On 2 Sep 2014, at 06:55, Kay Sievers <k...@vrfy.org> wrote:
> On Tue, Sep 2, 2014 at 5:22 AM, Zhenzhong Duan
> <zhenzhong.d...@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,
I’m curious. Are you thinking of 40-redhat.rules in the RHEL6 udev as not
being part of the legacy distribution?
Should there be a rule that uses a systemd target to hot-add CPUs to provide
the conditional aspect that’s needed? Am I right in thinking that this is as
simple as turning the old redhat rule into something like
ACTION==“add” KERNEL==“cpu[0-9]*” TAG+=“systemd”
ENV{SYSTEMD_WANTS}+=“cpuadd.service”
And the corresponding service’s ExecStart is what actually puts the CPU on line?
Sorry for the questions, I’m still trying to find the time to get to grips with
systemd — that’s a poor excuse for something that’s been around for some
considerable time I know, but be kind to me :)
jch
>
> Kay
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