Kill a postgres session

Hello !

To kill a session i used KILL -INT <PID>.

This command wasn't successfull. The processus is still here when an
'ps ax' or a 'select * from pg_stat_activity'

Is there an other way to kill this process only because a web server
24/7 use postgres and cannot stop postgresql now.

Thanks !

HM

PS : To stop postgres i use 'pg_ctl -m immediate stop' to stop
postgresql because the '/etc/init.d/postgresql stop' fails when a
session is blocked.