1.\" Copyright (c) 2004 Poul-Henning Kamp <phk@FreeBSD.org> 2.\" Copyright (c) 2003, 2004 Sean M. Kelly <smkelly@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd December 21, 2009 29.Dt WATCHDOG 4 30.Os 31.Sh NAME 32.Nm watchdog 33.Nd "hardware and software watchdog" 34.Sh SYNOPSIS 35.In sys/watchdog.h 36.Sh DESCRIPTION 37The 38.Nm 39facility is used for controlling hardware and software watchdogs. 40.Pp 41.Pa /dev/fido 42responds to a single 43.Xr ioctl 2 44call, 45.Dv WDIOCPATPAT . 46It takes a single argument which represents a timeout value specified as a 47power of two nanoseconds, or-ed with a flag selecting active or passive control 48of the watchdog. 49.Pp 50.Dv WD_ACTIVE 51indicates that the 52.Nm 53will be kept from timing out from userland, for instance by the 54.Xr watchdogd 8 55daemon. 56.Dv WD_PASSIVE 57indicates that the 58.Nm 59will be kept from timing out from the kernel. 60.Pp 61The 62.Xr ioctl 2 63call will return success if just one of the available 64.Xr watchdog 9 65implementations supports setting the timeout to the specified timeout. 66This 67means that at least one watchdog is armed. 68If the call fails, for instance if 69none of 70.Xr watchdog 9 71implementations support the timeout length, all watchdogs are disabled and must 72be explicitly re-enabled. 73.Pp 74To disable the watchdogs pass 75.Dv WD_TO_NEVER . 76If disarming the watchdog(s) failed an error is returned. 77The watchdog might 78still be armed! 79.Sh RETURN VALUES 80The ioctl returns zero on success and non-zero on failure. 81.Bl -tag -width Er 82.It Bq Er EOPNOTSUPP 83No watchdog present in the kernel or 84none of the watchdogs supports the requested timeout value 85(timeout value other than 0). 86.It Bq Er EOPNOTSUPP 87Watchdog could not be disabled (timeout value of 0). 88.It Bq Er EINVAL 89Invalid flag combination passed. 90.El 91.Sh EXAMPLES 92.Bd -literal -offset indent 93#include <paths.h> 94#include <sys/watchdog.h> 95 96#define WDPATH "/dev/" _PATH_WATCHDOG 97int wdfd = -1; 98 99static void 100wd_init(void) 101{ 102 wdfd = open(WDPATH, O_RDWR); 103 if (wdfd == -1) 104 err(1, WDPATH); 105} 106static void 107wd_reset(u_int timeout) 108{ 109 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1) 110 err(1, "WDIOCPATPAT"); 111} 112 113/* in main() */ 114wd_init(); 115wd_reset(WD_ACTIVE|WD_TO_8SEC); 116/* potential freeze point */ 117wd_reset(WD_TO_NEVER); 118.Ed 119.Pp 120Enables a watchdog to recover from a potentially freezing piece of code. 121.Pp 122.Dl "options SW_WATCHDOG" 123.Pp 124in your kernel config adds a software watchdog in the kernel, dropping to KDB 125or panic-ing when firing. 126.Sh SEE ALSO 127.Xr watchdogd 8 , 128.Xr watchdog 9 129.Sh HISTORY 130The 131.Nm 132code first appeared in 133.Fx 5.1 . 134.Sh AUTHORS 135.An -nosplit 136The 137.Nm 138facility was written by 139.An Poul-Henning Kamp Aq phk@FreeBSD.org . 140The software watchdog code and this manual page were written by 141.An Sean Kelly Aq smkelly@FreeBSD.org . 142Some contributions were made by 143.An Jeff Roberson Aq jeff@FreeBSD.org . 144.Sh BUGS 145The 146.Dv WD_PASSIVE 147option has not yet been implemented. 148