Re: [patch 2/2] sched/idle: Make default_idle_call() NOHZ aware

[K Prateek Nayak]

Hello Thomas,

On 3/2/2026 1:00 AM, Thomas Gleixner wrote:
> +static void default_idle_enter(void)
> +{
> +	this_cpu_write(nohz_data.entry_time, sched_clock());
> +}
> +
> +#else  /* CONFIG_NO_HZ_COMMON */
> +static inline void default_idle_call(void { __default_idle_call(); }

                                            ^
s/void/void)/ to add a closing bracket here for !CONFIG_NO_HZ_COMMON.

> +static inline void default_idle_enter(void) { }
> +#endif /* !CONFIG_NO_HZ_COMMON */
> +
>  static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
>  			       struct cpuidle_device *dev,
>  			       u64 max_latency_ns)
> @@ -186,8 +236,6 @@ static void cpuidle_idle_call(void)
>  	}
>  
>  	if (cpuidle_not_available(drv, dev)) {
> -		tick_nohz_idle_stop_tick();
> -
>  		default_idle_call();
>  		goto exit_idle;
>  	}
> @@ -276,6 +324,7 @@ static void do_idle(void)
>  
>  	__current_set_polling();
>  	tick_nohz_idle_enter();
> +	default_idle_enter();

Can we defer this to until after do_idle() disables IRQs to avoid a
per-CPU write when we exit out immediately if it is semantically same?
As a bonus, we can then use __this_cpu_write().

>  
>  	while (!need_resched()) {
>  
> 
> 

-- 
Thanks and Regards,
Prateek