--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMarkThread.cpp	Mon Jun 28 14:13:18 2010 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMarkThread.cpp	Mon Jun 28 14:13:17 2010 -0400
@@ -266,6 +266,12 @@
       _cm->clearNextBitmap();
       _sts.leave();
     }
+
+    // Update the number of full collections that have been
+    // completed. This will also notify the FullGCCount_lock in case a
+    // Java thread is waiting for a full GC to happen (e.g., it
+    // called System.gc() with +ExplicitGCInvokesConcurrent).
+    g1->increment_full_collections_completed(true /* outer */);
   }
   assert(_should_terminate, "just checking");