SWWDOG(4)

SWWDOG(4) | Device Drivers Manual | SWWDOG(4)

# NAME

`swwdog` — software watchdog timer

# SYNOPSIS

`pseudo-device swwdog`

# DESCRIPTION

The `swwdog` 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

sysctl(8), wdogctl(8)

# 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.

June 8, 2011 | NetBSD 11.0