http://glen.alkohol.ee/pld/aff.c when this program is ran from SMP kernel (AMD Athlon(tm) 64 X2 Dual Core Processor 3800+), it just hungs and goes to D state: $ ./aff cpus: 2 <DEAD> in ps: $ ps a PID TTY STAT TIME COMMAND 5594 pts/1 D+ 0:00 ./aff -- glen