RFR: 8265754: Move suspend/resume API from HandshakeState [v2]

[Anton Artemov]

On Wed, 28 May 2025 18:36:05 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> Anton Artemov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'origin/master' into JDK-8265754
>>  - Merge remote-tracking branch 'origin/master' into JDK-8265754
>>  - 8265754: Refactoring to static methods.
>>  - 8265754: Fixed indentation.
>>  - 8265754: Fixed indentation
>>  - 8265754: Fixed indentation and lost newline.
>>  - 8265754: Fixed whitespaces errors.
>>  - 8265754: More work.
>>  - Merge remote-tracking branch 'origin/master' into JDK-8265754
>>  - 8265754: Refactoring suspend/resume in the HandshakeState away
>
> In order to fully move suspend/resume code outside of `HandshakeState` we should also move `_suspended`/`_async_suspend_handshake`, otherwise we are just adding an extra indirection with class `HandshakeSuspender` IMO. The idea behind this bug was to define suspend/resume and related HandshakeClosure definitions without needing extra knowledge in `HandshakeState`, like any other HandshakeClosures. The reason why this is not straightforward is because of the interaction with the `HandshakeState` lock. But if we are going to give access to it to `HandshakeSuspender` we might as well give it to `JavaThread` instead and move everything there as that’s where all methods naturally belong. Something like this: https://github.com/pchilano/jdk/commit/4e870069e207ad2e8ba11ab1904a8df04961cef3

@pchilano Do you expect to have any performance impact of having an indirection layer? 

Since we found out that the suspend/resume code used to belong to JavaThread and then was moved out of there for (some) reason, I do not see a good explanation of why one should bring it back there. JavaThread class is already huge and from maintainability perspective I think it is better to have the suspend/resume API separated. At the same time it is clearly not a part of `HandshakeState`. 

An option might be, if I understand correctly, to do a less straightforward refactoring as suggested above, i.e. without giving `HandshakeState` lock access to `HandshakeSuspender`. I do not yet know if it is doable. Would be a compromise approach?

-------------

PR Comment: https://git.openjdk.org/jdk/pull/25407#issuecomment-2929698192