Re: [PATCH] mm/hotplug: Remove stop_machine() from try_offline_node()

[KOSAKI Motohiro]

> > > 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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