A running gpg-agent may be controlled by signals, i.e. using the kill command to send a signal to the process.
Here is a list of supported signals:
SIGHUPquiet,
verbose, debug, debug-all, debug-level,
no-grab, pinentry-program, default-cache-ttl,
max-cache-ttl, ignore-cache-for-signing,
allow-mark-trusted, disable-scdaemon, and
disable-check-own-socket. scdaemon-program is also
supported but due to the current implementation, which calls the
scdaemon only once, it is not of much use unless you manually kill the
scdaemon.
SIGTERMSIGINTSIGUSR1SIGUSR2