Explain why we have explicit marshaling methods

actionview/lib/action_view/template.rb

@@ -235,11 +235,15 @@ def encode!
       end
     end
 
-    def marshal_dump
+    
+    # Exceptions are marshaled when using the parallel test runner with DRb, so we need
+    # to ensure that references to the template object can be marshaled as well. This means forgoing
+    # the marshalling of the compiler mutex and instantiating that again on unmarshaling.
+    def marshal_dump # :nodoc:
       [ @source, @identifier, @handler, @compiled, @original_encoding, @locals, @virtual_path, @updated_at, @formats, @variants ]
     end
 
-    def marshal_load(array)
+    def marshal_load(array) # :nodoc:
       @source, @identifier, @handler, @compiled, @original_encoding, @locals, @virtual_path, @updated_at, @formats, @variants = *array
       @compile_mutex = Mutex.new
     end