--- old/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	2013-09-09 10:14:26.593378452 +0200
+++ new/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	2013-09-09 10:14:26.497376688 +0200
@@ -36,6 +36,12 @@
   _kind = G1SATBCT;
 }
 
+void G1SATBCardTableModRefBS::g1_dirty_young(const MemRegion& mr) {
+  jbyte *const first = byte_for(mr.start());
+  jbyte *const last = byte_after(mr.last());
+
+  memset(first, g1_young_gen, last - first);
+}
 
 void G1SATBCardTableModRefBS::enqueue(oop pre_val) {
   // Nulls should have been already filtered.
@@ -76,7 +82,11 @@
 void
 G1SATBCardTableLoggingModRefBS::write_ref_field_work(void* field,
                                                      oop new_val) {
-  jbyte* byte = byte_for(field);
+  volatile jbyte* byte = byte_for(field);
+  if (*byte == g1_young_gen) {
+    return;
+  }
+  OrderAccess::storeload();
   if (*byte != dirty_card) {
     *byte = dirty_card;
     Thread* thr = Thread::current();
@@ -108,7 +118,7 @@
 
 void
 G1SATBCardTableLoggingModRefBS::invalidate(MemRegion mr, bool whole_heap) {
-  jbyte* byte = byte_for(mr.start());
+  volatile jbyte* byte = byte_for(mr.start());
   jbyte* last_byte = byte_for(mr.last());
   Thread* thr = Thread::current();
   if (whole_heap) {
@@ -120,22 +130,28 @@
     // Enqueue if necessary.
     if (thr->is_Java_thread()) {
       JavaThread* jt = (JavaThread*)thr;
-      while (byte <= last_byte) {
+      for (; byte <= last_byte; byte++) {
+        if (*byte == g1_young_gen) {
+          continue;
+        }
+        OrderAccess::storeload();
         if (*byte != dirty_card) {
           *byte = dirty_card;
           jt->dirty_card_queue().enqueue(byte);
         }
-        byte++;
       }
     } else {
       MutexLockerEx x(Shared_DirtyCardQ_lock,
                       Mutex::_no_safepoint_check_flag);
-      while (byte <= last_byte) {
+      for (; byte <= last_byte; byte++) {
+        if (*byte == g1_young_gen) {
+          continue;
+        }
+        OrderAccess::storeload();
         if (*byte != dirty_card) {
           *byte = dirty_card;
           _dcqs.shared_dirty_card_queue()->enqueue(byte);
         }
-        byte++;
       }
     }
   }