ALSA: control: Use guard() for locking

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

The lops calls under multiple rwsems are factored out as a simple
macro, so that it can be called easily from snd_ctl_dev_register()
and snd_ctl_dev_disconnect().

There are a few remaining explicit rwsem and spinlock calls, and those
are the places where the lock downgrade happens or where the temporary
unlock/relocking happens -- which guard() doens't cover well yet.

Only the code refactoring, and no functional changes.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20240227085306.9764-9-tiwai@suse.de

2 files changed, 176 insertions, 273 deletions

diff --git a/sound/core/control.c b/sound/core/control.c
index c8cd70aed6af4b..8367fd4853716a 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -44,7 +44,6 @@ static int snd_ctl_remove_locked(struct snd_card *card,
 
 static int snd_ctl_open(struct inode *inode, struct file *file)
 {
-	unsigned long flags;
 	struct snd_card *card;
 	struct snd_ctl_file *ctl;
 	int i, err;
@@ -80,9 +79,8 @@ static int snd_ctl_open(struct inode *inode, struct file *file)
 		ctl->preferred_subdevice[i] = -1;
 	ctl->pid = get_pid(task_pid(current));
 	file->private_data = ctl;
-	write_lock_irqsave(&card->ctl_files_rwlock, flags);
-	list_add_tail(&ctl->list, &card->ctl_files);
-	write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
+	scoped_guard(write_lock_irqsave, &card->ctl_files_rwlock)
+		list_add_tail(&ctl->list, &card->ctl_files);
 	snd_card_unref(card);
 	return 0;
 
@@ -98,21 +96,18 @@ static int snd_ctl_open(struct inode *inode, struct file *file)
 
 static void snd_ctl_empty_read_queue(struct snd_ctl_file * ctl)
 {
-	unsigned long flags;
 	struct snd_kctl_event *cread;
 
-	spin_lock_irqsave(&ctl->read_lock, flags);
+	guard(spinlock_irqsave)(&ctl->read_lock);
 	while (!list_empty(&ctl->events)) {
 		cread = snd_kctl_event(ctl->events.next);
 		list_del(&cread->list);
 		kfree(cread);
 	}
-	spin_unlock_irqrestore(&ctl->read_lock, flags);
 }
 
 static int snd_ctl_release(struct inode *inode, struct file *file)
 {
-	unsigned long flags;
 	struct snd_card *card;
 	struct snd_ctl_file *ctl;
 	struct snd_kcontrol *control;
@@ -121,15 +116,17 @@ static int snd_ctl_release(struct inode *inode, struct file *file)
 	ctl = file->private_data;
 	file->private_data = NULL;
 	card = ctl->card;
-	write_lock_irqsave(&card->ctl_files_rwlock, flags);
-	list_del(&ctl->list);
-	write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
-	down_write(&card->controls_rwsem);
-	list_for_each_entry(control, &card->controls, list)
-		for (idx = 0; idx < control->count; idx++)
-			if (control->vd[idx].owner == ctl)
-				control->vd[idx].owner = NULL;
-	up_write(&card->controls_rwsem);
+
+	scoped_guard(write_lock_irqsave, &card->ctl_files_rwlock)
+		list_del(&ctl->list);
+
+	scoped_guard(rwsem_write, &card->controls_rwsem) {
+		list_for_each_entry(control, &card->controls, list)
+			for (idx = 0; idx < control->count; idx++)
+				if (control->vd[idx].owner == ctl)
+					control->vd[idx].owner = NULL;
+	}
+
 	snd_fasync_free(ctl->fasync);
 	snd_ctl_empty_read_queue(ctl);
 	put_pid(ctl->pid);
@@ -152,7 +149,6 @@ static int snd_ctl_release(struct inode *inode, struct file *file)
 void snd_ctl_notify(struct snd_card *card, unsigned int mask,
 		    struct snd_ctl_elem_id *id)
 {
-	unsigned long flags;
 	struct snd_ctl_file *ctl;
 	struct snd_kctl_event *ev;
 
