[systemd-devel] [PATCH] Add the CPU hotplug rule

[Zhenzhong Duan]

On 2014-9-2 16:25, Kay Sievers wrote:
> On Tue, Sep 2, 2014 at 8:12 AM, Zhenzhong Duan
> <zhenzhong.duan at oracle.com> wrote:
>> On 2014-9-2 13:55, Kay Sievers wrote:
>>> On Tue, Sep 2, 2014 at 5:22 AM, Zhenzhong Duan
>>> <zhenzhong.duan at oracle.com> wrote:
>>>> Cpu doesn't get online automaticly after hotplug when we test guest cpu
>>>> add/remove in xen env.
>>>>
>>>> I don't have an baremetal env to test this, but I think it's same.
>>>>
>>>> The rule is missed in systemd but exist in legacy udev.
>>> Udev is not a mechanism to establish an unconditional loop from the
>>> kernel back to the kernel. Such rule makes no sense and we never
>>> shipped that and will not ship it upstream now.
>>>
>>> If a device should be unconditionally change its state, the kernel
>>> should just do that on its own, and not rely on userspace to do that.
>> Thanks for your suggestion. Maybe we should add this patch in our internal
>> branch.
>>
>> In fact, kernel does expect user level to control online/offline of cpus.
>> There are two step to make a cpu online, 1. plug it, 2. online it.
>>
>> Plug doesn't have to be followed by online op.
> But you rule does that unconditionally. Shipping such things in udev
> rules makes no sense.
>
> Kay
Hi
I treat this as a default rule for most of people. They want cpu online 
right after plug it.
And in kernel side, it expects which cpus getting online/offline is 
controlable from user side.

thanks
zduan