From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: Linux 3.6.x kernel crash in tcp_slow_start / bictcp_cong_avoid with wfica Date: Thu, 24 Jan 2013 14:51:20 +0100 Message-ID: <20130124135120.GD16641@order.stressinduktion.org> References: <20130123161238.GE8912@reaktio.net> <20130123214445.GA16641@order.stressinduktion.org> <20130123215151.GF8912@reaktio.net> <20130123152642.4a8389ba@nehalam.linuxnetplumber.net> <20130123234116.GC16641@order.stressinduktion.org> <1358984831.12374.1227.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Stephen Hemminger , Pasi =?utf-8?B?S8Okcmtrw6RpbmVu?= , netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:48595 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753286Ab3AXNvV (ORCPT ); Thu, 24 Jan 2013 08:51:21 -0500 Content-Disposition: inline In-Reply-To: <1358984831.12374.1227.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Jan 23, 2013 at 03:47:11PM -0800, Eric Dumazet wrote: > On Thu, 2013-01-24 at 00:41 +0100, Hannes Frederic Sowa wrote: > > On Wed, Jan 23, 2013 at 03:26:42PM -0800, Stephen Hemminger wrote: > > > I see no problems when using Citrix. > > > This is a normal strace of the program wifca (in idle loop) > > > > Thanks, could you also have a look at setsockopts while socket creation and > > connection establishment? > > As I said, tp->snd_cwnd is set to 0 by a bug in TCP stack. I saw this, too, but hoped to see a reproduceable pattern of setsockopts (window clamping, switching of congestion control) that could make citrix in some way the special application which causes this. > Probably a combination of changed sysctls, and a genuine bug. > > Please give us /etc/sysctl.conf content. > > Adding some BUG_ON(!tp->snd_cwnd) on every writes to tp->snd_cwnd should > catch the bug. But this is much more convenient, yes. :)