--- old/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Tue Nov 14 13:26:52 2017
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Tue Nov 14 13:26:51 2017
@@ -81,6 +81,7 @@
 #include "runtime/atomic.hpp"
 #include "runtime/init.hpp"
 #include "runtime/orderAccess.inline.hpp"
+#include "runtime/threadSMR.hpp"
 #include "runtime/vmThread.hpp"
 #include "utilities/align.hpp"
 #include "utilities/globalDefinitions.hpp"
@@ -2649,11 +2650,9 @@
 
 size_t G1CollectedHeap::pending_card_num() {
   size_t extra_cards = 0;
-  JavaThread *curr = Threads::first();
-  while (curr != NULL) {
+  for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
     DirtyCardQueue& dcq = curr->dirty_card_queue();
     extra_cards += dcq.size();
-    curr = curr->next();
   }
   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
   size_t buffer_size = dcqs.buffer_size();