--- old/src/hotspot/share/runtime/objectMonitor.inline.hpp	2019-10-17 17:31:42.000000000 -0400
+++ new/src/hotspot/share/runtime/objectMonitor.inline.hpp	2019-10-17 17:31:42.000000000 -0400
@@ -25,6 +25,7 @@
 #ifndef SHARE_RUNTIME_OBJECTMONITOR_INLINE_HPP
 #define SHARE_RUNTIME_OBJECTMONITOR_INLINE_HPP
 
+#include "logging/log.hpp"
 #include "runtime/atomic.hpp"
 
 inline intptr_t ObjectMonitor::is_entered(TRAPS) const {
@@ -118,8 +119,56 @@
   return _contentions;
 }
 
-inline void ObjectMonitor::set_owner(void* owner) {
-  _owner = owner;
+// Set _owner field to new_value; current value must match old_value.
+inline void ObjectMonitor::set_owner_from(void* new_value, void* old_value) {
+  void* prev = Atomic::cmpxchg(new_value, &_owner, old_value);
+  ADIM_guarantee(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
+                 ", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
+  log_trace(monitorinflation, owner)("mid=" INTPTR_FORMAT ", prev="
+                                     INTPTR_FORMAT ", new=" INTPTR_FORMAT,
+                                     p2i(this), p2i(prev), p2i(new_value));
+}
+
+// Set _owner field to new_value; current value must match old_value1 or old_value2.
+inline void ObjectMonitor::set_owner_from(void* new_value, void* old_value1, void* old_value2) {
+  void* prev = Atomic::cmpxchg(new_value, &_owner, old_value1);
+  if (prev != old_value1) {
+    prev = Atomic::cmpxchg(new_value, &_owner, old_value2);
+  }
+  ADIM_guarantee(prev == old_value1 || prev == old_value2,
+                 "unexpected prev owner=" INTPTR_FORMAT ", expected1="
+                 INTPTR_FORMAT " or expected2=" INTPTR_FORMAT, p2i(prev),
+                 p2i(old_value1), p2i(old_value2));
+  log_trace(monitorinflation, owner)("mid=" INTPTR_FORMAT ", prev="
+                                     INTPTR_FORMAT ", new=" INTPTR_FORMAT,
+                                     p2i(this), p2i(prev), p2i(new_value));
+}
+
+// Set _owner field to self; current value must match basic_lock_p.
+inline void ObjectMonitor::set_owner_from_BasicLock(Thread* self, void* basic_lock_p) {
+  assert(self->is_lock_owned((address)basic_lock_p), "self=" INTPTR_FORMAT
+         " must own basic_lock_p=" INTPTR_FORMAT, p2i(self), p2i(basic_lock_p));
+  void* prev = _owner;
+  ADIM_guarantee(prev == basic_lock_p, "unexpected prev owner=" INTPTR_FORMAT
+                 ", expected=" INTPTR_FORMAT, p2i(prev), p2i(basic_lock_p));
+  // Non-null owner field to non-null owner field is safe without
+  // cmpxchg() as long as all readers can tolerate either flavor.
+  _owner = self;
+  log_trace(monitorinflation, owner)("mid=" INTPTR_FORMAT ", prev="
+                                     INTPTR_FORMAT ", new=" INTPTR_FORMAT,
+                                     p2i(this), p2i(prev), p2i(self));
+}
+
+// Try to set _owner field to new_value if the current value matches
+// old_value. Otherwise, does not change the _owner field.
+inline void* ObjectMonitor::try_set_owner_from(void* new_value, void* old_value) {
+  void* prev = Atomic::cmpxchg(new_value, &_owner, old_value);
+  if (prev == old_value) {
+    log_trace(monitorinflation, owner)("mid=" INTPTR_FORMAT ", prev="
+                                       INTPTR_FORMAT ", new=" INTPTR_FORMAT,
+                                       p2i(this), p2i(prev), p2i(new_value));
+  }
+  return prev;
 }
 
 inline void ObjectMonitor::set_allocation_state(ObjectMonitor::AllocationState s) {