From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Linux PM <linux-pm@vger.kernel.org>,
        Zhang Rui <rui.zhang@intel.com>
Cc:     Linux ACPI <linux-acpi@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Quanxian Wang <quanxian.wang@intel.com>
Subject: [PATCH v3 3/4] thermal: core: Introduce thermal_cooling_device_update()
Date:   Fri, 17 Mar 2023 18:01:26 +0100
Message-ID: <2878875.e9J7NaK4W3@kreacher>
In-Reply-To: <2678096.mvXUDI8C0e@kreacher>
References: <2678096.mvXUDI8C0e@kreacher>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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

Introduce a core thermal API function, thermal_cooling_device_update(),
for updating the max_state value for a cooling device and rearranging
its statistics in sysfs after a possible change of its ->get_max_state()
callback return value.

That callback is now invoked only once, during cooling device
registration, to populate the max_state field in the cooling device
object, so if its return value changes, it needs to be invoked again
and the new return value needs to be stored as max_state.  Moreover,
the statistics presented in sysfs need to be rearranged in general,
because there may not be enough room in them to store data for all
of the possible states (in the case when max_state grows).

The new function takes care of that (and some other minor things
related to it), but some extra locking and lockdep annotations are
added in several places too to protect against crashes in the cases
when the statistics are not present or when a stale max_state value
might be used by sysfs attributes.

Note that the actual user of the new function will be added separately.

Link: https://lore.kernel.org/linux-pm/53ec1f06f61c984100868926f282647e57ecfb2d.camel@intel.com/
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Rui, please have a look at this again and give it a go if possible.  It is the
only patch in the series changing in v3.

v2 -> v3:
   Make thermal_cooling_device_update() check thermal instances involving the
   given thermal device and update the "upper" value for them if necessary (the
   "lower" and "target" values may need to be adjusted too in some cases) to avoid
   leaving thermal instances with "upper" above the new max_state of the
   corresponding cooling device.

v1 -> v2:
    * Make thermal_cooling_device_update() do the full IS_ERR_OR_NULL() check
      on cdev, so that its callers don't need to do it.
    * Remove ->set_cur_state() callback invocation from
      thermal_cooling_device_update(), because it is redundant (and it doesn't
      make sense to pass a state value exceeding max_state to it anyway).

---
 drivers/thermal/thermal_core.c  |   83 +++++++++++++++++++++++++++++++++++++++-
 drivers/thermal/thermal_core.h  |    2 
 drivers/thermal/thermal_sysfs.c |   72 ++++++++++++++++++++++++++++++----
 include/linux/thermal.h         |    1 
 4 files changed, 149 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
@@ -613,6 +613,7 @@ int thermal_zone_bind_cooling_device(str
 	struct thermal_instance *pos;
 	struct thermal_zone_device *pos1;
 	struct thermal_cooling_device *pos2;
+	bool upper_no_limit;
 	int result;
 
 	if (trip >= tz->num_trips || trip < 0)
@@ -632,7 +633,13 @@ int thermal_zone_bind_cooling_device(str
 
 	/* lower default 0, upper default max_state */
 	lower = lower == THERMAL_NO_LIMIT ? 0 : lower;
-	upper = upper == THERMAL_NO_LIMIT ? cdev->max_state : upper;
+
+	if (upper == THERMAL_NO_LIMIT) {
+		upper = cdev->max_state;
+		upper_no_limit = true;
+	} else {
+		upper_no_limit = false;
+	}
 
 	if (lower > upper || upper > cdev->max_state)
 		return -EINVAL;
@@ -644,6 +651,7 @@ int thermal_zone_bind_cooling_device(str
 	dev->cdev = cdev;
 	dev->trip = trip;
 	dev->upper = upper;
+	dev->upper_no_limit = upper_no_limit;
 	dev->lower = lower;
 	dev->target = THERMAL_NO_TARGET;
 	dev->weight = weight;
@@ -1057,6 +1065,79 @@ static bool thermal_cooling_device_prese
 	return false;
 }
 
