"default" watchdog device - ?

[lejeczek]

On 15/03/2022 11:21, Daniel P. Berrangé wrote:
> On Tue, Mar 15, 2022 at 10:39:50AM +0000, lejeczek wrote:
>> Hi guys.
>>
>> Without explicitly, manually using watchdog device for a VM, the VM (centOS
>> 8 Stream 4.18.0-365.el8.x86_64) shows '/dev/watchdog' exists.
>> To double check - 'dumpxml' does not show any such device - what kind of a
>> 'watchdog' that is?
> The kernel can always provide a pure software watchdog IIRC. It can be
> useful if a userspace app wants a watchdog. The limitation is that it
> relies on the kernel remaining functional, as there's no hardware
> backing it up.
>
> Regards,
> Daniel
On a related note - with 'i6300esb' watchdog which I tested 
and I believe is working.
I get often in my VMs from 'dmesg':
...
watchdog: BUG: soft lockup - CPU#0 stuck for xxxs! [swapper/0:0]
rcu: INFO: rcu_sched self-detected stall on CPU
...
This above is from Ubuntu and CentOS alike and when this 
happens, console via VNC responds to until first 'enter' 
then is non-resposive.
This happens after VM(s) was migrated between hosts, but 
anyway..
I do not see what I expected from 'watchdog' - there is no 
action whatsoever, which should be 'reset'. VM remains in 
such 'frozen' state forever.

any & all shared thoughts much appreciated.
L.