linux-kernel - Re: [alsa-devel] unload Audio drivers while playback stream is active case kernel crash

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Date:	Tue, 13 Jan 2015 21:54:12 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	"Wang, Jiada (ESD)" <Jiada_Wang@...tor.com>,
	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"perex@...ex.cz" <perex@...ex.cz>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Frkuska, Joshua" <Joshua_Frkuska@...tor.com>
Subject: Re: [alsa-devel] unload Audio drivers while playback stream is
 active case kernel crash

On Tue, Jan 13, 2015 at 06:24:44PM +0100, Takashi Iwai wrote:
> Wang, Jiada (ESD) wrote:

> > I am using i.MX6Q sabreSD board, which have imx_wm892 machine driver, wm8962 codec and SSI CPU DAI,

> > I got Kernel crash when unloading audio drivers (playback stream is active)
> > modprobe -r snd_soc_imx_wm8962
> > modprobe -r snd_soc_fsl_ssi
> > modprobe -r snd_soc_wm8962

> The root problem is that you can unload the module while playing.
> The corresponding module refcounts should have been increased during
> used.

> Do we miss [try_]module_get() somewhere in ASoC?

That doesn't help, users can still forcibly unbind the driver at runtime
without loading the module - and there's always the potential for
actually hotpluggable hardware.  The teardown paths should be able to
cope somewhat gracefully.

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