--- old/src/hotspot/share/services/threadService.cpp	2019-12-11 14:56:22.000000000 -0500
+++ new/src/hotspot/share/services/threadService.cpp	2019-12-11 14:56:21.000000000 -0500
@@ -208,6 +208,10 @@
   assert(thread != NULL, "should be non-NULL");
   debug_only(Thread::check_for_dangling_thread_pointer(thread);)
 
+  // This function can be called on a target JavaThread that is not
+  // the caller and we are not at a safepoint. This ObjectMonitorHandle
+  // keeps the ObjectMonitor from being async deflated so the object
+  // reference we fetch remains non-NULL.
   ObjectMonitorHandle omh;
   ObjectMonitor *wait_obj = thread->current_waiting_monitor(&omh);
 
@@ -217,7 +221,6 @@
     obj = (oop) wait_obj->object();
     assert(obj != NULL, "Object.wait() should have an object");
   } else {
-    ObjectMonitorHandle omh;
     ObjectMonitor *enter_obj = thread->current_pending_monitor(&omh);
     if (enter_obj != NULL) {
       // thread is trying to enter() an ObjectMonitor.
@@ -364,6 +367,8 @@
 
   // This code was modified from the original Threads::find_deadlocks code.
   int globalDfn = 0, thisDfn;
+  // This code is called at a safepoint so this ObjectMonitorHandle
+  // is not strictly necessary.
   ObjectMonitorHandle omh;
   ObjectMonitor* waitingToLockMonitor = NULL;
   JvmtiRawMonitor* waitingToLockRawMonitor = NULL;
@@ -985,6 +990,8 @@
   int len = _threads->length();
   for (int i = 0; i < len; i++) {
     currentThread = _threads->at(i);
+    // This code is called at a safepoint so this ObjectMonitorHandle
+    // is not strictly necessary.
     ObjectMonitorHandle omh;
     ObjectMonitor* waitingToLockMonitor = currentThread->current_pending_monitor(&omh);
     waitingToLockRawMonitor = currentThread->current_pending_raw_monitor();