Re: [PATCH RFC v3 10/11] platform/x86: ideapad-laptop: Serialize keyboard backlight notifications

ACPI notifications are delivered in dedicated work contexts and may
arrive simultaneously. In the following change, much work will be done
while handling the notification, which could lead to potential race
conditions.

Introduce a new mutex to serialize keyboard backlight notifications to
prevent potential race conditions.

Signed-off-by: Rong Zhang <redacted>
---
 drivers/platform/x86/lenovo/ideapad-laptop.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/platform/x86/lenovo/ideapad-laptop.c b/drivers/platform/x86/lenovo/ideapad-laptop.c
index 5aa2fedb8472..66e16abda5e3 100644
--- a/drivers/platform/x86/lenovo/ideapad-laptop.c
+++ b/drivers/platform/x86/lenovo/ideapad-laptop.c

@@ -26,7 +26,9 @@
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/leds.h>
+#include <linux/lockdep.h>

 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_device.h>
 #include <linux/platform_profile.h>
 #include <linux/power_supply.h>

@@ -228,6 +230,8 @@ struct ideapad_private {
 		int type;
 		struct led_classdev led;
 		atomic_t last_hw_brightness;
+
+		struct mutex notif_mutex; /* protects notifications */
 	} kbd_bl;
 	struct {
 		bool initialized;

@@ -1720,6 +1724,8 @@ static void ideapad_kbd_bl_notify(struct ideapad_private *priv)
 	if (!priv->kbd_bl.initialized)
 		return;
 
+	guard(mutex)(&priv->kbd_bl.notif_mutex);
+
 	hw_brightness = ideapad_kbd_bl_hw_brightness_get(priv);
 	if (hw_brightness < 0)
 		return;

@@ -1745,6 +1751,10 @@ static int ideapad_kbd_bl_init(struct ideapad_private *priv)
 	if (WARN_ON(priv->kbd_bl.initialized))
 		return -EEXIST;
 
+	err = devm_mutex_init(&priv->platform_device->dev, &priv->kbd_bl.notif_mutex);
+	if (err)
+		return err;
+
 	hw_brightness = ideapad_kbd_bl_hw_brightness_get(priv);
 	if (hw_brightness < 0)
 		return hw_brightness;