linux-kernel - Re: [PATCH] ASoC: soc-pcm: fix fe and be race when accessing substream->runtime

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Message-ID: <20220929162529.GA7982@lxhi-065>
Date:   Thu, 29 Sep 2022 18:25:29 +0200
From:   Eugeniu Rosca <erosca@...adit-jv.com>
To:     Cezary Rojewski <cezary.rojewski@...el.com>
CC:     Eugeniu Rosca <erosca@...adit-jv.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>,
        Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
        Eugeniu Rosca <roscaeugeniu@...il.com>,
        Jiada Wang <jiada_wang@...tor.com>,
        Zhang Yanmin <yanmin.zhang@...el.com>,
        Ramesh Babu <ramesh.babu@...el.com>,
        Dean Jenkins <Dean_Jenkins@...tor.com>,
        Ramesh Babu B <ramesh.babu.b@...el.com>,
        xiao jin <jin.xiao@...el.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Amadeusz Sławiński 
        <amadeuszx.slawinski@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>
Subject: Re: [PATCH] ASoC: soc-pcm: fix fe and be race when accessing
 substream->runtime

Hello Czarek,

Thank you for your friendly feedback.

On Mi, Sep 28, 2022 at 04:24:43 +0200, Cezary Rojewski wrote:
> On 2022-09-27 1:00 PM, Eugeniu Rosca wrote:
> >Hello Czarek,
> 
> ...
> 
> >>I'd like to know more about the scenario you guys reproduced the problem in.
> >
> >This patch was originally identified in the Intel Apollo Lake v4.1 KNLs.
> >Given that the change itself is in the core sound subsystem, our internal
> >assessment was that the patch might potentially be relevant/helpful
> >on other HW platforms.
> >
> >Our intention is to confirm or invalidate this assumption with the
> >original developers of the patch, as well as with the audio maintainers
> >and the members of the alsa-devel ML.
> >
> >>Configuration details and kernel base would be good to know too. Since our
> >>CI did not detect problem of such sort, if the problem actually exists, we
> >>would like to append a test or two to cover it later on.
> >
> >If there is no evidence that the patch is fixing a real-life issue
> >occurring in the latest vanilla, I agree to drop the patch.
> >
> >So far, I do not possess this evidence myself.
> 
> 
> I've spent some time to locate the change. Found it and it seems obsolete.
> Some tags are missing in the revision of yours and the original date does
> not match either - it's Apr 2018 for the original. Won't be mentioning the
> tags as some engineers no longer bear @intel.com.
> 
> soc-pcm and skylake-driver valuable bits from those trees are already part
> of the upstream. Most of what is left was later proven obsolete or redundant
> by my or Pierre's engineers. There seems to be no patch missing except for
> few fixes from the recent SKL/KBL up-revs for our clients. Nothing APL
> specific.

Thanks for this thorough check. That also gives us enough confidence
to drop the patch in some of our downstream kernels.

> 
> Following kernels related to APL are maintained by the IPG team from
> software perspective:
> 	4.1.42, 4.1.49, 4.4, 4.9, 4.14, 4.19
> 
> Multiple OSes. And then there are flavors for kernels/OS both. It's quite
> likely kernel base of yours fits into one of these buckets or at least have
> had changes ported from one of them.

Good to know and yes, you are right w.r.t. the origin of the patch.

> 
> TLDR: I agree here with my colleagues - if you believe the change is
> necessary, a proof e.g.: in form of reproduction steps, is needed. Otherwise
> it's no-go. Happy to hop on a call should you need any additional
> information.

That's a very kind attitude and we will definitely share any empirical
evidence if it turns out the patch is really contributing with healing
of any future runtime issues.

> 
> Regards,
> Czarek

Best Regards
Eugeniu