swwdog.4 revision 1.9
$NetBSD: swwdog.4,v 1.9 2015/04/14 10:50:25 pgoyette Exp $
Copyright (c) 2004, 2005 Steven M. Bellovin
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This product includes software developed by the NetBSD
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.Dd June 8, 2011 Written by Steven M. Bellovin
.Dt SWWDOG 4 .Os .Sh NAME .Nm swwdog .Nd software watchdog timer .Sh SYNOPSIS .Cd "pseudo-device swwdog" .Sh DESCRIPTION The .Nm driver provides a software watchdog timer that works with .Xr wdogctl 8 . If the timer expires, the system reboots if the boolean variable .Va swwdog_reboot is .Dv true ; otherwise, the system will panic. .Va swwdog_reboot is accessible as the .Xr sysctl 8 variable hw.swwdog.reboot and defaults to .Dv false .
Copyright (c) 2004, 2005 Steven M. Bellovin
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.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by the NetBSD
Foundation, Inc. and its contributors.
4. Neither the name of the author nor the names of its
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
.Dd June 8, 2011 Written by Steven M. Bellovin
.Dt SWWDOG 4 .Os .Sh NAME .Nm swwdog .Nd software watchdog timer .Sh SYNOPSIS .Cd "pseudo-device swwdog" .Sh DESCRIPTION The .Nm driver provides a software watchdog timer that works with .Xr wdogctl 8 . If the timer expires, the system reboots if the boolean variable .Va swwdog_reboot is .Dv true ; otherwise, the system will panic. .Va swwdog_reboot is accessible as the .Xr sysctl 8 variable hw.swwdog.reboot and defaults to .Dv false .
p The default period of .Nm is 60 seconds.
p As with other watchdog timers, the .Nm driver prevents a system from suspending when the watchdog is armed. .Sh SEE ALSO .Xr sysctl 8 , .Xr wdogctl 8 .Sh HISTORY The .Nm driver was written by .An Steven M. Bellovin . .Sh BUGS Only one watchdog timer can be active at any given time. (Arguably, this is a bug in the watchdog timer framework.) Therefore, only a single instance of the .Nm device can be created.
p Kernel tickle mode is useless with .Nm and arguably should be rejected, since both it and this driver rely on the same callout mechanism; if one is blocked, almost certainly the other is as well.
p The alarm option to .Xr wdogctl 8 isn't implemented.