linux-kernel - Re: Sound+USB: deadlock problem

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Date:	Tue, 13 Nov 2012 09:45:03 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	LKML <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: Sound+USB: deadlock problem

At Tue, 13 Nov 2012 09:30:10 +0100,
Jiri Slaby wrote:
> 
> On 11/13/2012 09:28 AM, Takashi Iwai wrote:
> > At Tue, 13 Nov 2012 09:26:17 +0100,
> > Jiri Slaby wrote:
> >>
> >> Hello,
> >>
> >> I've just plugged+unplugged+plugged my USB audio card and the audio
> >> subsystem got stuck:
> > 
> > Which kernel?  If it's older than 3.7-rc5, could you try 3.7-rc5?
> 
> Oh, forgot to mention:
> 3.7.0-rc5-next-20121112_64+

Through a quick glance, one of mutex locks seems stuck.
Just a blind short -- does the patch below cure the problem?


thanks,

Takashi

---
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 030102c..a66a7ca 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -1086,7 +1086,7 @@ static int snd_pcm_dev_disconnect(struct snd_device *device)
 	if (list_empty(&pcm->list))
 		goto unlock;
 
-	mutex_lock(&pcm->open_mutex);
+	/* mutex_lock(&pcm->open_mutex); */
 	wake_up(&pcm->open_wait);
 	list_del_init(&pcm->list);
 	for (cidx = 0; cidx < 2; cidx++)
@@ -1118,7 +1118,7 @@ static int snd_pcm_dev_disconnect(struct snd_device *device)
 			pcm->streams[cidx].chmap_kctl = NULL;
 		}
 	}
-	mutex_unlock(&pcm->open_mutex);
+	/* mutex_unlock(&pcm->open_mutex); */
  unlock:
 	mutex_unlock(&register_mutex);
 	return 0;
--
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