src/patches/suse-2.6.27.25/patches.arch/s390-04-08-cio-ungroup-race-fix.patch

   1 From: Gerald Schaefer <geraldsc@de.ibm.com>
   2 Subject: cio: ccwgroup online vs. ungroup race condition
   3 References: bnc#445100,LTC#50092
   4
   5 Symptom:     Kernel oops when a ccwgroup ungroup operation is triggered while
   6              online operation is still in progress.
   7 Problem:     Atomicity of ungroup operation is not guaranteed because of
   8              missing locking.
   9 Solution:    Introduce locking to ungroup operation.
  10
  11 Acked-by: John Jolly <jjolly@suse.de>
  12
  13 ---
  14  drivers/s390/cio/ccwgroup.c |   18 +++++++++++++-----
  15  1 file changed, 13 insertions(+), 5 deletions(-)
  16
  17 Index: linux-sles11/drivers/s390/cio/ccwgroup.c
  18 ===================================================================
  19 --- linux-sles11.orig/drivers/s390/cio/ccwgroup.c
  20 +++ linux-sles11/drivers/s390/cio/ccwgroup.c
  21 @@ -89,15 +89,23 @@ ccwgroup_ungroup_store(struct device *de
  22
  23         gdev = to_ccwgroupdev(dev);
  24
  25 -       if (gdev->state != CCWGROUP_OFFLINE)
  26 -               return -EINVAL;
  27 -
  28 +       /* Prevent concurrent online/offline processing and ungrouping. */
  29 +       if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
  30 +               return -EAGAIN;
  31 +       if (gdev->state != CCWGROUP_OFFLINE) {
  32 +               rc = -EINVAL;
  33 +               goto out;
  34 +       }
  35         /* Note that we cannot unregister the device from one of its
  36          * attribute methods, so we have to use this roundabout approach.
  37          */
  38         rc = device_schedule_callback(dev, ccwgroup_ungroup_callback);
  39 -       if (rc)
  40 -               count = rc;
  41 +out:
  42 +       if (rc) {
  43 +               /* Release onoff "lock" when ungrouping failed. */
  44 +               atomic_set(&gdev->onoff, 0);
  45 +               return rc;
  46 +       }
  47         return count;
  48  }
  49