RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v56]

[Johannes Bechberger]

On Wed, 4 Jun 2025 17:44:45 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> I also want to set it. Wanted to do a simple ::xchg, but this doesn't exist for booleans.
>
> 1 & 0 -> 0, are you setting _signal_handler_installed to false? Why?

You're right, it's not required. I removed it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2127135816