From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932847AbZHUSEy (ORCPT ); Fri, 21 Aug 2009 14:04:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932730AbZHUSEx (ORCPT ); Fri, 21 Aug 2009 14:04:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20496 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932691AbZHUSEx (ORCPT ); Fri, 21 Aug 2009 14:04:53 -0400 Subject: Re: kmemcheck in linux-next causes NULL pointer dereference at task_rq_lock From: Eric Paris To: Vegard Nossum Cc: linux-kernel@vger.kernel.org, penberg@cs.helsinki.fi, mingo@elte.hu In-Reply-To: <19f34abd0908211020l6888d68w5c14cbadbca5c6c4@mail.gmail.com> References: <1249925740.2501.9.camel@dhcp231-106.rdu.redhat.com> <19f34abd0908101156x2bc92b22ud1748abb153800fb@mail.gmail.com> <1249933887.2501.62.camel@dhcp231-106.rdu.redhat.com> <19f34abd0908211020l6888d68w5c14cbadbca5c6c4@mail.gmail.com> Content-Type: text/plain Date: Fri, 21 Aug 2009 14:04:35 -0400 Message-Id: <1250877875.2168.56.camel@dhcp231-106.rdu.redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2009-08-21 at 19:20 +0200, Vegard Nossum wrote: > 2009/8/10 Eric Paris : > > On Mon, 2009-08-10 at 20:56 +0200, Vegard Nossum wrote: > >> 2009/8/10 Eric Paris : > >> > I'm using 2.6.31-rc5-next-20090810 on a vmware server. Originally I saw > >> > messages about setting to one cpu, so I booted with maxcpu=1. I get > >> > this same panic with and without maxpu. Booting with kmemcheck=0 boots > >> > just fine. > >> > > >> > I have not tested kmemcheck in linus' tree but will start looking for a > >> > working version now. Any suggestions or things I should try? > >> > >> Hi, thanks for the report, and for trying it out. > >> > >> Does it crash with "kmemcheck=0 maxcpus=1" (it should be maxcpus, not > >> maxcpu). This should be a simple way of determining whether it was > >> kmemcheck or the existing maxcpus code, which we use, that broke. > > > > I boots fine with kmemcheck=0 > > > > I did get the command line right. maxcpus=1 kmemcheck=1 was the panic I > > showed in the last message. > > > >> If you can send config (off-list, probably), I will try to reproduce > >> and investigate more tomorrow. > > > > Will send it now. > > Thanks. I've tried your config with next-20090810, next-20090820, and > current mainline, and wasn't able to reproduce it anywhere :-/ > > Does it still occur for you with the most recent linux-next or current mainline? > > In any case, I think the kmemcheck SMP-handling code has to be fixed. > It seems that we currently allow CPU hotplug while kmemcheck is > enabled, which could lead to, erm, interesting crashes. Maybe we could > do something like what mmiotrace does. I just tried it again with 0821. The machine doesn't boot with kmemcheck=1 but it doesn't look like it's directly kmemcheck's fault. I poked others about their problems. I'm going to be giving it a shot on a different box. -Eric