From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 2941A6B0095 for ; Tue, 23 Feb 2010 02:33:02 -0500 (EST) 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 MIME-Version: 1.0 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: owner-linux-mm@kvack.org To: David Rientjes Cc: Nick Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Lee Schermerhorn List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org