[net-next-2.6.git] / kernel / cpu.c

/* 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 <linux/mutex.h>

/* Serializes the updates to cpu_online_map, cpu_present_map */
static DEFINE_MUTEX(cpu_add_remove_lock);

static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);

/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
 * Should always be manipulated under cpu_add_remove_lock
 */
static int cpu_hotplug_disabled;

static struct {
	struct task_struct *active_writer;
	struct mutex lock; /* Synchronizes accesses to refcount, */
	/*
	 * Also blocks the new readers during
	 * an ongoing cpu hotplug operation.
	 */
	int refcount;
	wait_queue_head_t writer_queue;
} cpu_hotplug;

#define writer_exists() (cpu_hotplug.active_writer != NULL)

void __init cpu_hotplug_init(void)
{
	cpu_hotplug.active_writer = NULL;
	mutex_init(&cpu_hotplug.lock);
	cpu_hotplug.refcount = 0;
	init_waitqueue_head(&cpu_hotplug.writer_queue);
}

#ifdef CONFIG_HOTPLUG_CPU

void lock_cpu_hotplug(void)
{
	might_sleep();
	if (cpu_hotplug.active_writer == current)
		return;
	mutex_lock(&cpu_hotplug.lock);
	cpu_hotplug.refcount++;
	mutex_unlock(&cpu_hotplug.lock);

}
EXPORT_SYMBOL_GPL(lock_cpu_hotplug);

void unlock_cpu_hotplug(void)
{
	if (cpu_hotplug.active_writer == current)
		return;
	mutex_lock(&cpu_hotplug.lock);
	cpu_hotplug.refcount--;

	if (unlikely(writer_exists()) && !cpu_hotplug.refcount)
		wake_up(&cpu_hotplug.writer_queue);

	mutex_unlock(&cpu_hotplug.lock);

}
EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);

#endif	/* CONFIG_HOTPLUG_CPU */

/*
 * The following two API's must be used when attempting
 * to serialize the updates to cpu_online_map, cpu_present_map.
 */
void cpu_maps_update_begin(void)
{
	mutex_lock(&cpu_add_remove_lock);
}

void cpu_maps_update_done(void)
{
	mutex_unlock(&cpu_add_remove_lock);
}

/*
 * This ensures that the hotplug operation can begin only when the
 * refcount goes to zero.
 *
 * Note that during a cpu-hotplug operation, the new readers, if any,
 * will be blocked by the cpu_hotplug.lock
 *
 * Since cpu_maps_update_begin is always called after invoking
 * cpu_maps_update_begin, we can be sure that only one writer is active.
 *
 * Note that theoretically, there is a possibility of a livelock:
 * - Refcount goes to zero, last reader wakes up the sleeping
 *   writer.
 * - Last reader unlocks the cpu_hotplug.lock.
 * - A new reader arrives at this moment, bumps up the refcount.
 * - The writer acquires the cpu_hotplug.lock finds the refcount
 *   non zero and goes to sleep again.
 *
 * However, this is very difficult to achieve in practice since
 * lock_cpu_hotplug() not an api which is called all that often.
 *
 */
static void cpu_hotplug_begin(void)
{
	DECLARE_WAITQUEUE(wait, current);

	mutex_lock(&cpu_hotplug.lock);

	cpu_hotplug.active_writer = current;
	add_wait_queue_exclusive(&cpu_hotplug.writer_queue, &wait);
	while (cpu_hotplug.refcount) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		mutex_unlock(&cpu_hotplug.lock);
		schedule();
		mutex_lock(&cpu_hotplug.lock);
	}
	remove_wait_queue_locked(&cpu_hotplug.writer_queue, &wait);
}

static void cpu_hotplug_done(void)
{
	cpu_hotplug.active_writer = NULL;
	mutex_unlock(&cpu_hotplug.lock);
}
/* Need to know about CPUs going up/down? */
int __cpuinit register_cpu_notifier(struct notifier_block *nb)
{
	int ret;
	cpu_maps_update_begin();
	ret = raw_notifier_chain_register(&cpu_chain, nb);
	cpu_maps_update_done();
	return ret;
}

