- avoids race conditions when geofence data is updated in flight. During
a transfer, the geofence module will not check for violations, which
is done with the new dm_trylock method.
- there is an update counter stored in dataman, and for each write
transaction this is increased, so that the geofence module can reload
the data upon data change (after it's unlocked).
- single dm item updates are atomic already, so resetting the polygons
to 0 does not need locking.
Beat Küng
6d85a3c4e4