README mentions, that server is not thread safe and threaded Apache and/or WSGI needs some care

warden3/warden_server/README

@@ -84,6 +84,10 @@ C. Installation
    You may need to change paths to certificate/key/ca material, path to
    warden_server.wsgi and web path alias.
 
+   Also note that warden_server itself is NOT thread safe, so included
+   configuration expects Apache with mpm-prefork worker, or you will have
+   to configure mod_wsgi as separate process with threads=1.
+
    Also, for warden_server.wsgi, you can use warden_server.wsgi.dist as
    a template. You will possibly need to change at least configuration
    file path.