--- old/src/share/vm/gc_implementation/g1/g1RootProcessor.cpp	2015-05-13 14:03:41.309390109 +0200
+++ new/src/share/vm/gc_implementation/g1/g1RootProcessor.cpp	2015-05-13 14:03:41.185385988 +0200
@@ -90,11 +90,10 @@
 
 
 void G1RootProcessor::worker_has_discovered_all_strong_classes() {
-  uint n_workers = _g1h->n_par_threads();
   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
 
   uint new_value = (uint)Atomic::add(1, &_n_workers_discovered_strong_classes);
-  if (new_value == n_workers) {
+  if (new_value == n_workers()) {
     // This thread is last. Notify the others.
     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
     _lock.notify_all();
@@ -102,21 +101,20 @@
 }
 
 void G1RootProcessor::wait_until_all_strong_classes_discovered() {
-  uint n_workers = _g1h->n_par_threads();
   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
 
-  if ((uint)_n_workers_discovered_strong_classes != n_workers) {
+  if ((uint)_n_workers_discovered_strong_classes != n_workers()) {
     MonitorLockerEx ml(&_lock, Mutex::_no_safepoint_check_flag);
-    while ((uint)_n_workers_discovered_strong_classes != n_workers) {
+    while ((uint)_n_workers_discovered_strong_classes != n_workers()) {
       _lock.wait(Mutex::_no_safepoint_check_flag, 0, false);
     }
   }
 }
 
-G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h) :
+G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h, uint n_workers) :
     _g1h(g1h),
     _process_strong_tasks(new SubTasksDone(G1RP_PS_NumElements)),
-    _srs(),
+    _srs(n_workers),
     _lock(Mutex::leaf, "G1 Root Scanning barrier lock", false, Monitor::_safepoint_check_never),
     _n_workers_discovered_strong_classes(0) {}
 
@@ -253,7 +251,7 @@
 
   {
     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_i);
-    bool is_par = _g1h->n_par_threads() > 1;
+    bool is_par = n_workers() > 1;
     Threads::possibly_parallel_oops_do(is_par, strong_roots, thread_stack_clds, strong_code);
   }
 }
@@ -330,5 +328,13 @@
 }
 
 void G1RootProcessor::set_num_workers(uint active_workers) {
+  assert(active_workers == _srs.n_threads(),
+      err_msg("Mismatch between number of worker threads. active_workers: %u and n_workers(): %u",
+              active_workers,
+              _srs.n_threads()));
   _process_strong_tasks->set_n_threads(active_workers);
 }
+
+uint G1RootProcessor::n_workers() const {
+  return _srs.n_threads();
+}