Ubuntu 12.04, nginx 1.2.0, uwsgi 1.0.3.
I start uwsgi with the following command:
uwsgi -s 127.0.0.1:9010 -M -t 30 -A 4 -p 4 -d /var/log/uwsgi.log
On each request nginx replies with 502 and uwsgi writes to log the following line:
-- unavailable modifier requested: 0 --