.\"	$NetBSD: swwdog.4,v 1.9 2015/04/14 10:50:25 pgoyette Exp $
.\"
.\" Copyright (c) 2004, 2005 Steven M. Bellovin
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.Dd June 8, 2011
.\" Written by Steven M. Bellovin
.Dt SWWDOG 4
.Os
.Sh NAME
.Nm swwdog
.Nd software watchdog timer
.Sh SYNOPSIS
.Cd "pseudo-device swwdog"
.Sh DESCRIPTION
The
.Nm
driver provides a software watchdog timer that works with
.Xr wdogctl 8 .
If the timer expires, the system reboots if the boolean variable
.Va swwdog_reboot
is
.Dv true ;
otherwise, the system will panic.
.Va swwdog_reboot
is accessible as the
.Xr sysctl 8
variable hw.swwdog.reboot and defaults to
.Dv false .
.Pp
The default period of
.Nm
is 60 seconds.
.Pp
As with other watchdog timers, the
.Nm
driver prevents a system from suspending when the watchdog is armed.
.Sh SEE ALSO
.Xr sysctl 8 ,
.Xr wdogctl 8
.Sh HISTORY
The
.Nm
driver was written by
.An Steven M. Bellovin .
.Sh 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
.Nm
device can be created.
.Pp
Kernel tickle mode is useless with
.Nm
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.
.Pp
The alarm option to
.Xr wdogctl 8
isn't implemented.