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Subject: Re: [PATCH -v3 5/8] fsnotify: unified filesystem notification
 backend
From: Eric Paris <eparis@redhat.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel@vger.kernel.org, malware-list@lists.printk.net,
       viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
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Date: Fri, 28 Nov 2008 18:22:48 -0500
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On Thu, 2008-11-27 at 17:20 +0100, Peter Zijlstra wrote:
> On Tue, 2008-11-25 at 12:21 -0500, Eric Paris wrote:
> > +int fsnotify_check_notif_queue(struct fsnotify_group *group)
> > +{
> > +       mutex_lock(&group->notification_mutex);
> > +       if (!list_empty(&group->notification_list))
> > +               return 1;
> > +       mutex_unlock(&group->notification_mutex);
> > +       return 0;
> > +}
> 
> > +void fsnotify_clear_notif(struct fsnotify_group *group)
> > +{
> > +       struct fsnotify_event *event;
> > +
> > +       while (fsnotify_check_notif_queue(group)) {
> > +               event = get_event_from_notif(group);
> > +               fsnotify_put_event(event);
> > +               /* fsnotify_check_notif_queue() took this lock */
> > +               mutex_unlock(&group->notification_mutex);
> > +       }
> > +}
> 
> That is quite horrible, please just open code that to keep the locking
> symmetric.

While horrible, I use fsnotify_check_notif_queue in my fsnotify (not in
this series as this only includes dnotify) has

wait_event_interruptible(group->notification_waitq, fanotify_check_notif_queue(group));

So I wouldn't know how to open code that...  I can open code this
instance, but it's going to mean redoing all of that other code to
handle having thing not be present when we return.  Since I didn't
submit that as well I guess I'm not allowed to use it as a reason...