ALSA: hwdep: Use guard() for locking

We can simplify the code gracefully with new guard() macro and co for
automatic cleanup of locks.

There are still a few remaining explicit mutex_lock/unlock calls, and
those are for the places where we do temporary unlock/relock, which
doesn't fit well with the guard(), so far.

Only the code refactoring, and no functional changes.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20240227085306.9764-6-tiwai@suse.de

sound/core/hwdep.c

@@ -149,12 +149,12 @@ static int snd_hwdep_release(struct inode *inode, struct file * file)
 	struct snd_hwdep *hw = file->private_data;
 	struct module *mod = hw->card->module;
 
-	mutex_lock(&hw->open_mutex);
-	if (hw->ops.release)
-		err = hw->ops.release(hw, file);
-	if (hw->used > 0)
-		hw->used--;
-	mutex_unlock(&hw->open_mutex);
+	scoped_guard(mutex, &hw->open_mutex) {
+		if (hw->ops.release)
+			err = hw->ops.release(hw, file);
+		if (hw->used > 0)
+			hw->used--;
+	}
 	wake_up(&hw->open_wait);
 
 	snd_card_file_remove(hw->card, file);
@@ -272,43 +272,43 @@ static int snd_hwdep_control_ioctl(struct snd_card *card,
 
 			if (get_user(device, (int __user *)arg))
 				return -EFAULT;
-			mutex_lock(&register_mutex);
-
-			if (device < 0)
-				device = 0;
-			else if (device < SNDRV_MINOR_HWDEPS)
-				device++;
-			else
-				device = SNDRV_MINOR_HWDEPS;
-
-			while (device < SNDRV_MINOR_HWDEPS) {
-				if (snd_hwdep_search(card, device))
-					break;
-				device++;
+
+			scoped_guard(mutex, &register_mutex) {
+				if (device < 0)
+					device = 0;
+				else if (device < SNDRV_MINOR_HWDEPS)
+					device++;
+				else
+					device = SNDRV_MINOR_HWDEPS;
+
+				while (device < SNDRV_MINOR_HWDEPS) {
+					if (snd_hwdep_search(card, device))
+						break;
+					device++;
+				}
+				if (device >= SNDRV_MINOR_HWDEPS)
+					device = -1;
+				if (put_user(device, (int __user *)arg))
+					return -EFAULT;
+				return 0;
 			}
-			if (device >= SNDRV_MINOR_HWDEPS)
-				device = -1;
-			mutex_unlock(&register_mutex);
-			if (put_user(device, (int __user *)arg))
-				return -EFAULT;
-			return 0;
+			break;
 		}
 	case SNDRV_CTL_IOCTL_HWDEP_INFO:
 		{
 			struct snd_hwdep_info __user *info = (struct snd_hwdep_info __user *)arg;
-			int device, err;
+			int device;
 			struct snd_hwdep *hwdep;
 
 			if (get_user(device, &info->device))
 				return -EFAULT;
-			mutex_lock(&register_mutex);
-			hwdep = snd_hwdep_search(card, device);
-			if (hwdep)
-				err = snd_hwdep_info(hwdep, info);
-			else
-				err = -ENXIO;
-			mutex_unlock(&register_mutex);
-			return err;
+			scoped_guard(mutex, &register_mutex) {
+				hwdep = snd_hwdep_search(card, device);
+				if (!hwdep)
+					return -ENXIO;
+				return snd_hwdep_info(hwdep, info);
+			}
+			break;
 		}
 	}
 	return -ENOIOCTLCMD;
@@ -422,11 +422,9 @@ static int snd_hwdep_dev_register(struct snd_device *device)
 	struct snd_card *card = hwdep->card;
 	int err;
 
-	mutex_lock(&register_mutex);
-	if (snd_hwdep_search(card, hwdep->device)) {
-		mutex_unlock(&register_mutex);
+	guard(mutex)(&register_mutex);
+	if (snd_hwdep_search(card, hwdep->device))
 		return -EBUSY;
-	}
 	list_add_tail(&hwdep->list, &snd_hwdep_devices);
 	err = snd_register_device(SNDRV_DEVICE_TYPE_HWDEP,
 				  hwdep->card, hwdep->device,
@@ -434,7 +432,6 @@ static int snd_hwdep_dev_register(struct snd_device *device)
 	if (err < 0) {
 		dev_err(hwdep->dev, "unable to register\n");
 		list_del(&hwdep->list);
-		mutex_unlock(&register_mutex);
 		return err;
 	}
 
@@ -454,7 +451,6 @@ static int snd_hwdep_dev_register(struct snd_device *device)
 			hwdep->ossreg = 1;
 	}
 #endif
-	mutex_unlock(&register_mutex);
 	return 0;
 }
 
@@ -464,12 +460,10 @@ static int snd_hwdep_dev_disconnect(struct snd_device *device)
 
 	if (snd_BUG_ON(!hwdep))
 		return -ENXIO;
-	mutex_lock(&register_mutex);
-	if (snd_hwdep_search(hwdep->card, hwdep->device) != hwdep) {
-		mutex_unlock(&register_mutex);
+	guard(mutex)(&register_mutex);
+	if (snd_hwdep_search(hwdep->card, hwdep->device) != hwdep)
 		return -EINVAL;
-	}
-	mutex_lock(&hwdep->open_mutex);
+	guard(mutex)(&hwdep->open_mutex);
 	wake_up(&hwdep->open_wait);
 #ifdef CONFIG_SND_OSSEMUL
 	if (hwdep->ossreg)
@@ -477,8 +471,6 @@ static int snd_hwdep_dev_disconnect(struct snd_device *device)
 #endif
 	snd_unregister_device(hwdep->dev);
 	list_del_init(&hwdep->list);
-	mutex_unlock(&hwdep->open_mutex);
-	mutex_unlock(&register_mutex);
 	return 0;
 }
 
@@ -492,11 +484,10 @@ static void snd_hwdep_proc_read(struct snd_info_entry *entry,
 {
 	struct snd_hwdep *hwdep;
 
-	mutex_lock(&register_mutex);
+	guard(mutex)(&register_mutex);
 	list_for_each_entry(hwdep, &snd_hwdep_devices, list)
 		snd_iprintf(buffer, "%02i-%02i: %s\n",
 			    hwdep->card->number, hwdep->device, hwdep->name);
-	mutex_unlock(&register_mutex);
 }
 
 static struct snd_info_entry *snd_hwdep_proc_entry;