With this patchset, your chances of getting a shell with smp is about 1/3. Unfortunately, there is occasionally kernel traps when either booting, or using the system, depending if you reach a login shell or not.
I was able to boot with -smp 3 and run "stress -c 3" for about 1 minute. Then I ran "git log" and crashed my system with a divide by zero. This is getting better, but not quite ready for production use yet. Damien