--- old/src/share/vm/gc/g1/g1CollectedHeap.cpp	2017-07-28 14:29:29.453715802 +0200
+++ new/src/share/vm/gc/g1/g1CollectedHeap.cpp	2017-07-28 14:29:29.325710530 +0200
@@ -4389,6 +4389,15 @@
   rp->verify_no_references_recorded();
   assert(!rp->discovery_enabled(), "should have been disabled");
 
+  // If during an initial mark pause we install a pending list head which is not otherwise reachable
+  // ensure that it is marked in the bitmap for concurrent marking to discover.
+  if (collector_state()->during_initial_mark_pause()) {
+    oop pll_head = Universe::reference_pending_list();
+    if (pll_head != NULL) {
+      _cm->grayRoot(pll_head);
+    }
+  }
+
   // FIXME
   // CM's reference processing also cleans up the string and symbol tables.
   // Should we do that here also? We could, but it is a serial operation
--- old/src/share/vm/memory/universe.cpp	2017-07-28 14:29:29.961736726 +0200
+++ new/src/share/vm/memory/universe.cpp	2017-07-28 14:29:29.833731454 +0200
@@ -497,7 +497,11 @@
 #define assert_pll_ownership() assert_pll_locked(owned_by_self)
 
 oop Universe::reference_pending_list() {
-  assert_pll_ownership();
+  if (Thread::current()->is_VM_thread()) {
+    assert_pll_locked(is_locked);
+  } else {
+    assert_pll_ownership();
+  }
   return _reference_pending_list;
 }