RFR: 8341544: Restore fence() in Mutex

[Coleen Phillimore]

On Mon, 12 May 2025 08:16:38 GMT, Anton Artemov <duke at openjdk.org> wrote:

>> src/hotspot/share/runtime/handshake.cpp line 259:
>> 
>>> 257:     if (UseSystemMemoryBarrier) {
>>> 258:       SystemMemoryBarrier::emit();
>>> 259:     } else {
>> 
>> I don't think this change should mess around with random handshaking code. This PR is concerned with fortifying the memory ordering of Mutex, which is orthogonal.
>
> I agree with this point, addressed in the latest commit.

Okay good, I liked those there even if they're covered by the mutex fence.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25033#discussion_r2085137170