“Welcome back to our series on IRIX binary compatibility. In this part, we will study IRIX and NetBSD threading models. We will also examine how it is possible to emulate IRIX native threads on NetBSD, though NetBSD does not support a similar feature for its native binaries.” Read the article at OnLamp.
I’ve been following these articles with some interest, and they’re very good. However I’d have to take issue with the assertion that POSIX threads must be user threads. That is certainly not true. POSIX goes out of its way to ensure that it does not dictate the implementation, in fact. So there is nothing stopping a kernel developer from implementing their kernel threads with a POSIX.1c API, or as we have done with Syllable, wrapping a thin POSIX.1c API around the native kernel thread API.
Still a very good series of articles, though.