proposed smp_rendezvous change

John Baldwin jhb at freebsd.org
Tue May 17 17:01:19 UTC 2011


On Tuesday, May 17, 2011 10:34:41 am Andriy Gapon wrote:
> on 17/05/2011 16:58 John Baldwin said the following:
> > No, it doesn't quite work that way.  It wouldn't work on Alpha for example.
> > 
> > All load_acq is a load with a memory barrier to order other loads after it.
> > It is still free to load stale data.  Only a read-modify-write operation
> > would actually block until it could access an up-to-date value.
> 
> Hmm, ok.
> How about atomic_add_acq_int(&smp_rv_waiters[0], 0) ? :-)
> Or an equivalent MI action that doesn't actually change smp_rv_waiters[0] value,
> if there could be any.
> Maybe explicit atomic_cmpset_acq_int(&smp_rv_waiters[0], 0, 0) ?
> 
> You see at what I am getting?

Yeah, either of those would work.  At this point just leaving the
atomic_add_int() as-is would be the smallest diff. :)

-- 
John Baldwin


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