Return processing lock to dispatcher. This fixes class reloading race…

… in development mode.

Without this fix class reloading is unguarded and our app easily hits this race.

This reverts commit 19db0b7 "Added back ActionController::Base.allow_concurrency flag and moved lock down to controller processing."

actionpack/lib/action_controller/base.rb

@@ -284,14 +284,6 @@ class Base
     @@debug_routes = true
     cattr_accessor :debug_routes
 
-    # Indicates whether to allow concurrent action processing. Your
-    # controller actions and any other code they call must also behave well
-    # when called from concurrent threads. Turned off by default.
-    @@allow_concurrency = false
-    cattr_accessor :allow_concurrency
-
-    @@guard = Monitor.new
-
     # Modern REST web services often need to submit complex data to the web application.
     # The <tt>@@param_parsers</tt> hash lets you register handlers which will process the HTTP body and add parameters to the
     # <tt>params</tt> hash. These handlers are invoked for POST and PUT requests.
@@ -532,12 +524,7 @@ def process(request, response, method = :perform_action, *arguments) #:nodoc:
         assign_names
 
         log_processing
-
-        if @@allow_concurrency
-          send(method, *arguments)
-        else
-          @@guard.synchronize { send(method, *arguments) }
-        end
+        send(method, *arguments)
 
         send_response
       ensure

actionpack/lib/action_controller/dispatcher.rb

@@ -2,6 +2,8 @@ module ActionController
   # Dispatches requests to the appropriate controller and takes care of
   # reloading the app after each request when Dependencies.load? is true.
   class Dispatcher
+    @@guard = Mutex.new
+
     class << self
       def define_dispatcher_callbacks(cache_classes)
         unless cache_classes
@@ -99,13 +101,15 @@ def initialize(output = $stdout, request = nil, response = nil)
     end
 
     def dispatch
-      begin
-        run_callbacks :before_dispatch
-        handle_request
-      rescue Exception => exception
-        failsafe_rescue exception
-      ensure
-        run_callbacks :after_dispatch, :enumerator => :reverse_each
+      @@guard.synchronize do
+        begin
+          run_callbacks :before_dispatch
+          handle_request
+        rescue Exception => exception
+          failsafe_rescue exception
+        ensure
+          run_callbacks :after_dispatch, :enumerator => :reverse_each
+        end
       end
     end