RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v26]

[David Holmes]

On Mon, 2 Jun 2025 09:24:53 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 119:
>> 
>>> 117:   _data = new_data;
>>> 118:   _capacity = capacity;
>>> 119: }
>> 
>> I assume there is a lock protecting this so it happens atomically?
>
> This happens before the signal handler is attached to thread. So it does happen before any parallelism is introduced on thread creation.

I'm missing the big picture here unfortunately. This looks like it can get called repeatedly as needed to change capacity. Are you saying it only gets called once before we create the sampler thread? Is the concurrency model described somewhere?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2122365626