Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933190Ab0GOMza (ORCPT ); Thu, 15 Jul 2010 08:55:30 -0400 Received: from mail-i4.nets.RWTH-Aachen.DE ([137.226.12.21]:44298 "EHLO MAIL-i4.nets.rwth-aachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933120Ab0GOMz3 (ORCPT ); Thu, 15 Jul 2010 08:55:29 -0400 Message-ID: <4C3F053F.7090704@nets.rwth-aachen.de> Date: Thu, 15 Jul 2010 14:55:27 +0200 From: Lennart Schulte User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.10) Gecko/20100527 Thunderbird/3.0.5 MIME-Version: 1.0 To: Eric Dumazet CC: =?UTF-8?B?SWxwbyBKw6RydmluZW4=?= , Tejun Heo , "David S. Miller" , lkml , "netdev@vger.kernel.org" , "Fehrmann, Henning" , Carsten Aulbert Subject: Re: oops in tcp_xmit_retransmit_queue() w/ v2.6.32.15 References: <4C358AAA.9080400@kernel.org> <4C3EF7EA.2040900@nets.rwth-aachen.de> <1279195528.2496.2.camel@edumazet-laptop> In-Reply-To: <1279195528.2496.2.camel@edumazet-laptop> Content-Type: text/plain; charset="UTF-8"; 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: 1814 Lines: 55 Since tcp_xmit_retransmit_queue also gets skb == NULL I'm pretty sure it is the same bug. Up to now I only experienced the problem with ACK loss (without ACK loss the test ran about 30min without problems, with ACK loss it had paniced within 10min). The data sender only has a HTB queue for traffic shaping (set to 20 Mbit/s). The ACK loss is done by another router. The setup looks like this. This way it seems to be the most realistic. o sender with HTB | | o netem queue for forward path delay | o netem queue for a queue limit | o netem queue for backward path delay | o netem queue for ACK loss | | o receiver with HTB Perhaps now it is a little big clearer. On 15.07.2010 14:05, Eric Dumazet wrote: > Le jeudi 15 juillet 2010 à 13:58 +0200, Lennart Schulte a écrit : > >> I'm testing new reordering algorithms in a virtual testbed, that is the >> nodes are emulated with xen and all the network parameters can be tuned >> with queues. >> With one of the algorithms I also got tracebacks which include >> tcp_xmit_retransmit_queue. It only happens with ACK loss. The kernel >> version however is 2.6.31. >> When I read this thread I tried the debug patch and got the following: >> >> [ 2754.413150] NULL head, pkts 0 >> [ 2754.413156] Errors caught so far 1 >> >> Hope that is of any help. >> > Not sure I understand. > > Are you saying you reproduce same tcp_xmit_retransmit_queue() bug, with > a special tc qdisc/class droppping some ACK frames ? > > Could it be some sched problem and incorrect return codes in case of > congestion ? > -- 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/