@@ -160,34 +156,34 @@ void snd_ctl_notify(struct snd_card *card, unsigned int mask,
 		return;
 	if (card->shutdown)
 		return;
-	read_lock_irqsave(&card->ctl_files_rwlock, flags);
+
+	guard(read_lock_irqsave)(&card->ctl_files_rwlock);
 #if IS_ENABLED(CONFIG_SND_MIXER_OSS)
 	card->mixer_oss_change_count++;
 #endif
 	list_for_each_entry(ctl, &card->ctl_files, list) {
 		if (!ctl->subscribed)
 			continue;
-		spin_lock(&ctl->read_lock);
-		list_for_each_entry(ev, &ctl->events, list) {
-			if (ev->id.numid == id->numid) {
-				ev->mask |= mask;
-				goto _found;
+		scoped_guard(spinlock, &ctl->read_lock) {
+			list_for_each_entry(ev, &ctl->events, list) {
+				if (ev->id.numid == id->numid) {
+					ev->mask |= mask;
+					goto _found;
+				}
 			}
+			ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
+			if (ev) {
+				ev->id = *id;
+				ev->mask = mask;
+				list_add_tail(&ev->list, &ctl->events);
+			} else {
+				dev_err(card->dev, "No memory available to allocate event\n");
+			}
+_found:
+			wake_up(&ctl->change_sleep);
 		}
-		ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
-		if (ev) {
-			ev->id = *id;
-			ev->mask = mask;
-			list_add_tail(&ev->list, &ctl->events);
-		} else {
-			dev_err(card->dev, "No memory available to allocate event\n");
-		}
-	_found:
-		wake_up(&ctl->change_sleep);
-		spin_unlock(&ctl->read_lock);
 		snd_kill_fasync(ctl->fasync, SIGIO, POLL_IN);
 	}
-	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
 }
 EXPORT_SYMBOL(snd_ctl_notify);
 
@@ -210,10 +206,9 @@ void snd_ctl_notify_one(struct snd_card *card, unsigned int mask,
 	id.index += ioff;
 	id.numid += ioff;
 	snd_ctl_notify(card, mask, &id);
-	down_read(&snd_ctl_layer_rwsem);
+	guard(rwsem_read)(&snd_ctl_layer_rwsem);
 	for (lops = snd_ctl_layer; lops; lops = lops->next)
 		lops->lnotify(card, mask, kctl, ioff);
-	up_read(&snd_ctl_layer_rwsem);
 }
 EXPORT_SYMBOL(snd_ctl_notify_one);
 
@@ -520,9 +515,9 @@ static int snd_ctl_add_replace(struct snd_card *card,
 	if (snd_BUG_ON(!card || !kcontrol->info))
 		goto error;
 
-	down_write(&card->controls_rwsem);
-	err = __snd_ctl_add_replace(card, kcontrol, mode);
-	up_write(&card->controls_rwsem);
+	scoped_guard(rwsem_write, &card->controls_rwsem)
+		err = __snd_ctl_add_replace(card, kcontrol, mode);
+
 	if (err < 0)
 		goto error;
 	return 0;
@@ -616,12 +611,8 @@ static inline int snd_ctl_remove_locked(struct snd_card *card,
  */
 int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
 {
-	int ret;
-
-	down_write(&card->controls_rwsem);
-	ret = snd_ctl_remove_locked(card, kcontrol);
-	up_write(&card->controls_rwsem);
-	return ret;
+	guard(rwsem_write)(&card->controls_rwsem);
+	return snd_ctl_remove_locked(card, kcontrol);
 }
 EXPORT_SYMBOL(snd_ctl_remove);
 
@@ -638,17 +629,12 @@ EXPORT_SYMBOL(snd_ctl_remove);
 int snd_ctl_remove_id(struct snd_card *card, struct snd_ctl_elem_id *id)
 {
 	struct snd_kcontrol *kctl;
-	int ret;
 
-	down_write(&card->controls_rwsem);
+	guard(rwsem_write)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, id);
-	if (kctl == NULL) {
-		up_write(&card->controls_rwsem);
+	if (kctl == NULL)
 		return -ENOENT;
-	}
-	ret = snd_ctl_remove_locked(card, kctl);
-	up_write(&card->controls_rwsem);
-	return ret;
+	return snd_ctl_remove_locked(card, kctl);
 }
 EXPORT_SYMBOL(snd_ctl_remove_id);
 
@@ -667,27 +653,18 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file,
 {
 	struct snd_card *card = file->card;
 	struct snd_kcontrol *kctl;
-	int idx, ret;
+	int idx;
 
