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From: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
To: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Alexander Shishkin
	<virtuoso-0lOfPCoBze7YtjvyW6yDsg@public.gmane.org>,
	Alexander Viro
	<viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
	Greg Kroah-Hartman <gregkh-l3A5Bk7waGM@public.gmane.org>,
	Feng Tang <feng.tang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Michael Tokarev <mjt-XAri/EZa3C4vJsYlp49lxw@public.gmane.org>,
	Marcelo Tosatti
	<mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	John Stultz <johnstul-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>,
	Chris Friesen
	<chris.friesen-b7o/lNNmKxtBDgjK7y7TUQ@public.gmane.org>,
	Kay Sievers <kay.sievers-tD+1rO4QERM@public.gmane.org>,
	"Kirill A. Shutemov"
	<kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>,
	Artem Bityutskiy
	<dedekind1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Davide Libenzi <davidel-AhlLAIvw+VEjIGhXcJzhZg@public.gmane.org>,
	Michael Kerrisk
	<mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: timerfd-add-tfd_notify_clock_set-to-watch-for-clock-changes.patch added to -mm tree
Date: Fri, 11 Mar 2011 17:23:36 +0100 (CET)	[thread overview]
Message-ID: <alpine.LFD.2.00.1103111722521.2787@localhost6.localdomain6> (raw)
In-Reply-To: <20110311135023.GA23552-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

On Fri, 11 Mar 2011, Oleg Nesterov wrote:

> > @@ -218,10 +266,12 @@ SYSCALL_DEFINE4(timerfd_settime, int, uf
> >  	 * it to the new values.
> >  	 */
> >  	for (;;) {
> > +		spin_lock(&notifiers_lock);
> >  		spin_lock_irq(&ctx->wqh.lock);
> > -		if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
> > +		if (!list_empty(&notifiers_list) || hrtimer_try_to_cancel(&ctx->tmr) >= 0)
> >  			break;
> 
> Confused. Why do we check the global notifiers_list?
> 
> IOW. Suppose that this list is not empty and timerfd_settime() is called
> without TFD_NOTIFY_CLOCK_SET. Now we are going to reprogramm the timer
> without stopping it?
> 
> And. What if timerfd_settime(TFD_NOTIFY_CLOCK_SET, utmr => NULL) is called
> twice? timerfd_setup() blindly does list_add(), and we corrupt the list, no?

And why is this hack in -mm at all ?

Thanks,

	tglx

      parent reply	other threads:[~2011-03-11 16:23 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-03-11 13:50 timerfd-add-tfd_notify_clock_set-to-watch-for-clock-changes.patch added to -mm tree Oleg Nesterov
     [not found] ` <20110311135023.GA23552-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-03-11 15:08   ` Alexander Shishkin
2011-03-11 16:23   ` Thomas Gleixner [this message]

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