--- a/src/hotspot/share/runtime/synchronizer.cpp	Wed Jan 03 17:29:20 2018 +0000
+++ b/src/hotspot/share/runtime/synchronizer.cpp	Thu Jan 04 18:18:18 2018 -0500
@@ -238,8 +238,7 @@
     // and last are the inflated Java Monitor (ObjectMonitor) checks.
     lock->set_displaced_header(markOopDesc::unused_mark());
 
-    if (owner == NULL &&
-        Atomic::cmpxchg(Self, &(m->_owner), (void*)NULL) == NULL) {
+    if (owner == NULL && Atomic::replace_if_null(Self, &(m->_owner))) {
       assert(m->_recursions == 0, "invariant");
       assert(m->_owner == Self, "invariant");
       return true;