--- a/src/hotspot/share/compiler/abstractCompiler.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/compiler/abstractCompiler.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
+// Copyright (c) 2007, 2019, Oracle and/or its affiliates. All rights reserved.
 // DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 //
 // This code is free software; you can redistribute it and/or modify it
@@ -28,14 +28,14 @@
 
 bool AbstractCompiler::should_perform_init() {
   if (_compiler_state != initialized) {
-    MutexLocker only_one(CompileThread_lock);
+    MonitorLocker only_one(CompileThread_lock);
 
     if (_compiler_state == uninitialized) {
       _compiler_state = initializing;
       return true;
     } else {
       while (_compiler_state == initializing) {
-        CompileThread_lock->wait();
+        only_one.wait();
       }
     }
   }

--- a/src/hotspot/share/compiler/compileBroker.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/compiler/compileBroker.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -402,7 +402,7 @@
   methodHandle save_method;
   methodHandle save_hot_method;
 
-  MutexLocker locker(MethodCompileQueue_lock);
+  MonitorLocker locker(MethodCompileQueue_lock);
   // If _first is NULL we have no more compile jobs. There are two reasons for
   // having no compile jobs: First, we compiled everything we wanted. Second,
   // we ran out of code cache so compilation has been disabled. In the latter
@@ -423,7 +423,7 @@
     // We need a timed wait here, since compiler threads can exit if compilation
     // is disabled forever. We use 5 seconds wait time; the exiting of compiler threads
     // is not critical and we do not want idle compiler threads to wake up too often.
-    MethodCompileQueue_lock->wait(5*1000);
+    locker.wait(5*1000);
 
     if (UseDynamicNumberOfCompilerThreads && _first == NULL) {
       // Still nothing to compile. Give caller a chance to stop this thread.
@@ -1496,11 +1496,11 @@
  * @return true if this thread needs to free/recycle the task
  */
 bool CompileBroker::wait_for_jvmci_completion(JVMCICompiler* jvmci, CompileTask* task, JavaThread* thread) {
-  MutexLocker waiter(task->lock(), thread);
+  MonitorLocker ml(task->lock(), thread);
   int progress_wait_attempts = 0;
   int methods_compiled = jvmci->methods_compiled();
   while (!task->is_complete() && !is_compilation_disabled_forever() &&
-         task->lock()->wait(JVMCI_COMPILATION_PROGRESS_WAIT_TIMESLICE)) {
+         ml.wait(JVMCI_COMPILATION_PROGRESS_WAIT_TIMESLICE)) {
     CompilerThread* jvmci_compiler_thread = task->jvmci_compiler_thread();
 
     bool progress;
@@ -1558,10 +1558,10 @@
   } else
 #endif
   {
-    MutexLocker waiter(task->lock(), thread);
+    MonitorLocker ml(task->lock(), thread);
     free_task = true;
     while (!task->is_complete() && !is_compilation_disabled_forever()) {
-      task->lock()->wait();
+      ml.wait();
     }
   }
 

--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -338,9 +338,9 @@
   }
 
   {
-    MutexLocker x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
+    MonitorLocker ml(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
     while (scan_in_progress()) {
-      RootRegionScan_lock->wait_without_safepoint_check();
+      ml.wait();
     }
   }
   return true;

--- a/src/hotspot/share/gc/g1/g1ConcurrentMarkThread.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMarkThread.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -407,9 +407,9 @@
   // below while the world is otherwise stopped.
   assert(!in_progress(), "should have been cleared");
 
-  MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
   while (!started() && !should_terminate()) {
-    CGC_lock->wait_without_safepoint_check();
+    ml.wait();
   }
 
   if (started()) {

--- a/src/hotspot/share/gc/g1/g1ConcurrentRefineThread.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1ConcurrentRefineThread.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -59,9 +59,9 @@
 }
 
 void G1ConcurrentRefineThread::wait_for_completed_buffers() {
-  MutexLocker x(_monitor, Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(_monitor, Mutex::_no_safepoint_check_flag);
   while (!should_terminate() && !is_active()) {
-    _monitor->wait_without_safepoint_check();
+    ml.wait();
   }
 }
 

