This option serves two purposes. First, it configures the time
to wait for each ExecStop= command. If any of them times out,
subsequent ExecStop= commands are skipped and the service will
be terminated by SIGTERM. If no ExecStop= commands are
specified, the service gets the SIGTERM immediately. This
default behavior can be changed by the TimeoutStopFailureMode=
option. Second, it configures the time to wait for the service
itself to stop. If it does not terminate in the specified
time, it will be forcibly terminated by SIGKILL (see KillMode=
in systemd.kill(5)). Takes a unit-less value in seconds, or a
time span value such as "5min 20s". Pass "infinity" to disable
the timeout logic. Defaults to DefaultTimeoutStopSec= from the
manager configuration file (see systemd-system.conf(5)).
If a service of Type=notify/Type=notify-reload sends
"EXTEND_TIMEOUT_USEC=...", this may cause the stop time to be
extended beyond TimeoutStopSec=. The first receipt of this
message must occur before TimeoutStopSec= is exceeded, and
once the stop time has extended beyond TimeoutStopSec=, the
service manager will allow the service to continue to stop,
provided the service repeats "EXTEND_TIMEOUT_USEC=..." within
the interval specified, or terminates itself (see
sd_notify(3)).