Re: [PATCH v9 05/10] cpuidle: Return nohz hint from cpuidle_select()

[Frederic Weisbecker]

On Wed, Apr 04, 2018 at 10:39:50AM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Index: linux-pm/kernel/time/tick-sched.c
> ===================================================================
> --- linux-pm.orig/kernel/time/tick-sched.c
> +++ linux-pm/kernel/time/tick-sched.c
> @@ -991,6 +991,20 @@ void tick_nohz_irq_exit(void)
>  }
>  
>  /**
> + * tick_nohz_idle_got_tick - Check whether or not the tick handler has run
> + */
> +bool tick_nohz_idle_got_tick(void)
> +{
> +	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
> +
> +	if (ts->inidle > 1) {
> +		ts->inidle = 1;
> +		return true;
> +	}
> +	return false;
> +}
> +
> +/**
>   * tick_nohz_get_sleep_length - return the length of the current sleep
>   *
>   * Called from power state control code with interrupts disabled
> @@ -1101,6 +1115,9 @@ static void tick_nohz_handler(struct clo
>  	struct pt_regs *regs = get_irq_regs();
>  	ktime_t now = ktime_get();
>  
> +	if (ts->inidle)
> +		ts->inidle = 2;
> +

You can move that to tick_sched_do_timer() to avoid code duplication.

Also these constants are very opaque. And even with proper symbols it wouldn't look
right to extend ts->inidle that way.

Perhaps you should add a field such as ts->got_idle_tick under the boolean fields
after the below patch:

--