RFR: 8364343: Virtual Thread transition management needs to be independent of JVM TI [v7]

[Patricio Chilano Mateo]

On Tue, 25 Nov 2025 23:45:14 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> src/hotspot/share/runtime/javaThread.cpp line 1152:
>> 
>>> 1150: bool JavaThread::is_in_VTMS_transition() const {
>>> 1151:   return AtomicAccess::load(&_is_in_VTMS_transition);
>>> 1152: }
>> 
>> Is the JavaThread version always the same as the java_lang_Thread::is_in_VTMS_transition(threadOop()) value?
>
> Why is there the same flag with the same name in both the Java class and C++ JavaThread?  Might be an efficient cache, so something should say that (if true).

The one in `JavaThread` is needed for the `disable_transition_for_all` case. Processing each vthread is not viable, so we instead process all `JavaThreads`. If no `JavaThread` is in a transition then it implies no vthread is in a transition.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28361#discussion_r2566665257