linux-kernel - Re: [PATCH v1 2/9] cpuidle: teo: Reorder candidate state index checks

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Message-ID: <a61647e9-dedd-4053-8f65-126564748950@arm.com>
Date: Thu, 16 Jan 2025 13:27:39 +0000
From: Christian Loehle <christian.loehle@....com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
Subject: Re: [PATCH v1 2/9] cpuidle: teo: Reorder candidate state index checks

On 1/13/25 18:36, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Since constraint_idx may be 0, the candidate state index may change to 0
> after assigning constraint_idx to it, so first check if it is greater
> than constraint_idx (and update it if so) and then check it against 0.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Fine with me now, since the posted patch addresses my concern.
Reviewed-by: Christian Loehle <christian.loehle@....com>

> ---
> 
> This is a rebased variant of
> 
> https://lore.kernel.org/linux-pm/8476650.T7Z3S40VBb@rjwysocki.net/
> 
> ---
>  drivers/cpuidle/governors/teo.c |   15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> --- a/drivers/cpuidle/governors/teo.c
> +++ b/drivers/cpuidle/governors/teo.c
> @@ -428,6 +428,14 @@
>  				break;
>  		}
>  	}
> +
> +	/*
> +	 * If there is a latency constraint, it may be necessary to select an
> +	 * idle state shallower than the current candidate one.
> +	 */
> +	if (idx > constraint_idx)
> +		idx = constraint_idx;
> +
>  	if (!idx && prev_intercept_idx) {
>  		/*
>  		 * We have to query the sleep length here otherwise we don't
> @@ -439,13 +447,6 @@
>  	}
>  
>  	/*
> -	 * If there is a latency constraint, it may be necessary to select an
> -	 * idle state shallower than the current candidate one.
> -	 */
> -	if (idx > constraint_idx)
> -		idx = constraint_idx;
> -
> -	/*
>  	 * Skip the timers check if state 0 is the current candidate one,
>  	 * because an immediate non-timer wakeup is expected in that case.
>  	 */
> 
> 
>