From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1756501Ab0CIBZX (ORCPT <rfc822;w@1wt.eu>);
	Mon, 8 Mar 2010 20:25:23 -0500
Received: from cn.fujitsu.com ([222.73.24.84]:60525 "EHLO song.cn.fujitsu.com"
	rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP
	id S1756467Ab0CIBZV (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 8 Mar 2010 20:25:21 -0500
Message-ID: <4B95A379.4000207@cn.fujitsu.com>
Date: Tue, 09 Mar 2010 09:25:13 +0800
From: Miao Xie <miaox@cn.fujitsu.com>
Reply-To: miaox@cn.fujitsu.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3
MIME-Version: 1.0
To: David Rientjes <rientjes@google.com>
CC: Lee Schermerhorn <lee.schermerhorn@hp.com>, Nick Piggin <npiggin@suse.de>,
       Paul Menage <menage@google.com>,
       Linux-Kernel <linux-kernel@vger.kernel.org>,
       Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH V2 1/4] cpuset: fix the problem that cpuset_mem_spread_node()
 returns an offline node
References: <4B94CB6C.8090601@cn.fujitsu.com> <alpine.DEB.2.00.1003081318460.14689@chino.kir.corp.google.com>
In-Reply-To: <alpine.DEB.2.00.1003081318460.14689@chino.kir.corp.google.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

on 2010-3-9 5:22, David Rientjes wrote:
> On Mon, 8 Mar 2010, Miao Xie wrote:
> 
>> Changes from V1 to V2:
>> - cleanup two unnecessary smp_wmb() at cpuset_migrate_mm()
>>
> 
> This patch is already in -mm without this update, so it's probably better 
> to make this an incremental series basedo n mmotm-2010-03-04-18-05 or 
> later.

ok, I'll do it.

> 
>> @@ -2090,15 +2086,19 @@ 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;
>> +
>>  	cgroup_lock();
>>  	switch (action) {
>>  	case MEM_ONLINE:
>> -	case MEM_OFFLINE:
>> +		oldmems = top_cpuset.mems_allowed;
>>  		mutex_lock(&callback_mutex);
>>  		top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
>>  		mutex_unlock(&callback_mutex);
>> -		if (action == MEM_OFFLINE)
>> -			scan_for_empty_cpusets(&top_cpuset);
>> +		update_tasks_nodemask(&top_cpuset, &oldmems, NULL);
>> +		break;
>> +	case MEM_OFFLINE:
>> +		scan_for_empty_cpusets(&top_cpuset);
>>  		break;
>>  	default:
>>  		break;
> 
> This looks wrong, why isn't top_cpuset.mems_allowed updated for 
> MEM_OFFLINE?  If you're going to update it when a new node comes online 
> for (struct memory_notify *)arg->status_change_nid is >= 0, then it should 
> be removed from the nodemask when offlined as well.  You'd be calling 
> scan_for_empty_cpusets() needlessly in this code since it'll never change 
> under your hotplug code.

scan_for_empty_cpusets() will update top_cpuset.mems_allowed when doing MEM_OFFLINE.

The comment of this source is necessary. I'll add it.

Thanks!
Miao

> 
>