docs: private HostThreadData getData() {
          Thread thread = Thread.currentThread();
          if (!(thread instanceof XnioIoThread)) {
              throw UndertowMessages.MESSAGES.canOnlyBeCalledByIoThread();
          }
          XnioIoThread ioThread = (XnioIoThread) thread;
          HostThreadData data = hostThreadData.get(ioThread);
          if (data != null) {
              return data;
          }
          data = new HostThreadData();
          HostThreadData existing = hostThreadData.putIfAbsent(ioThread, data);
          if (existing != null) {
              return existing;
          }
          return data;
      }