Re: [PATCH] watchdog: Respect watchdog cpumask on CPU hotplug

[Maxime Coquelin]

On 3/27/19 8:10 PM, Thomas Gleixner wrote:
> On Wed, 27 Mar 2019, Oleg Nesterov wrote:
> > On 03/26, Thomas Gleixner wrote:
> > > The rework of the watchdog core to use cpu_stop_work broke the watchdog
> > > cpumask on CPU hotplug.
> > >
> > > The watchdog_enable/disable() functions are now called unconditionally from
> > > the hotplug callback, i.e. even on CPUs which are not in the watchdog
> > > cpumask.
> > >
> > > Only invoke them when the plugged CPU is in the watchdog cpumask.
> >
> > IIUC without this fix an NMI watchdog can too be enabled at boot time even
> > if the initial watchdog_cpumask = housekeeping_cpumask(HK_FLAG_TIMER) doesn't
> > include the plugged CPU.
>
> Yes.
>
> > And after that writing 0 to /proc/sys/kernel/nmi_watchdog clears
> > NMI_WATCHDOG_ENABLED but this can't disable NMI watchdog's outside of
> > watchdog_allowed_mask.
>
> Correct
>
> > So may be this can explain the problem reported by Maxime ?
> > See https://lore.kernel.org/lkml/b99c5a25-a5fe-18dd-2f1d-bdd6834f03e5@xxxxxxxxxx/
>
> That looks so.

I had a trial with your patch, and I can confirm it fixes my issue:

Tested-by: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>

Thanks,
Maxime

> Thanks,
>
> 	tglx