diff -r b294421fa3c5 -r 2f50bc369470 src/share/vm/gc_implementation/g1/g1MarkSweep.cpp
--- a/src/share/vm/gc_implementation/g1/g1MarkSweep.cpp	Fri Apr 26 09:53:22 2013 +0200
+++ b/src/share/vm/gc_implementation/g1/g1MarkSweep.cpp	Fri Apr 26 10:40:36 2013 +0200
@@ -144,29 +144,25 @@
                                     &GenMarkSweep::follow_stack_closure,
                                     NULL);
 
-  // Follow system dictionary roots and unload classes
+
+  // This is the point where the entire marking should have completed.
+  assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
+
+  // Unload classes and purge the SystemDictionary.
   bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
-  assert(GenMarkSweep::_marking_stack.is_empty(),
-         "stack should be empty by now");
 
-  // Follow code cache roots (has to be done after system dictionary,
-  // assumes all live klasses are marked)
+  // Unload nmethods.
   CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
-  GenMarkSweep::follow_stack();
 
-  // Update subklass/sibling/implementor links of live klasses
+  // Prune dead klasses from subklass/sibling/implementor lists.
   Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
-  assert(GenMarkSweep::_marking_stack.is_empty(),
-         "stack should be empty by now");
 
-  // Visit interned string tables and delete unmarked oops
+  // Delete entries for dead interned strings.
   StringTable::unlink(&GenMarkSweep::is_alive);
+
   // Clean up unreferenced symbols in symbol table.
   SymbolTable::unlink();
 
-  assert(GenMarkSweep::_marking_stack.is_empty(),
-         "stack should be empty by now");
-
   if (VerifyDuringGC) {
     HandleMark hm;  // handle scope
     COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);