diff --git a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
index 3749a99bb..ef8fb4ac0 100644
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 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
@@ -2202,7 +2202,10 @@ void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) {
 }
 
 bool G1CMTask::should_exit_termination() {
-  regular_clock_call();
+  if (!regular_clock_call()) {
+    return true;
+  }
+
   // This is called when we are in the termination protocol. We should
   // quit if, for some reason, this task wants to abort or the global
   // stack is not empty (this means that we can get work from it).
@@ -2213,12 +2216,12 @@ void G1CMTask::reached_limit() {
   assert(_words_scanned >= _words_scanned_limit ||
          _refs_reached >= _refs_reached_limit ,
          "shouldn't have been called otherwise");
-  regular_clock_call();
+  abort_marking_if_regular_check_fail();
 }
 
-void G1CMTask::regular_clock_call() {
+bool G1CMTask::regular_clock_call() {
   if (has_aborted()) {
-    return;
+    return false;
   }
 
   // First, we need to recalculate the words scanned and refs reached
@@ -2229,21 +2232,19 @@ void G1CMTask::regular_clock_call() {
 
   // (1) If an overflow has been flagged, then we abort.
   if (_cm->has_overflown()) {
-    set_has_aborted();
-    return;
+    return false;
   }
 
   // If we are not concurrent (i.e. we're doing remark) we don't need
   // to check anything else. The other steps are only needed during
   // the concurrent marking phase.
   if (!_cm->concurrent()) {
-    return;
+    return true;
   }
 
   // (2) If marking has been aborted for Full GC, then we also abort.
   if (_cm->has_aborted()) {
-    set_has_aborted();
-    return;
+    return false;
   }
 
   double curr_time_ms = os::elapsedVTime() * 1000.0;
@@ -2252,17 +2253,15 @@ void G1CMTask::regular_clock_call() {
   if (SuspendibleThreadSet::should_yield()) {
     // We should yield. To do this we abort the task. The caller is
     // responsible for yielding.
-    set_has_aborted();
-    return;
+    return false;
   }
 
   // (5) We check whether we've reached our time quota. If we have,
   // then we abort.
   double elapsed_time_ms = curr_time_ms - _start_time_ms;
   if (elapsed_time_ms > _time_target_ms) {
-    set_has_aborted();
     _has_timed_out = true;
-    return;
+    return false;
   }
 
   // (6) Finally, we check whether there are enough completed STAB
@@ -2271,9 +2270,9 @@ void G1CMTask::regular_clock_call() {
   if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
     // we do need to process SATB buffers, we'll abort and restart
     // the marking task to do so
-    set_has_aborted();
-    return;
+    return false;
   }
+  return true;
 }
 
 void G1CMTask::recalculate_limits() {
@@ -2428,7 +2427,7 @@ void G1CMTask::drain_satb_buffers() {
   // until we run out of buffers or we need to abort.
   while (!has_aborted() &&
          satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
-    regular_clock_call();
+    abort_marking_if_regular_check_fail();
   }
 
   _draining_satb_buffers = false;
@@ -2671,7 +2670,7 @@ void G1CMTask::do_marking_step(double time_target_ms,
       // If the iteration is successful, give up the region.
       if (mr.is_empty()) {
         giveup_current_region();
-        regular_clock_call();
+        abort_marking_if_regular_check_fail();
       } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
         if (_next_mark_bitmap->is_marked(mr.start())) {
           // The object is marked - apply the closure
@@ -2680,10 +2679,10 @@ void G1CMTask::do_marking_step(double time_target_ms,
         // Even if this task aborted while scanning the humongous object
         // we can (and should) give up the current region.
         giveup_current_region();
-        regular_clock_call();
+        abort_marking_if_regular_check_fail();
       } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) {
         giveup_current_region();
-        regular_clock_call();
+        abort_marking_if_regular_check_fail();
       } else {
         assert(has_aborted(), "currently the only way to do so");
         // The only way to abort the bitmap iteration is to return
@@ -2738,7 +2737,7 @@ void G1CMTask::do_marking_step(double time_target_ms,
       // block of empty regions. So we need to call the regular clock
       // method once round the loop to make sure it's called
       // frequently enough.
-      regular_clock_call();
+      abort_marking_if_regular_check_fail();
     }
 
     if (!has_aborted() && _curr_region == NULL) {
@@ -2816,6 +2815,7 @@ void G1CMTask::do_marking_step(double time_target_ms,
       guarantee(_cm->mark_stack_empty(), "only way to reach here");
       guarantee(_task_queue->size() == 0, "only way to reach here");
       guarantee(!_cm->has_overflown(), "only way to reach here");
+      guarantee(!has_aborted(), "should never happen if termination has completed");
     } else {
       // Apparently there's more work to do. Let's abort this task. It
       // will restart it and we can hopefully find more things to do.
diff --git a/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp b/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp
index b5eb26197..b760fe977 100644
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp
@@ -730,7 +730,11 @@ private:
   // Supposed to be called regularly during a marking step as
   // it checks a bunch of conditions that might cause the marking step
   // to abort
-  void regular_clock_call();
+  // Return true if the marking step should continue. Otherwise, return false to abort
+  bool regular_clock_call();
+
+  // Set abort flag if regular_clock_call() check fails
+  inline void abort_marking_if_regular_check_fail();
 
