Re: [PATCH 2/2] clocksource: arm_arch_timer: set arch_mem_timer cpumask to cpu_possible_mask

[Thomas Gleixner]

On Mon, 9 Jul 2018, Sudeep Holla wrote:

> Currently, arch_mem_timer cpumask is set to cpu_all_mask which should be
> fine. However, cpu_possible_mask is more accurate and if there are other
> clockevent source in the system which are set to cpu_possible_mask, then
> having cpu_all_mask may result in issue.
> 
> E.g. on a platform with arm,sp804 timer with rating 300 and
> cpu_possible_mask and this arch_mem_timer timer with rating 400 and
> cpu_all_mask, tick_check_preferred may choose both preferred as the
> cpumasks are not equal though they must be.
> 
> This issue was root caused incorrectly initially and a fix was merged as
> commit 1332a9055801 ("tick: Prefer a lower rating device only if it's CPU
> local device").

To avoid that in the future we really should fix the decision logic to mask
out the non possible CPUs from the supplied masks.

Thanks,

	tgkx