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

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Message-ID: <865abcff-9f52-dca4-df38-b11189c739ff@amd.com>
Date:   Thu, 17 Mar 2022 17:04:48 +0100
From:   Christian König <christian.koenig@....com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Andrey Grodzovsky <andrey.grodzovsky@....com>,
        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

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.

Regards,
Christian.

>
> BR,
> -R
>