linux-kernel - RE: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

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Date:   Wed, 16 Nov 2022 04:35:48 +0000
From:   "Lin, Wayne" <Wayne.Lin@....com>
To:     Lyude Paul <lyude@...hat.com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>
CC:     "Wentland, Harry" <Harry.Wentland@....com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "Li, Sun peng (Leo)" <Sunpeng.Li@....com>,
        "Siqueira, Rodrigo" <Rodrigo.Siqueira@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        "Kazlauskas, Nicholas" <Nicholas.Kazlauskas@....com>,
        "Pillai, Aurabindo" <Aurabindo.Pillai@....com>,
        "Li, Roman" <Roman.Li@....com>, "Zuo, Jerry" <Jerry.Zuo@....com>,
        "Wu, Hersen" <hersenxs.wu@....com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        "Mahfooz, Hamza" <Hamza.Mahfooz@....com>,
        "Hung, Alex" <Alex.Hung@....com>,
        "Francis, David" <David.Francis@....com>,
        Mikita Lipski <mikita.lipski@....com>,
        "Liu, Wenjing" <Wenjing.Liu@....com>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
 deadlocking

[Public]



> -----Original Message-----
> From: Lyude Paul <lyude@...hat.com>
> Sent: Tuesday, November 15, 2022 5:55 AM
> To: Lin, Wayne <Wayne.Lin@....com>; amd-gfx@...ts.freedesktop.org
> Cc: Wentland, Harry <Harry.Wentland@....com>; stable@...r.kernel.org;
> Li, Sun peng (Leo) <Sunpeng.Li@....com>; Siqueira, Rodrigo
> <Rodrigo.Siqueira@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Koenig, Christian
> <Christian.Koenig@....com>; Pan, Xinhui <Xinhui.Pan@....com>; David
> Airlie <airlied@...il.com>; Daniel Vetter <daniel@...ll.ch>; Kazlauskas,
> Nicholas <Nicholas.Kazlauskas@....com>; Pillai, Aurabindo
> <Aurabindo.Pillai@....com>; Li, Roman <Roman.Li@....com>; Zuo, Jerry
> <Jerry.Zuo@....com>; Wu, Hersen <hersenxs.wu@....com>; Thomas
> Zimmermann <tzimmermann@...e.de>; Mahfooz, Hamza
> <Hamza.Mahfooz@....com>; Hung, Alex <Alex.Hung@....com>; Francis,
> David <David.Francis@....com>; Mikita Lipski <mikita.lipski@....com>; Liu,
> Wenjing <Wenjing.Liu@....com>; open list:DRM DRIVERS <dri-
> devel@...ts.freedesktop.org>; open list <linux-kernel@...r.kernel.org>
> Subject: Re: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
> deadlocking
> 
> On Wed, 2022-11-09 at 09:48 +0000, Lin, Wayne wrote:
> > >   	}
> > > -	if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > > +	ret = drm_dp_mst_atomic_check(state);
> > > +	if (ret == 0 && !debugfs_overwrite) {
> > >   		set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > -		return true;
> > > +		return 0;
> > > +	} else if (ret == -EDEADLK) {
> > > +		return ret;
> >
> > I think we should return here whenever there is an error. Not just for
> > EDEADLK case.
> 
> Are we sure about this one? I think we may actually want to make this so it
> returns on ret != -ENOSPC, since we want the function to continue if there's
> no space in the atomic state available so it can try recomputing things with
> compression enabled. On ret == 0 it should return early without doing
> compression, and on ret == -ENOSPC it should just continue the function
> from there
> 
Oh, right.. Thanks for saving me from causing disaster : )

> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
--
Regards,
Wayne