[PATCH v2] EM28xx - fix deadlock when unplugging and replugging a DVB adapter

[Chris Rankin <rankincj@yahoo.com>]

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Mauro,

Pending the complete rethink about how USB devices manage their resources, I am 
resubmitting my fix for the PCTV 290e deadlock that occurs with either multiple 
adapters or when an adapter is replugged.

For DVB devices, the device lock must now *not* be held when adding/removing 
either a device or an extension to the respective lists. (Because 
em28xx_init_dvb() will want to take the lock instead).

Conversely, for Audio-Only devices, the device lock *must* be held when 
adding/removing either a device or an extension to the respective lists.

Signed-off-by: Chris Rankin <rankincj@yahoo.com>

Cheers,
Chris

[-- Attachment #2: EM28xx-replug-deadlock-2.diff --]
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--- linux/drivers/media/video/em28xx/em28xx-cards.c.orig	2011-09-24 21:25:01.000000000 +0100
+++ linux/drivers/media/video/em28xx/em28xx-cards.c	2011-09-24 21:37:42.000000000 +0100
@@ -3005,9 +3005,7 @@
 		goto fail;
 	}
 
-	mutex_unlock(&dev->lock);
 	em28xx_init_extension(dev);
-	mutex_lock(&dev->lock);
 
 	/* Save some power by putting tuner to sleep */
 	v4l2_device_call_all(&dev->v4l2_dev, 0, core, s_power, 0);
@@ -3303,10 +3301,10 @@
 		em28xx_release_resources(dev);
 	}
 
-	mutex_unlock(&dev->lock);
-
 	em28xx_close_extension(dev);
 
+	mutex_unlock(&dev->lock);
+
 	if (!dev->users) {
 		kfree(dev->alt_max_pkt_size);
 		kfree(dev);