Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030413AbWBPKVJ (ORCPT ); Thu, 16 Feb 2006 05:21:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030454AbWBPKVI (ORCPT ); Thu, 16 Feb 2006 05:21:08 -0500 Received: from caramon.arm.linux.org.uk ([212.18.232.186]:59913 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S1030413AbWBPKVH (ORCPT ); Thu, 16 Feb 2006 05:21:07 -0500 Date: Thu, 16 Feb 2006 10:20:56 +0000 From: Russell King To: Linus Torvalds Cc: Hubertus Franke , Linux Kernel Mailing List , Andrew Morton Subject: Re: SMP BUG Message-ID: <20060216102056.GA24741@flint.arm.linux.org.uk> Mail-Followup-To: Linus Torvalds , Hubertus Franke , Linux Kernel Mailing List , Andrew Morton References: <43F12207.9010507@watson.ibm.com> <20060215230701.GD1508@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1243 Lines: 31 On Wed, Feb 15, 2006 at 03:23:02PM -0800, Linus Torvalds wrote: > Does this fix the ARM oops? It fixes that exact oops but only by preventing us getting that far due to another oops. We call cpu_up, which sends a CPU_UP_PREPARE event. This causes the migration thread to be spawned, and rq->migration_thread to be set. Eventually, we call the architecture __cpu_up(), which ends up calling init_idle(). Due to this patch, init_idle() then NULLs out rq->migration_thread. Later, we send a CPU_ONLINE event, which then tries to do wake_up_process(rq->migration_thread) - resulting in a NULL pointer deref in try_to_wake_up(). Hence, with this patch, it looks like rq will be used prior to initialisation. I could try commenting out the migration_thread initialisation to NULL, but I suspect that there may be other problems associated with this patch (eg, rq->migration_queue). -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - 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/