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From: "Geoffrey D. Bennett" <g@b4.vu>
To: alsa-devel@alsa-project.org, Takashi Iwai <tiwai@suse.de>
Cc: Hin-Tak Leung <htl10@users.sourceforge.net>,
	Vladimir Sadovnikov <sadko4u@gmail.com>
Subject: [PATCH 10/14] ALSA: usb-audio: scarlett2: Fix data_mutex lock
Date: Mon, 21 Jun 2021 02:16:43 +0930	[thread overview]
Message-ID: <20210620164643.GA9216@m.b4.vu> (raw)

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 <g@b4.vu>
---
 sound/usb/mixer_scarlett_gen2.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c
index cb8483d3c58a..d6298ab1de56 100644
--- a/sound/usb/mixer_scarlett_gen2.c
+++ b/sound/usb/mixer_scarlett_gen2.c
@@ -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;
-- 
2.31.1


                 reply	other threads:[~2021-06-20 16:51 UTC|newest]

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