-	down_write(&card->controls_rwsem);
+	guard(rwsem_write)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, id);
-	if (kctl == NULL) {
-		ret = -ENOENT;
-		goto error;
-	}
-	if (!(kctl->vd[0].access & SNDRV_CTL_ELEM_ACCESS_USER)) {
-		ret = -EINVAL;
-		goto error;
-	}
+	if (kctl == NULL)
+		return -ENOENT;
+	if (!(kctl->vd[0].access & SNDRV_CTL_ELEM_ACCESS_USER))
+		return -EINVAL;
 	for (idx = 0; idx < kctl->count; idx++)
-		if (kctl->vd[idx].owner != NULL && kctl->vd[idx].owner != file) {
-			ret = -EBUSY;
-			goto error;
-		}
-	ret = snd_ctl_remove_locked(card, kctl);
-error:
-	up_write(&card->controls_rwsem);
-	return ret;
+		if (kctl->vd[idx].owner != NULL && kctl->vd[idx].owner != file)
+			return -EBUSY;
+	return snd_ctl_remove_locked(card, kctl);
 }
 
 /**
@@ -764,18 +741,15 @@ int snd_ctl_rename_id(struct snd_card *card, struct snd_ctl_elem_id *src_id,
 	struct snd_kcontrol *kctl;
 	int saved_numid;
 
-	down_write(&card->controls_rwsem);
+	guard(rwsem_write)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, src_id);
-	if (kctl == NULL) {
-		up_write(&card->controls_rwsem);
+	if (kctl == NULL)
 		return -ENOENT;
-	}
 	saved_numid = kctl->id.numid;
 	remove_hash_entries(card, kctl);
 	kctl->id = *dst_id;
 	kctl->id.numid = saved_numid;
 	add_hash_entries(card, kctl);
-	up_write(&card->controls_rwsem);
 	return 0;
 }
 EXPORT_SYMBOL(snd_ctl_rename_id);
@@ -793,7 +767,7 @@ EXPORT_SYMBOL(snd_ctl_rename_id);
 void snd_ctl_rename(struct snd_card *card, struct snd_kcontrol *kctl,
 		    const char *name)
 {
-	down_write(&card->controls_rwsem);
+	guard(rwsem_write)(&card->controls_rwsem);
 	remove_hash_entries(card, kctl);
 
 	if (strscpy(kctl->id.name, name, sizeof(kctl->id.name)) < 0)
@@ -801,7 +775,6 @@ void snd_ctl_rename(struct snd_card *card, struct snd_kcontrol *kctl,
 			name, kctl->id.name);
 
 	add_hash_entries(card, kctl);
-	up_write(&card->controls_rwsem);
 }
 EXPORT_SYMBOL(snd_ctl_rename);
 
@@ -859,12 +832,8 @@ EXPORT_SYMBOL(snd_ctl_find_numid_locked);
 struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card,
 					unsigned int numid)
 {
-	struct snd_kcontrol *kctl;
-
-	down_read(&card->controls_rwsem);
-	kctl = snd_ctl_find_numid_locked(card, numid);
-	up_read(&card->controls_rwsem);
-	return kctl;
+	guard(rwsem_read)(&card->controls_rwsem);
+	return snd_ctl_find_numid_locked(card, numid);
 }
 EXPORT_SYMBOL(snd_ctl_find_numid);
 
@@ -920,12 +889,8 @@ EXPORT_SYMBOL(snd_ctl_find_id_locked);
 struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card,
 				     const struct snd_ctl_elem_id *id)
 {
-	struct snd_kcontrol *kctl;
-
-	down_read(&card->controls_rwsem);
-	kctl = snd_ctl_find_id_locked(card, id);
-	up_read(&card->controls_rwsem);
-	return kctl;
+	guard(rwsem_read)(&card->controls_rwsem);
+	return snd_ctl_find_id_locked(card, id);
 }
 EXPORT_SYMBOL(snd_ctl_find_id);
 
