Re: [PATCH 09/32] nohz: Move ts->idle_calls into strict idle logic

Peter Zijlstra
2011-08-29T14:48:31Z

On Mon, 2011-08-15 at 17:52 +0200, Frederic Weisbecker wrote:
> +static bool tick_nohz_can_stop_tick(int cpu, struct tick_sched *ts)
> +{
> + /*
> + * If this cpu is offline and it is the one which updates
> + * jiffies, then give up the assignment and let it be taken by
> + * the cpu which runs the tick timer next. If we don't drop
> + * this here the jiffies might be stale and do_timer() never
> + * invoked.
> + */
> + if (unlikely(!cpu_online(cpu))) {
> + if (cpu == tick_do_timer_cpu)
> + tick_do_timer_cpu = TICK_DO_TIMER_NONE;
> + }
> +
> + if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
> + return false;
> +
> + if (need_resched())
> + return false;
> +
> + if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
> + static int ratelimit;
> +
> + if (ratelimit < 10) {
> + printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
> + (unsigned int) local_softirq_pending());
> + ratelimit++;
> + }
> + return false;
> + }
> +
> + return true;
> +}

Why aren't rcu_needs_cpu(), printk_needs_cpu() and arch_needs_cpu() not
in there?

That are typical 'can we go sleep now?' functions.