Index: task_io_service.ipp
===================================================================
--- task_io_service.ipp	(revision 83651)
+++ task_io_service.ipp	(working copy)
@@ -452,7 +452,11 @@
 
     o = op_queue_.front();
     if (o == &task_operation_)
+    {
+      if (!one_thread_)
+        wake_one_thread_and_unlock(lock);
       return 0;
+    }
   }
 
   if (o == 0)