--- a/hotspot/src/share/vm/gc/shared/workgroup.cpp	Tue Sep 20 00:34:54 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/workgroup.cpp	Tue Sep 20 11:41:43 2016 +0200
@@ -472,23 +472,21 @@
 }
 
 bool SequentialSubTasksDone::is_task_claimed(uint& t) {
-  uint* n_claimed_ptr = &_n_claimed;
-  t = *n_claimed_ptr;
+  t = _n_claimed;
   while (t < _n_tasks) {
-    jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
+    jint res = Atomic::cmpxchg(t+1, &_n_claimed, t);
     if (res == (jint)t) {
       return false;
     }
-    t = *n_claimed_ptr;
+    t = res;
   }
   return true;
 }
 
 bool SequentialSubTasksDone::all_tasks_completed() {
-  uint* n_completed_ptr = &_n_completed;
-  uint  complete        = *n_completed_ptr;
+  uint complete = _n_completed;
   while (true) {
-    uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
+    uint res = Atomic::cmpxchg(complete+1, &_n_completed, complete);
     if (res == complete) {
       break;
     }

--- a/hotspot/src/share/vm/gc/shared/workgroup.hpp	Tue Sep 20 00:34:54 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/workgroup.hpp	Tue Sep 20 11:41:43 2016 +0200
@@ -318,9 +318,9 @@
 // enumeration type.
 
 class SubTasksDone: public CHeapObj<mtInternal> {
-  uint* _tasks;
+  volatile uint* _tasks;
   uint _n_tasks;
-  uint _threads_completed;
+  volatile uint _threads_completed;
 #ifdef ASSERT
   volatile uint _claimed;
 #endif
@@ -363,11 +363,11 @@
 class SequentialSubTasksDone : public StackObj {
 protected:
   uint _n_tasks;     // Total number of tasks available.
-  uint _n_claimed;   // Number of tasks claimed.
+  volatile uint _n_claimed;   // Number of tasks claimed.
   // _n_threads is used to determine when a sub task is done.
   // See comments on SubTasksDone::_n_threads
   uint _n_threads;   // Total number of parallel threads.
-  uint _n_completed; // Number of completed threads.
+  volatile uint _n_completed; // Number of completed threads.
 
   void clear();