@@ -937,15 +902,15 @@ static int snd_ctl_card_info(struct snd_card *card, struct snd_ctl_file * ctl,
 	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (! info)
 		return -ENOMEM;
-	down_read(&snd_ioctl_rwsem);
-	info->card = card->number;
-	strscpy(info->id, card->id, sizeof(info->id));
-	strscpy(info->driver, card->driver, sizeof(info->driver));
-	strscpy(info->name, card->shortname, sizeof(info->name));
-	strscpy(info->longname, card->longname, sizeof(info->longname));
-	strscpy(info->mixername, card->mixername, sizeof(info->mixername));
-	strscpy(info->components, card->components, sizeof(info->components));
-	up_read(&snd_ioctl_rwsem);
+	scoped_guard(rwsem_read, &snd_ioctl_rwsem) {
+		info->card = card->number;
+		strscpy(info->id, card->id, sizeof(info->id));
+		strscpy(info->driver, card->driver, sizeof(info->driver));
+		strscpy(info->name, card->shortname, sizeof(info->name));
+		strscpy(info->longname, card->longname, sizeof(info->longname));
+		strscpy(info->mixername, card->mixername, sizeof(info->mixername));
+		strscpy(info->components, card->components, sizeof(info->components));
+	}
 	if (copy_to_user(arg, info, sizeof(struct snd_ctl_card_info)))
 		return -EFAULT;
 	return 0;
@@ -957,37 +922,31 @@ static int snd_ctl_elem_list(struct snd_card *card,
 	struct snd_kcontrol *kctl;
 	struct snd_ctl_elem_id id;
 	unsigned int offset, space, jidx;
-	int err = 0;
 
 	offset = list->offset;
 	space = list->space;
 
-	down_read(&card->controls_rwsem);
+	guard(rwsem_read)(&card->controls_rwsem);
 	list->count = card->controls_count;
 	list->used = 0;
-	if (space > 0) {
-		list_for_each_entry(kctl, &card->controls, list) {
-			if (offset >= kctl->count) {
-				offset -= kctl->count;
-				continue;
-			}
-			for (jidx = offset; jidx < kctl->count; jidx++) {
-				snd_ctl_build_ioff(&id, kctl, jidx);
-				if (copy_to_user(list->pids + list->used, &id,
-						 sizeof(id))) {
-					err = -EFAULT;
-					goto out;
-				}
-				list->used++;
-				if (!--space)
-					goto out;
-			}
-			offset = 0;
+	if (!space)
+		return 0;
+	list_for_each_entry(kctl, &card->controls, list) {
+		if (offset >= kctl->count) {
+			offset -= kctl->count;
+			continue;
+		}
+		for (jidx = offset; jidx < kctl->count; jidx++) {
+			snd_ctl_build_ioff(&id, kctl, jidx);
+			if (copy_to_user(list->pids + list->used, &id, sizeof(id)))
+				return -EFAULT;
+			list->used++;
+			if (!--space)
+				return 0;
 		}
+		offset = 0;
 	}
- out:
-	up_read(&card->controls_rwsem);
-	return err;
+	return 0;
 }
 
 static int snd_ctl_elem_list_user(struct snd_card *card,
@@ -1235,16 +1194,12 @@ static int snd_ctl_elem_info(struct snd_ctl_file *ctl,
 {
 	struct snd_card *card = ctl->card;
 	struct snd_kcontrol *kctl;
-	int result;
 
-	down_read(&card->controls_rwsem);
+	guard(rwsem_read)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, &info->id);
-	if (kctl == NULL)
-		result = -ENOENT;
-	else
-		result = __snd_ctl_elem_info(card, kctl, info, ctl);
-	up_read(&card->controls_rwsem);
-	return result;
+	if (!kctl)
+		return -ENOENT;
+	return __snd_ctl_elem_info(card, kctl, info, ctl);
 }
 
 static int snd_ctl_elem_info_user(struct snd_ctl_file *ctl,
@@ -1276,19 +1231,15 @@ static int snd_ctl_elem_read(struct snd_card *card,
 	const u32 pattern = 0xdeadbeef;
 	int ret;
 
-	down_read(&card->controls_rwsem);
+	guard(rwsem_read)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, &control->id);
-	if (kctl == NULL) {
-		ret = -ENOENT;
-		goto unlock;
-	}
+	if (!kctl)
+		return -ENOENT;
 
 	index_offset = snd_ctl_get_ioff(kctl, &control->id);
 	vd = &kctl->vd[index_offset];
-	if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_READ) || kctl->get == NULL) {
-		ret = -EPERM;
-		goto unlock;
-	}
+	if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_READ) || !kctl->get)
+		return -EPERM;
 
 	snd_ctl_build_ioff(&control->id, kctl, index_offset);
 
