For pluggable ttys such as USB serial devices, the getty is restarted
and exits in a loop until the remove event reaches systemd. Under
certain circumstances the restart loop can overload the system in a
way that prevents the remove event from reaching systemd for a long
time (e.g. at least several minutes on a small embedded system).
Use the default RestartSec to prevent the restart loop from
overloading the system. Serial gettys are interactive units, so
waiting an extra 100ms really doesn't make a difference anyways
compared to the time it takes the user to log in.
ExecStart=-/sbin/agetty --keep-baud 115200,38400,9600 %I $TERM
Type=idle
Restart=always
-RestartSec=0
UtmpIdentifier=%I
TTYPath=/dev/%I
TTYReset=yes