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From: "Geoffrey D. Bennett" <g@b4.vu>
To: alsa-devel@alsa-project.org, Takashi Iwai <tiwai@suse.de>
Cc: Vladimir Sadovnikov <sadko4u@gmail.com>
Subject: [PATCH 8/8] ALSA: usb-audio: scarlett2: Fix data_mutex lock
Date: Mon, 7 Jun 2021 03:17:10 +0930	[thread overview]
Message-ID: <4d7ad2f3eea76a09c400c4f04d02d31da9cd7cea.1622999147.git.g@b4.vu> (raw)
In-Reply-To: <cover.1622999147.git.g@b4.vu>

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 8a4aa16cc364..9ea6abded26e 100644
--- a/sound/usb/mixer_scarlett_gen2.c
+++ b/sound/usb/mixer_scarlett_gen2.c
@@ -1155,11 +1155,10 @@ 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;
@@ -1173,11 +1172,10 @@ 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;
@@ -1441,11 +1439,10 @@ static int scarlett2_button_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->buttons[elem->control];
 	return 0;
-- 
2.31.1


      parent reply	other threads:[~2021-06-06 17:49 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-06 17:44 [PATCH 0/8] ALSA: usb-audio: scarlett2: cleanup Geoffrey D. Bennett
2021-06-06 17:45 ` [PATCH 1/8] ALSA: usb-audio: scarlett2: Remove incorrect S/PDIF comment Geoffrey D. Bennett
2021-06-06 17:45 ` [PATCH 2/8] ALSA: usb-audio: scarlett2: Coding style improvements Geoffrey D. Bennett
2021-06-06 17:45 ` [PATCH 3/8] ALSA: usb-audio: scarlett2: Remove unused/useless code Geoffrey D. Bennett
2021-06-06 17:46 ` [PATCH 4/8] ALSA: usb-audio: scarlett2: Remove interrupt debug message Geoffrey D. Bennett
2021-06-06 17:46 ` [PATCH 5/8] ALSA: usb-audio: scarlett2: Rename buttons/interrupts Geoffrey D. Bennett
2021-06-06 17:46 ` [PATCH 6/8] ALSA: usb-audio: scarlett2: Rename struct scarlett2_mixer_data Geoffrey D. Bennett
2021-06-06 17:46 ` [PATCH 7/8] ALSA: usb-audio: scarlett2: Add temp variable for consistency Geoffrey D. Bennett
2021-06-06 17:47 ` Geoffrey D. Bennett [this message]

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