But that still doesn't scale up to more locks of that size very well, because you start trying to take even more of them, and in dynamic orders, and etc etc.

I know about the theoretical solution of taking locks always in a defined order, but I don't consider it a practical solution. If taking locks willy-nilly lets you scale to program size X, this might give you 2X or 3X, but that's not nearly large enough in practice.

& dandelany, the community has chipped in and answered for me. I endorse this subthread, at least, as I write this comment. :)