public boolean registerListener(final SignalListener listener) {
    assertNotNull(listener,
        "The SignalListener to register, listening for all signals cannot be null!");

    boolean registered = false;

    for (Signal signal : Signal.values()) {
      registered |= registerListener(listener, signal);
    }

    return registered;
  }
Map used to register SignalListeners with SignalHandlers...
geode-core/src/main/java/org/apache/geode/internal/process/signal/AbstractSignalNotificationHandler.java