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.
Takashi