--- old/src/share/vm/gc/g1/g1CollectedHeap.cpp	2017-07-24 16:40:37.200313839 +0200
+++ new/src/share/vm/gc/g1/g1CollectedHeap.cpp	2017-07-24 16:40:37.040313845 +0200
@@ -2458,6 +2458,10 @@
   return _cmThread->request_concurrent_phase(phase);
 }
 
+void G1CollectedHeap::verify_nmethod_roots(nmethod* nmethod) {
+
+}
+
 class PrintRegionClosure: public HeapRegionClosure {
   outputStream* _st;
 public:
@@ -5419,16 +5423,14 @@
 };
 
 void G1CollectedHeap::register_nmethod(nmethod* nm) {
-  CollectedHeap::register_nmethod(nm);
-
+  assert_locked_or_safepoint(CodeCache_lock);
   guarantee(nm != NULL, "sanity");
   RegisterNMethodOopClosure reg_cl(this, nm);
   nm->oops_do(&reg_cl);
 }
 
 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
-  CollectedHeap::unregister_nmethod(nm);
-
+  assert_locked_or_safepoint(CodeCache_lock);
   guarantee(nm != NULL, "sanity");
   UnregisterNMethodOopClosure reg_cl(this, nm);
   nm->oops_do(&reg_cl, true);