On Sun, Nov 17, 2013 at 08:45:23PM -0800, Greg Kroah-Hartman wrote:
> On Sun, Nov 17, 2013 at 12:29:37PM +0900, Tejun Heo wrote:
> > On Sat, Nov 16, 2013 at 10:21:19PM -0500, Dave Jones wrote:
> > > On Sun, Nov 17, 2013 at 11:17:36AM +0900, Tejun Heo wrote:
> > >
> > >
> > > > + if (has_mmap)
> > > > + mutex_init(&of->mutex);
> > > > + else
> > > > + mutex_init(&of->mutex);
> > >
> > > ummm...
> >
> > Supposed to look that way. It'll give two separate static lock class
> > keys to of->mutex. Yeah, looks weird. Any better ideas?
>
> Doesn't gcc optimize that away to just one lock class anyway?
Well, it basically becomes
if (has_mmap) {
static struct lock_class_key key;
__mutex_init(blah, &key);
} else {
static struct lock_class_key key;
__mutex_init(blah, &key);
}
So, the compiler isn't allowed to merge the two keys and we actually
use constructs like the above from a few places. Yeah, it is weird
but does work.
Thanks.
--
tejun
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