2757fe1d8e
The safe offline processing needs, as well as the normal offline processing, to be locked against multiple parallel executions. But it should be able to be overtaken by a normal offline processing to make sure that the device does not wait forever for outstanding I/O if the user wants to. Unfortunately the parallel processing of safe offline and normal offline might lead to a race situation where both threads report successful execution to the CIO layer which in turn tries to deregister the kobject of the device twice. This leads to a refcount_t: underflow; use-after-free. error and the device is not able to be set online again afterwards without a reboot. Correct the locking of the safe offline processing by doing the following: - Use the cdev lock to secure all set and test operations to the device flags. - Two safe offline processes are locked against each other using the DASD_FLAG_SAFE_OFFLINE and DASD_FLAG_SAFE_OFFLINE_RUNNING device flags. The differentiation between offline triggered and offline running is needed since the normal offline attribute is owned by CIO and we have to pass over control in between. - The dasd_generic_set_offline process handles the offline processing. It is locked against parallel execution using the DASD_FLAG_OFFLINE. - Only a running safe offline should be able to be overtaken by a single normal offline. This is ensured by clearing the DASD_FLAG_SAFE_OFFLINE_RUNNING flag when a normal offline overtakes. So this can only happen ones. - The safe offline just aborts in this case doing nothing and the normal offline processing finishes as usual. Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> |
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| block | ||
| char | ||
| cio | ||
| crypto | ||
| net | ||
| scsi | ||
| virtio | ||
| Makefile | ||