sudo kill -19 <pidOfGetty>

ps a | grep getty

root       948  0.0  0.0   4656  2032 tty5     Ts+  Sep20   0:00 /sbin/getty -8 38400 tty5
root       958  0.0  0.0   4656  1880 tty2     Ss+  Sep20   0:00 /sbin/getty -8 38400 tty2

#AMA0:12345:respawn:/bin/start_getty 115200 ttyAMA0 vt102

kill -HUP 1

for pid in $(ls -l /proc/[0-9]*/fd/* | grep /dev/ttyPS0 | awk '{ print $9 }' | awk -F/ '{ print $3 }'); do
    echo "killing $pid"
    kill -9 $pid
done