Re: watchdog: how to enable?

From: Muni Sekhar <munisekharrms@gmail.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-watchdog@vger.kernel.org, linux-pci@vger.kernel.org,
	wim@linux-watchdog.org
Subject: Re: watchdog: how to enable?
Date: Sun, 17 Nov 2019 00:04:47 +0530	[thread overview]
Message-ID: <CAHhAz+i83WoGyNwF_sjN+rVH812Nvm=U8ddbv-gWuNbD05HPdg@mail.gmail.com> (raw)
In-Reply-To: <e5b24949-5215-9d3d-ca45-cab221d4f58a@roeck-us.net>

On Sat, Nov 16, 2019 at 9:31 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 11/15/19 7:03 PM, Muni Sekhar wrote:
> [ ... ]
> >>
> >> Another possibility, of course, might be to enable a hardware watchdog
> >> in your system (assuming it supports one). I personally would not trust
> >> the NMI watchdog because to detect a system hang, after all, there are
> >> situations where even NMIs no longer work.
> >
> >>From dmesg , Is it possible to know whether my system supports
> > hardware watchdog or not?
> > I assume that my system supports the hardware watchdog , then how to
> > enable the hardware watchdog to debug the system freeze issues?
> >
>
> Hardware watchdog support really depends on the board type. Most PC
> mainboards support a watchdog in the Super-IO chip, but on some it is
> not wired correctly. On embedded boards it is often built into the SoC.
> The easiest way to see if you have a watchdog would be to check for the
> existence of /dev/watchdog. However, on a PC that would most likely
> not be there because the necessary module is not auto-loaded.
> If you tell us your board type, or better the Super-IO chip on the board,
> we might be able to help.

I’m having two same configuration systems, in one system I installed
the Vanilla kernel and I see the /dev/watchdog and /dev/watchdog0
nodes. In other system I’m running with ubuntu distribution kernel,
but I don’t see any watchdog device node. So it looks like I need to
manually load the kernel module in distro kernel. Is there a way to
know what is the corresponding kernel module for  /dev/watchdog node?

# ls -l /dev/watchdog*
crw------- 1 root root  10, 130 Nov 15 17:15 /dev/watchdog
crw------- 1 root root 248,   0 Nov 15 17:15 /dev/watchdog0

# ps -ax | grep watchdog
  678 ?        S      0:00 [watchdogd]

Regarding Super-IO chip, how to find out the Super-IO chip model?

>
> Note though that this won't help to debug the problem. A hardware
> watchdog resets the system. It helps to recover, but it is not intended
> to help with debugging.
How do I use the hardware watchdog to reset my system when system is
frozen? It helps me to collect the crashdump and finally helps me to
find the root cause for the system frozen issue.

>
> Guenter

-- 
Thanks,
Sekhar