Unable to stop postgresql ("failed") -> [SOLVED]

Dear all,

For once, I will simply publish a solution instead of asking a question.
Let's hope it will be useful to someone.

I was unable to stop postgres, I always got "[FAILED] :
  * /etc/init.d/postgresql stop
  * service postgresql stop
  * /sbin/service postgresql stop

The only solution that worked in that case was :
  *  /usr/bin/pg_ctl stop

Have a nice day !

Denis