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

[Zhenzhong Duan]

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.
>
> Kay
Hi Kay

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.

thanks
zduan