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

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Message-ID: <db194b66-67fb-5ef3-4b3c-9bd140ca1c5b@amd.com>
Date:   Thu, 17 Mar 2022 13:46:22 -0400
From:   Andrey Grodzovsky <andrey.grodzovsky@....com>
To:     Christian König <christian.koenig@....com>,
        Rob Clark <robdclark@...il.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        David Airlie <airlied@...ux.ie>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>,
        Jonathan Marek <jonathan@...ek.ca>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] drm/msm/gpu: Park scheduler threads for system
 suspend


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
>>
>