linux-kernel - Re: [LOCKDEP] 33-rc8 Running aplay with pulse as the default

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Message-ID: <s5heikkndf2.wl%tiwai@suse.de>
Date:	Wed, 17 Feb 2010 15:29:37 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Ed Tomlinson <edt@....ca>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	alsa-devel@...a-project.org
Subject: Re: [LOCKDEP] 33-rc8 Running aplay with pulse as the default

At Wed, 17 Feb 2010 08:16:32 -0500,
Ed Tomlinson wrote:
> 
> On Tuesday 16 February 2010 08:37:46 Takashi Iwai wrote:
> > > Thanks for the patch.  It helps in that it eliminates the opps but lockdep still triggers and aplay still fails.  
> > > Here is the new traceback.
> > 
> > Hmm, fixing this isn't so trivial.  The same problem occurs on other
> > subsystems like NFS over years.  And it's still there, AFAIK.
> > The mmap mutex appears suddenly in the strange code path at close.
> > 
> > The patch below might fix, but I'm not 100% sure whether this has no
> > side effect.
> > 
> > Anyway, I doubt very much it being a regression.  There is no change
> > in ALSA core side, and also in V4L em28xx code.  Maybe the lockdep
> > wasn't triggered by some reason.  And, this lockdep warning is almost
> > harmless...
> 
> Takashi,
> 
> The second patch eliminating the lock causes oppes every time (one follows just in case
> its helpful).

Are you sure?  The patch should causes a compile error, so you must have
patched manually in a wrong place ;)

Try the patch below (again untested, though).


thanks,

Takashi

---
diff --git a/drivers/media/video/em28xx/em28xx-audio.c b/drivers/media/video/em28xx/em28xx-audio.c
index bd78338..c51e623 100644
--- a/drivers/media/video/em28xx/em28xx-audio.c
+++ b/drivers/media/video/em28xx/em28xx-audio.c
@@ -301,23 +301,12 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
 	/* Sets volume, mute, etc */
 
 	dev->mute = 0;
-	mutex_lock(&dev->lock);
 	ret = em28xx_audio_analog_set(dev);
-	mutex_unlock(&dev->lock);
 	if (ret < 0)
 		goto err;
 
 	runtime->hw = snd_em28xx_hw_capture;
-	if (dev->alt == 0 && dev->adev.users == 0) {
-		int errCode;
-		dev->alt = 7;
-		errCode = usb_set_interface(dev->udev, 0, 7);
-		dprintk("changing alternate number to 7\n");
-	}
-
-	mutex_lock(&dev->lock);
 	dev->adev.users++;
-	mutex_unlock(&dev->lock);
 
 	snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
 	dev->adev.capture_pcm_substream = substream;
@@ -336,7 +325,6 @@ static int snd_em28xx_pcm_close(struct snd_pcm_substream *substream)
 	dprintk("closing device\n");
 
 	dev->mute = 1;
-	mutex_lock(&dev->lock);
 	dev->adev.users--;
 	em28xx_audio_analog_set(dev);
 	if (substream->runtime->dma_area) {
@@ -344,7 +332,6 @@ static int snd_em28xx_pcm_close(struct snd_pcm_substream *substream)
 		vfree(substream->runtime->dma_area);
 		substream->runtime->dma_area = NULL;
 	}
-	mutex_unlock(&dev->lock);
 
 	return 0;
 }
@@ -352,6 +339,7 @@ static int snd_em28xx_pcm_close(struct snd_pcm_substream *substream)
 static int snd_em28xx_hw_capture_params(struct snd_pcm_substream *substream,
 					struct snd_pcm_hw_params *hw_params)
 {
+	struct em28xx *dev = snd_pcm_substream_chip(substream);
 	unsigned int channels, rate, format;
 	int ret;
 
@@ -366,6 +354,14 @@ static int snd_em28xx_hw_capture_params(struct snd_pcm_substream *substream,
 	/* TODO: set up em28xx audio chip to deliver the correct audio format,
 	   current default is 48000hz multiplexed => 96000hz mono
 	   which shouldn't matter since analogue TV only supports mono */
+
+	if (dev->alt == 0 && dev->adev.users == 1) {
+		int errCode;
+		dev->alt = 7;
+		errCode = usb_set_interface(dev->udev, 0, 7);
+		dprintk("changing alternate number to 7\n");
+	}
+
 	return 0;
 }
 
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