diff -r dd5c64326027 -r 2b48cedce327 src/hotspot/share/runtime/mutexLocker.cpp
--- a/src/hotspot/share/runtime/mutexLocker.cpp	Mon Apr 01 11:02:40 2019 -0700
+++ b/src/hotspot/share/runtime/mutexLocker.cpp	Mon Apr 01 17:11:38 2019 -0400
@@ -76,6 +76,7 @@
 Monitor* SerializePage_lock           = NULL;
 Monitor* Threads_lock                 = NULL;
 Mutex*   NonJavaThreadsList_lock      = NULL;
+Mutex*   NonJavaThreadsListSync_lock  = NULL;
 Monitor* CGC_lock                     = NULL;
 Monitor* STS_lock                     = NULL;
 Monitor* FullGCCount_lock             = NULL;
@@ -279,6 +280,7 @@
 
   def(Threads_lock                 , PaddedMonitor, barrier,     true,  Monitor::_safepoint_check_sometimes);
   def(NonJavaThreadsList_lock      , PaddedMutex,   leaf,        true,  Monitor::_safepoint_check_never);
+  def(NonJavaThreadsListSync_lock  , PaddedMutex,   leaf,        true,  Monitor::_safepoint_check_never);
 
   def(VMOperationQueue_lock        , PaddedMonitor, nonleaf,     true,  Monitor::_safepoint_check_sometimes);  // VM_thread allowed to block on these
   def(VMOperationRequest_lock      , PaddedMonitor, nonleaf,     true,  Monitor::_safepoint_check_sometimes);