RFR: 8342818: Implement CPU Time Profiling for JFR [v43]

[Johannes Bechberger]

On Mon, 28 Apr 2025 10:31:05 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Johannes Bechberger has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Improve placement of NoResourceMark
>>  - Add more checks for metadata_do
>
> src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 556:
> 
>> 554:     stop_timer();
>> 555:     Atomic::store(&_stop_signals, true);
>> 556:     while (_active_signal_handlers > 0) {
> 
> This will cause the system to hang.
> 
>  The thread calling disenroll() is a JavaThread, which can get stuck in this while loop here, preventing the system from moving to a safepoint.

I shouldn't get stuck here, as the signal handler is stopped and new signal handler invocations will not be incrementing _active_signal_handlers. Or do you I misunderstand your concerns?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20752#discussion_r2063394392