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Old 02-08-2010, 01:51 PM
Michael Meskes
 
Default why are the watchdog drivers blacklisted?

On Mon, Feb 08, 2010 at 04:45:53AM +0100, Marco d'Itri wrote:
> If the defaults for some drivers are wrong then I can't see why they
> should not be fixed, but if default configuration parameters are needed
> then they should be provided by the watchdog package.

If the watchdog package is the only one using these modules that would be fine.
But watchdog itself just expects a device to be present and only insmods a
module if one is manually configured. Other users might use these modules with
the user space daemon package but they still should get the right
configuration, don't you think? Or what am I missing.

> (BTW, is there any other watchdog daemon? The watchdog package reliably
> fails to detect when the system is half-killed by OOM.)

How about explaing your problem a little bit better and, if it's really a
failure in watchdog, reporting a bug? What exactly did you do? And how did you
configure watchdog?

Michael

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Old 02-08-2010, 02:02 PM
 
Default why are the watchdog drivers blacklisted?

On Feb 08, Michael Meskes <meskes@debian.org> wrote:

> On Mon, Feb 08, 2010 at 04:45:53AM +0100, Marco d'Itri wrote:
> > If the defaults for some drivers are wrong then I can't see why they
> > should not be fixed, but if default configuration parameters are needed
> > then they should be provided by the watchdog package.
> If the watchdog package is the only one using these modules that would be fine.
> But watchdog itself just expects a device to be present and only insmods a
> module if one is manually configured. Other users might use these modules with
> the user space daemon package but they still should get the right
> configuration, don't you think? Or what am I missing.
I am not aware of any other users of /dev/watchdog.

> > (BTW, is there any other watchdog daemon? The watchdog package reliably
> > fails to detect when the system is half-killed by OOM.)
> How about explaing your problem a little bit better and, if it's really a
> failure in watchdog, reporting a bug? What exactly did you do? And how did you
> configure watchdog?
I use the default configuration. The system is broken enough that new
TCP connections are established but apparently the running daemons
cannot fork (e.g. I do not get a SMTP banner).
I have no way of reproducing the issue.

--
ciao,
Marco
 
Old 02-08-2010, 03:12 PM
Mark Brown
 
Default why are the watchdog drivers blacklisted?

On Mon, Feb 08, 2010 at 03:51:24PM +0100, Michael Meskes wrote:
> On Mon, Feb 08, 2010 at 04:45:53AM +0100, Marco d'Itri wrote:

> > (BTW, is there any other watchdog daemon? The watchdog package reliably
> > fails to detect when the system is half-killed by OOM.)

> How about explaing your problem a little bit better and, if it's really a
> failure in watchdog, reporting a bug? What exactly did you do? And how did you
> configure watchdog?

The core problem with watchdog WRT stuff like that that is that it's a
fairly small program and doesn't monitor the state of the rest of
userspace so there's error conditions like being deep into swap which
make the actual application unusable but don't stop watchdog soldiering
on.


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Old 02-08-2010, 06:15 PM
Michael Meskes
 
Default why are the watchdog drivers blacklisted?

On Mon, Feb 08, 2010 at 04:02:17PM +0100, Marco d'Itri wrote:
> I am not aware of any other users of /dev/watchdog.

There used to be other programs accessing it, but maybe they all vanished.

> I use the default configuration. The system is broken enough that new

The default configuration in Debian does nothing, not even accessing
/dev/watchdog. So I take it you enabled the device. But then it does exactly
just that, triggering the device, which means you will only get a reset if the
device can't be triggered anymore because e.g the kernel oopsed.

Please keep in mind the OOM killer will only influence watchdog if it happens
to kill it. If you happen to run out of memory though, you can tell watchdog to
test if enough free mem is available.

> TCP connections are established but apparently the running daemons
> cannot fork (e.g. I do not get a SMTP banner).
> I have no way of reproducing the issue.

