From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Ostrowski Subject: Re: + ppp_generic-fix-lockdep-warning.patch added to -mm tree Date: Tue, 17 Apr 2007 08:26:32 -0500 Message-ID: <4624CB08.2070005@earthlink.net> References: <20070411000932.1f00f395.akpm@linux-foundation.org> <028701c77c16$bcd68a90$0202fea9@Jura> <20070417073744.GA1976@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: "Yuriy N. Shkandybin" , Andrew Morton , Paul Mackerras , netdev@vger.kernel.org, Michal Ostrowski To: Jarek Poplawski Return-path: Received: from e6.ny.us.ibm.com ([32.97.182.146]:43237 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754327AbXDQN0x (ORCPT ); Tue, 17 Apr 2007 09:26:53 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e6.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id l3HDRjI9018536 for ; Tue, 17 Apr 2007 09:27:45 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v8.3) with ESMTP id l3HDQqeE551376 for ; Tue, 17 Apr 2007 09:26:52 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l3HDQZ0T010553 for ; Tue, 17 Apr 2007 09:26:36 -0400 In-Reply-To: <20070417073744.GA1976@ff.dom.local> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org The "xmit" function of a PPP channel is a synchronous operation. If the transmission fails, we must notify the caller and let them re-submit the skb later. The return status of dev_queue_xmit is needed to determine the return code passed back to the caller and thus the call is made synchronously and not in a tasklet. Looking at the stack traces earlier in this thread, it seems to me that even if the PPPoE call was made in a tasklet, this same warning could be generated. -- Michal Ostrowski mostrows@earthlink.net Jarek Poplawski wrote: > On Wed, Apr 11, 2007 at 12:52:28PM +0400, Yuriy N. Shkandybin wrote: > ... >>> On Wed, 11 Apr 2007 09:57:33 +0400 "Yuriy N. Shkandybin" >>> wrote: >>> >>>> I've tested 2.6.21-rc6-mm1 >>>> Linux vpn1 2.6.21-rc6-mm1 #4 SMP Wed Apr 11 03:34:26 MSD 2007 x86_64 >>>> Intel(R) Pentium(R) D CPU 2.80GHz GenuineIntel GNU/Linux >>>> >>>> warn appeares upon first pppoe connection to rp-pppoe server in kernel >>>> mode >>>> >>> Thanks. So you're saying that >>> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc6/2.6.21-rc6-mm1/broken-out/ppp_generic-fix-lockdep-warning.patch >>> did not fix anything? >> As i understand this patch already in -mm tree, so I've booted into last mm >> kernel and received this locked warning. >> Or i've mistaked and should apply this patch manually? > > Hi! > > Yuriy - thanks for testing my patch ...(pause) Not! > > It seems this patch is not visible in this version - probably > is overpatched by something else. But your new log shows there > is another connection between these locks (ppp_xmit_process > and ppp_push instead of ppp_channel_push in "-> #0"), so the > patch is not sufficient (and could be dumped). > > I don't know your vlans configuration, but it seems the real > lockup isn't very probable here - it's rather lockdep question. > I think vlan's too broad lockdep class is the main "guilty" > here, but probably pppoe also could be enhanced: it's making > the things unnecessarily complicated by calling dev_queue_xmit > under ppp_generic's xmit locks. I wonder if there is any reason > against using a tasklet here. > > I'll try to find more time to untie this yet - or maybe some > maintainer will find this interesting, too... > > Regards, > Jarek P. > > PS: sorry for late responding (vacations). > >