RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v5]

[Johannes Bechberger]

On Sun, 25 May 2025 10:27:48 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix compilation
>
> src/hotspot/share/jfr/support/jfrThreadLocal.cpp line 548:
> 
>> 546: #ifdef LINUX
>> 547: 
>> 548: bool JfrThreadLocal::acquire_cpu_time_jfr_enqueue_lock() {
> 
> Can you describe the lock protocol and why a thread must lock its thread-local queue?
> 
> Is it because sampling interrupts can interleave after you have started to process a sample as part of a previous interrupt?

Yes and they can interleave with the safepoint too.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2106158610