linux-kernel - Re: [PATCH v8 3/3] ASoC: SOF: Fix deadlock when shutdown a frozen userspace

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Message-ID: <716e5175-7a44-7ae8-b6bb-10d9807552e6@suse.com>
Date:   Thu, 1 Dec 2022 13:28:50 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Ricardo Ribalda <ribalda@...omium.org>,
        Juergen Gross <jgross@...e.com>,
        Mark Brown <broonie@...nel.org>,
        Chromeos Kdump <chromeos-kdump@...gle.com>,
        Daniel Baluta <daniel.baluta@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Len Brown <len.brown@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Eric Biederman <ebiederm@...ssion.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Joel Fernandes <joel@...lfernandes.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Pavel Machek <pavel@....cz>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Ingo Molnar <mingo@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Takashi Iwai <tiwai@...e.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org
Cc:     kexec@...ts.infradead.org, alsa-devel@...a-project.org,
        stable@...r.kernel.org, sound-open-firmware@...a-project.org,
        linuxppc-dev@...ts.ozlabs.org, linux-hyperv@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v8 3/3] ASoC: SOF: Fix deadlock when shutdown a frozen
 userspace

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