   // Test whether obj might have already been passed over by the
   // mark bitmap scan, and so needs to be pushed onto the mark stack.
diff --git a/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp b/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp
index 4a969c511..383cdc563 100644
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp
@@ -210,6 +210,12 @@ inline void G1ConcurrentMark::add_to_liveness(uint worker_id, oop const obj, siz
   task(worker_id)->update_liveness(obj, size);
 }
 
+inline void G1CMTask::abort_marking_if_regular_check_fail() {
+  if (!regular_clock_call()) {
+    set_has_aborted();
+  }
+}
+
 inline bool G1CMTask::make_reference_grey(oop obj) {
   if (!_cm->mark_in_next_bitmap(_worker_id, obj)) {
     return false;
diff --git a/src/hotspot/share/gc/shared/owstTaskTerminator.cpp b/src/hotspot/share/gc/shared/owstTaskTerminator.cpp
index 3c32ab627..2856a9981 100644
--- a/src/hotspot/share/gc/shared/owstTaskTerminator.cpp
+++ b/src/hotspot/share/gc/shared/owstTaskTerminator.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
+ * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
@@ -38,15 +38,17 @@ bool OWSTTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
   // Single worker, done
   if (_n_threads == 1) {
     _offered_termination = 1;
+    assert(!peek_in_queue_set(), "Precondition");
     return true;
   }
 
   _blocker->lock_without_safepoint_check();
-  // All arrived, done
   _offered_termination++;
+  // All arrived, done
   if (_offered_termination == _n_threads) {
     _blocker->notify_all();
     _blocker->unlock();
+    assert(!peek_in_queue_set(), "Precondition");
     return true;
   }
 
@@ -59,21 +61,31 @@ bool OWSTTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
 
       if (do_spin_master_work(terminator)) {
         assert(_offered_termination == _n_threads, "termination condition");
+        assert(!peek_in_queue_set(), "Precondition");
         return true;
       } else {
         _blocker->lock_without_safepoint_check();
+        // There is possibility that termination is reached between dropping the lock
+        // before returning from do_spin_master_work() and acquiring lock above.
+        if (_offered_termination == _n_threads) {
+          _blocker->unlock();
+          assert(!peek_in_queue_set(), "Precondition");
+          return true;
+        }
       }
     } else {
       _blocker->wait(true, WorkStealingSleepMillis);
 
       if (_offered_termination == _n_threads) {
         _blocker->unlock();
+        assert(!peek_in_queue_set(), "Precondition");
         return true;
       }
     }
 
     size_t tasks = tasks_in_queue_set();
     if (exit_termination(tasks, terminator)) {
+      assert_lock_strong(_blocker);
       _offered_termination--;
       _blocker->unlock();
       return false;
@@ -153,19 +165,24 @@ bool OWSTTaskTerminator::do_spin_master_work(TerminatorTerminator* terminator) {
       _total_peeks++;
 #endif
     size_t tasks = tasks_in_queue_set();
-    if (exit_termination(tasks, terminator)) {
+    bool exit = exit_termination(tasks, terminator);
+    {
       MonitorLockerEx locker(_blocker, Mutex::_no_safepoint_check_flag);
-      if (tasks >= _offered_termination - 1) {
-        locker.notify_all();
-      } else {
-        for (; tasks > 1; tasks--) {
-          locker.notify();
+      // Termination condition reached
+      if (_offered_termination == _n_threads) {
+        _spin_master = NULL;
+        return true;
+      } else if (exit) {
+        if (tasks >= _offered_termination - 1) {
+          locker.notify_all();
+        } else {
+          for (; tasks > 1; tasks--) {
+            locker.notify();
+          }
         }
+        _spin_master = NULL;
+        return false;
       }
-      _spin_master = NULL;
-      return false;
-    } else if (_offered_termination == _n_threads) {
-      return true;
     }
   }
 }
diff --git a/src/hotspot/share/gc/shared/owstTaskTerminator.hpp b/src/hotspot/share/gc/shared/owstTaskTerminator.hpp
index 9e6fe135a..190033eb7 100644
--- a/src/hotspot/share/gc/shared/owstTaskTerminator.hpp
+++ b/src/hotspot/share/gc/shared/owstTaskTerminator.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
+ * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
@@ -55,6 +55,7 @@ public:
   }
 
   virtual ~OWSTTaskTerminator() {
+    assert(_spin_master == NULL, "Should have been reset");
     assert(_blocker != NULL, "Can not be NULL");
     delete _blocker;
   }
diff --git a/src/hotspot/share/gc/shared/taskqueue.cpp b/src/hotspot/share/gc/shared/taskqueue.cpp
index 47639bdf9..697c13645 100644
--- a/src/hotspot/share/gc/shared/taskqueue.cpp
+++ b/src/hotspot/share/gc/shared/taskqueue.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 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
@@ -25,6 +25,9 @@
 #include "precompiled.hpp"
 #include "gc/shared/taskqueue.hpp"
 #include "gc/shared/owstTaskTerminator.hpp"
+#if INCLUDE_SHENANDOAHGC
+#include "gc/shenandoah/shenandoahHeap.hpp"
+#endif
 #include "oops/oop.inline.hpp"
 #include "logging/log.hpp"
 #include "runtime/atomic.hpp"
@@ -118,6 +121,14 @@ ParallelTaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set) :
   _queue_set(queue_set),
   _offered_termination(0) {}
 
+ParallelTaskTerminator::~ParallelTaskTerminator() {
+  assert(_offered_termination == 0 || !peek_in_queue_set(), "Precondition");
+#if INCLUDE_SHENANDOAHGC
+  if (UseShenandoahGC && ShenandoahHeap::heap()->cancelled_gc()) return;
+#endif
+  assert(_offered_termination == 0 || _offered_termination == _n_threads, "Terminated or aborted" );
+}
+
 bool ParallelTaskTerminator::peek_in_queue_set() {
   return _queue_set->peek();
 }
@@ -162,6 +173,7 @@ ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
     assert(_offered_termination <= _n_threads, "Invariant");
     // Are all threads offering termination?
     if (_offered_termination == _n_threads) {
+      assert(!peek_in_queue_set(), "Precondition");
       return true;
     } else {
       // Look for more work.
@@ -211,9 +223,7 @@ ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
 #endif
       if (peek_in_queue_set() ||
           (terminator != NULL && terminator->should_exit_termination())) {
-        Atomic::dec(&_offered_termination);
-        assert(_offered_termination < _n_threads, "Invariant");
-        return false;
+        return complete_or_exit_termination();
       }
     }
   }
@@ -229,6 +239,23 @@ void ParallelTaskTerminator::print_termination_counts() {
 }
 #endif
 
+bool ParallelTaskTerminator::complete_or_exit_termination() {
+  // If termination is ever reached, terminator should stay in such state,
+  // so that all threads see the same state
+  uint current_offered = _offered_termination;
+  uint expected_value;
+  do {
+    if (current_offered == _n_threads) {
+      assert(!peek_in_queue_set(), "Precondition");
+      return true;
+    }
+    expected_value = current_offered;
+  } while ((current_offered = Atomic::cmpxchg(current_offered - 1, &_offered_termination, current_offered)) != expected_value);
+
+  assert(_offered_termination < _n_threads, "Invariant");
+  return false;
+}
+
 void ParallelTaskTerminator::reset_for_reuse() {
   if (_offered_termination != 0) {
     assert(_offered_termination == _n_threads,
diff --git a/src/hotspot/share/gc/shared/taskqueue.hpp b/src/hotspot/share/gc/shared/taskqueue.hpp
index 1b60a62c2..110757684 100644
--- a/src/hotspot/share/gc/shared/taskqueue.hpp
+++ b/src/hotspot/share/gc/shared/taskqueue.hpp
@@ -491,11 +491,18 @@ protected:
   virtual void yield();
   void sleep(uint millis);
 
+  // Called when exiting termination is requested.
+  // When the request is made, terminator may have already terminated
+  // (e.g. all threads are arrived and offered termination). In this case,
+  // it should ignore the request and complete the termination.
+  // Return true if termination is completed. Otherwise, return false.
+  bool complete_or_exit_termination();
 public:
 
   // "n_threads" is the number of threads to be terminated.  "queue_set" is a
   // queue sets of work queues of other threads.
   ParallelTaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set);
+  virtual ~ParallelTaskTerminator();
 
   // The current thread has no work, and is ready to terminate if everyone
   // else is.  If returns "true", all threads are terminated.  If returns
-- 
2.19.1