linux-kernel - [PATCH v2] thermal: core: Fix list sorting in __thermal_zone_device

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Message-ID: <12481676.O9o76ZdvQC@rjwysocki.net>
Date: Mon, 08 Jul 2024 17:16:00 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>, Lukasz Luba <lukasz.luba@....com>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject:
 [PATCH v2] thermal: core: Fix list sorting in __thermal_zone_device_update()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

The order in which lists are sorted in __thermal_zone_device_update()
is reverse with respect to what it should be due to a mistake in
thermal_trip_notify_cmp().

Fix it and observe that it is not necessary to sort the lists in
different orders.  They can both be sorted in ascending order if
way_down_list is walked in reverse order which allows the code to
be slightly more straightforward (and less prone to silly mistakes).

Fixes: 7454f2c42cce ("thermal: core: Sort trip point crossing notifications by temperature")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

This supersedes

https://lore.kernel.org/linux-pm/2745398.mvXUDI8C0e@rjwysocki.net/

and hence v2.

It is urgent and I have verified that it actually works, so I'm going to
fast track it to get it into final 6.10.

---
 drivers/thermal/thermal_core.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

Index: linux-pm/drivers/thermal/thermal_core.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.c
+++ linux-pm/drivers/thermal/thermal_core.c
@@ -487,16 +487,14 @@ static void thermal_trip_crossed(struct
 	thermal_governor_trip_crossed(governor, tz, trip, crossed_up);
 }

-static int thermal_trip_notify_cmp(void *ascending, const struct list_head *a,
+static int thermal_trip_notify_cmp(void *not_used, const struct list_head *a,
 				   const struct list_head *b)
 {
 	struct thermal_trip_desc *tda = container_of(a, struct thermal_trip_desc,
 						     notify_list_node);
 	struct thermal_trip_desc *tdb = container_of(b, struct thermal_trip_desc,
 						     notify_list_node);
-	int ret = tdb->notify_temp - tda->notify_temp;
-
-	return ascending ? ret : -ret;
+	return tda->notify_temp - tdb->notify_temp;
 }

 void __thermal_zone_device_update(struct thermal_zone_device *tz,
@@ -525,12 +523,12 @@ void __thermal_zone_device_update(struct

 	thermal_zone_set_trips(tz);

-	list_sort(&way_up_list, &way_up_list, thermal_trip_notify_cmp);
+	list_sort(NULL, &way_up_list, thermal_trip_notify_cmp);
 	list_for_each_entry(td, &way_up_list, notify_list_node)
 		thermal_trip_crossed(tz, &td->trip, governor, true);

 	list_sort(NULL, &way_down_list, thermal_trip_notify_cmp);
-	list_for_each_entry(td, &way_down_list, notify_list_node)
+	list_for_each_entry_reverse(td, &way_down_list, notify_list_node)
 		thermal_trip_crossed(tz, &td->trip, governor, false);

 	if (governor->manage)