src/hotspot/share/gc/shared/workgroup.cpp

*** 431,440 ****
--- 431,442 ----
    assert(t < _n_tasks, "bad task id.");
    uint old = _tasks[t];
    if (old == 0) {
      old = Atomic::cmpxchg(1u, &_tasks[t], 0u);
    }
+ 
+   DEBUG_ONLY(OrderAccess::fence()); // Prevent below load from floating up.
    assert(_tasks[t] == 1, "What else?");
    bool res = old == 0;
  #ifdef ASSERT
    if (res) {
      assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");