System.exit may not be sufficient to terminate the forked JVM

[dweiss]

Because shutdown hooks and finalizers can block the exiting thread indefinitely. Switch to using Runtime.halt() -- there is not much we can do to prevent finalizers from deadlocking.

[dweiss]

Even halt won't terminate the JVM if one of the threads is in native code or God knows what other condition holds. We should just ignore those JVMs, possibly firing some message back to the user.