6.8-stable review patch. If anyone has any objections, please let me know.
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From: Peter Oberparleiter oberpar@linux.ibm.com
[ Upstream commit 2d8527f2f911fab84aec04df4788c0c23af3df48 ]
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 2297791c92d0 ("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: 2297791c92d0 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/s390/cio/device.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c index 0cfb179e1bcb6..34b2567b8df49 100644 --- a/drivers/s390/cio/device.c +++ b/drivers/s390/cio/device.c @@ -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)) {