Control groups, part 1: On the history of process grouping

It wouldn't necessarily make the TTY layer less fragile (although as a userspace framework it'd be easier to test and keep stable). It would, however, help make the kernel less fragile. TTY is one of the touchiest bits of the kernel, where what looks like a minor cleanup can break behavior that a 15-year-old version of emacs depends on.

The kernel could provide raw-mode-only serial ports (a pure bytestream only), and allow the userspace TTY framework to provide any additional "cooked" functionality of ttyS* or ttyUSB* on top of that, analogous to how the kernel would not need need to provide tty[1-9]*.