On Tue, 13 Mar 2007 11:00:21 -0400 (EDT),
Alan Stern <[EMAIL PROTECTED]> wrote:

> The consensus is that we would be better off keeping Oliver's original 
> patch without your silly change, and instead fixing the particular method 
> call that deadlocked.

Another call that deadlocked with Oliver's patch is ungroup for s390
ccwgroup devices. It can be made to work again with a similar patch.

Signed-off-by: Cornelia Huck <[EMAIL PROTECTED]>

---
 drivers/s390/cio/ccwgroup.c |   35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

--- linux-2.6.orig/drivers/s390/cio/ccwgroup.c
+++ linux-2.6/drivers/s390/cio/ccwgroup.c
@@ -67,22 +67,49 @@ __ccwgroup_remove_symlinks(struct ccwgro
        
 }
 
+struct ccwgroup_work_struct {
+       struct ccwgroup_device *gdev;
+       struct work_struct work;
+};
+
+static void ccwgroup_ungroup_work(struct work_struct *work)
+{
+       struct ccwgroup_work_struct *ungroup_work
+               = container_of(work, struct ccwgroup_work_struct, work);
+
+       __ccwgroup_remove_symlinks(ungroup_work->gdev);
+       device_unregister(&ungroup_work->gdev->dev);
+       put_device(&ungroup_work->gdev->dev);
+       kfree(ungroup_work);
+}
+
 /*
  * Provide an 'ungroup' attribute so the user can remove group devices no
  * longer needed or accidentially created. Saves memory :)
+ * Note that we cannot unregister the device from one of its attribute
+ * methods, so we have to delay it.
  */
-static ssize_t
-ccwgroup_ungroup_store(struct device *dev, struct device_attribute *attr, 
const char *buf, size_t count)
+static ssize_t ccwgroup_ungroup_store(struct device *dev,
+                                     struct device_attribute *attr,
+                                     const char *buf, size_t count)
 {
        struct ccwgroup_device *gdev;
+       struct ccwgroup_work_struct *ungroup_work;
 
        gdev = to_ccwgroupdev(dev);
 
        if (gdev->state != CCWGROUP_OFFLINE)
                return -EINVAL;
 
-       __ccwgroup_remove_symlinks(gdev);
-       device_unregister(dev);
+       ungroup_work = kmalloc(sizeof(*ungroup_work), GFP_KERNEL);
+       if (!ungroup_work)
+               return -ENOMEM;
+       ungroup_work->gdev = gdev;
+       INIT_WORK(&ungroup_work->work, ccwgroup_ungroup_work);
+       if (!get_device(&gdev->dev))
+               kfree(ungroup_work);
+       else
+               schedule_work(&ungroup_work->work);
 
        return count;
 }
-
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