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From:   Ricardo Ribalda <ribalda@chromium.org>
Date:   Thu, 1 Dec 2022 14:03:54 +0100
Message-ID: <CANiDSCtwSb50sjn5tM7jJ6W2UpeKzpuzng+RdJuywiC3-j2zdg@mail.gmail.com>
Subject: Re: [PATCH v8 3/3] ASoC: SOF: Fix deadlock when shutdown a frozen userspace
To:     Oliver Neukum <oneukum@suse.com>
Cc:     Juergen Gross <jgross@suse.com>, Mark Brown <broonie@kernel.org>,
        Chromeos Kdump <chromeos-kdump@google.com>,
        Daniel Baluta <daniel.baluta@nxp.com>,
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Hi Oliver

Thanks for your review

On Thu, 1 Dec 2022 at 13:29, Oliver Neukum <oneukum@suse.com> wrote:
>
> On 01.12.22 12:08, Ricardo Ribalda wrote:
> > If we are shutting down due to kexec and the userspace is frozen, the
> > system will stall forever waiting for userspace to complete.
> >
> > Do not wait for the clients to complete in that case.
>
> Hi,
>
> I am afraid I have to state that this approach is bad in every case,
> not just this corner case. It basically means that user space can stall
> the kernel for an arbitrary amount of time. And we cannot have that.
>
>         Regards
>                 Oliver

This patchset does not modify this behaviour. It simply fixes the
stall for kexec().

The  patch that introduced the stall:
83bfc7e793b5 ("ASoC: SOF: core: unregister clients and machine drivers
in .shutdown")

was sent as a generalised version of:
https://github.com/thesofproject/linux/pull/3388

AFAIK, we would need a similar patch for every single board.... which
I am not sure it is doable in a reasonable timeframe.

On the meantime this seems like a decent compromises. Yes, a
miss-behaving userspace can still stall during suspend, but that was
not introduced in this patch.

Regards!
>


-- 
Ricardo Ribalda