Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752908Ab0BWHdD (ORCPT ); Tue, 23 Feb 2010 02:33:03 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:63346 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752656Ab0BWHdA (ORCPT ); Tue, 23 Feb 2010 02:33:00 -0500 Message-ID: <4B838490.1050908@cn.fujitsu.com> Date: Tue, 23 Feb 2010 15:32:32 +0800 From: Miao Xie Reply-To: miaox@cn.fujitsu.com User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.1.5) Gecko/20091204 Thunderbird/3.0 MIME-Version: 1.0 To: David Rientjes CC: Nick Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Lee Schermerhorn Subject: Re: [regression] cpuset,mm: update tasks' mems_allowed in time (58568d2) References: <20100218134921.GF9738@laptop> <20100219033126.GI9738@laptop> <4B827043.3060305@cn.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1953 Lines: 55 on 2010-2-23 6:06, David Rientjes wrote: >>>> Right, but the callback_mutex was being removed by this patch. >>>> >>> >>> I was making the case for it to be readded :) >> >> But cgroup_mutex is held when someone changes cs->cpus_allowed or doing hotplug, >> so I think callback_mutex is not necessary in this case. >> > > Then why is it taken in update_cpumask()? when we read cs->cpus_allowed, we need just hold one of callback_mutex and cgroup_mutex. If we want to change cs->cpus_allowed, we must hold callback_mutex and cgroup_mutex. >> /* >> @@ -1391,11 +1393,10 @@ static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont, >> >> if (cs == &top_cpuset) { >> cpumask_copy(cpus_attach, cpu_possible_mask); >> - to = node_possible_map; >> } else { >> guarantee_online_cpus(cs, cpus_attach); >> - guarantee_online_mems(cs, &to); >> } >> + guarantee_online_mems(cs, &to); >> >> /* do per-task migration stuff possibly for each in the threadgroup */ >> cpuset_attach_task(tsk, &to, cs); > > Do we need to set cpus_attach to cpu_possible_mask? Why won't > cpu_active_mask suffice? If we set cpus_attach to cpu_possible_mask, we needn't do anything for tasks in the top_cpuset when doing cpu hotplug. If not, we will update cpus_allowed of all tasks in the top_cpuset. > >> @@ -2090,15 +2091,19 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb, >> static int cpuset_track_online_nodes(struct notifier_block *self, >> unsigned long action, void *arg) >> { >> + nodemask_t oldmems; > > Is it possible to use NODEMASK_ALLOC() instead? Yes. I will write another patch to fix it.(These are the same problems in the other functions) -- 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/