At Wed, 14 Jan 2015 09:15:36 +0100, Lars-Peter Clausen wrote: > > On 01/14/2015 08:43 AM, Takashi Iwai wrote: > > At Tue, 13 Jan 2015 21:54:12 +0000, > > Mark Brown wrote: > >> > >> 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. > > > > The module refcount has to be handled while being used for stopping > > module unload. That's irrelevant from the dynamic unbinding support > > itself. Of course, the module refcount doesn't save the world, but > > it's the right fix for this particular scenario. > > Refcounting won't help in this case. The issue is caused by a delayed work > item that gets launched when the PCM stream is stopped. So if you decrease > the refcount when the stream is stopped you still have a window where it is > possible to remove the module while the work is still being scheduled.
OK, so it's not about active stream. From the reporter's description, I supposed that the module gets unloaded while playing a stream, which shouldn't be allowed. > And while we do flush the scheduled work when we remove the ASoC card this > is done before snd_card_free() is called. So when snd_card_free() is called > it gets re-scheduled again. I think the correct fix is to add a > snd_card_disconnect() at the very top of soc_cleanup_card_resources(). Or move the most code of soc_cleanup_card_resources() to card->private_free or such to be called from snd_card_free(), and snd_soc_unregister_card() just needs to call snd_card_free(). This will trigger the disconnection, settle down the device usages then release the soc resources gracefully. Takashi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
