Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754699Ab3ETG6j (ORCPT ); Mon, 20 May 2013 02:58:39 -0400 Received: from e23smtp04.au.ibm.com ([202.81.31.146]:59500 "EHLO e23smtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751611Ab3ETG6h (ORCPT ); Mon, 20 May 2013 02:58:37 -0400 Message-ID: <5199C990.3020602@linux.vnet.ibm.com> Date: Mon, 20 May 2013 14:58:24 +0800 From: Michael Wang User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: Borislav Petkov CC: Tejun Heo , "Paul E. McKenney" , Jiri Kosina , Frederic Weisbecker , Tony Luck , linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner Subject: Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule, round 2 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> In-Reply-To: <20130520064727.GD12690@pd.tnic> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13052006-9264-0000-0000-000003C72161 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1810 Lines: 48 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: >>> On Mon, May 20, 2013 at 11:16:33AM +0800, Michael Wang wrote: >>>> I suppose the reason is that the cpu we passed to >>>> mod_delayed_work_on() has a chance to become offline before we >>>> disabled irq, what about check it before send resched ipi? like: >>> >>> I think this is only addressing the symptoms - what we should be doing >>> instead is asking ourselves why are we even scheduling work on a cpu if >>> the machine goes offline? >>> >>> I don't know though who should be responsible for killing all that >>> work - the workqueue itself or the guy who created it, i.e. cpufreq >>> governor... >> >> So there are two questions here: >> 1. Is gov_queue_work() want to queue the work on offline cpu? >> 2. Is mod_delayed_work_on() allow offline cpu? >> >> I guess both should be false? > > Well, if we don't allow queueing work on a cpu which goes offline, i.e. > #2, the problem should be solved. I've take a look at the usage of queue_delayed_work_on() and mod_delayed_work_on(), mostly passed this_cpu, or those in online mask, I think offline cpu is not by designed. 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... Regards, Michael Wang > > Tejun? > > Here are the splats: http://marc.info/?l=linux-kernel&m=136879901425951 > -- 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/