[linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

[Andrew Morton]

Takashi Iwai <tiwai at suse.de> wrote:
>
> > You can do unlock_kernel()/lock_kernel() in soundcore_open().
> 
>  I remember ioctl() is also in lock_kernel()?

yes, you'll need to do unlock_kernel/lock_kernel there too.  If someone
changes the rules, or otherwise calls your ioctl withoht lock_kernel() held
it will reliably go BUG with spinlock debugging enabled, so make sure you
test with CONFIG_DEBUG_SPINLOCK=y.