On 22.09.2016 21:20, Jean-Roch Blais wrote:
> Hello Andrew,
>> Le 22 sept. 2016 à 13:53, Andrew <ni...@seti.kr.ua> a écrit :
>> Hi.
>> On 22.09.2016 20:32, Jean-Roch Blais wrote:
>>> Hello Andrew, Erich !
>>>> Le 21 sept. 2016 à 04:52, Andrew <ni...@seti.kr.ua> a écrit :
>>>> Most of boards have some kind of watchdog on board (in MIO or in south
>>>> bridge), or some of them. For ex., iTCO_wdt for Intel, it87_wdt for ITE
>>>> MIO, and so on.
>>>> But built-in watchdog behavior may differ depending board model (it may
>>>> reboot board, or it may just poweroff board, like ITE watchdog on old
>>>> Asus K8N).
>>>> Also, Intel watchdog driver is loaded automatically, MIO watchdog
>>>> drivers are loaded manually (from command line or from /etc/modules).
>>>> You can try it - load driver, and then do 'killall -9 watchdog' (to kill
>>>> watchdog process & simulate system hangup). If board will be rebooted -
>>>> all is OK.
>>> Yes it does that indeed, I killed the watchdog0 and 1 plus the watchdog 
>>> processes and my system rebooted, the drivers are already loaded in BUC ( 
>>> lsmod gives iTCO_wdt ), no need to load anything, but it’s good to know how 
>>> it works. But my question still stands, there is no hardware lockup 
>>> watchdog timer, it has to be an external contraption which would detect an 
>>> absence of activity on the motherboard and activate the hardware reset 
>>> button… I’ve seen some wifi switches that do this for routers 
>>> (https://www.amazon.com/gp/product/B01BU2ALGO/ for exemple).  It does not 
>>> ship to Canada though :-) !!!  I’ve started some preliminary tests to 
>>> perform the same basic thing using an Arduino on one of BUC’s USB port, and 
>>> it looks promising… if you are interested I could let you know how it goes !
>>> bye !
>> You are wrong, iTCO_wdt is hardware watchdog timer. It doesn't use CPU for 
>> rebooting - this is separate circuit in the chipset.
>> You may even try to disable reboot on kernel panic and initiate kernel 
>> panic, or even teke out one DIMM module - and system will be rebooted.
> Ok I gladly agree to this, since this means there is no need to devise an 
> external watchdog timer, right ? There is a lot of people who don’t know that 
> then… :-(
> My previous motherboard would not reboot when it hanged, this is why I 
> thought there was no hardware wdt, but it might be that the wdt on this mobo 
> only shuts down the mobo like you said before. ( it is a Foxconn 661MXPlus 
> [img]http://i.imgur.com/38JiUW9.jpg[/img] and the SIS900 onboard nic was now 
> and then sending me warning messages… ) So depending on the mobo, the wdt can 
> reboot or shutdown the mobo, do you know any way to choose which  ???
AFAIK no way, it depends on watchdog timer and it's connection on MB.

In your case you may have no loaded driver for onboard watchdog 
(watchdog is in MIO chip like ITE7805; it requires to specify driver 
module by hand). It have no iTCO_wdt watchdog (that loads driver 
automatically) because it have non-Intel chipset.
> thanks again !
> jrb

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