+/**
+ * thermal_cooling_device_update - Update a cooling device object
+ * @cdev: Target cooling device.
+ *
+ * Update @cdev to reflect a change of the underlying hardware or platform.
+ *
+ * Must be called when the maximum cooling state of @cdev becomes invalid and so
+ * its .get_max_state() callback needs to be run to produce the new maximum
+ * cooling state value.
+ */
+void thermal_cooling_device_update(struct thermal_cooling_device *cdev)
+{
+	struct thermal_instance *ti;
+	unsigned long state;
+
+	if (IS_ERR_OR_NULL(cdev))
+		return;
+
+	/*
+	 * Hold thermal_list_lock throughout the update to prevent the device
+	 * from going away while being updated.
+	 */
+	mutex_lock(&thermal_list_lock);
+
+	if (!thermal_cooling_device_present(cdev))
+		goto unlock_list;
+
+	/*
+	 * Update under the cdev lock to prevent the state from being set beyond
+	 * the new limit concurrently.
+	 */
+	mutex_lock(&cdev->lock);
+
+	if (cdev->ops->get_max_state(cdev, &cdev->max_state))
+		goto unlock;
+
+	thermal_cooling_device_stats_reinit(cdev);
+
+	list_for_each_entry(ti, &cdev->thermal_instances, cdev_node) {
+		if (ti->upper == cdev->max_state)
+			continue;
+
+		if (ti->upper < cdev->max_state) {
+			if (ti->upper_no_limit)
+				ti->upper = cdev->max_state;
+
+			continue;
+		}
+
+		ti->upper = cdev->max_state;
+		if (ti->lower > ti->upper)
+			ti->lower = ti->upper;
+
+		if (ti->target == THERMAL_NO_TARGET)
+			continue;
+
+		if (ti->target > ti->upper)
+			ti->target = ti->upper;
+	}
+
+	if (cdev->ops->get_cur_state(cdev, &state) || state > cdev->max_state)
+		goto unlock;
+
+	thermal_cooling_device_stats_update(cdev, state);
+
+unlock:
+	mutex_unlock(&cdev->lock);
+
+unlock_list:
+	mutex_unlock(&thermal_list_lock);
+}
+EXPORT_SYMBOL_GPL(thermal_cooling_device_update);
+
 static void __unbind(struct thermal_zone_device *tz, int mask,
 		     struct thermal_cooling_device *cdev)
 {
Index: linux-pm/drivers/thermal/thermal_sysfs.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_sysfs.c
+++ linux-pm/drivers/thermal/thermal_sysfs.c
@@ -685,6 +685,8 @@ void thermal_cooling_device_stats_update
 {
 	struct cooling_dev_stats *stats = cdev->stats;
 
+	lockdep_assert_held(&cdev->lock);
+
 	if (!stats)
 		return;
 
@@ -706,13 +708,22 @@ static ssize_t total_trans_show(struct d
 				struct device_attribute *attr, char *buf)
 {
 	struct thermal_cooling_device *cdev = to_cooling_device(dev);
-	struct cooling_dev_stats *stats = cdev->stats;
+	struct cooling_dev_stats *stats;
 	int ret;
 
+	mutex_lock(&cdev->lock);
+
+	stats = cdev->stats;
+	if (!stats)
+		goto unlock;
+
 	spin_lock(&stats->lock);
 	ret = sprintf(buf, "%u\n", stats->total_trans);
 	spin_unlock(&stats->lock);
 
+unlock:
+	mutex_unlock(&cdev->lock);
+
 	return ret;
 }
 
@@ -721,11 +732,18 @@ time_in_state_ms_show(struct device *dev
 		      char *buf)
 {
 	struct thermal_cooling_device *cdev = to_cooling_device(dev);
-	struct cooling_dev_stats *stats = cdev->stats;
+	struct cooling_dev_stats *stats;
 	ssize_t len = 0;
 	int i;
 
+	mutex_lock(&cdev->lock);
+
+	stats = cdev->stats;
+	if (!stats)
+		goto unlock;
+
 	spin_lock(&stats->lock);
+
 	update_time_in_state(stats);
 
 	for (i = 0; i <= cdev->max_state; i++) {
@@ -734,6 +752,9 @@ time_in_state_ms_show(struct device *dev
 	}
 	spin_unlock(&stats->lock);
 
+unlock:
+	mutex_unlock(&cdev->lock);
+
 	return len;
 }
 
@@ -742,8 +763,16 @@ reset_store(struct device *dev, struct d
 	    size_t count)
 {
 	struct thermal_cooling_device *cdev = to_cooling_device(dev);
-	struct cooling_dev_stats *stats = cdev->stats;
-	int i, states = cdev->max_state + 1;
+	struct cooling_dev_stats *stats;
+	int i, states;
+
+	mutex_lock(&cdev->lock);
+
+	stats = cdev->stats;
+	if (!stats)
+		goto unlock;
+
+	states = cdev->max_state + 1;
 
 	spin_lock(&stats->lock);
 
@@ -757,6 +786,9 @@ reset_store(struct device *dev, struct d
 
 	spin_unlock(&stats->lock);
 
