group_balance_mask
cpumask_copy(swb_cpus, group_balance_mask(sg));
.dst_grpmask = group_balance_mask(sd->groups),
!cpumask_equal(group_balance_mask(group), sched_group_span(group))) {
cpumask_pr_args(group_balance_mask(group)));
cpumask_copy(group_balance_mask(sg), sched_group_span(sg));
cpumask_set_cpu(cpu, group_balance_mask(sg));
return cpumask_first(group_balance_mask(sg));
cpumask_copy(group_balance_mask(sg), mask);
WARN_ON_ONCE(!cpumask_equal(group_balance_mask(sg), mask));