linux-kernel - [PATCH 5/5] leds: trigger: netdev: use mutex instead of spinlocks

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Date:   Wed, 19 Apr 2023 23:07:43 +0200
From:   Christian Marangi <ansuelsmth@...il.com>
To:     Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        Christian Marangi <ansuelsmth@...il.com>,
        Martin Schiller <ms@....tdt.de>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>
Subject: [PATCH 5/5] leds: trigger: netdev: use mutex instead of spinlocks

Some LEDs may require to sleep while doing some operation like setting
brightness and other cleanup.

For this reason, using a spinlock will cause a sleep under spinlock
warning.

It should be safe to convert this to a sleepable lock since:
- sysfs read/write can sleep
- netdev_trig_work is a work queue and can sleep
- netdev _trig_notify can sleep

The spinlock was used when brightness didn't support sleeping, but this
changed and now it supported with brightness_set_blocking().

Convert to mutex lock to permit sleeping using brightness_set_blocking().

Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
---
 drivers/leds/trigger/ledtrig-netdev.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index 5a47913c813c..115f2bae9eee 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -20,7 +20,7 @@
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
-#include <linux/spinlock.h>
+#include <linux/mutex.h>
 #include <linux/timer.h>
 #include "../leds.h"
 
@@ -37,7 +37,7 @@
  */
 
 struct led_netdev_data {
-	spinlock_t lock;
+	struct mutex lock;
 
 	struct delayed_work work;
 	struct notifier_block notifier;
@@ -97,9 +97,9 @@ static ssize_t device_name_show(struct device *dev,
 	struct led_netdev_data *trigger_data = led_trigger_get_drvdata(dev);
 	ssize_t len;
 
-	spin_lock_bh(&trigger_data->lock);
+	mutex_lock(&trigger_data->lock);
 	len = sprintf(buf, "%s\n", trigger_data->device_name);
-	spin_unlock_bh(&trigger_data->lock);
+	mutex_unlock(&trigger_data->lock);
 
 	return len;
 }
@@ -115,7 +115,7 @@ static ssize_t device_name_store(struct device *dev,
 
 	cancel_delayed_work_sync(&trigger_data->work);
 
-	spin_lock_bh(&trigger_data->lock);
+	mutex_lock(&trigger_data->lock);
 
 	if (trigger_data->net_dev) {
 		dev_put(trigger_data->net_dev);
@@ -138,7 +138,7 @@ static ssize_t device_name_store(struct device *dev,
 	trigger_data->last_activity = 0;
 
 	set_baseline_state(trigger_data);
-	spin_unlock_bh(&trigger_data->lock);
+	mutex_unlock(&trigger_data->lock);
 
 	return size;
 }
@@ -279,7 +279,7 @@ static int netdev_trig_notify(struct notifier_block *nb,
 
 	cancel_delayed_work_sync(&trigger_data->work);
 
-	spin_lock_bh(&trigger_data->lock);
+	mutex_lock(&trigger_data->lock);
 
 	trigger_data->carrier_link_up = false;
 	switch (evt) {
@@ -304,7 +304,7 @@ static int netdev_trig_notify(struct notifier_block *nb,
 
 	set_baseline_state(trigger_data);
 
-	spin_unlock_bh(&trigger_data->lock);
+	mutex_unlock(&trigger_data->lock);
 
 	return NOTIFY_DONE;
 }
@@ -365,7 +365,7 @@ static int netdev_trig_activate(struct led_classdev *led_cdev)
 	if (!trigger_data)
 		return -ENOMEM;
 
-	spin_lock_init(&trigger_data->lock);
+	mutex_init(&trigger_data->lock);
 
 	trigger_data->notifier.notifier_call = netdev_trig_notify;
 	trigger_data->notifier.priority = 10;
-- 
2.39.2