Temporary VTMS transitions are used on the hot code paths in 3 VirtualThread class methods: unpark(), scheduleUnpark() and cancel(). In these cases we can't use the same approach as for normal VTMS transitions because it will add a bid overhead and impact scalability in a bad way.

An alternate approach is to use a lightweight way of hiding of temporary transitions from the JVM TI agents. However, there are a couple of areas with potential problems:
  - suspending virtual/career threads which are in tmp transitions
  - class load, class prepare and CFLH events in tmp transition code path
  - VM operations and Handshakes on behalf of virtual threads in tmp transitions
  - virtual threads in tmp VTMS transitions can disable normal VTMS transitions

Some thread identity problems are well covered in the JNI related bug: JDK-8292674