From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755151AbZKIJoc (ORCPT ); Mon, 9 Nov 2009 04:44:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754767AbZKIJoc (ORCPT ); Mon, 9 Nov 2009 04:44:32 -0500 Received: from e28smtp03.in.ibm.com ([122.248.162.3]:59061 "EHLO e28smtp03.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754737AbZKIJob (ORCPT ); Mon, 9 Nov 2009 04:44:31 -0500 Date: Mon, 9 Nov 2009 15:14:25 +0530 From: Gautham R Shenoy To: Peter Zijlstra Cc: Mike Galbraith , "Zhang, Yanmin" , Ingo Molnar , LKML Subject: Re: specjbb2005 and aim7 regression with 2.6.32-rc kernels Message-ID: <20091109094425.GA26733@in.ibm.com> Reply-To: ego@in.ibm.com References: <1257493130.16282.109.camel@ymzhang> <20091106080418.GB28227@elte.hu> <1257747597.16282.120.camel@ymzhang> <1257750573.6414.29.camel@marge.simson.net> <1257758104.4108.152.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1257758104.4108.152.camel@laptop> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 09, 2009 at 10:15:04AM +0100, Peter Zijlstra wrote: > On Mon, 2009-11-09 at 08:09 +0100, Mike Galbraith wrote: > > + smp_read_barrier_depends(); > > cpumask_setall(cpus); > > + cpumask_and(cpus, cpus, cpu_online_mask); > > > how about: cpumask_copy(cpus, cpu_online_mask); ? > > Also, iirc cpu_online_mask is guaranteed stable when preemption is > disabled, otherwise you need to use get/put_online_cpus(), an > rmb_depends() won't do. preempt_disable() guarantees that any cpus won't go offline, since we use stop_machine() to take CPUs offline. I don't think it provides cover against new cpus coming online. -- Thanks and Regards gautham