diff -r 9de67bf4244d -r 899bbbdcb6ea src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp	Tue Nov 02 16:02:46 2010 -0700
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp	Fri Nov 05 13:20:37 2010 -0700
@@ -1093,7 +1093,8 @@
 // perm_gen_verify_bit_map where we store the "deadness" information if
 // we did not sweep the perm gen in the most recent previous GC cycle.
 bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
-  assert (block_is_obj(p), "The address should point to an object");
+  assert(block_is_obj(p), "The address should point to an object");
+  assert(SafepointSynchronize::is_at_safepoint(), "Else races are possible");
 
   // If we're sweeping, we use object liveness information from the main bit map
   // for both perm gen and old gen.
@@ -1102,9 +1103,14 @@
   // main marking bit map (live_map below) is locked,
   // OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
   // is stable, because it's mutated only in the sweeping phase.
+  // NOTE: This method is also used by jmap where, if class unloading is
+  // off, the results can return "false" for legitimate perm objects,
+  // when we are not in the midst of a sweeping phase, which can result
+  // in jmap not reporting certain perm gen objects. This will be moot
+  // if/when the perm gen goes away in the future.
   if (_collector->abstract_state() == CMSCollector::Sweeping) {
     CMSBitMap* live_map = _collector->markBitMap();
-    return live_map->isMarked((HeapWord*) p);
+    return live_map->par_isMarked((HeapWord*) p);
   } else {
     // If we're not currently sweeping and we haven't swept the perm gen in
     // the previous concurrent cycle then we may have dead but unswept objects