Re: [PATCH v8 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz

Chris Metcalf
2015-04-28T17:52:49Z

On 04/22/2015 04:20 AM, Ulrich Obergfell wrote:
> Chris,
>
> in principle the change looks o.k. to me, even though I'm not really familiar
> with the watchdog_nmi_disable_all() and watchdog_nmi_enable_all() functions.
> It is my understanding that those functions are only called once via 'initcall'
> early during kernel startup as shown in the following flow of execution:
>
> [...]
> It seems crucial that lockup_detector_init() is executed before fixup_ht_bug().

Uli, thanks for doing the follow-up analysis. I didn't know
about the fixup_ht_bug() path, but as you show, it seems to be OK.

We could think about doing some kind of additional paranoia here,
like a wrapper around &watchdog_cpumask that checks some additional
boolean that says whether it's been properly initialized or not.

But I think it's probably OK to leave it as-is; we already had the
potential of issues if any watchdog code was invoked prior to
init_watchdog(), for example due to the sample period being unset.

What do you think?

--
Chris Metcalf, EZChip Semiconductor