Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933095AbZFQLvy (ORCPT ); Wed, 17 Jun 2009 07:51:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759839AbZFQLvq (ORCPT ); Wed, 17 Jun 2009 07:51:46 -0400 Received: from stinky.trash.net ([213.144.137.162]:64930 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756772AbZFQLvp (ORCPT ); Wed, 17 Jun 2009 07:51:45 -0400 Message-ID: <4A38D8D1.6060004@trash.net> Date: Wed, 17 Jun 2009 13:51:45 +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> In-Reply-To: <4A38D5BD.2040502@trash.net> Content-Type: multipart/mixed; boundary="------------050408050902070403010807" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2637 Lines: 68 This is a multi-part message in MIME format. --------------050408050902070403010807 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Patrick McHardy wrote: > Eric Dumazet wrote: >> IPS_CONFIRMED_BIT is set under nf_conntrack_lock (in >> __nf_conntrack_confirm()), >> we probably want to add a synchronisation under ct->lock as well, >> or __nf_ct_refresh_acct() could set ct->timeout.expires to extra_jiffies, >> while a different cpu could confirm the conntrack. > > 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. > A slightly changed version which moves hash insertion to the end and adds a comment about ordering. This make sure the timer is actually running before the conntrack can be found be other CPUs. --------------050408050902070403010807 Content-Type: text/plain; name="x" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="x" diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 5f72b94..e2cc707 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -425,7 +425,6 @@ __nf_conntrack_confirm(struct sk_buff *skb) /* Remove from unconfirmed list */ hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode); - __nf_conntrack_hash_insert(ct, hash, repl_hash); /* Timer relative to confirmation time, not original setting time, otherwise we'd get timer wrap in weird delay cases. */ @@ -433,8 +432,15 @@ __nf_conntrack_confirm(struct sk_buff *skb) add_timer(&ct->timeout); atomic_inc(&ct->ct_general.use); set_bit(IPS_CONFIRMED_BIT, &ct->status); + + /* Since the lookup is lockless, hash insertion must be after starting the + * timer and setting the CONFIRMED bit. The RCU barriers guarantee that no + * other CPU can find the conntrack before the above stores are visible. + */ + __nf_conntrack_hash_insert(ct, hash, repl_hash); NF_CT_STAT_INC(net, insert); spin_unlock_bh(&nf_conntrack_lock); + help = nfct_help(ct); if (help && help->helper) nf_conntrack_event_cache(IPCT_HELPER, ct); --------------050408050902070403010807-- -- 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/