--- old/src/hotspot/share/runtime/objectMonitor.inline.hpp	2019-05-02 15:05:22.082391126 -0400
+++ new/src/hotspot/share/runtime/objectMonitor.inline.hpp	2019-05-02 15:05:21.574391144 -0400
@@ -49,19 +49,46 @@
   return _waiters;
 }
 
+// Returns NULL if DEFLATER_MARKER is observed.
 inline void* ObjectMonitor::owner() const {
-  return _owner;
+  void* owner = _owner;
+  return owner != DEFLATER_MARKER ? owner : NULL;
 }
 
 inline void ObjectMonitor::clear() {
   assert(_header != NULL, "must be non-NULL");
+  assert(_owner == NULL, "must be NULL: owner=" INTPTR_FORMAT, p2i(_owner));
+  assert(_ref_count == 0, "must be 0: ref_count=%d", _ref_count);
+
+  _header = NULL;
+
+  clear_using_JT();
+}
+
+inline void ObjectMonitor::clear_using_JT() {
+  // Unlike other *_using_JT() functions, we cannot assert
+  // AsyncDeflateIdleMonitors or Thread::current()->is_Java_thread()
+  // because clear() calls this function for the rest of its checks.
+
+  if (AsyncDeflateIdleMonitors) {
+    // Async deflation protocol uses the header, owner and ref_count
+    // fields. While the ObjectMonitor being deflated is on the global free
+    // list, we leave those three fields alone; owner == DEFLATER_MARKER
+    // and ref_count < 0 will force any racing threads to retry. The
+    // header field is used by install_displaced_markword_in_object()
+    // in the last part of the deflation protocol so we cannot check
+    // its value here.
+    guarantee(_owner == NULL || _owner == DEFLATER_MARKER,
+              "must be NULL or DEFLATER_MARKER: owner=" INTPTR_FORMAT,
+              p2i(_owner));
+    guarantee(_ref_count <= 0, "must be <= 0: ref_count=%d", _ref_count);
+  }
   assert(_contentions == 0, "must be 0: contentions=%d", _contentions);
   assert(_waiters == 0, "must be 0: waiters=%d", _waiters);
   assert(_recursions == 0, "must be 0: recursions=" INTPTR_FORMAT, _recursions);
   assert(_object != NULL, "must be non-NULL");
-  assert(_owner == NULL, "must be NULL: owner=" INTPTR_FORMAT, p2i(_owner));
 
-  _header = NULL;
+  set_allocation_state(Free);
   _object = NULL;
 }
 
@@ -103,4 +130,51 @@
   _recursions = 0;
 }
 
+inline void ObjectMonitor::set_allocation_state(ObjectMonitor::AllocationState s) {
+  _allocation_state = s;
+}
+
+inline ObjectMonitor::AllocationState ObjectMonitor::allocation_state() const {
+  return _allocation_state;
+}
+
+inline bool ObjectMonitor::is_free() const {
+  return _allocation_state == Free;
+}
+
+inline bool ObjectMonitor::is_active() const {
+  return !is_free();
+}
+
+inline bool ObjectMonitor::is_old() const {
+  return _allocation_state == Old;
+}
+
+inline bool ObjectMonitor::is_new() const {
+  return _allocation_state == New;
+}
+
+inline void ObjectMonitor::dec_ref_count() {
+  // The decrement only needs to be MO_ACQ_REL since the reference
+  // counter is volatile.
+  Atomic::dec(&_ref_count);
+  // Can be negative as part of async deflation protocol.
+  guarantee(AsyncDeflateIdleMonitors || _ref_count >= 0,
+            "sanity check: ref_count=%d", _ref_count);
+}
+
+inline void ObjectMonitor::inc_ref_count() {
+  // The increment needs to be MO_SEQ_CST so that the reference
+  // counter update is seen as soon as possible in a race with the
+  // async deflation protocol.
+  Atomic::inc(&_ref_count);
+  // Can be negative as part of async deflation protocol.
+  guarantee(AsyncDeflateIdleMonitors || _ref_count > 0,
+            "sanity check: ref_count=%d", _ref_count);
+}
+
+inline jint ObjectMonitor::ref_count() const {
+  return OrderAccess::load_acquire(&_ref_count);
+}
+
 #endif // SHARE_RUNTIME_OBJECTMONITOR_INLINE_HPP