What really makes this confusing is that I can't find any documentation explaining WHY /dev/shm is the default location where named semaphores go, or how to move/create your named semaphores elsewhere (like cal-tool does). So I don't even really know where to start, when it comes to figuring out how the cal-tool code works to achieve what it does.

Besides that, here's a headscratcher (although the question is just a pure why rather than it getting in the way of a solution at the moment): /dev/shm DOES show up as mounted if you run 'mount'. rdmod segfaults. Then you run 'mount -t tmpfs tmpfs /dev/shm'. /dev/shm shows up in the same exact way in 'mount' output again. No change what so ever. Yet rdmod stops segfaulting.

I want to know how @ paragraph 1 and why @ paragraph 2. But for the time being, I am content with the fact that some way of making rdmod finally work at early boot is possible.