ADDITIONAL SYSTEM INFORMATION :
Reproduced on OsX, and CentOS, Java 8 and 11.

A DESCRIPTION OF THE PROBLEM :
If while running a shutdown hook another thread will try to exit (i.e. System.exit) the machine will go into a deadlock.

A simple example:

This is because that System.exit is calling Runtime.exit which calls to Shutdown.exit which has synchronized (Shutdown.class) regardless of the status, while the Shutdown.class is already blocked y the thread that calls the shutdown hook (DestroyJavaVM)...

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the source code:
java TestShutdown.java



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Once the DestroyJavaVM had started, System.exit should do nothing or throw a runtime exception.
ACTUAL -
Deadlock

---------- BEGIN SOURCE ----------
public class TestShutdown {

    public static void main(String[] args) throws Exception {
        System.out.println("Adding shutdown");
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            System.out.println("In shutdown");
            System.out.println("Creating thread");
            Thread killMe = new Thread(() -> {
                System.out.println("Will exit now...");
                System.exit(1);
            });
            System.out.println("Starting thread");
            killMe.start();
            System.out.println("Joinging...");
            try {
                killMe.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }));
        System.out.println("Hello and goodbye");
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Avoid System.exit?
Run the shutdown hook in another thread and join to it with a timeout?

FREQUENCY : always