linux-kernel - Re: [PATCH v1 1/2] thermal: core: Fix rounding of delay jiffies

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Message-ID: <6893580d-53b2-4738-b49b-748f9310cb74@linaro.org>
Date: Fri, 23 Aug 2024 10:36:37 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Zhang Rui <rui.zhang@...el.com>,
 Lukasz Luba <lukasz.luba@....com>, Peter Kästle
 <peter@...e.net>
Subject: Re: [PATCH v1 1/2] thermal: core: Fix rounding of delay jiffies

On 22/08/2024 21:47, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Using round_jiffies() in thermal_set_delay_jiffies() is invalid because
> its argument should be time in the future in absolute jiffies and it
> computes the result with respect to the current jiffies value at the
> invocation time.  Fortunately, in the majority of cases it does not
> make any difference due to the time_is_after_jiffies() check in
> round_jiffies_common().
> 
> While using round_jiffies_relative() instead of round_jiffies() might
> reflect the intent a bit better, it still would not be defensible
> because that function should be called when the timer is about to be
> set and it is not suitable for pre-computation of delay values.
> 
> Accordingly, drop thermal_set_delay_jiffies() altogether, simply
> convert polling_delay and passive_delay to jiffies during thermal
> zone initialization and make thermal_zone_device_set_polling() call
> round_jiffies_relative() on the delay if it is greather than 1 second.

For the record:

In the history, the code was:

+       if (delay > 1000)
+               schedule_delayed_work(&(tz->poll_queue),
+ 
round_jiffies(msecs_to_jiffies(delay)));
+       else
+               schedule_delayed_work(&(tz->poll_queue),
+                                     msecs_to_jiffies(delay));


And the initial commit 21bc42ab852549f4a547d18d77e0e4d1b24ffd96:

"ACPI: thermal: use round_jiffies when thermal zone polling is enabled"

Good catch !

Reviewed-by: Daniel Lezcano <daniel.lezcano@...aro.org>


> Fixes: 17d399cd9c89 ("thermal/core: Precompute the delays from msecs to jiffies")
> Fixes: e5f2cda61d06 ("thermal/core: Move thermal_set_delay_jiffies to static")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>   drivers/thermal/thermal_core.c |   23 ++++++++++-------------
>   1 file changed, 10 insertions(+), 13 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -323,11 +323,15 @@ static void thermal_zone_broken_disable(
>   static void thermal_zone_device_set_polling(struct thermal_zone_device *tz,
>   					    unsigned long delay)
>   {
> -	if (delay)
> -		mod_delayed_work(system_freezable_power_efficient_wq,
> -				 &tz->poll_queue, delay);
> -	else
> +	if (!delay) {
>   		cancel_delayed_work(&tz->poll_queue);
> +		return;
> +	}
> +
> +	if (delay > HZ)
> +		delay = round_jiffies_relative(delay);
> +
> +	mod_delayed_work(system_freezable_power_efficient_wq, &tz->poll_queue, delay);
>   }
>   
>   static void thermal_zone_recheck(struct thermal_zone_device *tz, int error)
> @@ -1312,13 +1316,6 @@ void thermal_cooling_device_unregister(s
>   }
>   EXPORT_SYMBOL_GPL(thermal_cooling_device_unregister);
>   
> -static void thermal_set_delay_jiffies(unsigned long *delay_jiffies, int delay_ms)
> -{
> -	*delay_jiffies = msecs_to_jiffies(delay_ms);
> -	if (delay_ms > 1000)
> -		*delay_jiffies = round_jiffies(*delay_jiffies);
> -}
> -
>   int thermal_zone_get_crit_temp(struct thermal_zone_device *tz, int *temp)
>   {
>   	const struct thermal_trip_desc *td;
> @@ -1465,8 +1462,8 @@ thermal_zone_device_register_with_trips(
>   		td->threshold = INT_MAX;
>   	}
>   
> -	thermal_set_delay_jiffies(&tz->passive_delay_jiffies, passive_delay);
> -	thermal_set_delay_jiffies(&tz->polling_delay_jiffies, polling_delay);
> +	tz->polling_delay_jiffies = msecs_to_jiffies(polling_delay);
> +	tz->passive_delay_jiffies = msecs_to_jiffies(passive_delay);
>   	tz->recheck_delay_jiffies = THERMAL_RECHECK_DELAY;
>   
>   	/* sys I/F */
> 
> 
> 


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