I am using gpg-agent 2.0.17 with gpg 1.4.11 on ubuntu 12.04 and the Enigmail Addon for Thunderbird. When opening an encrypted email, Enigmail invokes gpg-agent with the associated pinentry program and asks for the password. I then have the option to set the lifetime for the cached password, usually set to end of the session.
Since I rarely shutdown or logout of my session, I would like to force gpg-agent to forget all cached passwords upon locking the session. I've searched for a way to do so and the man-page of gpg-agent states, that a -SIGHUP will flush all passwords - however, contrary to the manpage, the cached passwords are not forgotten.
Any ideas on how to force gpg-agent to forget the passwords?