linux-kernel - Re: [PATCH v6 2/2] ASoC: SOF: Fix deadlock when shutdown a frozen userspace

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Date:   Wed, 30 Nov 2022 09:54:11 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Ricardo Ribalda <ribalda@...omium.org>,
        Chromeos Kdump <chromeos-kdump@...gle.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Daniel Baluta <daniel.baluta@....com>,
        Mark Brown <broonie@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Takashi Iwai <tiwai@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, kexec@...ts.infradead.org,
        sound-open-firmware@...a-project.org
Subject: Re: [PATCH v6 2/2] ASoC: SOF: Fix deadlock when shutdown a frozen
 userspace



On 11/30/22 09:47, Ricardo Ribalda wrote:
> During kexec(), the userspace is frozen. Therefore we cannot wait for it
> to complete.
> 
> Avoid running snd_sof_machine_unregister during shutdown.

That's not what you are doing below - you only unregister clients
conditionally.

I don't know if that's a stale commit message and can't reconcile it
either with the initial discussions in this thread where we were
referring to snd_card_disconnect(), etc?

Confused.

> @@ -484,7 +485,8 @@ 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);
> +	if (!kexec_with_frozen_processes())
> +		sof_unregister_clients(sdev);
>  
>  	snd_sof_machine_unregister(sdev, pdata);
>  
>