diff -r 8d52b4c6f9d8 -r 05aaccf7d558 src/hotspot/share/jfr/recorder/service/jfrPostBox.cpp
--- a/src/hotspot/share/jfr/recorder/service/jfrPostBox.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/jfr/recorder/service/jfrPostBox.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -110,14 +110,14 @@
 void JfrPostBox::synchronous_post(int msg) {
   assert(is_synchronous(msg), "invariant");
   assert(!JfrMsg_lock->owned_by_self(), "should not hold JfrMsg_lock here!");
-  MutexLocker msg_lock(JfrMsg_lock);
+  MonitorLocker msg_lock(JfrMsg_lock);
   deposit(msg);
   // serial_id is used to check when what we send in has been processed.
   // _msg_read_serial is read under JfrMsg_lock protection.
   const uintptr_t serial_id = OrderAccess::load_acquire(&_msg_read_serial) + 1;
-  JfrMsg_lock->notify_all();
+  msg_lock.notify_all();
   while (!is_message_processed(serial_id)) {
-    JfrMsg_lock->wait();
+    msg_lock.wait();
   }
 }