virtio_ccw: fix hang in set offline processing

During set offline processing virtio_grab_drvdata() incorrectly
calls dev_set_drvdata() to remove the virtio_ccw_device from the
parent ccw_device's driver data. This is wrong and ends up in a
hang during virtio_ccw_reset(), as the interrupt handler still
has need of the virtio_ccw_device.

A new field 'going_away' is introduced in struct virtio_ccw_device
to control the usage of the ccw_device's driver data pointer in
virtio_grab_drvdata().

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 6a2b5fdcd552..1e1fc671f89a 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -61,6 +61,7 @@ struct virtio_ccw_device {
         unsigned long indicators2;
         struct vq_config_block *config_block;
         bool is_thinint;
+        bool going_away;
         void *airq_info;
 };
 
@@ -995,30 +996,39 @@ static struct virtio_ccw_device *virtio_grab_drvdata(struct ccw_device *cdev)
 
         spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
         vcdev = dev_get_drvdata(&cdev->dev);
-        if (!vcdev) {
+        if (!vcdev || vcdev->going_away) {
                 spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
                 return NULL;
         }
-        dev_set_drvdata(&cdev->dev, NULL);
+        vcdev->going_away = true;
         spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
         return vcdev;
 }
 
 static void virtio_ccw_remove(struct ccw_device *cdev)
 {
+        unsigned long flags;
         struct virtio_ccw_device *vcdev = virtio_grab_drvdata(cdev);
 
         if (vcdev && cdev->online)
                 unregister_virtio_device(&vcdev->vdev);
+        spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
+        dev_set_drvdata(&cdev->dev, NULL);
+        spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
         cdev->handler = NULL;
 }
 
 static int virtio_ccw_offline(struct ccw_device *cdev)
 {
+        unsigned long flags;
         struct virtio_ccw_device *vcdev = virtio_grab_drvdata(cdev);
 
-        if (vcdev)
+        if (vcdev) {
                 unregister_virtio_device(&vcdev->vdev);
+                spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
+                dev_set_drvdata(&cdev->dev, NULL);
+                spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
+        }
         return 0;
 }