Detecting pinning

The current prototype has rudimentary support for reporting when a thread is pinned, say when a virtual thread parks while owning a monitor or with a native frame on the stack. This reporting is enabled by running with if the system property jdk.tracePinnedThreads set on the command line is specified to the java launcher.

Running with -Djdk.tracePinnedThreads (or -Djdk.tracePinnedThreads=full) will print a complete stack trace of the virtual thread. Native frames, synchronized frames, or frames with synchronized blocks will be highlighted in the output.

Running with -Djdk.tracePinnedThreads=short will print a "short" stack trace that includes only just the frames with problematic code.

The reporting does filtering to reduce output is filtered to avoid the printing the same stack trace being reported repeatedly.

Thread dumps

For now, traditional thread dumps do not include virtual threads. If the thread dump is taken when a virtual thread is mounted then its stack will be shown in the stack trace of its carrier thread.

...