diff -r e9be0e04635a -r 0af8b0718fc9 src/share/vm/prims/jvmtiRedefineClasses.cpp
--- a/src/share/vm/prims/jvmtiRedefineClasses.cpp	Tue Jan 06 07:05:05 2009 -0800
+++ b/src/share/vm/prims/jvmtiRedefineClasses.cpp	Sun Jan 11 16:58:24 2009 -0800
@@ -1230,8 +1230,14 @@
 
   // Constant pools are not easily reused so we allocate a new one
   // each time.
+  // merge_cp is created unsafe for concurrent GC processing.  It
+  // should be marked safe before discarding it because, even if
+  // garbage.  If it crosses a card boundary, it may be scanned
+  // in order to find the start of the first complete object on the card.
   constantPoolHandle merge_cp(THREAD,
-    oopFactory::new_constantPool(merge_cp_length, THREAD));
+    oopFactory::new_constantPool(merge_cp_length,
+                                 methodOopDesc::IsUnsafeConc,
+                                 THREAD));
   int orig_length = old_cp->orig_length();
   if (orig_length == 0) {
     // This old_cp is an actual original constant pool. We save
@@ -1274,6 +1280,7 @@
       // rewriting so we can't use the old constant pool with the new
       // class.
 
+      merge_cp()->set_is_conc_safe(true);
       merge_cp = constantPoolHandle();  // toss the merged constant pool
     } else if (old_cp->length() < scratch_cp->length()) {
       // The old constant pool has fewer entries than the new constant
@@ -1283,6 +1290,7 @@
       // rewriting so we can't use the new constant pool with the old
       // class.
 
+      merge_cp()->set_is_conc_safe(true);
       merge_cp = constantPoolHandle();  // toss the merged constant pool
     } else {
       // The old constant pool has more entries than the new constant
@@ -1296,6 +1304,7 @@
       set_new_constant_pool(scratch_class, merge_cp, merge_cp_length, true,
         THREAD);
       // drop local ref to the merged constant pool
+      merge_cp()->set_is_conc_safe(true);
       merge_cp = constantPoolHandle();
     }
   } else {
@@ -1325,7 +1334,10 @@
     // GCed.
     set_new_constant_pool(scratch_class, merge_cp, merge_cp_length, true,
       THREAD);
+    merge_cp()->set_is_conc_safe(true);
   }
+  assert(old_cp()->is_conc_safe(), "Just checking");
+  assert(scratch_cp()->is_conc_safe(), "Just checking");
 
   return JVMTI_ERROR_NONE;
 } // end merge_cp_and_rewrite()
@@ -2314,13 +2326,16 @@
     // worst case merge situation. We want to associate the minimum
     // sized constant pool with the klass to save space.
     constantPoolHandle smaller_cp(THREAD,
-      oopFactory::new_constantPool(scratch_cp_length, THREAD));
+      oopFactory::new_constantPool(scratch_cp_length,
+                                   methodOopDesc::IsUnsafeConc,
+                                   THREAD));
     // preserve orig_length() value in the smaller copy
     int orig_length = scratch_cp->orig_length();
     assert(orig_length != 0, "sanity check");
     smaller_cp->set_orig_length(orig_length);
     scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
     scratch_cp = smaller_cp;
+    smaller_cp()->set_is_conc_safe(true);
   }
 
   // attach new constant pool to klass
@@ -2516,6 +2531,7 @@
 
     rewrite_cp_refs_in_stack_map_table(method, THREAD);
   } // end for each method
+  assert(scratch_cp()->is_conc_safe(), "Just checking");
 } // end set_new_constant_pool()