The workq can process work in parallel with a remove event, leading
to a condition where the workq handler can access freed memory.

To remedy, the workq should be terminated prior to freeing memory. Move
the termination call earlier in remove and use cancel_work_sync() instead
of flush_work() as there is not a need to process any scheduled work when
shutting down.
Signed-off-by: NMatthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: NManoj N. Kumar <manoj@linux.vnet.ibm.com>
Reviewed-by: NBrian King <brking@linux.vnet.ibm.com>
Reviewed-by: NTomas Henzl <thenzl@redhat.com>
Signed-off-by: NJames Bottomley <JBottomley@Odin.com>