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 41The device 42.Pa /dev/fido 43responds to a single 44.Xr ioctl 2 45call, 46.Dv WDIOCPATPAT . 47It takes a single argument which represents a timeout value specified as a 48power of two nanoseconds, or-ed with a flag selecting active or passive control 49of the watchdog. 50.Pp 51.Dv WD_ACTIVE 52indicates that the 53.Nm 54will be kept from timing out from userland, for instance by the 55.Xr watchdogd 8 56daemon. 57.Dv WD_PASSIVE 58indicates that the 59.Nm 60will be kept from timing out from the kernel. 61.Pp 62The 63.Xr ioctl 2 64call will return success if just one of the available 65.Xr watchdog 9 66implementations supports setting the timeout to the specified timeout. 67This 68means that at least one watchdog is armed. 69If the call fails, for instance if 70none of 71.Xr watchdog 9 72implementations support the timeout length, all watchdogs are disabled and must 73be explicitly re-enabled. 74.Pp 75To disable the watchdogs pass 76.Dv WD_TO_NEVER . 77If disarming the watchdog(s) failed an error is returned. 78The watchdog might 79still be armed! 80.Sh RETURN VALUES 81The ioctl returns zero on success and non-zero on failure. 82.Bl -tag -width Er 83.It Bq Er EOPNOTSUPP 84No watchdog present in the kernel or 85none of the watchdogs supports the requested timeout value 86(timeout value other than 0). 87.It Bq Er EOPNOTSUPP 88Watchdog could not be disabled (timeout value of 0). 89.It Bq Er EINVAL 90Invalid flag combination passed. 91.El 92.Sh EXAMPLES 93.Bd -literal -offset indent 94#include <paths.h> 95#include <sys/watchdog.h> 96 97#define WDPATH "/dev/" _PATH_WATCHDOG 98int wdfd = -1; 99 100static void 101wd_init(void) 102{ 103 wdfd = open(WDPATH, O_RDWR); 104 if (wdfd == -1) 105 err(1, WDPATH); 106} 107static void 108wd_reset(u_int timeout) 109{ 110 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1) 111 err(1, "WDIOCPATPAT"); 112} 113 114/* in main() */ 115wd_init(); 116wd_reset(WD_ACTIVE|WD_TO_8SEC); 117/* potential freeze point */ 118wd_reset(WD_TO_NEVER); 119.Ed 120.Pp 121Enables a watchdog to recover from a potentially freezing piece of code. 122.Pp 123.Dl "options SW_WATCHDOG" 124.Pp 125in your kernel config adds a software watchdog in the kernel, dropping to KDB 126or panic-ing when firing. 127.Sh SEE ALSO 128.Xr watchdogd 8 , 129.Xr watchdog 9 130.Sh HISTORY 131The 132.Nm 133code first appeared in 134.Fx 5.1 . 135.Sh AUTHORS 136.An -nosplit 137The 138.Nm 139facility was written by 140.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org . 141The software watchdog code and this manual page were written by 142.An Sean Kelly Aq Mt smkelly@FreeBSD.org . 143Some contributions were made by 144.An Jeff Roberson Aq Mt jeff@FreeBSD.org . 145.Sh BUGS 146The 147.Dv WD_PASSIVE 148option has not yet been implemented. 149