Re: [PATCH 1/10] memory-hotplug : check whether memory is offline or not when removing memory
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- To: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
- Subject: Re: [PATCH 1/10] memory-hotplug : check whether memory is offline or not when removing memory
- From: Wen Congyang <wency@xxxxxxxxxxxxxx>
- Date: Sat, 20 Oct 2012 08:50:45 +0800
- Cc: Wen Congyang <wencongyang@xxxxxxxxx>, Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>, x86@xxxxxxxxxx, linux-mm@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-acpi@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, cmetcalf@xxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, rientjes@xxxxxxxxxx, liuj97@xxxxxxxxx, len.brown@xxxxxxxxx, cl@xxxxxxxxx, minchan.kim@xxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx
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At 10/20/2012 02:33 AM, KOSAKI Motohiro Wrote:
>> I think it again, and found that this check is necessary. Because we only
>> lock memory hotplug when offlining pages. Here is the steps to offline and
>> remove memory:
>>
>> 1. lock memory hotplug
>> 2. offline a memory section
>> 3. unlock memory hotplug
>> 4. repeat 1-3 to offline all memory sections
>> 5. lock memory hotplug
>> 6. remove memory
>> 7. unlock memory hotplug
>>
>> All memory sections must be offlined before removing memory. But we don't
>> hold
>> the lock in the whole operation. So we should check whether all memory
>> sections
>> are offlined before step6.
>
> You should describe the race scenario in the patch description. OK?
>
OK
Thanks
Wen Congyang
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