RFR: 8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning [v12]

[Dean Long]

On Sat, 26 Oct 2024 00:27:25 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Restore use of atPointA in test StopThreadTest.java
>>  - remove interruptible check from conditional in Object::wait
>
> src/hotspot/cpu/aarch64/continuationFreezeThaw_aarch64.inline.hpp line 310:
> 
>> 308:     sp -= 2;
>> 309:     sp[-2] = sp[0];
>> 310:     sp[-1] = sp[1];
> 
> This also seems fragile.  This seems to depend on an intimate knowledge of what the stub will do when returning.  We don't need this when doing a regular return from the native call, so why do we need it here?  I'm guessing freeze/thaw hasn't restored the state quite the same way that the stub expects.  Why is this needed for C2 and not C1?

Could the problem be solved with a resume adapter instead, like the interpreter uses?

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PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1817556946