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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Mon, 22 Oct 2012 11:11:20 -0400
Message-ID: <CAHGf_=rYgA=yAjcvziGbN0k48zTZn8+5XQJxoMwZ4wvrX6x4sA@mail.gmail.com>
Subject: Re: [PATCH 1/4] acpi,memory-hotplug : add memory offline code to acpi_memory_device_remove()
To: Wen Congyang <wency@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>, x86@kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-acpi@vger.kernel.org, rientjes@google.com, liuj97@gmail.com,
        len.brown@intel.com, cl@linux.com, minchan.kim@gmail.com,
        akpm@linux-foundation.org
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>> ??
>> If resource was not allocated a driver, a driver doesn't need to
>> deallocate it when
>> error path. I haven't caught your point.
>>
>
> REMOVAL_NORMAL can be in 2 cases:
> 1. error path. If init call fails, we don't call it. We call this function
>    only when something fails after init.
> 2. unbind the device from the driver.
>    If we don't offline and remove memory when unbinding the device from the driver,
>    the device may be out of control. When we eject this driver, we don't offline and

Memory never be out of control by driver unloading. It is controled
from kernel core. It is an exception from regular linux driver model.


>    remove it, but we will eject and poweroff the device. It is very dangerous because
>    the kernel uses the memory but we poweroff it.
>
>    acpi_bus_hot_remove_device()
>        acpi_bus_trim() // this function successes because the device has no driver
>        _PS3 // poweroff
>        _EJ0 // eject
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