Re: [PATCH 2/2] ipc namespaces: implement support for posixmsqueues

[Serge E. Hallyn]

Quoting Dave Hansen (dave@xxxxxxxxxxxxxxxxxx):
> On Wed, 2008-12-17 at 11:55 -0600, Serge E. Hallyn wrote:
> > -void free_ipc_ns(struct kref *kref)
> > +void put_ipc_ns(struct ipc_namespace *ns)
> >  {
> > -       struct ipc_namespace *ns;
> > +       if (ns && atomic_dec_and_lock(&ns->count, &mq_lock)) {
> > +               mq_clear_sbinfo(ns);
> > +               spin_unlock(&mq_lock);
> > +               mq_put_mnt(ns);
> > +               free_ipc_ns(ns);
> > +       }
> > +}
> 
> OK, I see now why you wanted to remove the kref and add an atomic_t.
> That's probably worth a sentence in the patch description.

Good point, will do.

> I know that atomic_dec_and_lock() can be a nice logical thing to do, but
> is it necessary here?  Basically, is there something that happens under
> mq_lock that can re-raise the ns->count?

A racing task from another ipc namespace can open a mq file through
the VFS and thereby bump the ipc's refcount.  Will comment that here and
in the patch description.

thanks,
-serge
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/