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[S390] cio: fix ccwgroup online vs. ungroup race condition

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Ensure atomicity of ungroup operation to prevent concurrent ungroup
and online processing which may lead to use-after-release situations.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Peter Oberparleiter 2008-12-25 13:39:04 +01:00 committed by Martin Schwidefsky
parent 111e95a4ca
commit c619d4223e
1 changed files with 13 additions and 5 deletions
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18
drivers/s390/cio/ccwgroup.c
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@ -91,15 +91,23 @@ ccwgroup_ungroup_store(struct device *dev, struct device_attribute *attr, const
gdev = to_ccwgroupdev(dev);
if (gdev->state != CCWGROUP_OFFLINE)
return -EINVAL;
/* Prevent concurrent online/offline processing and ungrouping. */
if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
return -EAGAIN;
if (gdev->state != CCWGROUP_OFFLINE) {
rc = -EINVAL;
goto out;
}
/* Note that we cannot unregister the device from one of its
* attribute methods, so we have to use this roundabout approach.
*/
rc = device_schedule_callback(dev, ccwgroup_ungroup_callback);
if (rc)
count = rc;
out:
if (rc) {
/* Release onoff "lock" when ungrouping failed. */
atomic_set(&gdev->onoff, 0);
return rc;
}
return count;
}