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

[Ulrich Obergfell <uobergfe@redhat.com>]

----- Original Message -----
From: "Chris Metcalf" <cmetcalf@ezchip.com>
[...]
> 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,

I also think it's probably OK to leave it as-is, in particular because
you indicated in http://marc.info/?l=linux-kernel&m=143016646903545&w=2
that you are going to make watchdog_cpumask static instead of allocating
it dynamically.

Regards,

Uli