Pool: putlock must be created before child processes start.

celery/concurrency/processes/pool.py

@@ -562,13 +562,13 @@ class Pool(object):
 
         self._pool = []
         self._poolctrl = {}
+        self._putlock = LaxBoundedSemaphore(self._processes)
         for i in range(processes):
             self._create_worker_process()
 
         self._worker_handler = self.Supervisor(self)
         self._worker_handler.start()
 
-        self._putlock = LaxBoundedSemaphore(self._processes)
         self._task_handler = self.TaskHandler(self._taskqueue,
                                               self._quick_put,
                                               self._outqueue,