RFR: 8341544: Restore fence() in Mutex

[Erik Österlund]

On Tue, 13 May 2025 12:43:20 GMT, Anton Artemov <duke at openjdk.org> wrote:

> As per JBS comment I still think we only need to add the missing storeload part of the full-fence, to complement the existing barriers the platform sync primitives provide.

Pretty sure the comment that the old mutex implementation we removed had, describing the API guarantees, said the semantics was fence() lock() acquire(). Since we are putting back what used to be there - shouldn't that simply be fence()?

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PR Comment: https://git.openjdk.org/jdk/pull/25033#issuecomment-2876938251