linux-kernel - Re: [PATCH v3 0/3] ACPI: container hot remove support.

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Message-ID: <50B42798.4030402@cn.fujitsu.com>
Date:	Tue, 27 Nov 2012 10:38:16 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Hanjun Guo <guohanjun@...wei.com>
CC:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, yinghai@...nel.org,
	bhelgaas@...gle.com, lenb@...nel.org, jiang.liu@...wei.com,
	izumi.taku@...fujitsu.com, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wen Congyang <wency@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>
Subject: Re: [PATCH v3 0/3] ACPI: container hot remove support.

On 11/27/2012 09:08 AM, Hanjun Guo wrote:
> On 2012/11/26 14:06, Tang Chen wrote:
>> On 11/26/2012 01:42 PM, Hanjun Guo wrote:
>>>
>>> Hi all,
>>> I think Yasuaki mentioned the key point for the container device remove,
>>> that is dependency.
>>>
>>> Currently, container, processor, and memory hotpulg are managed by different ACPI
>>> hotplug drivers, the driver works when handle device hotplug individually, but they
>>> have no idea for each other.
>>>
>>> This may introduce some issues, such as Yasuaki mentioned above, that is to say, we
>>> should remove its child before remove the device itself, and hot add its parent before
>>> the device itself.
>>>
>>> According to the ACPI namespace, we can resolve most of dependency issues. On a typical
>>> two processor sockets system, the namespace is like this:
>>>
>>> /_SB                   ---container device, with HID ACPI0004
>>>       |_SCK0             ---container device, with HID ACPI0004
>>>        |_CPU0       ---processor device, with HID ACPI0009 or LNXCPU
>>>             |_...
>>>             |_CPUx
>>>             |_MEM0       ---Memory device, with HID PNP0C80
>>>       |_SCK1
>>>        |_CPU0
>>>             |_...
>>>             |_CPUx
>>>             |_MEM1
>>>       |_PCI0            ---Host bridge, with HID PNP0A03 or PNP0A08
>>>
>>> If hot remove the container device, such as SCK0, we can easily know the dependency list
>>> is CPU0~CPUx and MEM0, but I think the ACPI hotplug driver haven't resolve this now.
>>>
>>> And there is another corner case for hotplug devices in the namespace above, that is:
>>> 1) Remove SCK0. yes, we can remove it with no dependency to the host bridge PCI0;
>>>
>>> 2) Remove SCK1 after SCK0. we should remove the host bridge PCI0 first,
>>>      or the system will crash down. yes, dynamic dependency analysis is needed here.
>>>      and the ACPI hotplug driver totally have no idea of this.
>>>
>>> so, should we do something to settle this down ?
>>
>> Hi Guo,
>>
>> I am trying to do this too. :)
>
> Great， what's your idea of this?
>
Hi Guo,

I noticed they had a lot of discussion on this topic.
https://lkml.org/lkml/2012/11/15/159

And Vasilis's latest patches are here:
https://lkml.org/lkml/2012/11/23/335

I think we can have a review of this patchset first. :)

And also, as you said, the new ACPI hotplug framework from Liu Jiang
will settle this problem more properly.
So I think any solution now could be temporary. :)
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