--- a/src/hotspot/share/gc/g1/g1RootProcessor.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1RootProcessor.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -61,7 +61,7 @@
   if ((uint)_n_workers_discovered_strong_classes != n_workers()) {
     MonitorLocker ml(&_lock, Mutex::_no_safepoint_check_flag);
     while ((uint)_n_workers_discovered_strong_classes != n_workers()) {
-      _lock.wait_without_safepoint_check(0);
+      ml.wait(0);
     }
   }
 }

--- a/src/hotspot/share/gc/g1/g1VMOperations.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1VMOperations.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -191,10 +191,10 @@
       JavaThread* jt = (JavaThread*)thr;
       ThreadToNativeFromVM native(jt);
 
-      MutexLocker x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
+      MonitorLocker ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
       while (g1h->old_marking_cycles_completed() <=
                                           _old_marking_cycles_completed_before) {
-        FullGCCount_lock->wait_without_safepoint_check();
+        ml.wait();
       }
     }
   }

--- a/src/hotspot/share/gc/g1/g1YoungRemSetSamplingThread.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1YoungRemSetSamplingThread.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -47,10 +47,10 @@
 }
 
 void G1YoungRemSetSamplingThread::sleep_before_next_cycle() {
-  MutexLocker x(&_monitor, Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(&_monitor, Mutex::_no_safepoint_check_flag);
   if (!should_terminate()) {
     uintx waitms = G1ConcRefinementServiceIntervalMillis;
-    _monitor.wait_without_safepoint_check(waitms);
+    ml.wait(waitms);
   }
 }
 

--- a/src/hotspot/share/gc/parallel/gcTaskManager.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/parallel/gcTaskManager.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -654,7 +654,7 @@
 GCTask* GCTaskManager::get_task(uint which) {
   GCTask* result = NULL;
   // Grab the queue lock.
-  MutexLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
   // Wait while the queue is block or
   // there is nothing to do, except maybe release resources.
   while (is_blocked() ||
@@ -671,7 +671,7 @@
       tty->print_cr("    => (%s)->wait()",
                     monitor()->name());
     }
-    monitor()->wait_without_safepoint_check(0);
+    ml.wait(0);
   }
   // We've reacquired the queue lock here.
   // Figure out which condition caused us to exit the loop above.
@@ -872,15 +872,15 @@
   log_trace(gc, task)("[" INTPTR_FORMAT "] IdleGCTask:::do_it() should_wait: %s",
       p2i(this), wait_helper->should_wait() ? "true" : "false");
 
-  MutexLocker ml(manager->monitor(), Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(manager->monitor(), Mutex::_no_safepoint_check_flag);
   log_trace(gc, task)("--- idle %d", which);
   // Increment has to be done when the idle tasks are created.
   // manager->increment_idle_workers();
-  manager->monitor()->notify_all();
+  ml.notify_all();
   while (wait_helper->should_wait()) {
     log_trace(gc, task)("[" INTPTR_FORMAT "] IdleGCTask::do_it()  [" INTPTR_FORMAT "] (%s)->wait()",
       p2i(this), p2i(manager->monitor()), manager->monitor()->name());
-    manager->monitor()->wait_without_safepoint_check(0);
+    ml.wait(0);
   }
   manager->decrement_idle_workers();
 
@@ -991,7 +991,7 @@
   }
   {
     // Grab the lock and check again.
-    MutexLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
+    MonitorLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
     while (should_wait()) {
       if (TraceGCTaskManager) {
         tty->print_cr("[" INTPTR_FORMAT "]"
@@ -999,7 +999,7 @@
           "  [" INTPTR_FORMAT "] (%s)->wait()",
           p2i(this), p2i(monitor()), monitor()->name());
       }
-      monitor()->wait_without_safepoint_check(0);
+      ml.wait(0);
     }
     // Reset the flag in case someone reuses this task.
     if (reset) {

--- a/src/hotspot/share/gc/shared/gcLocker.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/shared/gcLocker.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -102,7 +102,7 @@
 
 void GCLocker::stall_until_clear() {
   assert(!JavaThread::current()->in_critical(), "Would deadlock");
-  MutexLocker   ml(JNICritical_lock);
+  MonitorLocker ml(JNICritical_lock);
 
   if (needs_gc()) {
     log_debug_jni("Allocation failed. Thread stalled by JNI critical section.");
@@ -110,20 +110,20 @@
 
