From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 50A8D6B0116 for ; Mon, 21 Sep 2009 02:23:55 -0400 (EDT) Subject: Re: [PATCH 1/3] slqb: Do not use DEFINE_PER_CPU for per-node data From: Pekka Enberg In-Reply-To: <4AB6508C.4070602@kernel.org> 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> Date: Mon, 21 Sep 2009 09:24:00 +0300 Message-Id: <1253514240.5216.3.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Tejun Heo Cc: Mel Gorman , Nick Piggin , Christoph Lameter , heiko.carstens@de.ibm.com, sachinp@in.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton List-ID: 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. 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); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org