@@ -1298,7 +1249,7 @@ static int snd_ctl_elem_read(struct snd_card *card,
 	info.id = control->id;
 	ret = __snd_ctl_elem_info(card, kctl, &info, NULL);
 	if (ret < 0)
-		goto unlock;
+		return ret;
 #endif
 
 	if (!snd_ctl_skip_validation(&info))
@@ -1308,7 +1259,7 @@ static int snd_ctl_elem_read(struct snd_card *card,
 		ret = kctl->get(kctl, control);
 	snd_power_unref(card);
 	if (ret < 0)
-		goto unlock;
+		return ret;
 	if (!snd_ctl_skip_validation(&info) &&
 	    sanity_check_elem_value(card, control, &info, pattern) < 0) {
 		dev_err(card->dev,
@@ -1316,12 +1267,9 @@ static int snd_ctl_elem_read(struct snd_card *card,
 			control->id.iface, control->id.device,
 			control->id.subdevice, control->id.name,
 			control->id.index);
-		ret = -EINVAL;
-		goto unlock;
+		return -EINVAL;
 	}
-unlock:
-	up_read(&card->controls_rwsem);
-	return ret;
+	return 0;
 }
 
 static int snd_ctl_elem_read_user(struct snd_card *card,
@@ -1426,25 +1374,18 @@ static int snd_ctl_elem_lock(struct snd_ctl_file *file,
 	struct snd_ctl_elem_id id;
 	struct snd_kcontrol *kctl;
 	struct snd_kcontrol_volatile *vd;
-	int result;
 
 	if (copy_from_user(&id, _id, sizeof(id)))
 		return -EFAULT;
-	down_write(&card->controls_rwsem);
+	guard(rwsem_write)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, &id);
-	if (kctl == NULL) {
-		result = -ENOENT;
-	} else {
-		vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
-		if (vd->owner != NULL)
-			result = -EBUSY;
-		else {
-			vd->owner = file;
-			result = 0;
-		}
-	}
-	up_write(&card->controls_rwsem);
-	return result;
+	if (!kctl)
+		return -ENOENT;
+	vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
+	if (vd->owner)
+		return -EBUSY;
+	vd->owner = file;
+	return 0;
 }
 
 static int snd_ctl_elem_unlock(struct snd_ctl_file *file,
@@ -1454,27 +1395,20 @@ static int snd_ctl_elem_unlock(struct snd_ctl_file *file,
 	struct snd_ctl_elem_id id;
 	struct snd_kcontrol *kctl;
 	struct snd_kcontrol_volatile *vd;
-	int result;
 
 	if (copy_from_user(&id, _id, sizeof(id)))
 		return -EFAULT;
-	down_write(&card->controls_rwsem);
+	guard(rwsem_write)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, &id);
-	if (kctl == NULL) {
-		result = -ENOENT;
-	} else {
-		vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
-		if (vd->owner == NULL)
-			result = -EINVAL;
-		else if (vd->owner != file)
-			result = -EPERM;
-		else {
-			vd->owner = NULL;
-			result = 0;
-		}
-	}
-	up_write(&card->controls_rwsem);
-	return result;
+	if (!kctl)
+		return -ENOENT;
+	vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
+	if (!vd->owner)
+		return -EINVAL;
+	if (vd->owner != file)
+		return -EPERM;
+	vd->owner = NULL;
+	return 0;
 }
 
 struct user_element {
@@ -1756,11 +1690,9 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 	private_size = value_sizes[info->type] * info->count;
 	alloc_size = compute_user_elem_size(private_size, count);
 
-	down_write(&card->controls_rwsem);
-	if (check_user_elem_overflow(card, alloc_size)) {
-		err = -ENOMEM;
-		goto unlock;
-	}
+	guard(rwsem_write)(&card->controls_rwsem);
+	if (check_user_elem_overflow(card, alloc_size))
+		return -ENOMEM;
 
 	/*
 	 * Keep memory object for this userspace control. After passing this
@@ -1770,13 +1702,12 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 	 */
 	err = snd_ctl_new(&kctl, count, access, file);
 	if (err < 0)
-		goto unlock;
+		return err;
 	memcpy(&kctl->id, &info->id, sizeof(kctl->id));
 	ue = kzalloc(alloc_size, GFP_KERNEL);
 	if (!ue) {
 		kfree(kctl);
-		err = -ENOMEM;
-		goto unlock;
+		return -ENOMEM;
 	}
 	kctl->private_data = ue;
 	kctl->private_free = snd_ctl_elem_user_free;
@@ -1794,7 +1725,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 		err = snd_ctl_elem_init_enum_names(ue);
 		if (err < 0) {
 			snd_ctl_free_one(kctl);
-			goto unlock;
+			return err;
 		}
 	}
 
