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

[Hanjun Guo <guohanjun@huawei.com>]

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. :)
> 
> But so far as I know, Vasilis Liaskovitis has provided an approach.
> Please refer to the following url.
> https://lkml.org/lkml/2012/11/15/159
> 
> I think we can review his patches first. :)

Yes, I noticed Vasilis Liaskovitis's patch and the discussion from
Greg and Toshi, Greg suggested that no driver core changes to resolve
this problem, so we should find another way.

> 
> And by the way, I think the ACPI based hotplug framework provided by
> Liu Jiang may also settle this problem. But I'm not quit sure yet. :)

The ACPI based hotplug framework provided by Jiang Liu has settle this
problem down, you may refer to:
https://lkml.org/lkml/2012/11/4/64

Thanks
Hanjun Guo