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Date: Sun, 15 May 2011 10:12:48 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: John Baldwin <jhb@FreeBSD.org>
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Cc: FreeBSD current <freebsd-current@FreeBSD.org>,
	Peter Grehan <grehan@FreeBSD.org>
Subject: Re: proposed smp_rendezvous change
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on 14/05/2011 18:25 John Baldwin said the following:
> Hmmm, so this is not actually sufficient.  NetApp ran into a very similar race
> with virtual CPUs in BHyVe.  In their case because virtual CPUs are threads that
> can be preempted, they have a chance at a longer race.
> 
> The problem that they see is that even though the values have been updated, the
> next CPU to start a rendezvous can clear smp_rv_waiters[2] to zero before one of
> the other CPUs notices that it has finished.

As a follow up to my previous question.  Have you noticed that in my patch no
slave CPU actually waits/spins on smp_rv_waiters[2]?  It's always only master
CPU (and under smp_ipi_mtx).

-- 
Andriy Gapon