   // Wait for _needs_gc  to be cleared
   while (needs_gc()) {
-    JNICritical_lock->wait();
+    ml.wait();
   }
 }
 
 void GCLocker::jni_lock(JavaThread* thread) {
   assert(!thread->in_critical(), "shouldn't currently be in a critical region");
-  MutexLocker mu(JNICritical_lock);
+  MonitorLocker ml(JNICritical_lock);
   // Block entering threads if we know at least one thread is in a
   // JNI critical region and we need a GC.
   // We check that at least one thread is in a critical region before
   // blocking because blocked threads are woken up by a thread exiting
   // a JNI critical region.
   while (is_active_and_needs_gc() || _doing_gc) {
-    JNICritical_lock->wait();
+    ml.wait();
   }
   thread->enter_critical();
   _jni_lock_count++;

--- a/src/hotspot/share/gc/shared/workgroup.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/gc/shared/workgroup.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -200,7 +200,7 @@
   }
 
   void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) {
-    MutexLocker ml(_monitor, Mutex::_no_safepoint_check_flag);
+    MonitorLocker ml(_monitor, Mutex::_no_safepoint_check_flag);
 
     _task        = task;
     _num_workers = num_workers;
@@ -210,7 +210,7 @@
 
     // Wait for them to finish.
     while (_finished < _num_workers) {
-      _monitor->wait_without_safepoint_check();
+      ml.wait();
     }
 
     _task        = NULL;
@@ -367,7 +367,7 @@
 }
 
 bool WorkGangBarrierSync::enter() {
-  MutexLocker x(monitor(), Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(monitor(), Mutex::_no_safepoint_check_flag);
   if (should_reset()) {
     // The should_reset() was set and we are the first worker to enter
     // the sync barrier. We will zero the n_completed() count which
@@ -387,10 +387,10 @@
     // should_reset() flag and the barrier will be reset the first
     // time a worker enters it again.
     set_should_reset(true);
-    monitor()->notify_all();
+    ml.notify_all();
   } else {
     while (n_completed() != n_workers() && !aborted()) {
-      monitor()->wait_without_safepoint_check();
+      ml.wait();
     }
   }
   return !aborted();

--- a/src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -395,9 +395,9 @@
   JfrThreadLocal* const tl = thread->jfr_thread_local();
   tl->set_trace_block();
   {
-    MutexLocker ml(transition_block(), Mutex::_no_safepoint_check_flag);
+    MonitorLocker ml(transition_block(), Mutex::_no_safepoint_check_flag);
     while (thread->is_trace_suspend()) {
-      transition_block()->wait_without_safepoint_check();
+      ml.wait();
     }
     tl->clear_trace_block();
   }

--- 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();
   }
 }
 

--- a/src/hotspot/share/prims/jvmtiRedefineClasses.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/prims/jvmtiRedefineClasses.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -90,14 +90,14 @@
 // If any of the classes are being redefined, wait
 // Parallel constant pool merging leads to indeterminate constant pools.
 void VM_RedefineClasses::lock_classes() {
-  MutexLocker ml(RedefineClasses_lock);
+  MonitorLocker ml(RedefineClasses_lock);
   bool has_redefined;
   do {
     has_redefined = false;
     // Go through classes each time until none are being redefined.
     for (int i = 0; i < _class_count; i++) {
       if (get_ik(_class_defs[i].klass)->is_being_redefined()) {
-        RedefineClasses_lock->wait();
+        ml.wait();
         has_redefined = true;
         break;  // for loop
       }
@@ -106,17 +106,17 @@
   for (int i = 0; i < _class_count; i++) {
     get_ik(_class_defs[i].klass)->set_is_being_redefined(true);
   }
-  RedefineClasses_lock->notify_all();
+  ml.notify_all();
 }
 
 void VM_RedefineClasses::unlock_classes() {
-  MutexLocker ml(RedefineClasses_lock);
+  MonitorLocker ml(RedefineClasses_lock);
   for (int i = 0; i < _class_count; i++) {
     assert(get_ik(_class_defs[i].klass)->is_being_redefined(),
            "should be being redefined to get here");
     get_ik(_class_defs[i].klass)->set_is_being_redefined(false);
   }
-  RedefineClasses_lock->notify_all();
+  ml.notify_all();
 }
 
