Re: Fw: 2.6.16 crashes when running numastat on p575

From: Nathan Lynch
Date: Mon Apr 03 2006 - 10:21:01 EST


Andi Kleen wrote:
> On Monday 03 April 2006 07:15, Paul Jackson wrote:
> > - for (cpu = 0; cpu < NR_CPUS; cpu++) {
> > + for_each_online_cpu(cpu) {
> >
> > Idle curiosity -- what keeps a cpu from going offline during
> > this scan, and leaving us with the same crash as before?
>
>
> CPU hotdown uses RCU like techniques to avoid this. Only potential
> problem could be on a preemptive kernel, but I hope nobody tries
> cpu unplug on such a beast.

I always turn on preempt when testing cpu hotplug (usually on ppc64).
There were several preempt vs cpu hotplug issues until around 2.6.10
or so, iirc, but I think the situation has been stable for a while
now.
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