--- a/src/share/vm/memory/cardTableModRefBS.cpp	Mon Mar 02 16:37:04 2009 -0800
+++ b/src/share/vm/memory/cardTableModRefBS.cpp	Fri Mar 06 13:50:14 2009 -0800
@@ -356,18 +356,62 @@
   inline_write_ref_field(field, newVal);
 }
 
+/*
+   Claimed and deferred bits are used together in G1 during the evacuation
+   pause. These bits can have the following state transitions:
+   1. The claimed bit can be put over any other card state. Except that
+      the "dirty -> dirty and claimed" transition is checked for in
+      G1 code and is not used.
+   2. Deferred bit can be set only if the previous state of the card
+      was either clean or claimed. mark_card_deferred() is wait-free.
+      We do not care if the operation is be successful because if
+      it does not it will only result in duplicate entry in the update
+      buffer because of the "cache-miss". So it's not worth spinning.
+ */
+
 
 bool CardTableModRefBS::claim_card(size_t card_index) {
   jbyte val = _byte_map[card_index];
-  if (val != claimed_card_val()) {
-    jbyte res = Atomic::cmpxchg((jbyte) claimed_card_val(), &_byte_map[card_index], val);
-    if (res == val)
+  assert(val != dirty_card_val(), "Shouldn't claim a dirty card");
+  while (val == clean_card_val() ||
+         (val & (clean_card_mask_val() | claimed_card_val())) != claimed_card_val()) {
+    jbyte new_val = val;
+    if (val == clean_card_val()) {
+      new_val = (jbyte)claimed_card_val();
+    } else {
+      new_val = val | (jbyte)claimed_card_val();
+    }
+    jbyte res = Atomic::cmpxchg(new_val, &_byte_map[card_index], val);
+    if (res == val) {
       return true;
-    else return false;
+    }
+    val = res;
   }
   return false;
 }
 
+bool CardTableModRefBS::mark_card_deferred(size_t card_index) {
+  jbyte val = _byte_map[card_index];
+  // It's already processed
+  if ((val & (clean_card_mask_val() | deferred_card_val())) == deferred_card_val()) {
+    return false;
+  }
+  // Cached bit can be installed either on a clean card or on a claimed card.
+  jbyte new_val = val;
+  if (val == clean_card_val()) {
+    new_val = (jbyte)deferred_card_val();
+  } else {
+    if (val & claimed_card_val()) {
+      new_val = val | (jbyte)deferred_card_val();
+    }
+  }
+  if (new_val != val) {
+    Atomic::cmpxchg(new_val, &_byte_map[card_index], val);
+  }
+  return true;
+}
+
+
 void CardTableModRefBS::non_clean_card_iterate(Space* sp,
                                                MemRegion mr,
                                                DirtyCardToOopClosure* dcto_cl,