RFR: 8275718: Relax memory constraint on exception counter updates

[Andrew Haley]

On Sat, 30 Oct 2021 14:04:33 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> We had internal discussion on this topic, Aleksey pointed out: "All modifications to any particular atomic variable occur in a total order that is specific to this one atomic variable". This guarantee holds even for relaxed atomic load/stores. This is a very basic guarantee.

I think that's true for most processors as a consequence of multi-copy atomicity, but we support Power which is not multi-copy atomic, where stores can become visible to one group of threads before they become visible to all threads.

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PR: https://git.openjdk.java.net/jdk/pull/6065