`mkfontdir' is run too many times. It would be cool if a set of packages, like the xfonts-* ones, could register a command to be run later, (like on a hook variable in emacs) and have it called after all of them have been installed. `update-menus' does a similar thing; I think it probably forks to the background if it's the first one, then continues when `dpkg' releases the lock.