[OpenWrt-Devel] regarding procd and manually controlling hardware watchdog

Valent Turkovic valent at otvorenamreza.org
Sat Mar 17 14:08:31 EDT 2018

Using internal hardware watchdog would mean that we could remove
external hardware watchdog that we currently have on some customers
I'm working on embedded products based upon OpenWrt and mips hardware
that use usb lte modems, openvpn, spi flash memory (actually now
replaced with onboard emmc drive)...

These are very complex devices when compared to "standard" embedded
devices, and with complexity you get more issues. We have software
watchdog scripts that try to fix things automatically, and last resort
is to reboot the device.

Have you even seen that device doesn't reboot after giving it reboot
command? Well, I have seen it. It is rare, but still it happens some
times. So if reboot command fails for three times in a row then we
stop tickling external watchdog which cuts power for 1 second.

Now I would tickle internal watchdog in same way. Other way would be
to just issue ubus command to stop tickling watchdog but when system
(very rarely) get into this weird state I'm not sure if ubus commands
would work.

Because our devices are spread all around Germany it is better to have
a really good and redundant watchdog then to drive somewhere for few
hundred kilometres.

Hope this satisfies your curiosity, John.


On Fri, Mar 16, 2018 at 8:14 PM, John Crispin <john at phrozen.org> wrote:
> On 16/03/18 19:48, Valent Turkovic wrote:
>> Hi,
>> i just finished writing a detailed blog post regarding how to use
>> hardware watchdog and how to manually take control over from procd:
>> http://kernelreloaded.com/manually-controlling-openwrt-hardware-watchdog/
>> Over the years there were few questions regarding this and first there
>> was no way to do it (missing magicclose feature) and documentation was
>> lacking even after it was implemented.
>> Hopefully this helps some people.
>> If you have any suggestions or comments regarding this blog post feel
>> free to write here or contact me directly.
>> Cheers,
>> Valent.
>> _______________________________________________
>> openwrt-devel mailing list
>> openwrt-devel at lists.openwrt.org
>> https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel
> Hey,
> just coz I am curious, why would you want to manually control the WDT ?
>     John
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