swwdog(4) - NetBSD Manual Pages

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SWWDOG(4)               NetBSD Kernel Interfaces 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 a 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 mecha-
     nism; if one is blocked, almost certainly the other is as well.

     The alarm option to wdogctl(8) isn't implemented.

NetBSD 6.0                       June 8, 2011                       NetBSD 6.0