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Message-ID: <54F67376.8050001@huawei.com>
Date: Wed, 4 Mar 2015 10:52:38 +0800
From: Xishi Qiu <qiuxishi@huawei.com>
MIME-Version: 1.0
Subject: Re: node-hotplug: is memset 0 safe in try_offline_node()?
References: <54F52ACF.4030103@huawei.com> <54F58AE3.50101@cn.fujitsu.com> <54F66C52.4070600@huawei.com>
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To: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>, Andrew Morton <akpm@linux-foundation.org>, Tang Chen <tangchen@cn.fujitsu.com>, Yinghai Lu <yinghai@kernel.org>, Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Toshi Kani <toshi.kani@hp.com>, Mel Gorman <mgorman@suse.de>, Tejun Heo <tj@kernel.org>, Xiexiuqi <xiexiuqi@huawei.com>, Hanjun Guo <guohanjun@huawei.com>, Li Zefan <lizefan@huawei.com>

On 2015/3/4 10:22, Xishi Qiu wrote:

> On 2015/3/3 18:20, Gu Zheng wrote:
> 
>> Hi Xishi,
>> On 03/03/2015 11:30 AM, Xishi Qiu wrote:
>>
>>> When hot-remove a numa node, we will clear pgdat,
>>> but is memset 0 safe in try_offline_node()?
>>
>> It is not safe here. In fact, this is a temporary solution here.
>> As you know, pgdat is accessed lock-less now, so protection
>> mechanism (RCUi 1/4 ?) is needed to make it completely safe here,
>> but it seems a bit over-kill.
>>

Hi Gu,

Can we just remove "memset(pgdat, 0, sizeof(*pgdat));" ?
I find this will be fine in the stress test except the warning 
when hot-add memory.

Thanks,
Xishi Qiu

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