RFR: 8287281: adjust guarantee in Handshake::execute for the case of target thread being current [v4]

[Johan Sjölén]

On Fri, 3 Jun 2022 09:45:31 GMT, Johan Sjölén <duke at openjdk.java.net> wrote:

>> Please review this PR for fixing JDK-8287281.
>> 
>> If a thread is handshake safe we immediately execute the closure, instead of going through the regular Handshake process. 
>> 
>> Finally:  Should `VirtualThreadGetThreadClosure` and its `do_thread()` body be inlined instead? We can do this in this PR, imho, but I'm hoping to get some input on this.
>> 
>> 
>> Passes tier1. Running tier2-5.
>
> Johan Sjölén has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - do_thread(target) not self
>  - Remove checks for is_handshake_for, instead call Handshake::execute
>  - Switch order of handshake check

Passed tier1-5.

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PR: https://git.openjdk.java.net/jdk/pull/8992