1 files changed, 21 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/rack/lock.rb b/actionpack/lib/action_dispatch/rack/lock.rb
new file mode 100644
index 0000000000..9bf1889065
--- /dev/null
+++ b/actionpack/lib/action_dispatch/rack/lock.rb
@@ -0,0 +1,21 @@
+module Rack
+  # Rack::Lock was commited to Rack core
+  # http://github.com/rack/rack/commit/7409b0c
+  # Remove this when Rack 1.0 is released
+  unless defined? Lock
+    class Lock
+      FLAG = 'rack.multithread'.freeze
+
+      def initialize(app, lock = Mutex.new)
+        @app, @lock = app, lock
+      end
+
+      def call(env)
+        old, env[FLAG] = env[FLAG], false
+        @lock.synchronize { @app.call(env) }
+      ensure
+        env[FLAG] = old
+      end
+    end
+  end
+end