From 6d31e431c3bb09cf386c0fbef169a5307e689775 Mon Sep 17 00:00:00 2001
From: Malcolm Tredinnick <malcolm.tredinnick@gmail.com>
Date: Sun, 12 Aug 2007 10:24:05 +0000
Subject: [PATCH] Fixed #4909 -- Fixed a race condition with middleware
 initialisation in multi-threaded setups. Thanks, colin@owlfish.com.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5868 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 AUTHORS                      | 1 +
 django/core/handlers/wsgi.py | 9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/AUTHORS b/AUTHORS
index d2f303c12b..27eaf5bd1d 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -78,6 +78,7 @@ answer newbie questions, and generally made Django that much better:
     Bryan Chow <bryan at verdjn dot com>
     Michal Chruszcz <troll@pld-linux.org>
     Ian Clelland <clelland@gmail.com>
+    colin@owlfish.com
     crankycoder@gmail.com
     Pete Crosier <pete.crosier@gmail.com>
     Matt Croydon <http://www.postneo.com/>
diff --git a/django/core/handlers/wsgi.py b/django/core/handlers/wsgi.py
index 2db83fccfc..99d400d1bb 100644
--- a/django/core/handlers/wsgi.py
+++ b/django/core/handlers/wsgi.py
@@ -6,6 +6,7 @@ from django.utils.encoding import force_unicode
 from django import http
 from pprint import pformat
 from shutil import copyfileobj
+from threading import Lock
 try:
     from cStringIO import StringIO
 except ImportError:
@@ -176,13 +177,19 @@ class WSGIRequest(http.HttpRequest):
     raw_post_data = property(_get_raw_post_data)
 
 class WSGIHandler(BaseHandler):
+    initLock = Lock()
+
     def __call__(self, environ, start_response):
         from django.conf import settings
 
         # Set up middleware if needed. We couldn't do this earlier, because
         # settings weren't available.
         if self._request_middleware is None:
-            self.load_middleware()
+            self.initLock.acquire()
+            # Check that middleware is still uninitialised.
+            if self._request_middleware is None:
+                self.load_middleware()
+            self.initLock.release()
 
         dispatcher.send(signal=signals.request_started)
         try: