--- a/src/hotspot/os/solaris/os_solaris.hpp	Tue Feb 05 13:21:59 2019 -0500
+++ b/src/hotspot/os/solaris/os_solaris.hpp	Tue Feb 05 15:12:13 2019 -0500
@@ -335,4 +335,21 @@
   }
 };
 
+// Platform specific implementation that underpins VM Monitor/Mutex class
+class PlatformMonitor : public CHeapObj<mtInternal> {
+ private:
+  mutex_t _mutex; // Native mutex for locking
+  cond_t  _cond;  // Native condition variable for blocking
+
+ public:
+  PlatformMonitor();
+  ~PlatformMonitor();
+  void lock();
+  void unlock();
+  bool try_lock();
+  int wait(jlong millis);
+  void notify();
+  void notify_all();
+};
+
 #endif // OS_SOLARIS_OS_SOLARIS_HPP