JDK-8364343 moved the transition-disabling mechanism out of JVMTI so it can be used by other non-JVMTI operations. A new Handshake::execute variant to handshake with a virtual thread was introduced with this patch.

Follow-up work required to MountUnmountDisabler::disable_transition_for_one to reduce the cost or eliminate the wait(10) when a virtual thread is in a transition. Initial experiments with an initial spin loop, followed by increasing wait, were profitable but there may be a better approach.

The micro benchmarks in test/micro/org/openjdk/bench/java/lang/VirtualThreadGetStackTraceXXX are useful.