linux-kernel - Re: node-hotplug: is memset 0 safe in try_offline

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Date:	Wed, 4 Mar 2015 10:52:38 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Gu Zheng <guz.fnst@...fujitsu.com>
CC:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tang Chen <tangchen@...fujitsu.com>,
	Yinghai Lu <yinghai@...nel.org>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Toshi Kani <toshi.kani@...com>, Mel Gorman <mgorman@...e.de>,
	Tejun Heo <tj@...nel.org>, Xiexiuqi <xiexiuqi@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	Li Zefan <lizefan@...wei.com>
Subject: Re: node-hotplug: is memset 0 safe in try_offline_node()?

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 (RCU？) 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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