Given that we're unlikely to see new consumers of lockmgr going forward, I wonder whether sleepgen would might someday be useful for avoiding the vnode interlock in some cases? If not, then this seems like a lot of machinery to deal with one lock, though the diff isn't too big.

This needs to retain proper authorship, so the Author field still needs to be hps. Add the end of the commit message you should mention this was extracted by you from a bigger patch of his. So add that, drop "in memoriam".

why even support something like this?