--- old/src/share/vm/gc_implementation/g1/g1StringDedup.cpp	2015-05-13 14:06:07.254241300 +0200
+++ new/src/share/vm/gc_implementation/g1/g1StringDedup.cpp	2015-05-13 14:06:07.146237711 +0200
@@ -153,9 +153,7 @@
 
   G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash, phase_times);
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
-  g1h->set_par_threads();
   g1h->workers()->run_task(&task);
-  g1h->set_par_threads(0);
 }
 
 void G1StringDedup::threads_do(ThreadClosure* tc) {