linux-kernel - [PATCH v2 17/22] Input: pegasus_notetaker - use guard notation when acquiring mutex

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Message-ID: <ZtjKJsArLu3byTU6@google.com>
Date: Wed, 4 Sep 2024 13:59:18 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>
Cc: linux-input@...r.kernel.org,
	Michael Hennerich <michael.hennerich@...log.com>,
	Ville Syrjala <syrjala@....fi>,
	Support Opensource <support.opensource@...semi.com>,
	Eddie James <eajames@...ux.ibm.com>,
	Andrey Moiseev <o2g.org.ru@...il.com>,
	Hans de Goede <hdegoede@...hat.com>,
	Jeff LaBundy <jeff@...undy.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 17/22] Input: pegasus_notetaker - use guard notation when
 acquiring mutex

Using guard notation makes the code more compact and error handling
more robust by ensuring that mutexes are released in all code paths
when control leaves critical section.

Reviewed-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---

V2: fixed whitespace issues, added Reviewed-by from Javier

 drivers/input/tablet/pegasus_notetaker.c |   86 +++++++++++++++++-------------
 1 file changed, 48 insertions(+), 38 deletions(-)

diff --git a/drivers/input/tablet/pegasus_notetaker.c b/drivers/input/tablet/pegasus_notetaker.c
index a68da2988f9c..8d6b71d59793 100644
--- a/drivers/input/tablet/pegasus_notetaker.c
+++ b/drivers/input/tablet/pegasus_notetaker.c
@@ -214,6 +214,28 @@ static void pegasus_init(struct work_struct *work)
 			error);
 }
 
+static int __pegasus_open(struct pegasus *pegasus)
+{
+	int error;
+
+	guard(mutex)(&pegasus->pm_mutex);
+
+	pegasus->irq->dev = pegasus->usbdev;
+	if (usb_submit_urb(pegasus->irq, GFP_KERNEL))
+		return -EIO;
+
+	error = pegasus_set_mode(pegasus, PEN_MODE_XY, NOTETAKER_LED_MOUSE);
+	if (error) {
+		usb_kill_urb(pegasus->irq);
+		cancel_work_sync(&pegasus->init);
+		return error;
+	}
+
+	pegasus->is_open = true;
+
+	return 0;
+}
+
 static int pegasus_open(struct input_dev *dev)
 {
 	struct pegasus *pegasus = input_get_drvdata(dev);
@@ -223,39 +245,25 @@ static int pegasus_open(struct input_dev *dev)
 	if (error)
 		return error;
 
-	mutex_lock(&pegasus->pm_mutex);
-	pegasus->irq->dev = pegasus->usbdev;
-	if (usb_submit_urb(pegasus->irq, GFP_KERNEL)) {
-		error = -EIO;
-		goto err_autopm_put;
+	error = __pegasus_open(pegasus);
+	if (error) {
+		usb_autopm_put_interface(pegasus->intf);
+		return error;
 	}
 
-	error = pegasus_set_mode(pegasus, PEN_MODE_XY, NOTETAKER_LED_MOUSE);
-	if (error)
-		goto err_kill_urb;
-
-	pegasus->is_open = true;
-	mutex_unlock(&pegasus->pm_mutex);
 	return 0;
-
-err_kill_urb:
-	usb_kill_urb(pegasus->irq);
-	cancel_work_sync(&pegasus->init);
-err_autopm_put:
-	mutex_unlock(&pegasus->pm_mutex);
-	usb_autopm_put_interface(pegasus->intf);
-	return error;
 }
 
 static void pegasus_close(struct input_dev *dev)
 {
 	struct pegasus *pegasus = input_get_drvdata(dev);
 
-	mutex_lock(&pegasus->pm_mutex);
-	usb_kill_urb(pegasus->irq);
-	cancel_work_sync(&pegasus->init);
-	pegasus->is_open = false;
-	mutex_unlock(&pegasus->pm_mutex);
+	scoped_guard(mutex, &pegasus->pm_mutex) {
+		usb_kill_urb(pegasus->irq);
+		cancel_work_sync(&pegasus->init);
+
+		pegasus->is_open = false;
+	}
 
 	usb_autopm_put_interface(pegasus->intf);
 }
@@ -411,10 +419,10 @@ static int pegasus_suspend(struct usb_interface *intf, pm_message_t message)
 {
 	struct pegasus *pegasus = usb_get_intfdata(intf);
 
-	mutex_lock(&pegasus->pm_mutex);
+	guard(mutex)(&pegasus->pm_mutex);
+
 	usb_kill_urb(pegasus->irq);
 	cancel_work_sync(&pegasus->init);
-	mutex_unlock(&pegasus->pm_mutex);
 
 	return 0;
 }
@@ -422,31 +430,33 @@ static int pegasus_suspend(struct usb_interface *intf, pm_message_t message)
 static int pegasus_resume(struct usb_interface *intf)
 {
 	struct pegasus *pegasus = usb_get_intfdata(intf);
-	int retval = 0;
 
-	mutex_lock(&pegasus->pm_mutex);
+	guard(mutex)(&pegasus->pm_mutex);
+
 	if (pegasus->is_open && usb_submit_urb(pegasus->irq, GFP_NOIO) < 0)
-		retval = -EIO;
-	mutex_unlock(&pegasus->pm_mutex);
+		return -EIO;
 
-	return retval;
+	return 0;
 }
 
 static int pegasus_reset_resume(struct usb_interface *intf)
 {
 	struct pegasus *pegasus = usb_get_intfdata(intf);
-	int retval = 0;
+	int error;
+
+	guard(mutex)(&pegasus->pm_mutex);
 
-	mutex_lock(&pegasus->pm_mutex);
 	if (pegasus->is_open) {
-		retval = pegasus_set_mode(pegasus, PEN_MODE_XY,
+		error = pegasus_set_mode(pegasus, PEN_MODE_XY,
 					  NOTETAKER_LED_MOUSE);
-		if (!retval && usb_submit_urb(pegasus->irq, GFP_NOIO) < 0)
-			retval = -EIO;
+		if (error)
+			return error;
+
+		if (usb_submit_urb(pegasus->irq, GFP_NOIO) < 0)
+			return -EIO;
 	}
-	mutex_unlock(&pegasus->pm_mutex);
 
-	return retval;
+	return 0;
 }
 
 static const struct usb_device_id pegasus_ids[] = {