--- old/src/hotspot/share/runtime/basicLock.cpp	2019-10-17 17:28:55.000000000 -0400
+++ new/src/hotspot/share/runtime/basicLock.cpp	2019-10-17 17:28:55.000000000 -0400
@@ -24,6 +24,7 @@
 
 #include "precompiled.hpp"
 #include "runtime/basicLock.hpp"
+#include "runtime/objectMonitor.hpp"
 #include "runtime/synchronizer.hpp"
 
 void BasicLock::print_on(outputStream* st) const {
@@ -62,8 +63,11 @@
   // is small (given the support for inflated fast-path locking in the fast_lock, etc)
   // we'll leave that optimization for another time.
 
+  // Disallow async deflation of the inflated monitor so the
+  // displaced header stays stable until we've copied it.
+  ObjectMonitorHandle omh;
   if (displaced_header().is_neutral()) {
-    ObjectSynchronizer::inflate_helper(obj);
+    ObjectSynchronizer::inflate_helper(&omh, obj);
     // WARNING: We can not put check here, because the inflation
     // will not update the displaced header. Once BasicLock is inflated,
     // no one should ever look at its content.