Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755424AbZIUIql (ORCPT ); Mon, 21 Sep 2009 04:46:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755363AbZIUIqj (ORCPT ); Mon, 21 Sep 2009 04:46:39 -0400 Received: from gir.skynet.ie ([193.1.99.77]:59299 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755350AbZIUIqj (ORCPT ); Mon, 21 Sep 2009 04:46:39 -0400 Date: Mon, 21 Sep 2009 09:46:44 +0100 From: Mel Gorman To: Pekka Enberg Cc: Tejun Heo , Nick Piggin , Christoph Lameter , heiko.carstens@de.ibm.com, sachinp@in.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton Subject: Re: [PATCH 1/3] slqb: Do not use DEFINE_PER_CPU for per-node data Message-ID: <20090921084644.GD12726@csn.ul.ie> References: <1253302451-27740-1-git-send-email-mel@csn.ul.ie> <1253302451-27740-2-git-send-email-mel@csn.ul.ie> <84144f020909200145w74037ab9vb66dae65d3b8a048@mail.gmail.com> <4AB5FD4D.3070005@kernel.org> <4AB5FFF8.7000602@cs.helsinki.fi> <4AB6508C.4070602@kernel.org> <1253514240.5216.3.camel@penberg-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1253514240.5216.3.camel@penberg-laptop> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2299 Lines: 56 On Mon, Sep 21, 2009 at 09:24:00AM +0300, Pekka Enberg wrote: > Hi Tejun, > > On Mon, 2009-09-21 at 00:55 +0900, Tejun Heo wrote: > > Pekka Enberg wrote: > > > Tejun Heo wrote: > > >> Pekka Enberg wrote: > > >>> On Fri, Sep 18, 2009 at 10:34 PM, Mel Gorman wrote: > > >>>> SLQB used a seemingly nice hack to allocate per-node data for the > > >>>> statically > > >>>> initialised caches. Unfortunately, due to some unknown per-cpu > > >>>> optimisation, these regions are being reused by something else as the > > >>>> per-node data is getting randomly scrambled. This patch fixes the > > >>>> problem but it's not fully understood *why* it fixes the problem at the > > >>>> moment. > > >>> Ouch, that sounds bad. I guess it's architecture specific bug as x86 > > >>> works ok? Lets CC Tejun. > > >> > > >> Is the corruption being seen on ppc or s390? > > > > > > On ppc. > > > > Can you please post full dmesg showing the corruption? Also, if you > > apply the attached patch, does the added BUG_ON() trigger? > > I don't have the affected machines, Sachin and Mel do. > More accurately, Sachin does but he gave me access to the machine for this bug so I can use it when it's otherwise idle. > Pekka > > > diff --git a/include/linux/percpu.h b/include/linux/percpu.h > > index 878836c..fb690d2 100644 > > --- a/include/linux/percpu.h > > +++ b/include/linux/percpu.h > > @@ -127,7 +127,7 @@ extern int __init pcpu_page_first_chunk(size_t reserved_size, > > * dynamically allocated. Non-atomic access to the current CPU's > > * version should probably be combined with get_cpu()/put_cpu(). > > */ > > -#define per_cpu_ptr(ptr, cpu) SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))) > > +#define per_cpu_ptr(ptr, cpu) ({ BUG_ON(!(ptr)); SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))); }) > > > > extern void *__alloc_reserved_percpu(size_t size, size_t align); > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/