1.\" $NetBSD: swwdog.4,v 1.9 2015/04/14 10:50:25 pgoyette Exp $ 2.\" 3.\" Copyright (c) 2004, 2005 Steven M. Bellovin 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the NetBSD 17.\" Foundation, Inc. and its contributors. 18.\" 4. Neither the name of the author nor the names of its 19.\" contributors may be used to endorse or promote products derived 20.\" from this software without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS 23.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 24.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 25.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS 26.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 27.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 28.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 29.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 30.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 31.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 32.\" POSSIBILITY OF SUCH DAMAGE. 33.\" 34.Dd June 8, 2011 35.\" Written by Steven M. Bellovin 36.Dt SWWDOG 4 37.Os 38.Sh NAME 39.Nm swwdog 40.Nd software watchdog timer 41.Sh SYNOPSIS 42.Cd "pseudo-device swwdog" 43.Sh DESCRIPTION 44The 45.Nm 46driver provides a software watchdog timer that works with 47.Xr wdogctl 8 . 48If the timer expires, the system reboots if the boolean variable 49.Va swwdog_reboot 50is 51.Dv true ; 52otherwise, the system will panic. 53.Va swwdog_reboot 54is accessible as the 55.Xr sysctl 8 56variable hw.swwdog.reboot and defaults to 57.Dv false . 58.Pp 59The default period of 60.Nm 61is 60 seconds. 62.Pp 63As with other watchdog timers, the 64.Nm 65driver prevents a system from suspending when the watchdog is armed. 66.Sh SEE ALSO 67.Xr sysctl 8 , 68.Xr wdogctl 8 69.Sh HISTORY 70The 71.Nm 72driver was written by 73.An Steven M. Bellovin . 74.Sh BUGS 75Only one watchdog timer can be active at any given time. 76(Arguably, this is a bug in the watchdog timer framework.) 77Therefore, only a single instance of the 78.Nm 79device can be created. 80.Pp 81Kernel tickle mode is useless with 82.Nm 83and arguably should be rejected, since both it and 84this driver rely on the same callout mechanism; if one is 85blocked, almost certainly the other is as well. 86.Pp 87The alarm option to 88.Xr wdogctl 8 89isn't implemented. 90