get_nohz_timer_target?

From: Richard Cochran
Date: Mon Apr 18 2016 - 09:37:23 EST



Looking at kernel/sched/core.c:get_nohz_timer_target(), I don't
understand the change made in:

commit 9642d18eee2cd169b60c6ac0f20bda745b5a3d1e
Author: Vatika Harlalka <vatikaharlalka@xxxxxxxxx>
Date: Tue Sep 1 16:50:59 2015 +0200
nohz: Affine unpinned timers to housekeepers

After that change, the code now reads like this:

int i, cpu = smp_processor_id();
struct sched_domain *sd;

if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu))
return cpu;

rcu_read_lock();
for_each_domain(cpu, sd) {
for_each_cpu(i, sched_domain_span(sd)) {
if (!idle_cpu(i) && is_housekeeping_cpu(cpu)) {
--------------------------------------------------------------- ^^^
Was this supposed to be 'i' instead?
If not, how does this test make any sense?
In any case, testing over and over again is surely wasteful.
---------------------------------------------------------------
cpu = i;
goto unlock;
}
}
}

if (!is_housekeeping_cpu(cpu))
cpu = housekeeping_any_cpu();
unlock:
rcu_read_unlock();
return cpu;

Thanks,
Richard