@@ -1814,7 +1745,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 	err = __snd_ctl_add_replace(card, kctl, CTL_ADD_EXCLUSIVE);
 	if (err < 0) {
 		snd_ctl_free_one(kctl);
-		goto unlock;
+		return err;
 	}
 	offset = snd_ctl_get_ioff(kctl, &info->id);
 	snd_ctl_build_ioff(&info->id, kctl, offset);
@@ -1825,9 +1756,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 	 * applications because the field originally means PID of a process
 	 * which locks the element.
 	 */
- unlock:
-	up_write(&card->controls_rwsem);
-	return err;
+	return 0;
 }
 
 static int snd_ctl_elem_add_user(struct snd_ctl_file *file,
@@ -2029,34 +1958,29 @@ static long snd_ctl_ioctl(struct file *file, unsigned int cmd, unsigned long arg
 	case SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS:
 		return snd_ctl_subscribe_events(ctl, ip);
 	case SNDRV_CTL_IOCTL_TLV_READ:
-		down_read(&ctl->card->controls_rwsem);
-		err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_READ);
-		up_read(&ctl->card->controls_rwsem);
+		scoped_guard(rwsem_read, &ctl->card->controls_rwsem)
+			err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_READ);
 		return err;
 	case SNDRV_CTL_IOCTL_TLV_WRITE:
-		down_write(&ctl->card->controls_rwsem);
-		err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_WRITE);
-		up_write(&ctl->card->controls_rwsem);
+		scoped_guard(rwsem_write, &ctl->card->controls_rwsem)
+			err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_WRITE);
 		return err;
 	case SNDRV_CTL_IOCTL_TLV_COMMAND:
-		down_write(&ctl->card->controls_rwsem);
-		err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_CMD);
-		up_write(&ctl->card->controls_rwsem);
+		scoped_guard(rwsem_write, &ctl->card->controls_rwsem)
+			err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_CMD);
 		return err;
 	case SNDRV_CTL_IOCTL_POWER:
 		return -ENOPROTOOPT;
 	case SNDRV_CTL_IOCTL_POWER_STATE:
 		return put_user(SNDRV_CTL_POWER_D0, ip) ? -EFAULT : 0;
 	}
-	down_read(&snd_ioctl_rwsem);
+
+	guard(rwsem_read)(&snd_ioctl_rwsem);
 	list_for_each_entry(p, &snd_control_ioctls, list) {
 		err = p->fioctl(card, ctl, cmd, arg);
-		if (err != -ENOIOCTLCMD) {
-			up_read(&snd_ioctl_rwsem);
+		if (err != -ENOIOCTLCMD)
 			return err;
-		}
 	}
-	up_read(&snd_ioctl_rwsem);
 	dev_dbg(card->dev, "unknown ioctl = 0x%x\n", cmd);
 	return -ENOTTY;
 }
@@ -2148,9 +2072,8 @@ static int _snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn, struct list_head *
 	if (pn == NULL)
 		return -ENOMEM;
 	pn->fioctl = fcn;
-	down_write(&snd_ioctl_rwsem);
+	guard(rwsem_write)(&snd_ioctl_rwsem);
 	list_add_tail(&pn->list, lists);
-	up_write(&snd_ioctl_rwsem);
 	return 0;
 }
 
@@ -2193,16 +2116,14 @@ static int _snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn,
 
 	if (snd_BUG_ON(!fcn))
 		return -EINVAL;
-	down_write(&snd_ioctl_rwsem);
+	guard(rwsem_write)(&snd_ioctl_rwsem);
 	list_for_each_entry(p, lists, list) {
 		if (p->fioctl == fcn) {
 			list_del(&p->list);
-			up_write(&snd_ioctl_rwsem);
 			kfree(p);
 			return 0;
 		}
 	}
-	up_write(&snd_ioctl_rwsem);
 	snd_BUG();
 	return -EINVAL;
 }
@@ -2249,9 +2170,8 @@ int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type)
 {
 	struct snd_ctl_file *kctl;
 	int subdevice = -1;
-	unsigned long flags;
 
