Re: [ACPI] Re: [RFC 5/6]clean cpu state after hotremove CPU

[Li Shaohua]

Hi,
On Mon, 2005-04-04 at 23:33, Nathan Lynch wrote:
> 
> I'd say fix the smpboot code so that it doesn't create new idle tasks
> except during boot.
I'd like the the CPU hotremove case just likes the case that CPU isn't
boot. A non-boot CPU hasn't a idle thread. But you may think it's not
worthy doing. Anyway, I will keep the idle thread in a updated patch
like what you said.

> > > We've been
> > > doing cpu removal on ppc64 logical partitions for a while and never
> > > needed to do anything like this. 
> > Did it remove idle thread? or dead cpu is in a busy loop of idle?
> 
> Neither.  The cpu is definitely offline, but there is no reason to
> free the idle thread.
> 
> > 
> > >  Maybe idle_task_exit would suffice?
> > idle_task_exit seems just drop mm. We need destroy the idle task for
> > physical CPU hotplug, right?
> 
> No.
> 
> > > 
> > > I don't understand the need for this, either.  The existing cpu
> > > hotplug notifier in the scheduler takes care of initializing the sched
> > > domains and groups appropriately for online/offline events; why do you
> > > need to touch the runqueue structures?
> > If a CPU is physically hotremoved from the system, shouldn't we clean
> > its runqueue?
> 
> No.  It should make zero difference to the scheduler whether the "play
> dead" cpu hotplug or "physical" hotplug is being used.  
Keeping some fields like 'cpu_load' are meanless for a hotadded CPU to
me. Just ignore them?

Thanks,
Shaohua

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