There is not much in the way of file locking available in the Hurd, and in particular we do not have facilities that match the POSIX semantics for fcntl locking, or (I think) the BSD semantics for flock. The specified semantics are not very elegant from a component-model perspective, and thus nontrivial to design Hurd protocols to properly support. We (the core Hurd developers) have discussed some ideas for new Hurd RPCs for locking, but never fully resolved on a plan and the main issue is that noone has had the time to make it a priority thing to work on. If there is active interest by someone who will do the implementation work, then I think we can manage to dig up our thoughts on the issue and figure out a good way to go about it. But I don't know when any of the core Hurd developers might have the time to actually do such an implementation.
