Re: [RFC/RFT][PATCH v2 1/6] time: tick-sched: Reorganize idle tick management code

[Frederic Weisbecker <frederic@kernel.org>]

On Tue, Mar 06, 2018 at 10:02:01AM +0100, Rafael J. Wysocki wrote:
> Index: linux-pm/kernel/time/tick-sched.c
> ===================================================================
> --- linux-pm.orig/kernel/time/tick-sched.c
> +++ linux-pm/kernel/time/tick-sched.c
> +
> +/**
> + * tick_nohz_idle_prepare - prepare for entering idle on the current CPU.
> + *
> + * Called when we start the idle loop.
> + */
> +void tick_nohz_idle_prepare(void)
> +{
> +	struct tick_sched *ts;
> +
> +	__tick_nohz_idle_prepare();
> +
> +	local_irq_disable();
> +
> +	ts = this_cpu_ptr(&tick_cpu_sched);
> +	ts->inidle = 1;
> +
> +	local_irq_enable();
> +}

Why not calling tick_nohz_start_idle() from there? This is going to
simplify the rest, you won't need to call tick_nohz_idle_go_idle()
from places that don't want to stop the tick and you can then remove
the stop_tick argument.

> +
> +/**
> + * tick_nohz_idle_go_idle - start idle period on the current CPU.
> + * @stop_tick: Whether or not to stop the idle tick.
> + *
> + * When @stop_tick is set and the next event is more than a tick into the
> + * future, stop the idle tick.
> + */
> +void tick_nohz_idle_go_idle(bool stop_tick)
> +{
> +	__tick_nohz_idle_enter(this_cpu_ptr(&tick_cpu_sched), stop_tick);
> +}
> +
> +void tick_nohz_idle_enter(void)
> +{
> +	struct tick_sched *ts;
> +
> +	__tick_nohz_idle_prepare();
>  
>  	local_irq_disable();
>  
>  	ts = this_cpu_ptr(&tick_cpu_sched);
>  	ts->inidle = 1;
> -	__tick_nohz_idle_enter(ts);
> +	__tick_nohz_idle_enter(ts, true);
>  
>  	local_irq_enable();
>  }

Ah I see you're keeping tick_nohz_idle_enter() around because of the callsite
in xen. It looks like a hack (from the xen part), I'll need to have a look at
it, just a note for myself...

Thanks.