linux-kernel - Re: [PATCH] posix-timer: fix deletion race

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Message-ID: <20070724145142.GA199@tv-sign.ru>
Date:	Tue, 24 Jul 2007 18:51:42 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Jeremy Katz <jeremy.katz@...driver.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	Stable Team <stable@...nel.org>
Subject: Re: [PATCH] posix-timer: fix deletion race

On 07/23, Jeremy Katz wrote:
>
> On Fri, 20 Jul 2007, Oleg Nesterov wrote:
> 
> >I still can't believe we have a double-free problem, this looks imposiible.
> >Do you see the
> >
> >	"idr_remove called for id=%d which is not allocated.\n"
> >
> >in syslog?
> 
> No.  I also added some accounting with atomic counters, and don't see 
> evidence of a second call to release_posix_timer.

Interesting. Could you show the patch? Where does sys_timer_create() set
counter == 1?

> >Could you try the patch below? Perhaps we have some wierd problem with
> >->sigq corruption.
> 
> Tried, with apparent effect.

You mean, "null pointer dereference" in release_posix_timer() ? Or it was
BUG_ON(timr && !timr->sigq) in lock_timer() ?

I assume you didn't apply any other patches except Thomas's, yes?

Oleg.

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