Re: [PATCH 2/3] drm/msm/gpu: Park scheduler threads for system suspend

Andrey Grodzovsky
2022-03-17T17:46:32Z

On 2022-03-17 12:04, Christian König wrote:
> Am 17.03.22 um 16:10 schrieb Rob Clark:
>> [SNIP]
>> userspace frozen != kthread frozen .. that is what this patch is
>> trying to address, so we aren't racing between shutting down the hw
>> and the scheduler shoveling more jobs at us.
>
> Well exactly that's the problem. The scheduler is supposed to
> shoveling more jobs at us until it is empty.
>
> Thinking more about it we will then keep some dma_fence instance
> unsignaled and that is and extremely bad idea since it can lead to
> deadlocks during suspend.
>
> So this patch here is an absolute clear NAK from my side. If amdgpu is
> doing something similar that is a severe bug and needs to be addressed
> somehow.

From looking at latest amd-stagin-drm-next we only use directly
kthread_park during in debugfs IB hooks.
For S3  suspend (amdgpu_pmops_suspend) we will only  flush all the HW
fences (amdgpu_fence_wait_empty) so we don't freeze the scheduler thread
and don't flush scheduler entities.

Andrey

>
> Regards,
> Christian.
>
>>
>> BR,
>> -R
>>
>