From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule, round 2 Date: Tue, 21 May 2013 09:21:40 +0200 Message-ID: <20130521072140.GA4866@pd.tnic> References: <20130520064727.GD12690@pd.tnic> <5199C990.3020602@linux.vnet.ibm.com> <5199CB59.1020309@linux.vnet.ibm.com> <5199CFD0.9030101@linux.vnet.ibm.com> <5199E54D.7030407@linux.vnet.ibm.com> <5199EBB5.7060209@linux.vnet.ibm.com> <20130520132355.GF12690@pd.tnic> <519ADA03.5060206@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <519ADA03.5060206@linux.vnet.ibm.com> Sender: cpufreq-owner@vger.kernel.org To: Michael Wang Cc: Viresh Kumar , 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 List-Id: linux-pm@vger.kernel.org On Tue, May 21, 2013 at 10:20:51AM +0800, Michael Wang wrote: > This is not enough to prove that policy->cpus is wrong, the cpu could > be online when get from policy->cpus, but offline when checked here, > since hotplug is able to happen during the period. Strictly speaking you're correct but I don't do any hotplug besides the one-time thing which is part of halting the box. > I don't get it... > > get_online_cpus() is just stop hotplug happen after it was invoked, so > unless policy->cpus is really wrong, otherwise all the cpu it masked > won't go offline any more. Yes, that's my impression too - at the point we do gov_queue_work, policy->cpus already contains offline cpus. > This protect nothing...before we go here, the cpu could already > offline, nothing changed... Yes, but I don't want to schedule work on an offlined cpu and that is ensured here. > If you really want to confirm the policy->cpus was wrong, the way > should be apply the fix I suggested, than check online in here. Sure, feel free to get a box, enable NO_HZ_FULL and do all the experimentations you desire. I surely cannot be the only one who triggers this. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --