ALSA: usb-audio: scarlett2: Fix data_mutex lock

PATCH New Geoffrey D. Bennett 1 participant 1 message Jun 20, 2021 Sound

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Geoffrey D. Bennett

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2021-06-20 16:51 UTC #0 lore raw

PATCH 10/14 ALSA: usb-audio: scarlett2: Fix data_mutex lock

The private->vol_updated flag was being checked outside of the mutex_lock/unlock() of private->data_mutex leading to the volume data being fetched twice from the device unnecessarily or old volume data being returned.

Update scarlett2_*_ctl_get() and include the private->vol_updated flag check inside the critical region.

Signed-off-by Geoffrey D. Bennett <[email protected]>

---
 sound/usb/mixer_scarlett_gen2.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

sound/usb/mixer_scarlett_gen2.c +9 ~~-12~~

index cb8483d3c58a..d6298ab1de56 100644
@@ -1153,11 +1153,10 @@ static int scarlett2_master_volume_ctl_get(struct snd_kcontrol *kctl,
 	struct usb_mixer_interface *mixer = elem->head.mixer;
 	struct scarlett2_data *private = mixer->private_data;
 
-	if (private->vol_updated) {
-		mutex_lock(&private->data_mutex);
+	mutex_lock(&private->data_mutex);
+	if (private->vol_updated)
 		scarlett2_update_volumes(mixer);
-		mutex_unlock(&private->data_mutex);
-	}
+	mutex_unlock(&private->data_mutex);
 
 	ucontrol->value.integer.value[0] = private->master_vol;
 	return 0;

@@ -1171,11 +1170,10 @@ static int scarlett2_volume_ctl_get(struct snd_kcontrol *kctl,
 	struct scarlett2_data *private = mixer->private_data;
 	int index = elem->control;
 
-	if (private->vol_updated) {
-		mutex_lock(&private->data_mutex);
+	mutex_lock(&private->data_mutex);
+	if (private->vol_updated)
 		scarlett2_update_volumes(mixer);
-		mutex_unlock(&private->data_mutex);
-	}
+	mutex_unlock(&private->data_mutex);
 
 	ucontrol->value.integer.value[0] = private->vol[index];
 	return 0;

@@ -1439,11 +1437,10 @@ static int scarlett2_dim_mute_ctl_get(struct snd_kcontrol *kctl,
 	struct usb_mixer_interface *mixer = elem->head.mixer;
 	struct scarlett2_data *private = mixer->private_data;
 
-	if (private->vol_updated) {
-		mutex_lock(&private->data_mutex);
+	mutex_lock(&private->data_mutex);
+	if (private->vol_updated)
 		scarlett2_update_volumes(mixer);
-		mutex_unlock(&private->data_mutex);
-	}
+	mutex_unlock(&private->data_mutex);
 
 	ucontrol->value.enumerated.item[0] = private->dim_mute[elem->control];
 	return 0;

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