--- old/src/share/vm/gc/g1/concurrentMark.cpp	2015-05-20 11:05:15.925869637 +0200
+++ new/src/share/vm/gc/g1/concurrentMark.cpp	2015-05-20 11:05:15.765864232 +0200
@@ -1937,18 +1937,10 @@
 
   HeapRegionRemSet::reset_for_cleanup_tasks();
 
-  uint n_workers;
-
   // Do counting once more with the world stopped for good measure.
   G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
 
-  g1h->set_par_threads();
-  n_workers = g1h->n_par_threads();
-  assert(g1h->n_par_threads() == n_workers,
-         "Should not have been reset");
   g1h->workers()->run_task(&g1_par_count_task);
-  // Done with the parallel phase so reset to 0.
-  g1h->set_par_threads(0);
 
   if (VerifyDuringGC) {
     // Verify that the counting data accumulated during marking matches
@@ -1964,10 +1956,7 @@
                                                  &expected_region_bm,
                                                  &expected_card_bm);
 
-    g1h->set_par_threads((int)n_workers);
     g1h->workers()->run_task(&g1_par_verify_task);
-    // Done with the parallel phase so reset to 0.
-    g1h->set_par_threads(0);
 
     guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
   }
@@ -1989,11 +1978,11 @@
 
   g1h->reset_gc_time_stamp();
 
+  uint n_workers = _g1h->workers()->active_workers();
+
   // Note end of marking in all heap regions.
   G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
-  g1h->set_par_threads((int)n_workers);
   g1h->workers()->run_task(&g1_par_note_end_task);
-  g1h->set_par_threads(0);
   g1h->check_gc_time_stamps();
 
   if (!cleanup_list_is_empty()) {
@@ -2008,9 +1997,7 @@
   if (G1ScrubRemSets) {
     double rs_scrub_start = os::elapsedTime();
     G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm, n_workers);
-    g1h->set_par_threads((int)n_workers);
     g1h->workers()->run_task(&g1_par_scrub_rs_task);
-    g1h->set_par_threads(0);
 
     double rs_scrub_end = os::elapsedTime();
     double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
@@ -2311,9 +2298,7 @@
   // and overflow handling in CMTask::do_marking_step() knows
   // how many workers to wait for.
   _cm->set_concurrency(_active_workers);
-  _g1h->set_par_threads(_active_workers);
   _workers->run_task(&proc_task_proxy);
-  _g1h->set_par_threads(0);
 }
 
 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
@@ -2343,9 +2328,7 @@
   // and overflow handling in CMTask::do_marking_step() knows
   // how many workers to wait for.
   _cm->set_concurrency(_active_workers);
-  _g1h->set_par_threads(_active_workers);
   _workers->run_task(&enq_task_proxy);
-  _g1h->set_par_threads(0);
 }
 
 void ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) {
@@ -2607,7 +2590,6 @@
 
   g1h->ensure_parsability(false);
 
-  StrongRootsScope srs;
   // this is remark, so we'll use up all active threads
   uint active_workers = g1h->workers()->active_workers();
   if (active_workers == 0) {
@@ -2621,13 +2603,15 @@
   // constructor and pass values of the active workers
   // through the gang in the task.
 
-  CMRemarkTask remarkTask(this, active_workers);
-  // We will start all available threads, even if we decide that the
-  // active_workers will be fewer. The extra ones will just bail out
-  // immediately.
-  g1h->set_par_threads(active_workers);
-  g1h->workers()->run_task(&remarkTask);
-  g1h->set_par_threads(0);
+  {
+    StrongRootsScope srs(active_workers);
+
+    CMRemarkTask remarkTask(this, active_workers);
+    // We will start all available threads, even if we decide that the
+    // active_workers will be fewer. The extra ones will just bail out
+    // immediately.
+    g1h->workers()->run_task(&remarkTask);
+  }
 
   SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
   guarantee(has_overflown() ||
@@ -3000,9 +2984,7 @@
   G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
                                            _max_worker_id, n_workers);
 
-  _g1h->set_par_threads(n_workers);
   _g1h->workers()->run_task(&g1_par_agg_task);
-  _g1h->set_par_threads(0);
 }
 
 // Clear the per-worker arrays used to store the per-region counting data