RFR: 8352738: Implement JEP 520: JFR Method Timing and Tracing

[Aleksey Shipilev]

On Fri, 23 May 2025 14:55:21 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Just so we are on the same page, the stores should be at least `Atomic::release_store`, but better even `Atomic::release_store_fence` to match `Atomic::load_acquire`.
>
> Why release_store_fence() over release_store() in this context?

`release_store_fence` would get stronger seqcst mode, instead of more relaxed acquire/release with just `release_store`. My rule of thumb is to default to a strongest mode, unless we can prove weaker mode is sufficient. Acquire/release is okay for simple uni-directional pub/sub transfer, which this one _looks_ to be, but I am not 100% sure.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25306#discussion_r2104826719