From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756419Ab0JKVCU (ORCPT ); Mon, 11 Oct 2010 17:02:20 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:35789 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756293Ab0JKVCT (ORCPT ); Mon, 11 Oct 2010 17:02:19 -0400 Date: Mon, 11 Oct 2010 14:00:39 -0700 From: Andrew Morton To: Mel Gorman Cc: pacman@kosh.dhis.org, linux-mm@kvack.org, Christoph Lameter , KOSAKI Motohiro , Yinghai Lu , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: PROBLEM: memory corrupting bug, bisected to 6dda9d55 Message-Id: <20101011140039.15a2c78d.akpm@linux-foundation.org> In-Reply-To: <20101011143022.GD30667@csn.ul.ie> References: <20101009095718.1775.qmail@kosh.dhis.org> <20101011143022.GD30667@csn.ul.ie> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.9; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (cc linuxppc-dev@lists.ozlabs.org) On Mon, 11 Oct 2010 15:30:22 +0100 Mel Gorman wrote: > On Sat, Oct 09, 2010 at 04:57:18AM -0500, pacman@kosh.dhis.org wrote: > > (What a big Cc: list... scripts/get_maintainer.pl made me do it.) > > > > This will be a long story with a weak conclusion, sorry about that, but it's > > been a long bug-hunt. > > > > With recent kernels I've seen a bug that appears to corrupt random 4-byte > > chunks of memory. It's not easy to reproduce. It seems to happen only once > > per boot, pretty quickly after userspace has gotten started, and sometimes it > > doesn't happen at all. > > > > A corruption of 4 bytes could be consistent with a pointer value being > written to an incorrect location. It's corruption of user memory, which is unusual. I'd be wondering if there was a pre-existing bug which 6dda9d55bf545013597 has exposed - previously the corruption was hitting something harmless. Something like a missed CPU cache writeback or invalidate operation. How sensitive/vulnerable is PPC32 to such things?