Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933381AbZFQN3w (ORCPT ); Wed, 17 Jun 2009 09:29:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765857AbZFQN3m (ORCPT ); Wed, 17 Jun 2009 09:29:42 -0400 Received: from stinky.trash.net ([213.144.137.162]:34236 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753231AbZFQN3l (ORCPT ); Wed, 17 Jun 2009 09:29:41 -0400 Message-ID: <4A38EFC4.8000907@trash.net> Date: Wed, 17 Jun 2009 15:29:40 +0200 From: Patrick McHardy User-Agent: Mozilla-Thunderbird 2.0.0.19 (X11/20090103) MIME-Version: 1.0 To: Eric Dumazet CC: Ingo Molnar , David Miller , Thomas Gleixner , torvalds@linux-foundation.org, akpm@linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [bug] __nf_ct_refresh_acct(): WARNING: at lib/list_debug.c:30 __list_add+0x7d/0xad() References: <20090615.050449.144947903.davem@davemloft.net> <20090616091538.GA4184@elte.hu> <20090616.034752.226811527.davem@davemloft.net> <20090616105304.GA3579@elte.hu> <20090616122415.GA16630@elte.hu> <20090617092152.GA17449@elte.hu> <4A38C2F3.3000009@gmail.com> <4A38D5BD.2040502@trash.net> <4A38D9BE.3020403@gmail.com> <4A38DAC4.2050902@trash.net> <4A38E2AE.3030106@gmail.com> <4A38E33E.1050006@trash.net> <4A38EF40.7040106@gmail.com> In-Reply-To: <4A38EF40.7040106@gmail.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1615 Lines: 37 Eric Dumazet wrote: > Patrick McHardy a ?crit : >> Eric Dumazet wrote: >>> Patrick McHardy a ?crit : >>>> Eric Dumazet wrote: >>>>> Patrick McHardy a ?crit : >>>>>> Before the conntrack is confirmed, it is exclusively handled by a >>>>>> single CPU. I agree that we need to make sure the IPS_CONFIRMED_BIT >>>>>> is visible before we add the conntrack to the hash table since the >>>>>> lookup is lockless, but simply moving the set_bit before the hash >>>>>> insertion should be fine I think. >>>>>> >>>>> Problem is timeout.expires is either a relative or absolute timeout, >>>>> and changes happen >>>>> in __nf_conntrack_confirm() or __nf_ct_refresh_acct(). >>>>> >>>>> We must have a synchronization (an barriers), a single bit wont be >>>>> enough. >>>> Please have a look at the second patch I just sent. It relies >>>> on the RCU barriers to make sure all stores are visible before >>>> other CPUs can find the conntrack. >>>> >>> Sorry, I dont understand how your second patch corrects the problem. >>> >>> This (unconfirmed) conntrack is visible by another cpu. >> No, before it is confirmed, its only visible to the CPU handling >> the initial packet of a connection. Confirmation is the step that >> makes it visible to other CPUs. > > Thanks Patrick, I missed this, and your patch seems fine now :) Thanks for your help, I'll send it to Dave later today. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/