[S390] ccwgroup: add locking around drvdata access

Several processes may concurrently try to create a group device
from the same ccw_device(s). Add locking arround the drvdata
access to prevent race conditions.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/ccwgroup.c

@@ -123,8 +123,10 @@ ccwgroup_release (struct device *dev)
 
 	for (i = 0; i < gdev->count; i++) {
 		if (gdev->cdev[i]) {
+			spin_lock_irq(gdev->cdev[i]->ccwlock);
 			if (dev_get_drvdata(&gdev->cdev[i]->dev) == gdev)
 				dev_set_drvdata(&gdev->cdev[i]->dev, NULL);
+			spin_unlock_irq(gdev->cdev[i]->ccwlock);
 			put_device(&gdev->cdev[i]->dev);
 		}
 	}
@@ -262,11 +264,14 @@ int ccwgroup_create_from_string(struct device *root, unsigned int creator_id,
 			goto error;
 		}
 		/* Don't allow a device to belong to more than one group. */
+		spin_lock_irq(gdev->cdev[i]->ccwlock);
 		if (dev_get_drvdata(&gdev->cdev[i]->dev)) {
+			spin_unlock_irq(gdev->cdev[i]->ccwlock);
 			rc = -EINVAL;
 			goto error;
 		}
 		dev_set_drvdata(&gdev->cdev[i]->dev, gdev);
+		spin_unlock_irq(gdev->cdev[i]->ccwlock);
 	}
 	/* Check for sufficient number of bus ids. */
 	if (i < num_devices && !curr_buf) {
@@ -303,8 +308,10 @@ int ccwgroup_create_from_string(struct device *root, unsigned int creator_id,
 error:
 	for (i = 0; i < num_devices; i++)
 		if (gdev->cdev[i]) {
+			spin_lock_irq(gdev->cdev[i]->ccwlock);
 			if (dev_get_drvdata(&gdev->cdev[i]->dev) == gdev)
 				dev_set_drvdata(&gdev->cdev[i]->dev, NULL);
+			spin_unlock_irq(gdev->cdev[i]->ccwlock);
 			put_device(&gdev->cdev[i]->dev);
 			gdev->cdev[i] = NULL;
 		}