linux-kernel - Re: [PATCH 4/4] posix-timers: turn it_signal into it

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Message-ID: <1315335878.3400.8.camel@edumazet-laptop>
Date:	Tue, 06 Sep 2011 21:04:38 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Oleg Nesterov <oleg@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/4] posix-timers: turn it_signal into it_valid flag

Le mardi 06 septembre 2011 à 20:47 +0200, Thomas Gleixner a écrit :
> On Tue, 6 Sep 2011, Eric Dumazet wrote:
> 
> > Le mardi 06 septembre 2011 à 16:51 +0200, Oleg Nesterov a écrit :
> > > On 09/05, Andi Kleen wrote:
> > > >
> > > > > I forgot everything I knew about ->it_requeue_pending logic, but it
> > > > > seems to me that do_schedule_next_timer()->lock_timer() can find and
> > > > > lock successfully the wrong timer. Another thread can do timer_delete()
> > > > > and then re-create the timer with the same id.
> > > >
> > > > Do you mean after my patches or even before?
> > > 
> > > Ah, sorry for confusion.
> > > 
> > > Before. And after. IOW, I think this has nothing to do with your patches.
> > > 
> > 
> > Hmm, you mean following patch is needed ?
> > 
> > Before release of timer id to idr pool, we should make sure
> > do_schedule_next_timer() wont be called, or it could find another timer
> > reusing the just released id.
> 
> I don't see how that makes it sure. If the signal is queued, then it
> stays queued and the put_pid() has no effect either.

Indeed, this is a real old bug then...



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