 bool VM_RedefineClasses::doit_prologue() {

--- a/src/hotspot/share/runtime/java.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/runtime/java.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -419,14 +419,14 @@
   // A CAS or OSMutex would work just fine but then we need to manipulate
   // thread state for Safepoint. Here we use Monitor wait() and notify_all()
   // for synchronization.
-  { MutexLocker ml(BeforeExit_lock);
+  { MonitorLocker ml(BeforeExit_lock);
     switch (_before_exit_status) {
     case BEFORE_EXIT_NOT_RUN:
       _before_exit_status = BEFORE_EXIT_RUNNING;
       break;
     case BEFORE_EXIT_RUNNING:
       while (_before_exit_status == BEFORE_EXIT_RUNNING) {
-        BeforeExit_lock->wait();
+        ml.wait();
       }
       assert(_before_exit_status == BEFORE_EXIT_DONE, "invalid state");
       return;

--- a/src/hotspot/share/runtime/mutexLocker.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/runtime/mutexLocker.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -216,9 +216,7 @@
   def(ResolvedMethodTableWeakAlloc_lock    , PaddedMutex  , vmweak,      true,  Monitor::_safepoint_check_never);
   def(ResolvedMethodTableWeakActive_lock   , PaddedMutex  , vmweak-1,    true,  Monitor::_safepoint_check_never);
 
-  if (UseConcMarkSweepGC || UseG1GC) {
-    def(FullGCCount_lock           , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);      // in support of ExplicitGCInvokesConcurrent
-  }
+  def(FullGCCount_lock             , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);      // in support of ExplicitGCInvokesConcurrent
   if (UseG1GC) {
     def(SATB_Q_CBL_mon             , PaddedMonitor, access,      true,  Monitor::_safepoint_check_never);
 

--- a/src/hotspot/share/runtime/mutexLocker.hpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/runtime/mutexLocker.hpp	Mon Apr 29 16:01:52 2019 -0400
@@ -229,6 +229,7 @@
 
 // A MonitorLocker is like a MutexLocker above, except it allows
 // wait/notify as well which are delegated to the underlying Monitor.
+// It also disallows NULL.
 
 class MonitorLocker: public MutexLocker {
   Mutex::SafepointCheckFlag _flag;
@@ -236,35 +237,31 @@
   MonitorLocker(Monitor* monitor, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
     MutexLocker(monitor, flag), _flag(flag) {
     // Superclass constructor did locking
+    assert(_mutex != NULL, "NULL monitor not allowed");
   }
 
   MonitorLocker(Monitor* monitor, Thread* thread, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
     MutexLocker(monitor, thread, flag), _flag(flag)  {
     // Superclass constructor did locking
+    assert(_mutex != NULL, "NULL monitor not allowed");
   }
 
   bool wait(long timeout = 0,
             bool as_suspend_equivalent = !Mutex::_as_suspend_equivalent_flag) {
-    if (_mutex != NULL) {
-      if (_flag == Mutex::_safepoint_check_flag) {
-        return _mutex->wait(timeout, as_suspend_equivalent);
-      } else {
-        return _mutex->wait_without_safepoint_check(timeout);
-      }
+    if (_flag == Mutex::_safepoint_check_flag) {
+      return _mutex->wait(timeout, as_suspend_equivalent);
+    } else {
+      return _mutex->wait_without_safepoint_check(timeout);
     }
     return false;
   }
 
   void notify_all() {
-    if (_mutex != NULL) {
-      _mutex->notify_all();
-    }
+    _mutex->notify_all();
   }
 
   void notify() {
-    if (_mutex != NULL) {
-      _mutex->notify();
-    }
+    _mutex->notify();
   }
 };
 

