90 lines
3.0 KiB
Groff
90 lines
3.0 KiB
Groff
.\" $NetBSD: swwdog.4,v 1.7 2010/10/23 03:27:03 pgoyette Exp $
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.\"
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.\" Copyright (c) 2004, 2005 Steven M. Bellovin
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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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of the author nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd October 23, 2010
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.\" Written by Steven M. Bellovin
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.Dt SWWDOG 4
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.Os
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.Sh NAME
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.Nm swwdog
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.Nd software watchdog timer
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.Sh SYNOPSIS
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.Cd "pseudo-device swwdog"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides a software watchdog timer that works with
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.Xr wdogctl 8 .
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If the timer expires, the system reboots unless the boolean variable
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.Va swwdog_panic
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is
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.Dv true ;
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if it is, the system will panic instead.
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.Va swwdog_reboot
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is accessible as a
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.Xr sysctl 8
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variable, hw.swwdog0.reboot and defaults to
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.Dv false .
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.Pp
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The default period of
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.Nm
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is 60 seconds.
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.Pp
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As with other watchdog timers, the
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.Nm
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driver prevents a system from suspending when the watchdog is armed.
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.Sh SEE ALSO
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.Xr sysctl 8 ,
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.Xr wdogctl 8
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.Sh HISTORY
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The
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.Nm
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driver was written by
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.An Steven M. Bellovin .
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.Sh BUGS
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Only one watchdog timer can be active at any given time.
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(Arguably, this is a bug in the watchdog timer framework.)
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Therefore, only a single instance of the
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.Nm
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device can be created.
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.Pp
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Kernel tickle mode is useless with
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.Nm
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and arguably should be rejected, since both it and
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this driver rely on the same callout mechanism; if one is
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blocked, almost certainly the other is as well.
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.Pp
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The alarm option to
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.Xr wdogctl 8
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isn't implemented.
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