RFR: 8364343: Virtual Thread transition management needs to be independent of JVM TI [v10]

[Patricio Chilano Mateo]

On Tue, 2 Dec 2025 08:15:53 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix comment in inline_native_vthread_start_transition
>
> src/hotspot/share/runtime/mountUnmountDisabler.cpp line 88:
> 
>> 86:         // We rebinded on start_transition but the mount/unmount operation
>> 87:         // failed so now we need to rebind to the original state.
>> 88:         _current->rebind_to_jvmti_thread_state_of(_is_mount ? _vthread() : _current->threadObj());
> 
> Q: Not sure I fully understand this comment. We have done a rebind at the line 67 for an unmount transition only. But this comment tells that it was done for mount transition as well. Also, before this update, we used to do a rebind of `JvmtiThreadState` to a vthread in the `JvmtiVTMSTransitionDisabler::VTMS_mount_end()` for the normal (not failed) case. Please, could you explain a little bit more? It feels like this comment needs a correction.

Yes, well spotted. I changed it to rebind the state only for the mount case, as in current code. This already handles a successful mount or a failed unmount. I also added and assert to verify we rebinded to the correct identity.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28361#discussion_r2582654454