linux-kernel - [PATCH v2 07/17] thermal: core: Move thermal zone locking out of bind/unbind functions

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Message-ID: <4611405.cEBGB3zze1@rjwysocki.net>
Date: Mon, 12 Aug 2024 16:04:38 +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:
 [PATCH v2 07/17] thermal: core: Move thermal zone locking out of bind/unbind
 functions

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

Since thermal_bind_cdev_to_trip() and thermal_unbind_cdev_from_trip()
acquire the thermal zone lock, the locking rules for their callers get
complicated.  In particular, the thermal zone lock cannot be acquired
in any code path leading to one of these functions even though it might
be useful to do so.

To address this, remove the thermal zone locking from both these
functions, add lockdep assertions for the thermal zone lock to both
of them and make their callers acquire the thermal zone lock instead.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

v1 -> v2: No changes

---
 drivers/acpi/thermal.c         |    2 +-
 drivers/thermal/thermal_core.c |   30 ++++++++++++++++++++++--------
 2 files changed, 23 insertions(+), 9 deletions(-)

Index: linux-pm/drivers/thermal/thermal_core.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.c
+++ linux-pm/drivers/thermal/thermal_core.c
@@ -789,6 +789,7 @@ int thermal_bind_cdev_to_trip(struct the
 	int result;
 
 	lockdep_assert_held(&thermal_list_lock);
+	lockdep_assert_held(&tz->lock);
 
 	if (list_empty(&tz->node) || list_empty(&cdev->node))
 		return -EINVAL;
@@ -851,7 +852,6 @@ int thermal_bind_cdev_to_trip(struct the
 	if (result)
 		goto remove_trip_file;
 
-	mutex_lock(&tz->lock);
 	mutex_lock(&cdev->lock);
 
 	list_for_each_entry(instance, &td->thermal_instances, trip_node) {
@@ -868,7 +868,6 @@ int thermal_bind_cdev_to_trip(struct the
 	thermal_governor_update_tz(tz, THERMAL_TZ_BIND_CDEV);
 
 	mutex_unlock(&cdev->lock);
-	mutex_unlock(&tz->lock);
 
 	return 0;
 
@@ -892,11 +891,19 @@ int thermal_zone_bind_cooling_device(str
 				     unsigned long upper, unsigned long lower,
 				     unsigned int weight)
 {
+	int ret;
+
 	if (trip_index < 0 || trip_index >= tz->num_trips)
 		return -EINVAL;
 
-	return thermal_bind_cdev_to_trip(tz, &tz->trips[trip_index].trip, cdev,
-					 upper, lower, weight);
+	mutex_lock(&tz->lock);
+
+	ret = thermal_bind_cdev_to_trip(tz, &tz->trips[trip_index].trip, cdev,
+					upper, lower, weight);
+
+	mutex_unlock(&tz->lock);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(thermal_zone_bind_cooling_device);
 
@@ -919,7 +926,8 @@ int thermal_unbind_cdev_from_trip(struct
 	struct thermal_trip_desc *td = trip_to_trip_desc(trip);
 	struct thermal_instance *pos, *next;
 
-	mutex_lock(&tz->lock);
+	lockdep_assert_held(&tz->lock);
+
 	mutex_lock(&cdev->lock);
 
 	list_for_each_entry_safe(pos, next, &td->thermal_instances, trip_node) {
@@ -930,13 +938,11 @@ int thermal_unbind_cdev_from_trip(struct
 			thermal_governor_update_tz(tz, THERMAL_TZ_UNBIND_CDEV);
 
 			mutex_unlock(&cdev->lock);
-			mutex_unlock(&tz->lock);
 			goto free;
 		}
 	}
 
 	mutex_unlock(&cdev->lock);
-	mutex_unlock(&tz->lock);
 
 	return -ENODEV;
 
@@ -954,10 +960,18 @@ int thermal_zone_unbind_cooling_device(s
 				       int trip_index,
 				       struct thermal_cooling_device *cdev)
 {
+	int ret;
+
 	if (trip_index < 0 || trip_index >= tz->num_trips)
 		return -EINVAL;
 
-	return thermal_unbind_cdev_from_trip(tz, &tz->trips[trip_index].trip, cdev);
+	mutex_lock(&tz->lock);
+
+	ret = thermal_unbind_cdev_from_trip(tz, &tz->trips[trip_index].trip, cdev);
+
+	mutex_unlock(&tz->lock);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(thermal_zone_unbind_cooling_device);
 
Index: linux-pm/drivers/acpi/thermal.c
===================================================================
--- linux-pm.orig/drivers/acpi/thermal.c
+++ linux-pm/drivers/acpi/thermal.c
@@ -609,7 +609,7 @@ static int acpi_thermal_bind_unbind_cdev
 		.thermal = thermal, .cdev = cdev, .bind = bind
 	};
 
-	return for_each_thermal_trip(thermal, bind_unbind_cdev_cb, &bd);
+	return thermal_zone_for_each_trip(thermal, bind_unbind_cdev_cb, &bd);
 }
 
 static int