pkgdata is currently shared which leads to two issues: a) do_package/do_packagedata can't run well in parallel due to the shared lock b) files can be accessed outside of the dependency chain An RSS approach to pkgdata would be better as it would remove the need to locking and mean recipes could only see things they depend upon.
http://git.yoctoproject.org/cgit.cgi/poky/commit/?id=99206cb7b41be7a124ea8339bc891077f02128a2