/*
     * By now we've cleared cpu_active_mask, wait for all preempt-disabled
     * and RCU users of this state to go away such that all new such users
     * will observe it.
     *
     * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
     * not imply sync_sched(), so explicitly call both.
     *
     * Do sync before park smpboot threads to take care the rcu boost case.
     */