RFR: 8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning [v19]

[Patricio Chilano Mateo]

On Wed, 30 Oct 2024 09:44:42 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Add klass_name check for is_object_wait0
>>  - Fix comment in continuation.hpp
>
> src/hotspot/share/runtime/continuation.cpp line 88:
> 
>> 86:       if (_target->has_async_exception_condition()) {
>> 87:         _failed = true;
>> 88:       }
> 
> Q: I wonder why the failed conditions are not checked before the `start_VTMS_transition()` call. At least, it'd be nice to add a comment about on this.

These will be rare conditions so I don't think it matters to check them before. But I can move them to some method that we call before and after if you prefer.

> src/hotspot/share/runtime/continuation.cpp line 115:
> 
>> 113:       if (jvmti_present) {
>> 114:         _target->rebind_to_jvmti_thread_state_of(_target->threadObj());
>> 115:         if (JvmtiExport::should_post_vthread_mount()) {
> 
> This has to be `JvmtiExport::should_post_vthread_unmount()` instead of `JvmtiExport::should_post_vthread_mount()`.
> Also, it'd be nice to add a comment explaining why the event posting is postponed to the `unmount` end point.

Fixed and added comment.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1823324965
PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1823323891