-	read_lock_irqsave(&card->ctl_files_rwlock, flags);
+	guard(read_lock_irqsave)(&card->ctl_files_rwlock);
 	list_for_each_entry(kctl, &card->ctl_files, list) {
 		if (kctl->pid == task_pid(current)) {
 			subdevice = kctl->preferred_subdevice[type];
@@ -2259,7 +2179,6 @@ int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type)
 				break;
 		}
 	}
-	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
 	return subdevice;
 }
 EXPORT_SYMBOL_GPL(snd_ctl_get_preferred_subdevice);
@@ -2289,13 +2208,11 @@ int snd_ctl_request_layer(const char *module_name)
 
 	if (module_name == NULL)
 		return 0;
-	down_read(&snd_ctl_layer_rwsem);
-	for (lops = snd_ctl_layer; lops; lops = lops->next)
-		if (strcmp(lops->module_name, module_name) == 0)
-			break;
-	up_read(&snd_ctl_layer_rwsem);
-	if (lops)
-		return 0;
+	scoped_guard(rwsem_read, &snd_ctl_layer_rwsem) {
+		for (lops = snd_ctl_layer; lops; lops = lops->next)
+			if (strcmp(lops->module_name, module_name) == 0)
+				return 0;
+	}
 	return request_module(module_name);
 }
 EXPORT_SYMBOL_GPL(snd_ctl_request_layer);
@@ -2312,16 +2229,15 @@ void snd_ctl_register_layer(struct snd_ctl_layer_ops *lops)
 	struct snd_card *card;
 	int card_number;
 
-	down_write(&snd_ctl_layer_rwsem);
-	lops->next = snd_ctl_layer;
-	snd_ctl_layer = lops;
-	up_write(&snd_ctl_layer_rwsem);
+	scoped_guard(rwsem_write, &snd_ctl_layer_rwsem) {
+		lops->next = snd_ctl_layer;
+		snd_ctl_layer = lops;
+	}
 	for (card_number = 0; card_number < SNDRV_CARDS; card_number++) {
 		card = snd_card_ref(card_number);
 		if (card) {
-			down_read(&card->controls_rwsem);
-			lops->lregister(card);
-			up_read(&card->controls_rwsem);
+			scoped_guard(rwsem_read, &card->controls_rwsem)
+				lops->lregister(card);
 			snd_card_unref(card);
 		}
 	}
@@ -2340,7 +2256,7 @@ void snd_ctl_disconnect_layer(struct snd_ctl_layer_ops *lops)
 {
 	struct snd_ctl_layer_ops *lops2, *prev_lops2;
 
-	down_write(&snd_ctl_layer_rwsem);
+	guard(rwsem_write)(&snd_ctl_layer_rwsem);
 	for (lops2 = snd_ctl_layer, prev_lops2 = NULL; lops2; lops2 = lops2->next) {
 		if (lops2 == lops) {
 			if (!prev_lops2)
@@ -2351,7 +2267,6 @@ void snd_ctl_disconnect_layer(struct snd_ctl_layer_ops *lops)
 		}
 		prev_lops2 = lops2;
 	}
-	up_write(&snd_ctl_layer_rwsem);
 }
 EXPORT_SYMBOL_GPL(snd_ctl_disconnect_layer);
 
@@ -2372,25 +2287,29 @@ static const struct file_operations snd_ctl_f_ops =
 	.fasync =	snd_ctl_fasync,
 };
 
+/* call lops under rwsems; called from snd_ctl_dev_*() below() */
+#define call_snd_ctl_lops(_card, _op)				    \
+	do {							    \
+		struct snd_ctl_layer_ops *lops;			    \
+		guard(rwsem_read)(&(_card)->controls_rwsem);	    \
+		guard(rwsem_read)(&snd_ctl_layer_rwsem);	    \
+		for (lops = snd_ctl_layer; lops; lops = lops->next) \
+			lops->_op(_card);			    \
+	} while (0)
+
 /*
  * registration of the control device
  */
 static int snd_ctl_dev_register(struct snd_device *device)
 {
 	struct snd_card *card = device->device_data;
-	struct snd_ctl_layer_ops *lops;
 	int err;
 
 	err = snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,
 				  &snd_ctl_f_ops, card, card->ctl_dev);
 	if (err < 0)
 		return err;
-	down_read(&card->controls_rwsem);
-	down_read(&snd_ctl_layer_rwsem);
-	for (lops = snd_ctl_layer; lops; lops = lops->next)
-		lops->lregister(card);
-	up_read(&snd_ctl_layer_rwsem);
-	up_read(&card->controls_rwsem);
+	call_snd_ctl_lops(card, lregister);
 	return 0;
 }
 
