d626b50b9d
Enable the hardclock-based watchdog previously conditional on the SW_WATCHDOG option whenever hardware watchdogs are not found, and watchdogd attempts to enable the watchdog. The SW_WATCHDOG option still causes the sofware watchdog to be enabled even if there is a hardware watchdog. This does not change the other software-based watchdog enabled by the --softtimeout option to watchdogd. Note that the code to reprime the watchdog during kernel core dumps is no longer conditional on SW_WATCHDOG. I think this was previously a bug. Reviewed by: imp alfred bjk MFC after: 1 week Relnotes: yes Differential Revision: https://reviews.freebsd.org/D13713
207 lines
5.7 KiB
Groff
207 lines
5.7 KiB
Groff
.\" Copyright (c) 2004 Poul-Henning Kamp <phk@FreeBSD.org>
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.\" Copyright (c) 2003, 2004 Sean M. Kelly <smkelly@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 2, 2018
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.Dt WATCHDOG 4
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.Os
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.Sh NAME
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.Nm watchdog
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.Nd "hardware and software watchdog"
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.Sh SYNOPSIS
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.In sys/watchdog.h
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.Sh DESCRIPTION
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The
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.Nm
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facility is used for controlling hardware and software watchdogs.
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.Pp
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The device
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.Pa /dev/fido
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supports several optional
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.Xr ioctl 2
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calls for configuration, and
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responds to a single operational
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.Xr ioctl
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call,
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.Dv WDIOCPATPAT .
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It takes a single argument which represents a timeout value specified as a
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power of two nanoseconds, or-ed with a flag selecting active or passive control
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of the watchdog.
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.Pp
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.Dv WD_ACTIVE
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indicates that the
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.Nm
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will be kept from timing out from userland, for instance by the
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.Xr watchdogd 8
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daemon.
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.Dv WD_PASSIVE
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indicates that the
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.Nm
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will be kept from timing out from the kernel.
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.Pp
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The
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.Dv WDIOCPATPAT
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.Xr ioctl 2
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call will return success if just one of the available
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.Xr watchdog 9
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implementations supports setting the timeout to the specified timeout.
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This
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means that at least one watchdog is armed.
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By default, this will be a hardware watchdog if one is present, but if
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no hardware watchdog is able to process the request, a default software
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watchdog is enabled.
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If the call fails, for instance if
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none of
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.Xr watchdog 9
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implementations support the timeout length, all watchdogs are disabled and must
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be explicitly re-enabled.
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.Pp
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To disable the watchdogs pass
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.Dv WD_TO_NEVER .
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If disarming the watchdog(s) failed an error is returned.
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The watchdog might
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still be armed!
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.Pp
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The optional configuration
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.Xr ioctl
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commands are listed here, along with the type of the parameter used.
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Examples of their use can be found in
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.Xr watchdogd 8 .
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.Bl -tag -width "WDIOC_SETSOFTTIMEOUTACT int "
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.It Dv WDIOC_SETTIMEOUT Fa int
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set/reset the timer
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.It Dv WDIOC_GETTIMEOUT Fa int
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get total timeout
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.It Dv WDIOC_GETTIMELEFT Fa int
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get time left
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.It Dv WDIOC_GETPRETIMEOUT Fa int
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get the pre-timeout
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.It Dv WDIOC_SETPRETIMEOUT Fa int
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set the pre-timeout
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.It Dv WDIOC_SETPRETIMEOUTACT Fa int
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Set the action when a pre-timeout occurs (see
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.Li WD_SOFT_*
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below).
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.It Dv WDIOC_SETSOFT Fa int
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Use an internal software watchdog instead of hardware.
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There is also an external software watchdog, which is used by default
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if no hardware watchdog was attached.
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.It Dv WDIOC_SETSOFTTIMEOUTACT Fa int
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Set the action whan a soft timeout occurs.
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.El
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.Pp
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The actions that may be specified for the pre-timeout or the internal software
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watchdog are listed here.
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Multiple actions can be specified by ORing values together.
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.Bl -tag -width WD_SOFT_PRINT
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.It Dv WD_SOFT_PANIC
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panic
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.It Dv WD_SOFT_DDB
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enter debugger
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.It Dv WD_SOFT_LOG
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log(9)
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.It Dv WD_SOFT_PRINT
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printf(9)
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.El
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.Sh RETURN VALUES
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The
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.Dv WDIOCPATPAT
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.Xr ioctl
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returns zero on success and non-zero on failure.
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.Bl -tag -width Er
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.It Bq Er EOPNOTSUPP
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No watchdog present in the kernel or
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none of the watchdogs supports the requested timeout value
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(timeout value other than 0).
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.It Bq Er EOPNOTSUPP
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Watchdog could not be disabled (timeout value of 0).
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.It Bq Er EINVAL
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Invalid flag combination passed.
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.El
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.Pp
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The configuration
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.Xr ioctl
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operations return zero on success and non-zero on failure.
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.Sh EXAMPLES
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.Bd -literal -offset indent
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#include <paths.h>
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#include <sys/watchdog.h>
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#define WDPATH "/dev/" _PATH_WATCHDOG
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int wdfd = -1;
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static void
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wd_init(void)
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{
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wdfd = open(WDPATH, O_RDWR);
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if (wdfd == -1)
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err(1, WDPATH);
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}
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static void
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wd_reset(u_int timeout)
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{
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if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1)
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err(1, "WDIOCPATPAT");
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}
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/* in main() */
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wd_init();
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wd_reset(WD_ACTIVE|WD_TO_8SEC);
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/* potential freeze point */
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wd_reset(WD_TO_NEVER);
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.Ed
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.Pp
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Enables a watchdog to recover from a potentially freezing piece of code.
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.Pp
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.Dl "options SW_WATCHDOG"
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.Pp
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in your kernel config forces a software watchdog in the kernel
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to be configured even if a hardware watchdog is configured,
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dropping to KDB or panicking when firing, depending
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on the KDB and KDB_UNATTENDED kernel configuration options.
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.Sh SEE ALSO
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.Xr watchdogd 8 ,
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.Xr watchdog 9
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.Sh HISTORY
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The
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.Nm
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code first appeared in
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.Fx 5.1 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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facility was written by
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.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .
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The software watchdog code and this manual page were written by
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.An Sean Kelly Aq Mt smkelly@FreeBSD.org .
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Some contributions were made by
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.An Jeff Roberson Aq Mt jeff@FreeBSD.org .
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.Sh BUGS
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The
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.Dv WD_PASSIVE
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option has not yet been implemented.
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