--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Thu Nov 06 09:15:23 2014 -0800
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Wed Nov 19 12:52:56 2014 -0800
@@ -27,6 +27,7 @@
 #endif
 
 #include "precompiled.hpp"
+#include "classfile/metadataOnStackMark.hpp"
 #include "code/codeCache.hpp"
 #include "code/icBuffer.hpp"
 #include "gc_implementation/g1/bufferingOopClosure.hpp"
@@ -5133,6 +5134,10 @@
         clean_nmethod(claimed_nmethods[i]);
       }
     }
+
+    // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
+    // Need to retire the buffers now that this thread has stopped cleaning nmethods.
+    MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
   }
 
   void work_second_pass(uint worker_id) {
@@ -5185,6 +5190,9 @@
     // G1 specific cleanup work that has
     // been moved here to be done in parallel.
     ik->clean_dependent_nmethods();
+    if (JvmtiExport::has_redefined_a_class()) {
+      InstanceKlass::purge_previous_versions(ik);
+    }
   }
 
   void work() {
@@ -5219,8 +5227,18 @@
       _klass_cleaning_task(is_alive) {
   }
 
+  void pre_work_verification() {
+    assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
+  }
+
+  void post_work_verification() {
+    assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
+  }
+
   // The parallel work done by all worker threads.
   void work(uint worker_id) {
+    pre_work_verification();
+
     // Do first pass of code cache cleaning.
     _code_cache_task.work_first_pass(worker_id);
 
@@ -5239,6 +5257,8 @@
 
     // Clean all klasses that were not unloaded.
     _klass_cleaning_task.work();
+
+    post_work_verification();
   }
 };