r < 0 || (r == 0 && !single_shadow) || tmo <= 0) {
>>> 		DRM_ERROR("recover vram bo from shadow failed\n");
>>> 		return -EIO;
>>> 	}
>>> --
>>> 2.7.4
>>>
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>>> amd-gfx at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
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