--- old/src/hotspot/share/gc/shared/taskqueue.hpp	2020-01-17 17:08:35.860135673 +0100
+++ new/src/hotspot/share/gc/shared/taskqueue.hpp	2020-01-17 17:08:35.757135678 +0100
@@ -357,7 +357,8 @@
   static int randomParkAndMiller(int* seed0);
 public:
   // Returns "true" if some TaskQueue in the set contains a task.
-  virtual bool peek() = 0;
+  virtual bool   peek() = 0;
+  virtual size_t tasks() = 0;
 };
 
 template <MEMFLAGS F> class TaskQueueSetSuperImpl: public CHeapObj<F>, public TaskQueueSetSuper {
@@ -389,6 +390,7 @@
   bool steal(uint queue_num, int* seed, E& t);
 
   bool peek();
+  size_t tasks();
 
   uint size() const { return _n; }
 };
@@ -414,6 +416,16 @@
   return false;
 }
 
+template<class T, MEMFLAGS F>
+size_t GenericTaskQueueSet<T, F>::tasks() {
+  size_t n = 0;
+  for (uint j = 0; j < _n; j++) {
+    n += _queues[j]->size();
+  }
+  return n;
+}
+
+
 // When to terminate from the termination protocol.
 class TerminatorTerminator: public CHeapObj<mtInternal> {
 public:
@@ -426,7 +438,7 @@
 #undef TRACESPINNING
 
 class ParallelTaskTerminator: public StackObj {
-private:
+protected:
   uint _n_threads;
   TaskQueueSetSuper* _queue_set;
 
@@ -462,7 +474,7 @@
   // As above, but it also terminates if the should_exit_termination()
   // method of the terminator parameter returns true. If terminator is
   // NULL, then it is ignored.
-  bool offer_termination(TerminatorTerminator* terminator);
+  virtual bool offer_termination(TerminatorTerminator* terminator);
 
   // Reset the terminator, so that it may be reused again.
   // The caller is responsible for ensuring that this is done