--- a/src/hotspot/share/runtime/sweeper.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/runtime/sweeper.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -341,9 +341,9 @@
   while (true) {
     {
       ThreadBlockInVM tbivm(JavaThread::current());
-      MutexLocker waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+      MonitorLocker waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
       const long wait_time = 60*60*24 * 1000;
-      timeout = CodeCache_lock->wait_without_safepoint_check(wait_time);
+      timeout = waiter.wait(wait_time);
     }
     if (!timeout) {
       possibly_sweep();
@@ -369,7 +369,7 @@
   */
 void NMethodSweeper::force_sweep() {
   ThreadBlockInVM tbivm(JavaThread::current());
-  MutexLocker waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+  MonitorLocker waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
   // Request forced sweep
   _force_sweep = true;
   while (_force_sweep) {
@@ -377,7 +377,7 @@
     // In case a sweep currently takes place we timeout and try again because
     // we want to enforce a full sweep.
     CodeCache_lock->notify();
-    CodeCache_lock->wait_without_safepoint_check(1000);
+    waiter.wait(1000);
   }
 }
 

--- a/src/hotspot/share/runtime/thread.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/runtime/thread.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -794,14 +794,12 @@
     // safepoint requests from the VMThread
 
     {
-      MutexLocker ml(SR_lock());
+      Thread* t = Thread::current();
+      MonitorLocker ml(SR_lock(),
+                       t->is_Java_thread() ? Mutex::_safepoint_check_flag : Mutex::_no_safepoint_check_flag);
       // wait with safepoint check (if we're a JavaThread - the WatcherThread
       // can also call this)  and increase delay with each retry
-      if (Thread::current()->is_Java_thread()) {
-        SR_lock()->wait(i * delay);
-      } else {
-        SR_lock()->wait_without_safepoint_check(i * delay);
-      }
+      ml.wait(i * delay);
 
       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
                                               delay, bits);
@@ -1405,7 +1403,7 @@
 int WatcherThread::sleep() const {
   // The WatcherThread does not participate in the safepoint protocol
   // for the PeriodicTask_lock because it is not a JavaThread.
-  MutexLocker ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
 
   if (_should_terminate) {
     // check for termination before we do any housekeeping or wait
@@ -1425,7 +1423,7 @@
   jlong time_before_loop = os::javaTimeNanos();
 
   while (true) {
-    bool timedout = PeriodicTask_lock->wait_without_safepoint_check(remaining);
+    bool timedout = ml.wait(remaining);
     jlong now = os::javaTimeNanos();
 
     if (remaining == 0) {
@@ -1548,12 +1546,12 @@
     }
   }
 
-  MutexLocker mu(Terminator_lock);
+  MonitorLocker mu(Terminator_lock);
 
   while (watcher_thread() != NULL) {
     // This wait should make safepoint checks, wait without a timeout,
     // and wait as a suspend-equivalent condition.
-    Terminator_lock->wait(0, Mutex::_as_suspend_equivalent_flag);
+    mu.wait(0, Mutex::_as_suspend_equivalent_flag);
   }
 }
 
@@ -2424,7 +2422,7 @@
          (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
          "must have walkable stack");
 
-  MutexLocker ml(SR_lock(), Mutex::_no_safepoint_check_flag);
+  MonitorLocker ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 
   assert(!this->is_ext_suspended(),
          "a thread trying to self-suspend should not already be suspended");
@@ -2452,7 +2450,7 @@
 
     // _ext_suspended flag is cleared by java_resume()
     while (is_ext_suspended()) {
-      this->SR_lock()->wait_without_safepoint_check();
+      ml.wait();
     }
   }
   return ret;
@@ -3844,10 +3842,10 @@
     // Wait for the VM thread to become ready, and VMThread::run to initialize
     // Monitors can have spurious returns, must always check another state flag
     {
-      MutexLocker ml(Notify_lock);
+      MonitorLocker ml(Notify_lock);
       os::start_thread(vmthread);
       while (vmthread->active_handles() == NULL) {
-        Notify_lock->wait();
+        ml.wait();
       }
     }
   }
@@ -4325,11 +4323,11 @@
   _vm_complete = false;
 #endif
   // Wait until we are the last non-daemon thread to execute
-  { MutexLocker nu(Threads_lock);
+  { MonitorLocker nu(Threads_lock);
     while (Threads::number_of_non_daemon_threads() > 1)
       // This wait should make safepoint checks, wait without a timeout,
       // and wait as a suspend-equivalent condition.
-      Threads_lock->wait(0, Mutex::_as_suspend_equivalent_flag);
+      nu.wait(0, Mutex::_as_suspend_equivalent_flag);
   }
 
