linux-kernel - Re: [PATCH] mm/hotplug: Remove stop_machine() from try_offline

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Message-ID: <520E8C13.5020406@gmail.com>
Date:	Fri, 16 Aug 2013 16:31:15 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Toshi Kani <toshi.kani@...com>
CC:	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	rjw@...k.pl, kosaki.motohiro@...fujitsu.com,
	kamezawa.hiroyu@...fujitsu.com, tangchen@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, liwanp@...ux.vnet.ibm.com
Subject: Re: [PATCH] mm/hotplug: Remove stop_machine() from try_offline_node()

>>> This patch removes the use of stop_machine() in try_offline_node() and
>>> adds comments to try_offline_node() and remove_memory() that
>>> lock_device_hotplug() is required.
>>
>> This patch need more verbose explanation. check_cpu_on_node() traverse cpus
>> and cpu hotplug seems to use cpu_hotplug_driver_lock() instead of lock_device_hotplug().
>
> As described:
>
> | lock_device_hotplug() serializes hotplug & online/offline operations.
> | The lock is held in common sysfs online/offline interfaces and ACPI
> | hotplug code paths.
>
> And here are their code paths.
>
> - CPU & Mem online/offline via sysfs online
> 	store_online()->lock_device_hotplug()
>
> - Mem online via sysfs state:
> 	store_mem_state()->lock_device_hotplug()
>
> - ACPI CPU & Mem hot-add:
> 	acpi_scan_bus_device_check()->lock_device_hotplug()
>
> - ACPI CPU & Mem hot-delete:
> 	acpi_scan_hot_remove()->lock_device_hotplug()

O.K.


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