RFR: 8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning [v16]

[Fredrik Bredberg]

On Fri, 25 Oct 2024 13:11:38 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/sharedRuntime_aarch64.cpp line 2032:
>> 
>>> 2030:     // Force freeze slow path in case we try to preempt. We will pin the
>>> 2031:     // vthread to the carrier (see FreezeBase::recurse_freeze_native_frame()).
>>> 2032:     __ push_cont_fastpath();
>> 
>> We need to do this because we might freeze, so JavaThread::_cont_fastpath should be set in case we do?
>
> Right. We want to take the slow path to find the compiled native wrapper frame and fail to freeze. Otherwise the fast path won't find it since we don't walk the stack.

It would be nice if Coleen's question and your answer could be turned into a source comment. It really describes what's going more clearly than the current comment.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1820487130