svn commit: r223061 - head/sys/kern

[Kenneth D. Merry]

On Tue, Jun 14, 2011 at 00:31:50 +0300, Kostik Belousov wrote:
> On Mon, Jun 13, 2011 at 09:21:02PM +0000, Justin T. Gibbs wrote:
> > Author: gibbs
> > Date: Mon Jun 13 21:21:02 2011
> > New Revision: 223061
> > URL: http://svn.freebsd.org/changeset/base/223061
> > 
> > Log:
> >   Fix a couple of race conditions in devstat(9) initialization.
> >   
> >   In devstat_new_entry(), there is no need to initialize the queue
> >   and the mutex in this function.  There are ways to do static
> >   initialization on both, so use STAILQ_HEAD_INITIALIZER and
> >   MTX_SYSINIT to initialize the queue and the mutex.
> >   
> >   In devstat_alloc(), use an atomic test and set routine to guard
> >   making our entry in /dev.  Using just a plain static variable
> >   creates a race condition on multiprocessor machines.  If you
> >   attempt to create a second entry in devfs, the kernel will panic.
> Devfs returns an error if MAKEDEV_CHECKNAME flag is supplied and
> attempt is made to create the existing node. The static guard is
> still useful, since make_dev() call is costly, but you can remove
> the atomic, since the race should be of limited scope.

Done, thanks for the suggestion!

Ken
-- 
Kenneth Merry
ken at FreeBSD.org