1.\" $NetBSD: swwdog.4,v 1.4 2010/01/30 21:55:28 pooka 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 January 30, 2010 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 unless the variable 49.Va swwdog_panic 50is non-zero; if it is, the system will panic instead. 51.Pp 52The default period of 53.Nm 54is 60 seconds. 55.Sh SEE ALSO 56.Xr wdogctl 8 57.Sh HISTORY 58The 59.Nm 60driver was written by 61.An Steven M. Bellovin . 62.Sh BUGS 63Only one watchdog timer can be active at any given time. 64Arguably, this is a bug in the watchdog timer framework. 65.Pp 66Kernel tickle mode is useless with 67.Nm 68and arguably should be rejected, since both it and 69this driver rely on the same callout mechanism; if one is 70blocked, almost certainly the other is as well. 71.Pp 72The alarm option to 73.Xr wdogctl 8 74isn't implemented. 75