[PATCH v2] PM / devfreq: Don't delete sysfs group twice

[Chris Diamand <chris.diamand@arm.com>]

The 'userspace' governor adds a sysfs entry, which is removed when
the governor is changed, or the devfreq device is released. However,
when the latter occurs via device_unregister(), device_del() is
called first, which removes the sysfs entries recursively and deletes
the kobject.

This means we get an Oops when the governor calls
sysfs_remove_group() on the deleted kobject. Fix this by only doing
the call when kobj *hasn't* been kobject_del()'d.

Note that we can't just remove the call to sysfs_remove_group()
entirely - it's needed for when the governor is changed to one which
doesn't need a sysfs entry.

Signed-off-by: Chris Diamand <chris.diamand@arm.com>
---
This takes a different approach to v1, and fixes the issue in the governor
instead. This means reference counting should still work as usual, so anything
which doesn't call devfreq_remove_device() should still work.

 drivers/devfreq/governor_userspace.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
index 35de6e8..9db4d6f 100644
--- a/drivers/devfreq/governor_userspace.c
+++ b/drivers/devfreq/governor_userspace.c
@@ -112,7 +112,13 @@ static int userspace_init(struct devfreq *devfreq)
 
 static void userspace_exit(struct devfreq *devfreq)
 {
-	sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
+	/*
+	 * Remove the sysfs entry, unless this is being called after
+	 * device_del(), which should have done this already via kobject_del().
+	 */
+	if (devfreq->dev.kobj.sd)
+		sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
+
 	kfree(devfreq->data);
 	devfreq->data = NULL;
 }
-- 
1.9.1