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Subject: Re: [PATCH -v3 5/8] fsnotify: unified filesystem notification
 backend
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Eric Paris <eparis@redhat.com>
Cc: linux-kernel@vger.kernel.org, malware-list@lists.printk.net,
       viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
       alan@lxorguk.ukuu.org.uk, arjan@infradead.org, hch@infradead.org
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	 <20081125172117.17115.4875.stgit@paris.rdu.redhat.com>
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Date: Thu, 27 Nov 2008 17:20:49 +0100
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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.