Re: [PATCH v2 2/2] Do not change worker's running cpu in cmci_rediscover().

From: Tang Chen
Date: Mon Oct 22 2012 - 21:32:52 EST

On 10/22/2012 06:18 PM, Borislav Petkov wrote:
On Mon, Oct 22, 2012 at 11:33:16AM +0800, Tang Chen wrote:
I have 2 nodes, node0 and node1. node1 could be hotpluged.
node0 has cpu0 ~ cpu15, node1 has cpu16 ~ cpu31.

I online all the cpus on node1, and hot-remove node1 directly.

Hold on, I need to ask here: you soft-online all cores on node1 and
*then* you *hot* *remove* it? So with all cores online you physically
take out the processor from the socket? Am I reading this correctly?

Hi Borislav,

No, it's not like that. I'm sorry to make you confused.

Firstly, let me do a little explanation here. :)

I was doing ACPI based hotplug. In a container device, it contains
cpus and memories and so on. I didn't physically remove cpus from
hardware. I emulated a SCI with my own test module, and the
container_notify_cb() was called, and it recursively remove all the

The "remove" here doesn't mean "taking it away". And of course, when
the "remove" is done, you can physically take the whole system board

Please refer to this url:
This is the module we are doing the SCI emulation.

In summary, the hotplug process could be like the following:

hot-add(SCI) -> online(softly) -> device working -> offline(softly) -> hot-remove(SCI)

Secondly, in kernel, before a container device is removed, all its
sub-devices will be offlined and removed first. So I have all the cpus
online, and hot-remove a container(which I think is a node, maybe not)
directly. This operation has no problem, I think.

Maybe I should not say container as a node. :)

And again, sorry for the confusion.

Thanks. :)


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