Re: JavaMemoryModel: JMM problems with latch or copy-on-write?

From: David Smiley (dsmiley@mitre.org)
Date: Thu Mar 29 2001 - 15:31:46 EST


> Specifically, in our model, a read of a volatile field v allows the
> reading thread to "see" all of the writes (to volatiles and normal
> variables) that were seen by the thread that wrote to v up until the
> point at which the thread wrote to it. For further info, check out the
> paper,
>
> http://www.cs.umd.edu/~pugh/java/memoryModel/semantics.pdf
>
> A revised version of which will shortly be available; this one is way
> out of date.

    Ooooh, I thought Joseph Bowbeer was talking about the proposed
semantics. The current semantics are almost useless, so I thought that the
general context of such questions on this list assume the proposed
semantics; which I think is a reasonable assumption. It is good that
volatile will someday be useful.

> As a side note, and Bill mentioned this recently, the current memory
> model is irrelevant, because a) it is well-nigh incomprehensible and b)
> no one follows whatever parts of it they understand anyway. This is why
> this list exists. Specifically, volatile isn't even implemented in some
> JVMs, even though the architecture requires it. So the use of volatile
> now isn't going to buy you anything.

    I have been listening to this list for a while now and so I understand
that.

-- David Smiley

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