--- /dev/null	2018-04-03 12:55:20.301839954 +0200
+++ new/src/hotspot/share/gc/z/zMessagePort.hpp	2018-06-06 00:42:04.387156080 +0200
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#ifndef SHARE_GC_Z_ZMESSAGEPORT_HPP
+#define SHARE_GC_Z_ZMESSAGEPORT_HPP
+
+#include "gc/z/zFuture.hpp"
+#include "gc/z/zList.hpp"
+#include "memory/allocation.hpp"
+#include "runtime/mutex.hpp"
+
+template <typename T> class ZMessageRequest;
+
+template <typename T>
+class ZMessagePort {
+private:
+  typedef ZMessageRequest<T> Request;
+
+  Monitor        _monitor;
+  bool           _has_message;
+  T              _message;
+  uint64_t       _seqnum;
+  ZList<Request> _queue;
+
+public:
+  ZMessagePort();
+
+  void send_sync(T message);
+  void send_async(T message);
+
+  T receive();
+  void ack();
+};
+
+class ZRendezvousPort {
+private:
+  ZMessagePort<bool> _port;
+
+public:
+  void signal();
+  void wait();
+  void ack();
+};
+
+#endif // SHARE_GC_Z_ZMESSAGEPORT_HPP