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

[Karl Palsson]

Valent Turkovic <valent at otvorenamreza.org> wrote:
> Using internal hardware watchdog would mean that we could
> remove external hardware watchdog that we currently have on
> some customers products. 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.

yes! see https://github.com/openwrt/openwrt/pull/747
and
https://dev.openwrt.org/ticket/12121
and
https://dev.openwrt.org/ticket/17839#comment:51
and also, for what's likely the same issue...
errata ERR007117 for IMX6DQCE

though, honestly, these are cases where the _watchdog_ is the
problem. You _need_ to do a "nice" reboot, watchdog reboots make
it worse.

> 
> 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.
> 
> Cheers,
> Valent.
> 
> 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
> _______________________________________________
> openwrt-devel mailing list
> openwrt-devel at lists.openwrt.org
> https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel
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