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Date:   Sat, 15 Jul 2023 02:01:51 +0200
From:   Frederic Weisbecker <frederic@kernel.org>
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] tick/nohz: Don't shutdown the lowres tick from itself
Message-ID: <ZLHh71KIIioR85aa@lothringen>
References: <20230714120852.23573-1-frederic@kernel.org>
 <20230714120852.23573-4-frederic@kernel.org>
 <9347e3d4-e774-f75f-22c4-6c2dba294423@joelfernandes.org>
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On Fri, Jul 14, 2023 at 02:44:49PM -0400, Joel Fernandes wrote:
> On 7/14/23 08:08, Frederic Weisbecker wrote:
> One slight concern here though, where in the idle loop is the removed
> statement "tick_program_event(KTIME_MAX, 1);" happening if the tick was
> already stopped before? If it is happening in tick_nohz_stop_tick(), don't
> we early return from there and avoid doing that
> "tick_program_event(KTIME_MAX, 1);" altogether, if the tick was already
> stopped and the next event has not changed?
> 
>         /* Skip reprogram of event if its not changed */
>         if (ts->tick_stopped && (expires == ts->next_tick)) {
>                 /* Sanity check: make sure clockevent is actually programmed */
>                 if (tick == KTIME_MAX || ts->next_tick ==  [...]
>                         return;
> 		[...]
> 	}

Sure, if tick_program_event(KTIME_MAX, 1) was already called in the
previous idle loop iteration, then there is no need to call that again.

Or am I missing something else?

> 
> Also just a nit, here you can remove indent by doing:
> 
> if (unlikely(ts->tick_stopped))
>     return;
> hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
> tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
> 
> Which is pretty much the original code except for the tick_program_event().

Either I remove an indent or I remove a statement. I guess it's a matter of
personal taste. I don't mind either way :-)

Thanks.