Re: [RFC PATCH 0/6] CPU hotplug: Reverse invocation of notifiers during CPU hotplug

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

On 07/26/2012 04:32 PM, Thomas Gleixner wrote:
> On Wed, 25 Jul 2012, Srivatsa S. Bhat wrote:
>> On 07/25/2012 10:00 PM, Thomas Gleixner wrote:
>>> While I thought about having a full dependency tracking system, I'm
>>> quite convinced by now, that hotplug is a rather linear sequence which
>>> does not provide much room for paralell setup/teardown.
>>>
>>
>> Pretty much, when considering hotplug of a single CPU.
>>
>> (But when considering booting, Arjan had proposed (while discussing
>> about his asynchronous booting patch) that it would be good to split
>> up physical vs logical parts of the booting/hotplug, so that the
>> physical part can happen in parallel with other CPUs, while the
>> logical online can be done serially, much later. Anyway, this is
>> slightly off-topic here, since we are mainly talking about hotplug
>> of a single cpu here. I just thought of putting a word about that
>> here, since we are discussing hotplug redesign anyways..)
> 
> Well, the nice thing about having a proper state machine is that you
> can tell the code to advance the BP only to the "kick the other cpu"
> step, which is before the first sync point, so you can leave the state
> there and continue with "bring it fully online" later. 
> 
> So that feature comes basically for free. :)
> 

Ah! Nice :-)

Regards,
Srivatsa S. Bhat