Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752762AbYL3RCR (ORCPT ); Tue, 30 Dec 2008 12:02:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751846AbYL3RB6 (ORCPT ); Tue, 30 Dec 2008 12:01:58 -0500 Received: from wine.ocn.ne.jp ([122.1.235.145]:61065 "EHLO smtp.wine.ocn.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751813AbYL3RB5 (ORCPT ); Tue, 30 Dec 2008 12:01:57 -0500 To: frederik.deweerdt@xprog.eu Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, kosaki.motohiro@jp.fujitsu.com, netdev@vger.kernel.org Subject: Re: [2.6.28] NULL pointer dereference at get_stats() From: Tetsuo Handa References: <200812302153.ECH86976.MFLOQFJHtSOOFV@I-love.SAKURA.ne.jp> <20081230155215.GA31531@gambetta> In-Reply-To: <20081230155215.GA31531@gambetta> Message-Id: <200812310201.GJH43235.OFFLHFMStOJVOQ@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.50 PL2] X-Accept-Language: ja,en Date: Wed, 31 Dec 2008 02:01:56 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1521 Lines: 36 Hello. Frederik Deweerdt wrote: > Does adding maxcpus=0 to the boot parameters solve the problem? Stephen > suspected a per-cpu variable related problem. No, but I got interestring results. Result | # of virtual CPUs | Kernel command line -------+-------------------+----------------------------------------- OK | 2 | ro root=LABEL=/ BUG | 2 | ro root=LABEL=/ noapic nolapic BUG | 2 | ro root=LABEL=/ noapic nolapic maxcpus=0 BUG | 2 | ro root=LABEL=/ noapic nolapic nosmp BUG | 2 | ro root=LABEL=/ maxcpus=0 BUG | 2 | ro root=LABEL=/ nosmp OK | 1 | ro root=LABEL=/ OK | 1 | ro root=LABEL=/ nolapic noapic OK | 1 | ro root=LABEL=/ nolapic noapic maxcpus=0 OK | 1 | ro root=LABEL=/ nolapic noapic nosmp "OK" means NULL pointer dereference didn't happen. "BUG" means NULL pointer dereference happened. I was adding "noapic" "nolapic" to command line while assigning 2 vcpus. Thus, I encountered this problem. Workaround is to remove "noapic" "nolapic". Now, it seems to me that this problem is caused by interaction of "noapic" "nolapic" "maxcpus=0" "nosmp" options. Regards. -- 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/