code: private boolean handleMessageMessengerMsg(Message.MSG message) {
          if (!message.isMessenger())
              return false;
          if (receiver == null)
              return true;
  
          setOwnerClockPut(message);
  
          if (message.getLine() == -1) {
              receiver.receive(message);
              if (message.isReplyRequired())
                  send(Message.MSGACK(message));
              return true;
          }
  
          CacheLine line = getLine(message.getLine());
          if (line == null) {
              boolean res = handleMessageNoLine(message);
              assert res;
              return true;
          }
  
          synchronized (line) {
              if (handleNotOwner(message, line))
                  return true;
  
              receiver.receive(message);
          }
  
          if (message.isReplyRequired())
              send(Message.MSGACK(message));
          return true;
      }
docs: Special handling for msg.