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s390/cio: fix race condition during online processing 

A race condition exists in ccw_device_set_online() that can cause the
online process to fail, leaving the affected device in an inconsistent
state. As a result, subsequent attempts to set that device online fail
with return code ENODEV.

The problem occurs when a path verification request arrives after
a wait for final device state completed, but before the result state
is evaluated.

Fix this by ensuring that the CCW-device lock is held between
determining final state and checking result state.

Note that since:

commit 2297791c92 ("s390/cio: dont unregister subchannel from child-drivers")

path verification requests are much more likely to occur during boot,
resulting in an increased chance of this race condition occurring.

Fixes: 2297791c92 ("s390/cio: dont unregister subchannel from child-drivers")
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Peter Oberparleiter 2024-04-10 11:46:19 +02:00 committed by Alexander Gordeev
parent 607638faf2
commit 2d8527f2f9
1 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/s390/cio/device.c
View File

@ -363,10 +363,8 @@ int ccw_device_set_online(struct ccw_device *cdev)
spin_lock_irq(cdev->ccwlock);
ret = ccw_device_online(cdev);
spin_unlock_irq(cdev->ccwlock);
if (ret == 0)
wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
else {
if (ret) {
spin_unlock_irq(cdev->ccwlock);
CIO_MSG_EVENT(0, "ccw_device_online returned %d, "
"device 0.%x.%04x\n",
ret, cdev->private->dev_id.ssid,
@ -375,7 +373,12 @@ int ccw_device_set_online(struct ccw_device *cdev)
put_device(&cdev->dev);
return ret;
}
spin_lock_irq(cdev->ccwlock);
/* Wait until a final state is reached */
while (!dev_fsm_final_state(cdev)) {
spin_unlock_irq(cdev->ccwlock);
wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
spin_lock_irq(cdev->ccwlock);
}
/* Check if online processing was successful */
if ((cdev->private->state != DEV_STATE_ONLINE) &&
(cdev->private->state != DEV_STATE_W4SENSE)) {