NAME
swwdog —
software watchdog timer
SYNOPSIS
pseudo-device swwdog
DESCRIPTION
Theswwdog driver provides a software watchdog timer
that works with
wdogctl(8). If the timer expires, the system reboots if the boolean
variable swwdog_reboot is true;
otherwise, the system will panic. swwdog_reboot is
accessible as the
sysctl(8) variable hw.swwdog.reboot and defaults to
false.
The default period of swwdog is 60
seconds.
As with other watchdog timers, the swwdog
driver prevents a system from suspending when the watchdog is armed.
SEE ALSO
HISTORY
The swwdog driver was written by
Steven M. Bellovin.
BUGS
Only one watchdog timer can be active at any given time.
(Arguably, this is a bug in the watchdog timer framework.) Therefore, only a
single instance of the swwdog device can be
created.
Kernel tickle mode is useless with swwdog
and arguably should be rejected, since both it and this driver rely on the
same callout mechanism; if one is blocked, almost certainly the other is as
well.
The alarm option to wdogctl(8) isn't implemented.