[dm-devel] [PATCH] multipathd: check and cleanup zombie paths

[Chongyun Wu]

On 2018/3/20 23:14, Bart Van Assche wrote:
> On Tue, 2018-03-20 at 16:12 +0100, Xose Vazquez Perez wrote:
>> On 03/20/2018 03:58 PM, Bart Van Assche wrote:
>>
>>> It is on purpose that the SCSI core does not remove stale SCSI device nodes.
>>> If you want that these stale SCSI device nodes get removed automatically,
>>> two possible approaches are (there might be other approaches):
>>> * Write a new user space daemon that periodically checks for stale devices
>>>    (e.g. by running grep -aH . /sys/class/scsi_device/*/*/state |
>>>     grep -v running) and that triggers a SCSI rescan if any stale devices are
>>>    found.
>>> * Write a udev rule that listens for SDEV_UA=REPORTED_LUNS_DATA_HAS_CHANGED
>>>    and that triggers a SCSI rescan if this event is triggered by the kernel.
>>
>> There are some "remove" flags in rescan-scsi-bus.sh:
>> https://github.com/hreinecke/sg3_utils/blob/d4dbbede04db21c206e4c2acc1cf766117f003c3/scripts/rescan-scsi-bus.sh#L1080
>>
>> -r      enables removing of devices        [default: disabled]
>> --forceremove:   Remove stale devices (DANGEROUS)
>> --forcerescan:   Remove and readd existing devices (DANGEROUS)
> 
> Last time I checked the rescan-scsi-bus.sh script relied on the SCSI sysfs
> delete attribute to remove stale devices. That is the mechanism that can
> trigger a deadlock in the kernel.
> 
> Bart.
> 

Hi Bart,

Is there any special operation or conditions to reproduce the dead lock? 
  I have use SCSI sysfs delete atrribute to remove stale devices in my 
previous patch and test many times, but I haven't encountered any 
deadlock problems.

Regards,
Chongyun