diff -urNp linux-2.5.55/kernel/sched.c linux-2.5.55-fix/kernel/sched.c
--- linux-2.5.55/kernel/sched.c	2003-01-09 05:04:22.000000000 +0100
+++ linux-2.5.55-fix/kernel/sched.c	2003-01-10 13:37:40.000000000 +0100
@@ -2108,7 +2108,7 @@ static int migration_thread(void * data)
 		spin_unlock_irqrestore(&rq->lock, flags);
 
 		p = req->task;
-		cpu_dest = __ffs(p->cpus_allowed);
+		cpu_dest = __ffs(p->cpus_allowed & cpu_online_map);
 		rq_dest = cpu_rq(cpu_dest);
 repeat:
 		cpu_src = task_cpu(p);