   EventShutdown e;
@@ -4465,7 +4463,7 @@
 
   // Extra scope needed for Thread_lock, so we can check
   // that we do not remove thread without safepoint code notice
-  { MutexLocker ml(Threads_lock);
+  { MonitorLocker ml(Threads_lock);
 
     assert(ThreadsSMRSupport::get_java_thread_list()->includes(p), "p must be present");
 
@@ -4493,7 +4491,7 @@
       // Only one thread left, do a notify on the Threads_lock so a thread waiting
       // on destroy_vm will wake up.
       if (number_of_non_daemon_threads() == 1) {
-        Threads_lock->notify_all();
+        ml.notify_all();
       }
     }
     ThreadService::remove_thread(p, is_daemon);

--- a/src/hotspot/share/runtime/vmOperations.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/runtime/vmOperations.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -450,8 +450,8 @@
 
     attempts++;
 
-    MutexLocker ml(&timer, Mutex::_no_safepoint_check_flag);
-    timer.wait_without_safepoint_check(10);
+    MonitorLocker ml(&timer, Mutex::_no_safepoint_check_flag);
+    ml.wait(10);
   }
 }
 

--- a/src/hotspot/share/runtime/vmThread.cpp	Mon Apr 29 14:34:10 2019 -0400
+++ b/src/hotspot/share/runtime/vmThread.cpp	Mon Apr 29 16:01:52 2019 -0400
@@ -342,9 +342,9 @@
     // but before it actually drops the lock and waits, the notification below
     // may get lost and we will have a hang. To avoid this, we need to use
     // Mutex::lock_without_safepoint_check().
-    MutexLocker ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
+    MonitorLocker ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
     _terminated = true;
-    _terminate_lock->notify();
+    ml.notify();
   }
 
   // We are now racing with the VM termination being carried out in
@@ -373,9 +373,9 @@
   // Note: it should be OK to use Terminator_lock here. But this is called
   // at a very delicate time (VM shutdown) and we are operating in non- VM
   // thread at Safepoint. It's safer to not share lock with other threads.
-  { MutexLocker ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
+  { MonitorLocker ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
     while(!VMThread::is_terminated()) {
-        _terminate_lock->wait_without_safepoint_check();
+      ml.wait();
     }
   }
 }
@@ -476,8 +476,8 @@
     // Wait for VM operation
     //
     // use no_safepoint_check to get lock without attempting to "sneak"
-    { MutexLocker mu_queue(VMOperationQueue_lock,
-                           Mutex::_no_safepoint_check_flag);
+    { MonitorLocker mu_queue(VMOperationQueue_lock,
+                             Mutex::_no_safepoint_check_flag);
 
       // Look for new operation
       assert(_cur_vm_operation == NULL, "no current one should be executing");
@@ -494,7 +494,7 @@
       while (!should_terminate() && _cur_vm_operation == NULL) {
         // wait with a timeout to guarantee safepoints at regular intervals
         bool timedout =
-          VMOperationQueue_lock->wait_without_safepoint_check(GuaranteedSafepointInterval);
+          mu_queue.wait(GuaranteedSafepointInterval);
 
         // Support for self destruction
         if ((SelfDestructTimer != 0) && !VMError::is_error_reported() &&
@@ -718,13 +718,10 @@
     if (!concurrent) {
       // Wait for completion of request (non-concurrent)
       // Note: only a JavaThread triggers the safepoint check when locking
-      MutexLocker mu(VMOperationRequest_lock);
+      MonitorLocker ml(VMOperationRequest_lock,
+                       t->is_Java_thread() ? Mutex::_safepoint_check_flag : Mutex::_no_safepoint_check_flag);
       while(t->vm_operation_completed_count() < ticket) {
-        if (t->is_Java_thread()) {
-          VMOperationRequest_lock->wait();
-        } else {
-          VMOperationRequest_lock->wait_without_safepoint_check();
-        }
+        ml.wait();
       }
     }