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

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Message-ID: <1994438.PYKUYFuaPT@rjwysocki.net>
Date: Thu, 22 Aug 2024 21:47:36 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Zhang Rui <rui.zhang@...el.com>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Lukasz Luba <lukasz.luba@....com>,
 Peter Kästle <peter@...e.net>
Subject: [PATCH v1 1/2] thermal: core: Fix rounding of delay jiffies

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.

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 */