I don't know that p9p has ever been built on a MIPS machine, so you might run into more problems after this one.
You are almost certainly running Linux 2.6 so you shouldn't need to edit u.h -- it should be using pthreads already. You probably need to edit src/libthread/sysofiles.sh to add a case mips-Linux-2.6.*) echo pthread.o Linux-mips-context.o ;; Then you'll need to write Linux-mips-context.S and mips-context.h to provide useful versions of getcontext and setcontext and change threadimpl.h to use them on MIPS (like it does for __APPLE__ and __OpenBSD__). I looked around but I don't think I have any such implementations lying around. They're not too hard: just save and restore every register (technically, just the callee-saves, but I'm too lazy to look up which ones are which and too paranoid to trust them not to change). Russ