From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753587Ab2BTMtZ (ORCPT ); Mon, 20 Feb 2012 07:49:25 -0500 Received: from merlin.infradead.org ([205.233.59.134]:55618 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752686Ab2BTMtX convert rfc822-to-8bit (ORCPT ); Mon, 20 Feb 2012 07:49:23 -0500 Message-ID: <1329742145.2293.337.camel@twins> Subject: Re: [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handling related to cpusets From: Peter Zijlstra To: "Srivatsa S. Bhat" Cc: "Rafael J. Wysocki" , Alan Stern , paulmck@linux.vnet.ibm.com, Ingo Molnar , paul@paulmenage.org, tj@kernel.org, frank.rowand@am.sony.com, pjt@google.com, tglx@linutronix.de, lizf@cn.fujitsu.com, prashanth@linux.vnet.ibm.com, vatsa@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, "akpm@linux-foundation.org" Date: Mon, 20 Feb 2012 13:49:05 +0100 In-Reply-To: <4F3E44DB.20201@linux.vnet.ibm.com> References: <201202102339.02702.rjw@sisk.pl> <1328926042.2476.3.camel@laptop> <4F35EE11.5010202@linux.vnet.ibm.com> <4F394CA0.9020902@linux.vnet.ibm.com> <4F3E44DB.20201@linux.vnet.ibm.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-02-17 at 17:45 +0530, Srivatsa S. Bhat wrote: > > Trivially removing CPU_TASKS_FROZEN as shown below doesn't look right to me: > > > > --- > > > > kernel/sched/core.c | 4 ++-- > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 5255c9d..43a166e 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -6729,7 +6729,7 @@ int __init sched_create_sysfs_power_savings_entries(struct device *dev) > > static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action, > > void *hcpu) > > { > > - switch (action & ~CPU_TASKS_FROZEN) { > > + switch (action) { > > case CPU_ONLINE: > > case CPU_DOWN_FAILED: > > cpuset_update_active_cpus(); > > @@ -6742,7 +6742,7 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action, > > static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action, > > void *hcpu) > > { > > - switch (action & ~CPU_TASKS_FROZEN) { > > + switch (action) { > > case CPU_DOWN_PREPARE: > > cpuset_update_active_cpus(); > > return NOTIFY_OK; > > > > > > IMO, irrespective of whether we keep cpusets unaware of all CPU Hotplug or > > only unaware of the CPU hotplug in the suspend/resume path, I feel the > > scheduler should always know the true state of the system, ie., offline CPUs > > must not be part of any sched domain, at any point in time. That's really not a problem as long as they're not in the active mask. > > At the moment, I am exploring several ways to achieve this (I can think of 2 > > ways at the moment, will see which one is better). But in case this approach > > itself seems wrong for any reason, please let me know. Have you actually tried the simple patch? Calling partition_sched_domains() like you do doesn't seem right, it completely ignores cpusets, it will make certain cpuset configurations mis-behave.