Re: JavaMemoryModel: Total orders

From: Sylvia Else (
Date: Thu Dec 11 2003 - 00:15:48 EST

At 12:57 PM 11/12/2003, Jeremy Manson wrote:
> > Since no one has picked up on this, I decided to have a look at whether or
> > not the absence of a total order could be visible to a program. My first
> > problem is in deciding how the existence of a total order interacts with
> > the happens before rules. I've concluded that the specification implies
> > that they do, and that in the example, either X hb Y, or Y hb X.
>I'm afraid this is not quite right. The happens-before relationships are
>defined in Section 5 of the community draft. Nowhere is it stated that a
>happens-before relationship can be inferred if one action happens to
>preceed another in the total order over synchronization actions.

OK, but then I'm left with the question of whether or not the non-existence
of a total order could be visible to the program. If it cannot, then why is
a total order stated to exist? On the other hand, if a lack of total order
has detectable consequences, then my objection stands, even though my
example doesn't.


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