[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20131120063039.GB16081@mtj.dyndns.org>
Date: Wed, 20 Nov 2013 01:30:39 -0500
From: Tejun Heo <tj@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Dave Jones <davej@...hat.com>, Al Viro <viro@...IV.linux.org.uk>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sysfs: use a separate locking class for open files
depending on mmap
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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists