The liblockdep userspace lock debugging tool was merged to the mainline kernel tree in version 3.14. Unfortunately, the very next official release, linux 3.15, had a lockdep change that happened to break liblockdep. The patch for this regression was submitted just after Linux tagged 3.16-rc4, and being a fix for a regression (as opposed to a new feature) Linus was still willing to merge it in time for the 3.16 release without any fuss. Users of liblockdep should thus upgrade to 3.16 or later.