RFR: Implement JEP 509: JFR CPU-Time Profiling [v45]

[Johannes Bechberger]

On Mon, 5 May 2025 13:23:11 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> But eh, if I'm reading Zenghyu's comments correctly then what I'm saying doesn't matter???
>
>> I see. If it is only used in signal handlers, does it really need to be multi-threaded?
> 
> I might be able to simplify the thread-local stacks.

But the global queue of fresh elements (that are then enqueued into the thread-local stacks) needs to signal handler safe (dequeue in multiple signal handlers in multiple thread at the same time) and is pushed to from all threads at their safepoints.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20752#discussion_r2073446031