RFR: 8341544: Restore fence() in Mutex

[David Holmes]

On Mon, 5 May 2025 11:13:05 GMT, Anton Artemov <duke at openjdk.org> wrote:

> Added a fence in the mutex code in order to restore the old documented semantics of fence - lock - acquire. 
> 
> No significant performance impact observed in an extending testing.
> 
> Tested in tiers 1-3.

Marked as reviewed by dholmes (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/25033#pullrequestreview-2845369104