linux-kernel - [RFC PATCH for 6.13 v1 06/20] thermal: core: Consolidate thermal zone locking during initialization

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Message-ID: <10548633.nUPlyArG6x@rjwysocki.net>
Date: Sat, 14 Sep 2024 12:32:45 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Lukasz Luba <lukasz.luba@....com>, Zhang Rui <rui.zhang@...el.com>
Subject:
 [RFC PATCH for 6.13 v1 06/20] thermal: core: Consolidate thermal zone locking
 during initialization

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

The part of thermal zone initialization carried out under
thermal_list_lock acquires the thermal zone lock and releases it
multiple times back-to-back which is not really necessary.

Instead of doing this, acquire the thermal zone lock once after
acquiring thermal_list_lock and release it along with that lock.

For this purpose, move all of the code in question to
thermal_zone_init_complete() introduced previously and provide an
"unloacked" variant of thermal_zone_cdev_bind() to be invoked from
there.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/thermal/thermal_core.c |   40 ++++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

Index: linux-pm/drivers/thermal/thermal_core.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.c
+++ linux-pm/drivers/thermal/thermal_core.c
@@ -919,16 +919,14 @@ void print_bind_err_msg(struct thermal_z
 		cdev->type, thermal_zone_trip_id(tz, &td->trip), ret);
 }
 
-static void thermal_zone_cdev_bind(struct thermal_zone_device *tz,
-				   struct thermal_cooling_device *cdev)
+static void __thermal_zone_cdev_bind(struct thermal_zone_device *tz,
+				     struct thermal_cooling_device *cdev)
 {
 	struct thermal_trip_desc *td;
 
 	if (!tz->ops.should_bind)
 		return;
 
-	guard(thermal_zone)(tz);
-
 	for_each_trip_desc(tz, td) {
 		struct cooling_spec c = {
 			.upper = THERMAL_NO_LIMIT,
@@ -946,6 +944,14 @@ static void thermal_zone_cdev_bind(struc
 	}
 }
 
+static void thermal_zone_cdev_bind(struct thermal_zone_device *tz,
+				   struct thermal_cooling_device *cdev)
+{
+	guard(thermal_zone)(tz);
+
+	__thermal_zone_cdev_bind(tz, cdev);
+}
+
 /**
  * __thermal_cooling_device_register() - register a new thermal cooling device
  * @np:		a pointer to a device tree node.
@@ -1313,17 +1319,20 @@ int thermal_zone_get_crit_temp(struct th
 }
 EXPORT_SYMBOL_GPL(thermal_zone_get_crit_temp);
 
-static void thermal_zone_add_to_list(struct thermal_zone_device *tz)
+static void thermal_zone_init_complete(struct thermal_zone_device *tz)
 {
-	guard(thermal_zone)(tz);
+	struct thermal_cooling_device *cdev;
+
+	mutex_lock(&thermal_list_lock);
 
 	list_add_tail(&tz->node, &thermal_tz_list);
-}
 
-static void thermal_zone_init_complete(struct thermal_zone_device *tz)
-{
 	guard(thermal_zone)(tz);
 
+	/* Bind cooling devices for this zone. */
+	list_for_each_entry(cdev, &thermal_cdev_list, node)
+		__thermal_zone_cdev_bind(tz, cdev);
+
 	tz->state &= ~TZ_STATE_FLAG_INIT;
 	/*
 	 * If system suspend or resume is in progress at this point, the
@@ -1334,6 +1343,8 @@ static void thermal_zone_init_complete(s
 		tz->state |= TZ_STATE_FLAG_SUSPENDED;
 
 	__thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
+
+	mutex_unlock(&thermal_list_lock);
 }
 
 /**
@@ -1370,7 +1381,6 @@ thermal_zone_device_register_with_trips(
 					unsigned int polling_delay)
 {
 	const struct thermal_trip *trip = trips;
-	struct thermal_cooling_device *cdev;
 	struct thermal_zone_device *tz;
 	struct thermal_trip_desc *td;
 	int id;
@@ -1496,18 +1506,8 @@ thermal_zone_device_register_with_trips(
 			goto unregister;
 	}
 
-	mutex_lock(&thermal_list_lock);
-
-	thermal_zone_add_to_list(tz);
-
-	/* Bind cooling devices for this zone */
-	list_for_each_entry(cdev, &thermal_cdev_list, node)
-		thermal_zone_cdev_bind(tz, cdev);
-
 	thermal_zone_init_complete(tz);
 
-	mutex_unlock(&thermal_list_lock);
-
 	thermal_notify_tz_create(tz);
 
 	thermal_debug_tz_add(tz);