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. :)
Thanks,
tglx
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