Hi Dave,
On 23/02/2016:09:14:10 AM, Dave Young wrote:
Hi, Pratyush
On 02/22/16 at 05:59pm, Pratyush Anand wrote:
> Also, does --host-only mode used by any other application than kdump? If yes,
> then should it be wise to keep same implementation for them as well? If not,
> then how can we detect that it is kdump who is using dracut?
--hostonly is a general option which is not only for kdump, that is why I think
we should do it in dracut. It may make sense to add hostonly wdt logic so that
it will help kexec reboot.
Lets say we have another application (non kdump) which creates an initramfs with
`dracut --host-only`. So what I wanted to confirm here that, with proposed
implementation initramfs of that non-kdump application will also load drivers
for active watchdog. Will that be acceptable to other applications?
>
>
> Well, I did not made any change in design of this patch. It seems that systemd
> is behaving like that. Then, it seemed more reasonable to me as well, because in
> this way we can also get benefit of watchdog in kdump kernel. If something goes
> wrong during dump process then watchdog will restart the machine (if it was
> active in primary kernel as well).
>
Thanks, I agree that current approatch in the patchset is good enough.
Thanks :-)
> >
> > One case is like we talked before if wdt driver failed to disable the wdt then
> > it will still be active, then does systemd still work as expected?
>
> OK, I will get back on this soon.
I did some change in iTCO_wdt.c's probe to not to stop wdt specifically. Kicked
watchdog, restarted kdump and crashed the system. I made kdump kernel to stop at
dracut and then waited for sufficient time, but did not see system rebooting
with watchdog, so it seems that some other operation in probe caused to stop
watchdog. So, that exact situation what you were suggesting is difficult to
reproduce (atleast) with iTCO.
However, I am wondering, why would any driver not insure that wdt is stopped
specifically. If it is left started by any chance then, won't it be an unstable
situation where system could reset before an application start kicking it's wdt.
So, in my understanding if a watchdog is not specifically stopping it in probe()
then, its a bug in the driver which need to be fixed.
~Pratyush