src/share/vm/gc/serial/defNewGeneration.cpp

@@ -625,11 +625,13 @@
 
   assert(gch->no_allocs_since_save_marks(0),
          "save marks have not been newly set.");
 
   {
-    // SerialGC runs with n_workers == 0.
+    // DefNew needs to run with n_threads == 0, to make sure the serial
+    // version of the card table scanning code is used.
+    // See: CardTableModRefBS::non_clean_card_iterate_possibly_parallel.
     StrongRootsScope srs(0);
 
     gch->gen_process_roots(&srs,
                            _level,
                            true,  // Process younger gens, if any,