ALSA: Remove BKL from open multiplexer

Use a local mutex instead of BKL.  This should suffice since each device
type has also its open_mutex.
Also, a bit of clean-up of the legacy device auto-loading code.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/sound.c

@@ -120,19 +120,12 @@ void *snd_lookup_minor_data(unsigned int minor, int type)
 
 EXPORT_SYMBOL(snd_lookup_minor_data);
 
-static int __snd_open(struct inode *inode, struct file *file)
-{
-	unsigned int minor = iminor(inode);
-	struct snd_minor *mptr = NULL;
-	const struct file_operations *old_fops;
-	int err = 0;
-
-	if (minor >= ARRAY_SIZE(snd_minors))
-		return -ENODEV;
-	mptr = snd_minors[minor];
-	if (mptr == NULL) {
 #ifdef CONFIG_MODULES
-		int dev = SNDRV_MINOR_DEVICE(minor);
+static struct snd_minor *autoload_device(unsigned int minor)
+{
+	int dev;
+	mutex_unlock(&sound_mutex); /* release lock temporarily */
+	dev = SNDRV_MINOR_DEVICE(minor);
 	if (dev == SNDRV_MINOR_CONTROL) {
 		/* /dev/aloadC? */
 		int card = SNDRV_MINOR_CARD(minor);
@@ -142,42 +135,52 @@ static int __snd_open(struct inode *inode, struct file *file)
 		/* /dev/aloadSEQ */
 		snd_request_other(minor);
 	}
-#ifndef CONFIG_SND_DYNAMIC_MINORS
-		/* /dev/snd/{controlC?,seq} */
-		mptr = snd_minors[minor];
-		if (mptr == NULL)
-#endif
-#endif
+	mutex_lock(&sound_mutex); /* reacuire lock */
+	return snd_minors[minor];
+}
+#else /* !CONFIG_MODULES */
+#define autoload_device(minor)	NULL
+#endif /* CONFIG_MODULES */
+
+static int snd_open(struct inode *inode, struct file *file)
+{
+	unsigned int minor = iminor(inode);
+	struct snd_minor *mptr = NULL;
+	const struct file_operations *old_fops;
+	int err = 0;
+
+	if (minor >= ARRAY_SIZE(snd_minors))
 		return -ENODEV;
+	mutex_lock(&sound_mutex);
+	mptr = snd_minors[minor];
+	if (mptr == NULL) {
+		mptr = autoload_device(minor);
+		if (!mptr) {
+			mutex_unlock(&sound_mutex);
+			return -ENODEV;
+		}
 	}
 	old_fops = file->f_op;
 	file->f_op = fops_get(mptr->f_ops);
 	if (file->f_op == NULL) {
 		file->f_op = old_fops;
-		return -ENODEV;
+		err = -ENODEV;
 	}
-	if (file->f_op->open)
+	mutex_unlock(&sound_mutex);
+	if (err < 0)
+		return err;
+
+	if (file->f_op->open) {
 		err = file->f_op->open(inode, file);
 		if (err) {
 			fops_put(file->f_op);
 			file->f_op = fops_get(old_fops);
 		}
+	}
 	fops_put(old_fops);
 	return err;
 }
 
-
-/* BKL pushdown: nasty #ifdef avoidance wrapper */
-static int snd_open(struct inode *inode, struct file *file)
-{
-	int ret;
-
-	lock_kernel();
-	ret = __snd_open(inode, file);
-	unlock_kernel();
-	return ret;
-}
-
 static const struct file_operations snd_fops =
 {
 	.owner =	THIS_MODULE,