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

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Message-ID: <87v8mvmeg6.wl-tiwai@suse.de>
Date:   Thu, 01 Dec 2022 14:38:33 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     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,
        kexec@...ts.infradead.org, alsa-devel@...a-project.org,
        stable@...r.kernel.org, sound-open-firmware@...a-project.org,
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        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 Thu, 01 Dec 2022 14:22:12 +0100,
Oliver Neukum wrote:
> 
> On 01.12.22 14:03, Ricardo Ribalda wrote:
> 
> Hi,
>  
> > 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")
> 
> That patch is problematic. I would go as far as saying that
> it needs to be reverted.

... or fixed.

> > 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.
> 
> Well, I mean if you know what wrong then I'd say at least return to
> a sanely broken state.
> 
> The whole approach is wrong. You need to be able to deal with user
> space talking to removed devices by returning an error and keeping
> the resources association with the open file allocated until
> user space calls close()

As I already mentioned in another thread, if the user-space action has
to be cut off, we just need to call snd_card_disconnect() instead
without sync.  A quick hack would be like below (totally untested and
might be wrong, though).

In anyway, Ricardo, please stop spinning too frequently; v8 in a few 
days is way too much, and now the recipient list became unmanageable.
Let's give people some time to review and consider a better solution
at first.


thanks,

Takashi

-- 8< --
--- a/sound/soc/sof/core.c
+++ b/sound/soc/sof/core.c
@@ -475,7 +475,7 @@ EXPORT_SYMBOL(snd_sof_device_remove);
 int snd_sof_device_shutdown(struct device *dev)
 {
 	struct snd_sof_dev *sdev = dev_get_drvdata(dev);
-	struct snd_sof_pdata *pdata = sdev->pdata;
+	struct snd_soc_component *component;
 
 	if (IS_ENABLED(CONFIG_SND_SOC_SOF_PROBE_WORK_QUEUE))
 		cancel_work_sync(&sdev->probe_work);
@@ -484,9 +484,9 @@ int snd_sof_device_shutdown(struct device *dev)
 	 * make sure clients and machine driver(s) are unregistered to force
 	 * all userspace devices to be closed prior to the DSP shutdown sequence
 	 */
-	sof_unregister_clients(sdev);
-
-	snd_sof_machine_unregister(sdev, pdata);
+	component = snd_soc_lookup_component(sdev->dev, NULL);
+	if (component && component->card && component->card->snd_card)
+		snd_card_disconnect(component->card->snd_card);
 
 	if (sdev->fw_state == SOF_FW_BOOT_COMPLETE)
 		return snd_sof_shutdown(sdev);