linux-kernel - Re: [PATCH 01/15] tick/nohz: Remove duplicate between tick_nohz_switch_to_nohz() and tick_setup_sched

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Date: Thu, 25 Jan 2024 10:12:20 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Frederic Weisbecker <frederic@...nel.org>, LKML
 <linux-kernel@...r.kernel.org>
Cc: Peng Liu <liupeng17@...ovo.com>, Ingo Molnar <mingo@...nel.org>,
 Anna-Maria Behnsen <anna-maria@...utronix.de>, Joel Fernandes
 <joel@...lfernandes.org>, Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH 01/15] tick/nohz: Remove duplicate between
 tick_nohz_switch_to_nohz() and tick_setup_sched_timer()

On Wed, Jan 24 2024 at 18:04, Frederic Weisbecker wrote:
>  
>  /**
>   * tick_setup_sched_timer - setup the tick emulation timer
> + * @mode: tick_nohz_mode to setup for
>   */
> -void tick_setup_sched_timer(void)
> +void tick_setup_sched_timer(int mode)
>  {
>  	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
> -	ktime_t now = ktime_get();
>  
>  	/* Emulate tick processing via per-CPU hrtimers: */
>  	hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
> -	ts->sched_timer.function = tick_nohz_highres_handler;
> +#ifdef CONFIG_HIGH_RES_TIMERS
> +	if (mode == NOHZ_MODE_HIGHRES)
> +		ts->sched_timer.function = tick_nohz_highres_handler;
> +#endif

Adding

#define tick_nohz_highres_handler NULL

for CONFIG_HIGH_RES_TIMERS=n somewhere allows you to write that as:

	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
		ts->sched_timer.function = tick_nohz_highres_handler;
    
> +	hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
> +	if (mode == NOHZ_MODE_HIGHRES)

Wants a (IS_ENABLED(HIGRES) && mode == ...) no?

Thanks,

        tglx