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Re: [Xen-devel] Re: [patch 0/3]Enable CMCI (Corrected Machine Check Error Interrupt) for Intel CPUs

On 24/12/2008 15:08, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

>> Every CPU will have IRQs disabled on entry to the on_each_cpu() IPI
>> function. I couldn't mean much else -- for example, it's not
>> even valid for
>> the caller of on_each_cpu() to enter it with IRQs disabled.
> Currently on_each_cpu() has no gurantee that the fn() will be called with all
> CPU has entered the IPI. For example, maybe on CPU has been working on the
> fn() while the IPI is still pending on other CPU.

In which case you can explicitly rendezvous in the handler, as we do for
time_calibration_rendezvous(). Notice there that we snapshot cpu_online_map
and use that as cpumask argument to on_selected_cpus() and to count CPUs
into a barrier.

If you absolutely need all CPUs to have IRQs disabled before you start your
work on any CPU, that's the way to do it.

 -- Keir

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