Hi Brendon, This bug seems to be fixed in >= gcc-4.4 . I tried it with gcc 4.4.5 20100909, also with gcc-snapshot 4.6.0 20100828. gcc-4.4 -c -Os -fno-unit-at-a-time sched.i /usr/lib/gcc-snapshot/bin/gcc -c -Os -fno-unit-at-a-time sched.i and there is no ICE. The sched.i is downloaded from http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35618 . Could you try to rebuild the user-mode Linux using gcc-4.4 and see if it works? thanks raju