Are real-time linux extensions obsolete?

Question

Do the new real-time and low latency patches from Ingo Molnar render previous real-time extensions for Linux (such as RTAI, Xenomai) obsolete?

Answer 1

Doesn't look like it to me, although I've not endeavoured to build a real-time system on Linux (yet). RTAI look like APIs. POSIX.4 would be similar (and of course infinitely superior in my humble opinion as the former vice-chair of that committee and author of the book :) .

Molnar's work looks to me as if it is designed to actually provide real-time performance to Linux. So to write a real, real-time application, you're probably talking about (1) using real-time APIs as well as the standard *nix calls, and (2) building your application very carefully, taking account of techniques mentioned on the Real-Time Linux Wiki. So in general, I'd say you need both. And probably even more than those two!