private static void stopWatchDog() {
    Thread watchDogSnapshot = null;
    synchronized (failureSync) {
      stopping = true;
      if (watchDog != null && watchDog.isAlive()) {
        failureSync.notifyAll();
        watchDogSnapshot = watchDog;
      }
    }
    if (watchDogSnapshot != null) {
      try {
        watchDogSnapshot.join(100);
      } catch (InterruptedException ignore) {
      }
      if (watchDogSnapshot.isAlive()) {
        watchDogSnapshot.interrupt();
        try {
          watchDogSnapshot.join(SHUTDOWN_WAIT);
        } catch (InterruptedException ignore) {
        }
      }
    }
  }
Start the watchdog thread, if it isn't already running.
geode-core/src/main/java/org/apache/geode/SystemFailure.java