1 files changed, 35 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/dependencies/interlock.rb b/activesupport/lib/active_support/dependencies/interlock.rb
new file mode 100644
index 0000000000..c3601bac13
--- /dev/null
+++ b/activesupport/lib/active_support/dependencies/interlock.rb
@@ -0,0 +1,35 @@
+require 'active_support/concurrency/share_lock'
+
+module ActiveSupport
+  module Dependencies #:nodoc:
+    class Interlock
+      def initialize
+        @lock = ActiveSupport::Concurrency::ShareLock.new(true)
+      end
+
+      def loading
+        @lock.exclusive do
+          yield
+        end
+      end
+
+      def start_running
+        @lock.start_sharing
+      end
+
+      def done_running
+        @lock.stop_sharing
+      end
+
+      def running
+        @lock.sharing do
+          yield
+        end
+      end
+
+      # Match the Mutex API, so we can be used by Rack::Lock
+      alias :lock :start_running
+      alias :unlock :done_running
+    end
+  end
+end