V4L/DVB (7491): vivi: make vivi openable only once

vivi currently doesn't have the infrastructure to handle being opened more than
one time and will crash if it is.  So, make it openable only once.
Signed-off-by: Brandon Philips <bphilips@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/vivi.c

@@ -164,6 +164,7 @@ struct vivi_dev {
 
 	struct mutex               lock;
 	spinlock_t                 slock;
+	struct mutex		   mutex;
 
 	int                        users;
 
@@ -1036,6 +1037,7 @@ static int vivi_open(struct inode *inode, struct file *file)
 	struct vivi_dev *dev;
 	struct vivi_fh *fh;
 	int i;
+	int retval = 0;
 
 	printk(KERN_DEBUG "vivi: open called (minor=%d)\n", minor);
 
@@ -1045,9 +1047,15 @@ static int vivi_open(struct inode *inode, struct file *file)
 	return -ENODEV;
 
 found:
-	/* If more than one user, mutex should be added */
+	mutex_lock(&dev->mutex);
 	dev->users++;
 
+	if (dev->users > 1) {
+		dev->users--;
+		retval = -EBUSY;
+		goto unlock;
+	}
+
 	dprintk(dev, 1, "open minor=%d type=%s users=%d\n", minor,
 		v4l2_type_names[V4L2_BUF_TYPE_VIDEO_CAPTURE], dev->users);
 
@@ -1055,8 +1063,13 @@ found:
 	fh = kzalloc(sizeof(*fh), GFP_KERNEL);
 	if (NULL == fh) {
 		dev->users--;
-		return -ENOMEM;
+		retval = -ENOMEM;
+		goto unlock;
 	}
+unlock:
+	mutex_unlock(&dev->mutex);
+	if (retval)
+		return retval;
 
 	file->private_data = fh;
 	fh->dev      = dev;
@@ -1128,7 +1141,9 @@ static int vivi_close(struct inode *inode, struct file *file)
 
 	kfree(fh);
 
+	mutex_lock(&dev->mutex);
 	dev->users--;
+	mutex_unlock(&dev->mutex);
 
 	dprintk(dev, 1, "close called (minor=%d, users=%d)\n",
 		minor, dev->users);
@@ -1243,6 +1258,7 @@ static int __init vivi_init(void)
 		/* initialize locks */
 		mutex_init(&dev->lock);
 		spin_lock_init(&dev->slock);
+		mutex_init(&dev->mutex);
 
 		dev->vidq.timeout.function = vivi_vid_timeout;
 		dev->vidq.timeout.data     = (unsigned long)dev;