--- old/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	2015-05-13 14:06:06.194206065 +0200
+++ new/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	2015-05-13 14:06:06.074202076 +0200
@@ -3016,14 +3016,12 @@
       StrongRootsScope srs(n_workers);
 
       CMSParInitialMarkTask tsk(this, &srs, n_workers);
-      gch->set_par_threads(n_workers);
       initialize_sequential_subtasks_for_young_gen_rescan(n_workers);
       if (n_workers > 1) {
         workers->run_task(&tsk);
       } else {
         tsk.work(0);
       }
-      gch->set_par_threads(0);
     } else {
       // The serial version.
       CLDToOopClosure cld_closure(&notOlder, true);
@@ -5087,8 +5085,6 @@
 
   CMSParRemarkTask tsk(this, cms_space, n_workers, workers, task_queues(), &srs);
 
-  // Set up for parallel process_roots work.
-  gch->set_par_threads(n_workers);
   // We won't be iterating over the cards in the card table updating
   // the younger_gen cards, so we shouldn't call the following else
   // the verification code as well as subsequent younger_refs_iterate
@@ -5126,7 +5122,6 @@
     tsk.work(0);
   }
 
-  gch->set_par_threads(0);  // 0 ==> non-parallel.
   // restore, single-threaded for now, any preserved marks
   // as a result of work_q overflow
   restore_preserved_marks_if_any();