linux-kernel - Re: [PATCH v3 0/2] ALSA: core: Fix deadlock when shutdown a frozen userspace

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Date:   Mon, 28 Nov 2022 10:26:50 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Ricardo Ribalda <ribalda@...omium.org>,
        Takashi Iwai <tiwai@...e.com>, Len Brown <len.brown@...el.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     alsa-devel@...a-project.org,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 0/2] ALSA: core: Fix deadlock when shutdown a frozen
 userspace



On 28.11.22 10:10, Ricardo Ribalda wrote:
> Since 83bfc7e793b5 ("ASoC: SOF: core: unregister clients and machine drivers in .shutdown")
> we wait for userspace to close its fds.
> 
> But that will never occur with a frozen userspace (like during kexec()).


Hi,

that means that user space can delay an unplugging process for an
indefinite time. And that is a problem. I am afraid there is a problem
with the basic approach, even outside of times user space is frozen.

	Regards
		Oliver