On Thu, Feb 18 2016, Shaohua Li wrote: > On Wed, Feb 17, 2016 at 05:25:00PM +0100, Sebastian Parschauer wrote: >> When stopping an MD device, then its device node /dev/mdX may still >> exist afterwards or it is recreated by udev. The next open() call >> can lead to creation of an inoperable MD device. The reason for >> this is that a change event (KOBJ_CHANGE) is sent to udev which >> races against the remove event (KOBJ_REMOVE) from md_free(). >> So drop sending the change event. >> >> A change is likely also required in mdadm as many versions send the >> change event to udev as well. > > Makes sense, it's unlikely we need the CHANGE event. Applied. > > Thanks, > Shaohua It would be worth checking, but I think that with this change, you can write "inactive" to /sys/block/mdXXX/md/array_state and the array will become inactive, but no uevent will be generated, which isn't good. Maybe send the uevent that was just removed from the 'inactive' case of array_state_store() instead. (But I still think this is just a bandaid and doesn't provide any guarantees that there will be no races with udev) NeilBrown
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