- Add a software watchdog facility.

This commit has two pieces. One half is the watchdog kernel code which lives
primarily in hardclock() in sys/kern/kern_clock.c. The other half is a userland
daemon which, when run, will keep the watchdog from firing while the userland
is intact and functioning.

Approved by:	jeff (mentor)

2 files changed, 78 insertions, 0 deletions

diff --git a/share/man/man4/Makefile b/share/man/man4/Makefile
index b598875..3198567 100644
--- a/share/man/man4/Makefile
+++ b/share/man/man4/Makefile
@@ -270,6 +270,7 @@ MAN=	aac.4 \
 	vlan.4 \
 	vpo.4 \
 	vr.4 \
+	watchdog.4 \
 	wb.4 \
 	wi.4 \
 	witness.4 \
diff --git a/share/man/man4/watchdog.4 b/share/man/man4/watchdog.4
new file mode 100644
index 0000000..b00ccda
--- /dev/null
+++ b/share/man/man4/watchdog.4
@@ -0,0 +1,77 @@
+
+.\" Copyright (c) 2003  Sean M. Kelly <smkelly@FreeBSD.org>
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd June 25, 2003
+.Dt WATCHDOG 4
+.Os
+.Sh NAME
+.Nm watchdog
+.Nd Software watchdog
+.Sh SYNOPSIS
+.Cd options WATCHDOG
+.Sh DESCRIPTION
+.Nm
+is a set of checks and routines which allow the implementation of a software
+watchdog solution.
+.Pp
+The user interface for
+.Nm
+is implemented via a trio of sysctl OIDs.
+When
+.Li debug.watchdog.enabled
+is set to a positive value,
+.Nm
+timeout checks are performed.
+In order to keep the watchdog from triggering,
+.Li debug.watchdog.reset
+must be accessed,
+by reading or writing,
+within every
+.Li debug.watchdog.timeout
+seconds.
+Failure to keep the
+.Nm
+updated will result in the kernel outputting interrupt counts,
+backtraces,
+and then attempting to enter
+.Xr ddb 9 .
+.Sh SEE ALSO
+.Xr sysctl 8 ,
+.Xr watchdogd 8
+.Sh HISTORY
+The
+.Nm
+code first appeared in
+.Fx 5.1 .
+.Sh AUTHORS
+.An -nosplit
+The
+.Nm
+code and manual page were written by
+.An Sean Kelly Aq smkelly@FreeBSD.org .
+Some contributions were made by
+.An Jeff Roberson Aq jeff@FreeBSD.org .