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Date: Sun, 30 Dec 2012 14:02:28 +0800
From: Wen Congyang <wency@cn.fujitsu.com>
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To: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH v5 14/14] memory-hotplug: free node_data when a node is
 offlined
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Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
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At 12/28/2012 08:28 AM, Kamezawa Hiroyuki Wrote:
> (2012/12/27 21:16), Wen Congyang wrote:
>> At 12/26/2012 11:55 AM, Kamezawa Hiroyuki Wrote:
>>> (2012/12/24 21:09), Tang Chen wrote:
>>>> From: Wen Congyang <wency@cn.fujitsu.com>
>>>>
>>>> We call hotadd_new_pgdat() to allocate memory to store node_data. So we
>>>> should free it when removing a node.
>>>>
>>>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
>>>
>>> I'm sorry but is it safe to remove pgdat ? All zone cache and zonelists are
>>> properly cleared/rebuilded in synchronous way ? and No threads are visinting
>>> zone in vmscan.c ?
>>
>> We have rebuilt zonelists when a zone has no memory after offlining some pages.
>>
> 
> How do you guarantee that the address of pgdat/zone is not on stack of any kernel
> threads or other kernel objects without reference counting or other syncing method ?

No way to guarentee this. But, the kernel should not use the address of pgdat/zone when
it is offlined.

Hmm, what about this: reuse the memory when the node is onlined again?

Thanks
Wen Congyang

> 
> 
> Thanks,
> -Kame
> 
> 
>