From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Mackall Subject: Re: 2.6.23 WARNING: at kernel/softirq.c:139 local_bh_enable() Date: Fri, 23 Nov 2007 11:07:56 -0600 Message-ID: <20071123170756.GV19691@waste.org> References: <4745DCD7.8070805@simon.arlott.org.uk> <20071123002157.cb27f4a1.akpm@linux-foundation.org> <20071123105518.GA22062@2ka.mipt.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrew Morton , Simon Arlott , Linux Kernel Mailing List , netdev@vger.kernel.org, Ingo Molnar To: Evgeniy Polyakov Return-path: Received: from waste.org ([66.93.16.53]:39581 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752597AbXKWRJI (ORCPT ); Fri, 23 Nov 2007 12:09:08 -0500 Content-Disposition: inline In-Reply-To: <20071123105518.GA22062@2ka.mipt.ru> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Nov 23, 2007 at 01:55:19PM +0300, Evgeniy Polyakov wrote: > On Fri, Nov 23, 2007 at 12:21:57AM -0800, Andrew Morton (akpm@linux-foundation.org) wrote: > > > [2059664.615816] __iptables__: init4 IN=ppp0 OUT=ppp0 WARNING: at kernel/softirq.c:139 local_bh_enable() > > > [2059664.620535] [<80120364>] local_bh_enable+0x3c/0x97 > > > > [2059664.620657] [<8011c205>] __call_console_drivers+0x61/0x6d > > > [2059664.620669] [<8011c3fc>] release_console_sem+0x164/0x1bf > > > [2059664.620679] [<8011c81f>] vprintk+0x27a/0x2ff > > > If that trace is to be beieved we're doing nefilter stuff on packets which > > were sent across netconsole. > > > > This probably isn't anything the netfilter guys have thought about. And > > probably we don't want them to. Is there some simple way in which we can > > exempt netconsole from netfilter processing? > > This is not about netfilter, but about freeing skb in interrupt context, > which is not allowed, and in interrupt skbs are queued to be freed in softirq, > but netcnsole wants to flush softirq freeing queue. That is a question: why? My memory here is hazy, but I think this exists to rescue netconsole in low-memory situations. This bit originated with Ingo, so maybe he can recall. Netpoll can process an arbitrary number of skbs inside a single interrupt. Think sysrq-t at one packet per line or kgdboe where the entire trace session can happen inside one very long interrupt. Perhaps we can refine this to mark netpoll's skbs (perhaps with ->destructor?) and delete only skbs we own. As these are never passed through any of the other route/xfrm/filter code, they should be safe to delete even in irq context, yes? > Removing zap_completion_queue() from find_skb() will fix the warning, > but I'm not sure this is a correct fix. I've added Matt to the Cc list. Care to try the sysrq-t or OOM message tests? -- Mathematics is the supreme nostalgia of our time.