Re: [PATCH] watchdog: nohz: don't run watchdog on nohz_full cores

Frederic Weisbecker
2015-04-02T16:48:52Z

On Thu, Apr 02, 2015 at 11:42:43AM -0400, Chris Metcalf wrote:
> OK, I will respin v2 of the patch as follows:
>
> - Provide a watchdog_cpumask as suggested by Don.
> - On a non-NO_HZ_FULL build, it defaults to cpu_possible as normal
> - On a NO_HZ_FULL build, it defaults to the housekeeping cpus

Ah note that NO_HZ_FULL is only the capability. Nohz full is actually
only running if the nohz_full parameter is passed (or NO_HZ_FULL_ALL=y).

And now generalist distros enable NO_HZ_FULL so that anybody can use it.

So better check tick_nohz_full_enabled() instead of the CONFIG.

Thanks.

> - If the mask is modified, we disable and then re-enable the watchdog,
> so that the watchdog init code can exit() the appropriate threads as
> they start up
>
> This should address the various concerns that have been raised.
>
> --
> Chris Metcalf, EZChip Semiconductor
> http://www.ezchip.com
>