Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754775Ab3ETHMN (ORCPT ); Mon, 20 May 2013 03:12:13 -0400 Received: from mail-ob0-f176.google.com ([209.85.214.176]:64584 "EHLO mail-ob0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752576Ab3ETHMJ (ORCPT ); Mon, 20 May 2013 03:12:09 -0400 MIME-Version: 1.0 In-Reply-To: <5199CB59.1020309@linux.vnet.ibm.com> References: <20130509125040.GF27333@pd.tnic> <20130509125859.GG27333@pd.tnic> <20130515184528.GO4442@linux.vnet.ibm.com> <20130515224358.GF11783@pd.tnic> <20130515235512.GT4442@linux.vnet.ibm.com> <20130517135641.GF23035@pd.tnic> <51999591.8030401@linux.vnet.ibm.com> <20130520045023.GA12690@pd.tnic> <5199C169.7060504@linux.vnet.ibm.com> <20130520064727.GD12690@pd.tnic> <5199C990.3020602@linux.vnet.ibm.com> <5199CB59.1020309@linux.vnet.ibm.com> Date: Mon, 20 May 2013 12:42:08 +0530 Message-ID: Subject: Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule, round 2 From: Viresh Kumar To: Michael Wang Cc: Borislav Petkov , Tejun Heo , "Paul E. McKenney" , Jiri Kosina , Frederic Weisbecker , Tony Luck , linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , rjw@sisk.pl, cpufreq@vger.kernel.org, linux-pm@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1969 Lines: 48 Hi Michael, I haven't followed this mail chain earlier and saw this mail only as I am added in cc now. I probably have answers to few questions here: On 20 May 2013 12:36, Michael Wang wrote: > On 05/20/2013 02:58 PM, Michael Wang wrote: >> On 05/20/2013 02:47 PM, Borislav Petkov wrote: >>> On Mon, May 20, 2013 at 02:23:37PM +0800, Michael Wang wrote: >>>> On 05/20/2013 12:50 PM, Borislav Petkov wrote: >>>> So there are two questions here: >>>> 1. Is gov_queue_work() want to queue the work on offline cpu? No. We are only working with online cpus now in cpufreq core and governors. >> Besides, the cpu gov_queue_work() is using 'policy->cpus' which seems to >> be updated during UP DOWN notify, I think they are supposed to be online. >> >> But we need expert in cpufreq to confirm all these... I confirm this. policy->cpus only contains online cpus.. and policy->related_cpus always contain online+offline cpus. > And I guess this may help to reduce the chance to trigger WARN: > > diff --git a/drivers/cpufreq/cpufreq_governor.c > b/drivers/cpufreq/cpufreq_governor.c > index 443442d..0f96013 100644 > --- a/drivers/cpufreq/cpufreq_governor.c > +++ b/drivers/cpufreq/cpufreq_governor.c > @@ -180,7 +180,7 @@ void gov_queue_work(struct dbs_data *dbs_data, > struct cpufreq_policy *policy, > if (!all_cpus) { > __gov_queue_work(smp_processor_id(), dbs_data, delay); > } else { > - for_each_cpu(i, policy->cpus) > + for_each_cpu_and(i, policy->cpus, cpu_online_mask) > __gov_queue_work(i, dbs_data, delay); > } > } Not required at all... policy->cpus is guaranteed to have only online cpus. -- 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/