From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Thu, 7 Aug 2008 13:16:44 +0200
Subject: [s390] cio: fix double unregistering of subchannels
Message-id: 20080807111644.GB6319@redhat.com
O-Subject: [RHEL5 U3 PATCH 2/5] s390 - cio: fix double unregistering of subchannels
Bugzilla: 456087
RH-Acked-by: Jarod Wilson <jwilson@redhat.com>
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>

Description
============

In some cases where the channel subsystem decides to drop a subchannel
device device_unregister may be called twice, which results in an oops.

The patch prevents this by only unregistering registered devices.

Bugzilla
=========

BZ 456087
https://bugzilla.redhat.com/show_bug.cgi?id=456087

Upstream status of the patch:
=============================

Patch is contained in linux-2.6 as of git commit
ef60cd13ecee0ccf2439d63013cbfc798aea2bb9

Test status:
============

The patch has been tested and fixes the problem.
The fix has been verified by the IBM test department.

Please ACK.

With best regards,

	-Hans

diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 8caf089..51ec6ff 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -123,7 +123,8 @@ int css_sch_device_register(struct subchannel *sch)
 void css_sch_device_unregister(struct subchannel *sch)
 {
 	mutex_lock(&sch->reg_mutex);
-	device_unregister(&sch->dev);
+	if (device_is_registered(&sch->dev))
+		device_unregister(&sch->dev);
 	mutex_unlock(&sch->reg_mutex);
 }