On Wed, 27 Jul 2016, Chris Metcalf wrote:

quoted

Should we just cycle through the cpus that are not isolated? Otherwise we
need to have some means to check the clocksources for accuracy remotely
(probably impossible for TSC etc).

That sounds like the right idea - use the housekeeping cpu mask instead of the
cpu online mask.  Should be a straightforward patch; do you want to do that
and test it in your configuration, and I'll include it in the next spin of the
patch series?

Sadly housekeeping_mask is defined the following way:

static inline const struct cpumask *housekeeping_cpumask(void)
{
#ifdef CONFIG_NO_HZ_FULL
        if (tick_nohz_full_enabled())
                return housekeeping_mask;
#endif
        return cpu_possible_mask;
}

Why is it not returning cpu_online_mask?