From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933134Ab0JRTjQ (ORCPT ); Mon, 18 Oct 2010 15:39:16 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:56250 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754961Ab0JRTjQ (ORCPT ); Mon, 18 Oct 2010 15:39:16 -0400 Date: Mon, 18 Oct 2010 12:37:50 -0700 From: Andrew Morton To: Mel Gorman Cc: pacman@kosh.dhis.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: PROBLEM: memory corrupting bug, bisected to 6dda9d55 Message-Id: <20101018123750.ef7d6d48.akpm@linux-foundation.org> In-Reply-To: <20101018113331.GB30667@csn.ul.ie> References: <20101013144044.GS30667@csn.ul.ie> <20101013175205.21187.qmail@kosh.dhis.org> <20101018113331.GB30667@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 On Mon, 18 Oct 2010 12:33:31 +0100 Mel Gorman wrote: > A bit but I still don't know why it would cause corruption. Maybe this is still > a caching issue but the difference in timing between list_add and list_add_tail > is enough to hide the bug. It's also possible there are some registers > ioremapped after the memmap array and reading them is causing some > problem. > > Andrew, what is the right thing to do here? We could flail around looking > for explanations as to why the bug causes a user buffer corruption but never > get an answer or do we go with this patch, preferably before 2.6.36 releases? Well, you've spotted a bug so I'd say we fix it asap. It's a bit of a shame that we lose the only known way of reproducing a different bug, but presumably that will come back and bite someone else one day, and we'll fix it then :(