[S390] cio: Fix ungroup vs. machine check race in ccwgroup.

There are two ways for a ccwgroup device to be unregistered:
Via the ungroup attribute, or when on of the slave devices is killed
by a machine check. As we have to unregister the ccwgroup device
via a callback, we'll now have to check whether it hasn't been
already unregistered because of a machine check.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c
index dc1c5f4dd256..3964056a9a47 100644
--- a/drivers/s390/cio/ccwgroup.c
+++ b/drivers/s390/cio/ccwgroup.c
@@ -75,8 +75,10 @@ static void ccwgroup_ungroup_callback(struct device *dev)
         struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
 
         mutex_lock(&gdev->reg_mutex);
-        __ccwgroup_remove_symlinks(gdev);
-        device_unregister(dev);
+        if (device_is_registered(&gdev->dev)) {
+                __ccwgroup_remove_symlinks(gdev);
+                device_unregister(dev);
+        }
         mutex_unlock(&gdev->reg_mutex);
 }