Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755220AbZKIJ5Q (ORCPT ); Mon, 9 Nov 2009 04:57:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754905AbZKIJ5Q (ORCPT ); Mon, 9 Nov 2009 04:57:16 -0500 Received: from mail.gmx.net ([213.165.64.20]:57541 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754780AbZKIJ5P (ORCPT ); Mon, 9 Nov 2009 04:57:15 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX19PqwR1qhhPPwnLS/99Lqlfad6rlWwTreDHueIQvU na8VpPD7QigHzp Subject: Re: specjbb2005 and aim7 regression with 2.6.32-rc kernels From: Mike Galbraith To: ego@in.ibm.com Cc: Peter Zijlstra , "Zhang, Yanmin" , Ingo Molnar , LKML In-Reply-To: <20091109094425.GA26733@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> <20091109094425.GA26733@in.ibm.com> Content-Type: text/plain Date: Mon, 09 Nov 2009 10:57:17 +0100 Message-Id: <1257760637.7124.26.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 X-FuHaFi: 0.62 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1129 Lines: 28 On Mon, 2009-11-09 at 15:14 +0530, Gautham R Shenoy wrote: > 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. That's exactly the problem I'm having with newidle. Without that barrier, even with the cpumask_and(), it still balances offline cpus. -Mike -- 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/