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

[Markus Grönlund]

On Wed, 4 Jun 2025 17:41:46 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 300:
>> 
>>> 298:   if (!Atomic::cmpxchg(&_disenrolled, false, true)) {
>>> 299:     log_trace(jfr)("Disenrolling CPU thread sampler");
>>> 300:     if (Atomic::fetch_then_and(&_signal_handler_installed, false)) {
>> 
>> fetch_then_and with false? Must be simpler way to express this? Like Atomic::load(&_signal_handler_installed)?
>
> 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?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2127125344