RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v48]

[Johannes Bechberger]

On Wed, 4 Jun 2025 13:04:28 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> Using `sigaction(SIG, NULL, &sa)` ?
>
> I'm currently implementing the check against SIG_IGN and SIG_DFL, as `handle_timer_signal` should never occur.

I implemented what you want. This prevents confusion of users.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2126701277