Re: [patch 1/2] OSS: soundcard: locking bug in sound_ioctl()

[Johannes Berg <johannes@sipsolutions.net>]

On Mon, 2010-10-11 at 12:50 +0200, Arnd Bergmann wrote:
> On Monday 11 October 2010, Johannes Berg wrote:
> > On Mon, 2010-10-11 at 10:13 +0200, Arnd Bergmann wrote:
> > 
> > > Hmm, actually sparse does not warn about sound_ioctl returning in
> > > different lock contexts. Sparse developers: is there a known limitation
> > > in sparse for this? I expected to see context warnings because
> > > sound_ioctl normally releases soundcard_mutex (previously lock_kernel)
> > > in some cases returns while holding the lock.
> > 
> > Arnd, mutexes aren't annotated in the kernel source to make use of
> > sparse's context checking.
> 
> D'oh. I never realized this was only done for some types of locks.
> Is there a reason why we don't want mutexes to be annotated or do
> we just need someone to do it?

I don't know. Could be related to trylock issues, could be just historic
since semaphores can't really be annotated, or could be something else
entirely... I would expect a huge amount of warnings from sparse though
if you "just" annotate them since there are things like rtnl_lock()
which would have to propagate context.

johannes