If you want to test forking ability just enable test-binary test without giving
it a test-binary or use an empty one. This will make watchdog fork() and react
if not possible.

Michael

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Old 02-08-2010, 06:17 PM
Michael Meskes
 
Default why are the watchdog drivers blacklisted?

On Mon, Feb 08, 2010 at 04:12:10PM +0000, Mark Brown wrote:
> The core problem with watchdog WRT stuff like that that is that it's a
> fairly small program and doesn't monitor the state of the rest of

Plus it locks itself into main memory and will not suffer from swappiness
itself.

> userspace so there's error conditions like being deep into swap which
> make the actual application unusable but don't stop watchdog soldiering
> on.

You can configure the watchdog daemon to also test quite some system conditions
and react accordingly. This will however be done in user space.

Michael

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Old 02-08-2010, 06:54 PM
Guillem Jover
 
Default why are the watchdog drivers blacklisted?

Hi!

On Mon, 2010-02-08 at 20:15:30 +0100, Michael Meskes wrote:
> Please keep in mind the OOM killer will only influence watchdog if it happens
> to kill it. If you happen to run out of memory though, you can tell watchdog to
> test if enough free mem is available.

The OOM killer can be disabled for precious processes by writting the
string "-17" to “/proc/<pid>/oom_adj”.

regards,
guillem


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Old 02-09-2010, 12:20 AM
Darren Salt
 
Default why are the watchdog drivers blacklisted?

I demand that Guillem Jover may or may not have written...

> On Mon, 2010-02-08 at 20:15:30 +0100, Michael Meskes wrote:
>> Please keep in mind the OOM killer will only influence watchdog if it
>> happens to kill it. If you happen to run out of memory though, you can
>> tell watchdog to test if enough free mem is available.

> The OOM killer can be disabled for precious processes by writting the
> string "-17" to “/proc/<pid>/oom_adj”.

That sounds to me like a good thing to do by default.

--
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Old 02-09-2010, 12:44 AM
Henrique de Moraes Holschuh
 
Default why are the watchdog drivers blacklisted?

On Tue, 09 Feb 2010, Darren Salt wrote:
> I demand that Guillem Jover may or may not have written...
> > On Mon, 2010-02-08 at 20:15:30 +0100, Michael Meskes wrote:
> >> Please keep in mind the OOM killer will only influence watchdog if it
> >> happens to kill it. If you happen to run out of memory though, you can
> >> tell watchdog to test if enough free mem is available.
>
> > The OOM killer can be disabled for precious processes by writting the
> > string "-17" to ???/proc/<pid>/oom_adj???.
>
> That sounds to me like a good thing to do by default.

And while at it, change wd_keepalive and watchdog to default to pat at 1Hz
instead of 0.1Hz. That will reduce a _lot_ the changes of spurious
reboots.

--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh


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Old 02-09-2010, 07:43 AM
Michael Meskes
 
Default why are the watchdog drivers blacklisted?

On Tue, Feb 09, 2010 at 01:20:31AM +0000, Darren Salt wrote:
> > The OOM killer can be disabled for precious processes by writting the
> > string "-17" to “/proc/<pid>/oom_adj”.
>
> That sounds to me like a good thing to do by default.

Absolutely agreed. As soon as I find the time.

Michael
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Old 02-09-2010, 07:47 AM
Michael Meskes
 
Default why are the watchdog drivers blacklisted?

TOn Mon, Feb 08, 2010 at 11:44:55PM -0200, Henrique de Moraes Holschuh wrote:
> And while at it, change wd_keepalive and watchdog to default to pat at 1Hz
> instead of 0.1Hz. That will reduce a _lot_ the changes of spurious
> reboots.

This looks like a workaround for some other problem to me. Patting at 0.1Hz
should be sufficient if the kernel expects a change at 0.016 Hz. I don't have
any report about a spurious reboot, but if you do have some I'd like to learn
more about it to see where this problem stems from.

Michael

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