+unlock:
+	mutex_unlock(&cdev->lock);
+
 	return count;
 }
 
@@ -764,10 +796,18 @@ static ssize_t trans_table_show(struct d
 				struct device_attribute *attr, char *buf)
 {
 	struct thermal_cooling_device *cdev = to_cooling_device(dev);
-	struct cooling_dev_stats *stats = cdev->stats;
+	struct cooling_dev_stats *stats;
 	ssize_t len = 0;
 	int i, j;
 
+	mutex_lock(&cdev->lock);
+
+	stats = cdev->stats;
+	if (!stats) {
+		len = -ENODATA;
+		goto unlock;
+	}
+
 	len += snprintf(buf + len, PAGE_SIZE - len, " From  :    To\n");
 	len += snprintf(buf + len, PAGE_SIZE - len, "       : ");
 	for (i = 0; i <= cdev->max_state; i++) {
@@ -775,8 +815,10 @@ static ssize_t trans_table_show(struct d
 			break;
 		len += snprintf(buf + len, PAGE_SIZE - len, "state%2u  ", i);
 	}
-	if (len >= PAGE_SIZE)
-		return PAGE_SIZE;
+	if (len >= PAGE_SIZE) {
+		len = PAGE_SIZE;
+		goto unlock;
+	}
 
 	len += snprintf(buf + len, PAGE_SIZE - len, "\n");
 
@@ -799,8 +841,12 @@ static ssize_t trans_table_show(struct d
 
 	if (len >= PAGE_SIZE) {
 		pr_warn_once("Thermal transition table exceeds PAGE_SIZE. Disabling\n");
-		return -EFBIG;
+		len = -EFBIG;
 	}
+
+unlock:
+	mutex_unlock(&cdev->lock);
+
 	return len;
 }
 
@@ -830,6 +876,8 @@ static void cooling_device_stats_setup(s
 	unsigned long states = cdev->max_state + 1;
 	int var;
 
+	lockdep_assert_held(&cdev->lock);
+
 	var = sizeof(*stats);
 	var += sizeof(*stats->time_in_state) * states;
 	var += sizeof(*stats->trans_table) * states * states;
@@ -855,6 +903,8 @@ out:
 
 static void cooling_device_stats_destroy(struct thermal_cooling_device *cdev)
 {
+	lockdep_assert_held(&cdev->lock);
+
 	kfree(cdev->stats);
 	cdev->stats = NULL;
 }
@@ -879,6 +929,12 @@ void thermal_cooling_device_destroy_sysf
 	cooling_device_stats_destroy(cdev);
 }
 
+void thermal_cooling_device_stats_reinit(struct thermal_cooling_device *cdev)
+{
+	cooling_device_stats_destroy(cdev);
+	cooling_device_stats_setup(cdev);
+}
+
 /* these helper will be used only at the time of bindig */
 ssize_t
 trip_point_show(struct device *dev, struct device_attribute *attr, char *buf)
Index: linux-pm/drivers/thermal/thermal_core.h
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.h
+++ linux-pm/drivers/thermal/thermal_core.h
@@ -101,6 +101,7 @@ struct thermal_instance {
 	struct list_head tz_node; /* node in tz->thermal_instances */
 	struct list_head cdev_node; /* node in cdev->thermal_instances */
 	unsigned int weight; /* The weight of the cooling device */
+	bool upper_no_limit;
 };
 
 #define to_thermal_zone(_dev) \
@@ -127,6 +128,7 @@ int thermal_zone_create_device_groups(st
 void thermal_zone_destroy_device_groups(struct thermal_zone_device *);
 void thermal_cooling_device_setup_sysfs(struct thermal_cooling_device *);
 void thermal_cooling_device_destroy_sysfs(struct thermal_cooling_device *cdev);
+void thermal_cooling_device_stats_reinit(struct thermal_cooling_device *cdev);
 /* used only at binding time */
 ssize_t trip_point_show(struct device *, struct device_attribute *, char *);
 ssize_t weight_show(struct device *, struct device_attribute *, char *);
Index: linux-pm/include/linux/thermal.h
===================================================================
--- linux-pm.orig/include/linux/thermal.h
+++ linux-pm/include/linux/thermal.h
@@ -388,6 +388,7 @@ devm_thermal_of_cooling_device_register(
 				struct device_node *np,
 				char *type, void *devdata,
 				const struct thermal_cooling_device_ops *ops);
+void thermal_cooling_device_update(struct thermal_cooling_device *);
 void thermal_cooling_device_unregister(struct thermal_cooling_device *);
 struct thermal_zone_device *thermal_zone_get_zone_by_name(const char *name);
 int thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp);