boolean unregisterListener(final SignalListener listener, final Signal signal) {
    assertNotNull(signal, "The signal from which to unregister the listener cannot be null!");

    return signalListeners.get(signal).remove(listener);
  }
Map used to register SignalListeners with SignalHandlers...
geode-core/src/main/java/org/apache/geode/internal/process/signal/AbstractSignalNotificationHandler.java