RFR: 8352251: Implement Cooperative JFR Sampling [v16]

[Markus Grönlund]

On Mon, 5 May 2025 17:38:44 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

> > Can we let _last_sender_Java_fp be a state field that can be tested?
> 
> I still couldn't hit any failures or errors with my simple version, but I understand that it might be problematic.
> 
> I have an implementation: [TheRealMDoerr at b2f83fa](https://github.com/TheRealMDoerr/jdk/commit/b2f83fae262f129f864e109d7adce169e28f0c7c) Please take a look. I hope we don't need more ;-) I'm planning to run more test when I find more time.
> 
> If `_last_sender_Java_fp` is needed on all platforms, shouldn't it be better moved to shared javaFrameAnchor.hpp and javaThread.hpp?

Implementation seems to be in the correct direction, but its missing locations in TemplateInterpreterGenerator and TemplateTable. Also, i do not see any pre-emptive move of the fp, which is required for fetching a correct (non-racy) CPU context.

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PR Comment: https://git.openjdk.org/jdk/pull/24296#issuecomment-2851919560