--- old/src/hotspot/share/runtime/serviceThread.cpp	2019-08-28 15:04:01.314957339 -0400
+++ new/src/hotspot/share/runtime/serviceThread.cpp	2019-08-28 15:04:01.130957346 -0400
@@ -190,25 +190,21 @@
       // Deflate any global idle monitors.
       ObjectSynchronizer::deflate_global_idle_monitors_using_JT();
 
-      // deflate_per_thread_idle_monitors_using_JT() is called by
-      // each JavaThread from ObjectSynchronizer::omAlloc() as needed.
       int count = 0;
       for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
-        if (jt->om_in_use_count > 0) {
-          // This JavaThread is using monitors so request deflation.
-          jt->om_request_deflation = true;
+        if (jt->om_in_use_count > 0 && !jt->is_exiting()) {
+          // This JavaThread is using ObjectMonitors so deflate any that
+          // are idle unless this JavaThread is exiting; do not race with
+          // ObjectSynchronizer::om_flush().
+          ObjectSynchronizer::deflate_per_thread_idle_monitors_using_JT(jt);
           count++;
         }
       }
       if (count > 0) {
-        log_debug(monitorinflation)("requesting async deflation of idle monitors for %d thread(s).", count);
+        log_debug(monitorinflation)("did async deflation of idle monitors for %d thread(s).", count);
       }
       // The ServiceThread's async deflation request has been processed.
       ObjectSynchronizer::set_is_async_deflation_requested(false);
-
-      // The global in-use list was handled above, but the request won't
-      // be complete until the JavaThreads have handled their in-use
-      // lists. This is the nature of an async deflation request.
     }
   }
 }