[concurrency-interest] Enforcing total sync order on modern hardware

Marko Topolnik marko at hazelcast.com
Fri Mar 20 14:12:57 EDT 2015


On Fri, Mar 20, 2015 at 5:45 PM, Oleksandr Otenko <
oleksandr.otenko at oracle.com> wrote:

>  No, that doesn't answer the question. You need to modify how
> happens-before is built - because happens-before in JMM and in some other
> model are two different happens-befores. If you get rid of synchronization
> order, then you need to explain which reads the write will or will not
> synchronize-with.
>

I think it's quite simple: the read may synchronize-with any write as long
as that doesn't break happens-before consistency.


> I am only involved in this discussion because you said it isn't IRIW, but
> I see all signs that it is. I remember the discussion here doubting that
> IRIW should be supported, and I appreciate the arguments, but without the
> specification it is difficult to continue a meaningful discussion.
>

That's strange to hear since I have pointed out exactly why it's not IRIW:
if we broaden the definition such that it covers my case, then we must
accept that Intel allows IRIW to happen because it explicitly excludes the
writing thread from the guarantee which is supposed to disallow it.

---
Marko
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