commit 49e44e317fdb73d75a00a058df75a6b6fe172c08
author Takashi Iwai <tiwai@suse.de> Wed Nov 07 12:42:45 2012 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> Sat Nov 17 13:16:12 2012 -0800
tree abeaf4b344a9f59e76fce60b7d129d7fa6a36582
parent 799c92f2aecb348e4a4c6dab80c7206e48caf201

ALSA: usb-audio: Use rwsem for disconnect protection

commit 34f3c89fda4fba9fe689db22253ca8db2f5e6386 upstream.

Replace mutex with rwsem for codec->shutdown protection so that
concurrent accesses are allowed.

Also add the protection to snd_usb_autosuspend() and
snd_usb_autoresume(), too.

Reported-by: Matthieu CASTET <matthieu.castet@parrot.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

sound/usb/card.c

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 4a7be7b..147a5c4 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -336,7 +336,7 @@
 		return -ENOMEM;
 	}
 
-	mutex_init(&chip->shutdown_mutex);
+	init_rwsem(&chip->shutdown_rwsem);
 	chip->index = idx;
 	chip->dev = dev;
 	chip->card = card;
@@ -556,7 +556,7 @@
 
 	card = chip->card;
 	mutex_lock(&register_mutex);
-	mutex_lock(&chip->shutdown_mutex);
+	down_write(&chip->shutdown_rwsem);
 	chip->shutdown = 1;
 	chip->num_interfaces--;
 	if (chip->num_interfaces <= 0) {
@@ -574,11 +574,11 @@
 			snd_usb_mixer_disconnect(p);
 		}
 		usb_chip[chip->index] = NULL;
-		mutex_unlock(&chip->shutdown_mutex);
+		up_write(&chip->shutdown_rwsem);
 		mutex_unlock(&register_mutex);
 		snd_card_free_when_closed(card);
 	} else {
-		mutex_unlock(&chip->shutdown_mutex);
+		up_write(&chip->shutdown_rwsem);
 		mutex_unlock(&register_mutex);
 	}
 }
@@ -610,16 +610,20 @@
 {
 	int err = -ENODEV;
 
+	down_read(&chip->shutdown_rwsem);
 	if (!chip->shutdown && !chip->probing)
 		err = usb_autopm_get_interface(chip->pm_intf);
+	up_read(&chip->shutdown_rwsem);
 
 	return err;
 }
 
 void snd_usb_autosuspend(struct snd_usb_audio *chip)
 {
+	down_read(&chip->shutdown_rwsem);
 	if (!chip->shutdown && !chip->probing)
 		usb_autopm_put_interface(chip->pm_intf);
+	up_read(&chip->shutdown_rwsem);
 }
 
 static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)