Fix another race condition.

From 2c667f69aa2daac5ee6c29ca9679616e2a71532a.

Thanks @pwnall for the heads-up.

Conflicts:

	activerecord/lib/active_record/core.rb

1 files changed, 10 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index fa5846de39..198db715b2 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -5,6 +5,7 @@ end
 
 require 'yaml'
 require 'set'
+require 'thread'
 require 'active_support/benchmarkable'
 require 'active_support/dependencies'
 require 'active_support/descendants_tracker'
@@ -390,12 +391,18 @@ module ActiveRecord #:nodoc:
 
     class << self # Class methods
       def inherited(child_class) #:nodoc:
-        # force attribute methods to be higher in inheritance hierarchy than other generated methods
-        child_class.generated_attribute_methods
-        child_class.generated_feature_methods
+        child_class.initialize_generated_modules
         super
       end
 
+      def initialize_generated_modules #:nodoc:
+        @attribute_methods_mutex = Mutex.new
+
+        # force attribute methods to be higher in inheritance hierarchy than other generated methods
+        generated_attribute_methods
+        generated_feature_methods
+      end
+
       def generated_feature_methods
         @generated_feature_methods ||= begin
           mod = const_set(:GeneratedFeatureMethods, Module.new)