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From: Thomas Gleixner <tglx@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Alexander Shishkin <virtuoso@slind.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	Feng Tang <feng.tang@intel.com>, Michael Tokarev <mjt@tls.msk.ru>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	John Stultz <johnstul@us.ibm.com>,
	Chris Friesen <chris.friesen@genband.com>,
	Kay Sievers <kay.sievers@vrfy.org>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Artem Bityutskiy <dedekind1@gmail.com>,
	Davide Libenzi <davidel@xmailserver.org>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	linux-api@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.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@redhat.com>

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 16:24 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-03-11 13:50 Oleg Nesterov
2011-03-11 15:08 ` Alexander Shishkin
2011-03-11 16:23 ` Thomas Gleixner [this message]

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