Re: Fw: 2.6.16 crashes when running numastat on p575

[Nathan Lynch]

Christoph Lameter wrote:
> On Sun, 2 Apr 2006, 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?
> 
> Nothing keeps a processor from going offline. We could take the hotplug 
> lock for every for_each_online_cpu() in the kernel.

In this case, disabling preempt around the for_each_online_cpu loop
would prevent any cpu from going down in the meantime.  But since this
function doesn't look like it's a hot path, and we're potentially
traversing lots of zones and cpus, lock_cpu_hotplug might be preferable.

As Paul noted, the fix as it stands isn't adequate.
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