module ActiveRecord::AttributeMethods::ClassMethods

def define_attribute_methods # :nodoc:
  return false if @attribute_methods_generated
  # Use a mutex; we don't want two threads simultaneously trying to define
  # attribute methods.
  generated_attribute_methods.synchronize do
    return false if @attribute_methods_generated
    superclass.define_attribute_methods unless base_class?
    super(attribute_names)
    @attribute_methods_generated = true
  end
end