Re: BUG_ON(!cpus_equal(cpumask, tmp));

From: Andrew Morton
Date: Tue Mar 30 2004 - 19:40:14 EST

"Martin J. Bligh" <mbligh@xxxxxxxxxxx> wrote:
> > I'll just say that kexec fails without this patch and works with
> > it applied, so I'd like to see it merged. If this patch isn't
> > acceptable, let's find out why and try to make one that is.
> >
> > Thanks for the patch, Hari.
> >From discussions with Andy, it seems this still has the same race as before
> just smaller. I don't see how we can fix this properly without having some
> locking on cpu_online_map .... probably RCU as it's massively read-biased
> and we don't want to pay a spinlock cost to read it.

We do want to avoid adding stuff to the IPI path. If the going-away CPU
still responds to IPIs after it has gone away then do we actually need to
do anything? For x86, at least?
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