@@ -2401,23 +2320,15 @@ static int snd_ctl_dev_disconnect(struct snd_device *device)
 {
 	struct snd_card *card = device->device_data;
 	struct snd_ctl_file *ctl;
-	struct snd_ctl_layer_ops *lops;
-	unsigned long flags;
 
-	read_lock_irqsave(&card->ctl_files_rwlock, flags);
-	list_for_each_entry(ctl, &card->ctl_files, list) {
-		wake_up(&ctl->change_sleep);
-		snd_kill_fasync(ctl->fasync, SIGIO, POLL_ERR);
+	scoped_guard(read_lock_irqsave, &card->ctl_files_rwlock) {
+		list_for_each_entry(ctl, &card->ctl_files, list) {
+			wake_up(&ctl->change_sleep);
+			snd_kill_fasync(ctl->fasync, SIGIO, POLL_ERR);
+		}
 	}
-	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
-
-	down_read(&card->controls_rwsem);
-	down_read(&snd_ctl_layer_rwsem);
-	for (lops = snd_ctl_layer; lops; lops = lops->next)
-		lops->ldisconnect(card);
-	up_read(&snd_ctl_layer_rwsem);
-	up_read(&card->controls_rwsem);
 
+	call_snd_ctl_lops(card, ldisconnect);
 	return snd_unregister_device(card->ctl_dev);
 }
 
@@ -2429,17 +2340,17 @@ static int snd_ctl_dev_free(struct snd_device *device)
 	struct snd_card *card = device->device_data;
 	struct snd_kcontrol *control;
 
-	down_write(&card->controls_rwsem);
-	while (!list_empty(&card->controls)) {
-		control = snd_kcontrol(card->controls.next);
-		__snd_ctl_remove(card, control, false);
-	}
+	scoped_guard(rwsem_write, &card->controls_rwsem) {
+		while (!list_empty(&card->controls)) {
+			control = snd_kcontrol(card->controls.next);
+			__snd_ctl_remove(card, control, false);
+		}
 
 #ifdef CONFIG_SND_CTL_FAST_LOOKUP
-	xa_destroy(&card->ctl_numids);
-	xa_destroy(&card->ctl_hash);
+		xa_destroy(&card->ctl_numids);
+		xa_destroy(&card->ctl_hash);
 #endif
-	up_write(&card->controls_rwsem);
+	}
 	put_device(card->ctl_dev);
 	return 0;
 }
diff --git a/sound/core/control_compat.c b/sound/core/control_compat.c
index 8392183c77ed3f..934bb945e702a2 100644
--- a/sound/core/control_compat.c
+++ b/sound/core/control_compat.c
@@ -167,23 +167,18 @@ static int get_ctl_type(struct snd_card *card, struct snd_ctl_elem_id *id,
 	struct snd_ctl_elem_info *info __free(kfree) = NULL;
 	int err;
 
-	down_read(&card->controls_rwsem);
+	guard(rwsem_read)(&card->controls_rwsem);
 	kctl = snd_ctl_find_id_locked(card, id);
-	if (! kctl) {
-		up_read(&card->controls_rwsem);
+	if (!kctl)
 		return -ENOENT;
-	}
 	info = kzalloc(sizeof(*info), GFP_KERNEL);
-	if (info == NULL) {
-		up_read(&card->controls_rwsem);
+	if (info == NULL)
 		return -ENOMEM;
-	}
 	info->id = *id;
 	err = snd_power_ref_and_wait(card);
 	if (!err)
 		err = kctl->info(kctl, info);
 	snd_power_unref(card);
-	up_read(&card->controls_rwsem);
 	if (err >= 0) {
 		err = info->type;
 		*countp = info->count;
@@ -451,16 +446,13 @@ static inline long snd_ctl_ioctl_compat(struct file *file, unsigned int cmd, uns
 #endif /* CONFIG_X86_X32_ABI */
 	}
 
-	down_read(&snd_ioctl_rwsem);
+	guard(rwsem_read)(&snd_ioctl_rwsem);
 	list_for_each_entry(p, &snd_control_compat_ioctls, list) {
 		if (p->fioctl) {
 			err = p->fioctl(ctl->card, ctl, cmd, arg);
-			if (err != -ENOIOCTLCMD) {
-				up_read(&snd_ioctl_rwsem);
+			if (err != -ENOIOCTLCMD)
 				return err;
-			}
 		}
 	}
-	up_read(&snd_ioctl_rwsem);
 	return -ENOIOCTLCMD;
 }