GNU + Linux = broken development model.

Sometimes it's not clear which codebase is "broken" and needs to be fixed. Alan Cox's changes may have been totally legal according to the RS-232 standards, but if Emacs and many other programs depend on the old behavior, it's difficult to say that all userspace programs must be changed. One person's "bug" is another person's "feature" :)

I do agree with Linus that increased kernel parallelism should avoid impacting userland code that depends (rightly or wrongly) on serialization.