diff --git a/kernel/cpu.c b/kernel/cpu.c
new file mode 100644
index 0000000..628f4cc
--- /dev/null
+++ b/kernel/cpu.c
@@ -0,0 +1,193 @@
+/* CPU control.
+ * (C) 2001, 2002, 2003, 2004 Rusty Russell
+ *
+ * This code is licenced under the GPL.
+ */
+#include <linux/proc_fs.h>
+#include <linux/smp.h>
+#include <linux/init.h>
+#include <linux/notifier.h>
+#include <linux/sched.h>
+#include <linux/unistd.h>
+#include <linux/cpu.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/stop_machine.h>
+#include <asm/semaphore.h>
+
+/* This protects CPUs going up and down... */
+DECLARE_MUTEX(cpucontrol);
+
+static struct notifier_block *cpu_chain;
+
+/* Need to know about CPUs going up/down? */
+int register_cpu_notifier(struct notifier_block *nb)
+{
+	int ret;
+
+	if ((ret = down_interruptible(&cpucontrol)) != 0)
+		return ret;
+	ret = notifier_chain_register(&cpu_chain, nb);
+	up(&cpucontrol);
+	return ret;
+}
+EXPORT_SYMBOL(register_cpu_notifier);
+
+void unregister_cpu_notifier(struct notifier_block *nb)
+{
+	down(&cpucontrol);
+	notifier_chain_unregister(&cpu_chain, nb);
+	up(&cpucontrol);
+}
+EXPORT_SYMBOL(unregister_cpu_notifier);
+
+#ifdef CONFIG_HOTPLUG_CPU
+static inline void check_for_tasks(int cpu)
+{
+	struct task_struct *p;
+
+	write_lock_irq(&tasklist_lock);
+	for_each_process(p) {
+		if (task_cpu(p) == cpu &&
+		    (!cputime_eq(p->utime, cputime_zero) ||
+		     !cputime_eq(p->stime, cputime_zero)))
+			printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
+				(state = %ld, flags = %lx) \n",
+				 p->comm, p->pid, cpu, p->state, p->flags);
+	}
+	write_unlock_irq(&tasklist_lock);
+}
+
+/* Take this CPU down. */
+static int take_cpu_down(void *unused)
+{
+	int err;
+
+	/* Take offline: makes arch_cpu_down somewhat easier. */
+	cpu_clear(smp_processor_id(), cpu_online_map);
+
+	/* Ensure this CPU doesn't handle any more interrupts. */
+	err = __cpu_disable();
+	if (err < 0)
+		cpu_set(smp_processor_id(), cpu_online_map);
+	else
+		/* Force idle task to run as soon as we yield: it should
+		   immediately notice cpu is offline and die quickly. */
+		sched_idle_next();
+
+	return err;
+}
+
+int cpu_down(unsigned int cpu)
+{
+	int err;
+	struct task_struct *p;
+	cpumask_t old_allowed, tmp;
+
+	if ((err = lock_cpu_hotplug_interruptible()) != 0)
+		return err;
+
+	if (num_online_cpus() == 1) {
+		err = -EBUSY;
+		goto out;
+	}
+
+	if (!cpu_online(cpu)) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
+						(void *)(long)cpu);
+	if (err == NOTIFY_BAD) {
+		printk("%s: attempt to take down CPU %u failed\n",
+				__FUNCTION__, cpu);
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* Ensure that we are not runnable on dying cpu */
+	old_allowed = current->cpus_allowed;
+	tmp = CPU_MASK_ALL;
+	cpu_clear(cpu, tmp);
+	set_cpus_allowed(current, tmp);
+
+	p = __stop_machine_run(take_cpu_down, NULL, cpu);
+	if (IS_ERR(p)) {
+		/* CPU didn't die: tell everyone.  Can't complain. */
+		if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
+				(void *)(long)cpu) == NOTIFY_BAD)
+			BUG();
+
+		err = PTR_ERR(p);
+		goto out_allowed;
+	}
+
+	if (cpu_online(cpu))
+		goto out_thread;
+
+	/* Wait for it to sleep (leaving idle task). */
+	while (!idle_cpu(cpu))
+		yield();
+
+	/* This actually kills the CPU. */
+	__cpu_die(cpu);
+
+	/* Move it here so it can run. */
+	kthread_bind(p, get_cpu());
+	put_cpu();
+
+	/* CPU is completely dead: tell everyone.  Too late to complain. */
+	if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
+	    == NOTIFY_BAD)
+		BUG();
+
+	check_for_tasks(cpu);
+
+out_thread:
+	err = kthread_stop(p);
+out_allowed:
+	set_cpus_allowed(current, old_allowed);
+out:
+	unlock_cpu_hotplug();
+	return err;
+}
+#endif /*CONFIG_HOTPLUG_CPU*/
+
+int __devinit cpu_up(unsigned int cpu)
+{
+	int ret;
+	void *hcpu = (void *)(long)cpu;
+
+	if ((ret = down_interruptible(&cpucontrol)) != 0)
+		return ret;
+
+	if (cpu_online(cpu) || !cpu_present(cpu)) {
+		ret = -EINVAL;
+		goto out;
+	}
+	ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
+	if (ret == NOTIFY_BAD) {
+		printk("%s: attempt to bring up CPU %u failed\n",
+				__FUNCTION__, cpu);
+		ret = -EINVAL;
+		goto out_notify;
+	}
+
+	/* Arch-specific enabling code. */
+	ret = __cpu_up(cpu);
+	if (ret != 0)
+		goto out_notify;
+	if (!cpu_online(cpu))
+		BUG();
+
+	/* Now call notifier in preparation. */
+	notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
+
+out_notify:
+	if (ret != 0)
+		notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
+out:
+	up(&cpucontrol);
+	return ret;
+}