Re: [PATCH v6 04/12] x86/smpboot.c: Don't offline CPU0 if any irqcan not be migrated out of it and remove CPU0 check in smp_callin()

[Suresh Siddha]

On Mon, 2012-05-14 at 14:17 +0200, Ingo Molnar wrote:
> * Tony Luck <tony.luck@xxxxxxxxx> wrote:
> 
> > Biggest code impact of that is the extra code to bring cpu0 
> > back online using NMI instead of INIT. We can't use INIT 
> > because if cpu0 gets one, it just resets the whole machine :-( 
> > But obviously we'd like to avoid special cases where there is 
> > a sane way to do so.
> 
> Could we just standardize on NMI bringup during regular bootup?

May be we can use the NMI or even better monitor/mwait based bringup to
re-online an AP that is currently offline in play_dead(), specifically
if we haven't lost that AP processor state because of suspend/resume
event etc.

This can speed-up online if we want to use light weight online/offline
of the AP's for saving power on mobile platforms.

thanks,
suresh

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