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Subject: RE: watchdog device
Date: Mon, 4 Jun 2007 20:22:02 -0700
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Thread-Topic: watchdog device
Thread-Index: Acem/kTIDxN75KDHRzKFKBMXvaheegAImqEW
From: "Tim Gardner" <tim.gardner@onstor.com>
To: "Andy Sharp" <andy.sharp@onstor.com>

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Thanks Andy. Very close to what we want but not quite.
We need to be able to enable/disable the watchdog as well as set the =
timeout value.
I will probably just steal the source for this driver and add a few =
ioctls.

________________________________

From: Andy Sharp
Sent: Mon 6/4/2007 4:15 PM
To: Tim Gardner
Subject: watchdog device



Here is the kernel help text for the watchdog device.  You can
configure the software watchdog by adding support for SOFT_WATCHDOG.
CONFIG_WATCHDOG is already set to 'y'.  So, add a line
CONFIG_SOFT_WATCHDOG=3Dy
after the CONFIG_WATCHDOG line in .config and do a 'make' in
linux-mips-2.6, or a 'make kernel-build' in the directory above
(cougar/linux/kernel).

The user process then has to open and write to the file descriptor at
least once a minute or the kernel will reboot.  I haven't tested it ~:^)


CONFIG_WATCHDOG=3Dy

If you say Y here (and to one of the following options) and create a
character special file /dev/watchdog with major number 10 and minor
number 130 using mknod ("man mknod"), you will get a watchdog, i.e.:
subsequently opening the file and then failing to write to it for
longer than 1 minute will result in rebooting the machine. This
could be useful for a networked machine that needs to come back
on-line as fast as possible after a lock-up. There's both a watchdog
implementation entirely in software (which can sometimes fail to
reboot the machine) and a driver for hardware watchdog boards, which
are more robust and can also keep track of the temperature inside
your computer. For details, read =
<file:Documentation/watchdog/watchdog.txt>
in the kernel source.

The watchdog is usually used together with the watchdog daemon
which is available from
<ftp://ibiblio.org/pub/Linux/system/daemons/watchdog/>. This daemon can
also monitor NFS connections and can reboot the machine when the process
table is full.




CONFIG_SOFT_WATCHDOG=3D[y|m]

A software monitoring watchdog. This will fail to reboot your system
from some situations that the hardware watchdog will recover
from. Equally it's a lot cheaper to install.

To compile this driver as a module, choose M here: the
module will be called softdog.



CONFIG_WATCHDOG_NOWAYOUT=3Dn

The default watchdog behaviour (which you get if you say N here) is
to stop the timer if the process managing it closes the file
/dev/watchdog. It's always remotely possible that this process might
get killed. If you say Y here, the watchdog cannot be stopped once
it has been started.



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<HTML dir=3Dltr><HEAD><TITLE>watchdog device</TITLE>=0A=
<META http-equiv=3DContent-Type content=3D"text/html; charset=3Dunicode">=0A=
<META content=3D"MSHTML 6.00.2800.1479" name=3DGENERATOR></HEAD>=0A=
<BODY>=0A=
<DIV id=3DidOWAReplyText29872 dir=3Dltr>=0A=
<DIV dir=3Dltr><FONT face=3DArial color=3D#000000 size=3D2>Thanks Andy. =
Very close to what we want but not quite.</FONT></DIV>=0A=
<DIV dir=3Dltr><FONT face=3DArial size=3D2>We need to be able to =
enable/disable the watchdog as well as set the timeout =
value.</FONT></DIV>=0A=
<DIV dir=3Dltr><FONT face=3DArial size=3D2>I will probably just steal =
the source for this driver and add a few ioctls.</FONT></DIV></DIV>=0A=
<DIV dir=3Dltr><BR>=0A=
<HR tabIndex=3D-1>=0A=
<FONT face=3DTahoma size=3D2><B>From:</B> Andy Sharp<BR><B>Sent:</B> Mon =
6/4/2007 4:15 PM<BR><B>To:</B> Tim Gardner<BR><B>Subject:</B> watchdog =
device<BR></FONT><BR></DIV>=0A=
<DIV>=0A=
<P><FONT size=3D2>Here is the kernel help text for the watchdog =
device.&nbsp; You can<BR>configure the software watchdog by adding =
support for SOFT_WATCHDOG.<BR>CONFIG_WATCHDOG is already set to =
'y'.&nbsp; So, add a line<BR>CONFIG_SOFT_WATCHDOG=3Dy<BR>after the =
CONFIG_WATCHDOG line in .config and do a 'make' in<BR>linux-mips-2.6, or =
a 'make kernel-build' in the directory =
above<BR>(cougar/linux/kernel).<BR><BR>The user process then has to open =
and write to the file descriptor at<BR>least once a minute or the kernel =
will reboot.&nbsp; I haven't tested it =
~:^)<BR><BR><BR>CONFIG_WATCHDOG=3Dy<BR><BR>If you say Y here (and to one =
of the following options) and create a<BR>character special file =
/dev/watchdog with major number 10 and minor<BR>number 130 using mknod =
("man mknod"), you will get a watchdog, i.e.:<BR>subsequently opening =
the file and then failing to write to it for<BR>longer than 1 minute =
will result in rebooting the machine. This<BR>could be useful for a =
networked machine that needs to come back<BR>on-line as fast as possible =
after a lock-up. There's both a watchdog<BR>implementation entirely in =
software (which can sometimes fail to<BR>reboot the machine) and a =
driver for hardware watchdog boards, which<BR>are more robust and can =
also keep track of the temperature inside<BR>your computer. For details, =
read &lt;<A =
href=3D"">file:Documentation/watchdog/watchdog.txt</A>&gt;<BR>in the =
kernel source.<BR><BR>The watchdog is usually used together with the =
watchdog daemon<BR>which is available from<BR>&lt;<A =
href=3D"ftp://ibiblio.org/pub/Linux/system/daemons/watchdog/">ftp://ibibl=
io.org/pub/Linux/system/daemons/watchdog/</A>&gt;. This daemon =
can<BR>also monitor NFS connections and can reboot the machine when the =
process<BR>table is =
full.<BR><BR><BR><BR><BR>CONFIG_SOFT_WATCHDOG=3D[y|m]<BR><BR>A software =
monitoring watchdog. This will fail to reboot your system<BR>from some =
situations that the hardware watchdog will recover<BR>from. Equally it's =
a lot cheaper to install.<BR><BR>To compile this driver as a module, =
choose M here: the<BR>module will be called =
softdog.<BR><BR><BR><BR>CONFIG_WATCHDOG_NOWAYOUT=3Dn<BR><BR>The default =
watchdog behaviour (which you get if you say N here) is<BR>to stop the =
timer if the process managing it closes the file<BR>/dev/watchdog. It's =
always remotely possible that this process might<BR>get killed. If you =
say Y here, the watchdog cannot be stopped once<BR>it has been =
started.<BR></FONT></P></DIV></BODY></HTML>
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