#ifdef CONFIG_HOTPLUG_CPU

EXPORT_SYMBOL(register_cpu_notifier);

void unregister_cpu_notifier(struct notifier_block *nb)
{
	cpu_maps_update_begin();
	raw_notifier_chain_unregister(&cpu_chain, nb);
	cpu_maps_update_done();
}
EXPORT_SYMBOL(unregister_cpu_notifier);

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 = %x) \n",
				 p->comm, task_pid_nr(p), cpu,
				 p->state, p->flags);
	}
	write_unlock_irq(&tasklist_lock);
}

struct take_cpu_down_param {
	unsigned long mod;
	void *hcpu;
};

/* Take this CPU down. */
static int take_cpu_down(void *_param)
{
	struct take_cpu_down_param *param = _param;
	int err;

	raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
				param->hcpu);
	/* Ensure this CPU doesn't handle any more interrupts. */
	err = __cpu_disable();
	if (err < 0)
		return err;

	/* Force idle task to run as soon as we yield: it should
	   immediately notice cpu is offline and die quickly. */
	sched_idle_next();
	return 0;
}

/* Requires cpu_add_remove_lock to be held */
static int _cpu_down(unsigned int cpu, int tasks_frozen)
{
	int err, nr_calls = 0;
	struct task_struct *p;
	cpumask_t old_allowed, tmp;
	void *hcpu = (void *)(long)cpu;
	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
	struct take_cpu_down_param tcd_param = {
		.mod = mod,
		.hcpu = hcpu,
	};

	if (num_online_cpus() == 1)
		return -EBUSY;

	if (!cpu_online(cpu))
		return -EINVAL;

	cpu_hotplug_begin();
	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
	err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
					hcpu, -1, &nr_calls);
	if (err == NOTIFY_BAD) {
		nr_calls--;
		__raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
					  hcpu, nr_calls, NULL);
		printk("%s: attempt to take down CPU %u failed\n",
				__FUNCTION__, cpu);
		err = -EINVAL;
		goto out_release;
	}

	/* 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, &tcd_param, cpu);

	if (IS_ERR(p) || cpu_online(cpu)) {
		/* CPU didn't die: tell everyone.  Can't complain. */
		if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
					    hcpu) == NOTIFY_BAD)
			BUG();

		if (IS_ERR(p)) {
			err = PTR_ERR(p);
			goto out_allowed;
		}
		goto out_thread;
	}

	/* Wait for it to sleep (leaving idle task). */
	while (!idle_cpu(cpu))
		yield();

	/* This actually kills the CPU. */
	__cpu_die(cpu);

	/* CPU is completely dead: tell everyone.  Too late to complain. */
	if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
				    hcpu) == NOTIFY_BAD)
		BUG();

	check_for_tasks(cpu);

out_thread:
	err = kthread_stop(p);
out_allowed:
	set_cpus_allowed(current, old_allowed);
out_release:
	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
	cpu_hotplug_done();
	return err;
}

int cpu_down(unsigned int cpu)
{
	int err = 0;

	cpu_maps_update_begin();
	if (cpu_hotplug_disabled)
		err = -EBUSY;
	else
		err = _cpu_down(cpu, 0);

	cpu_maps_update_done();
	return err;
}
#endif /*CONFIG_HOTPLUG_CPU*/

/* Requires cpu_add_remove_lock to be held */
static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
{
	int ret, nr_calls = 0;
	void *hcpu = (void *)(long)cpu;
	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;

	if (cpu_online(cpu) || !cpu_present(cpu))
		return -EINVAL;

	cpu_hotplug_begin();
	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
	ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
							-1, &nr_calls);
	if (ret == NOTIFY_BAD) {
		nr_calls--;
		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;
	BUG_ON(!cpu_online(cpu));

	/* Now call notifier in preparation. */
	raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);

out_notify:
	if (ret != 0)
		__raw_notifier_call_chain(&cpu_chain,
				CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
	cpu_hotplug_done();

	return ret;
}

int __cpuinit cpu_up(unsigned int cpu)
{
	int err = 0;
	if (!cpu_isset(cpu, cpu_possible_map)) {
		printk(KERN_ERR "can't online cpu %d because it is not "
			"configured as may-hotadd at boot time\n", cpu);
#if defined(CONFIG_IA64) || defined(CONFIG_X86_64) || defined(CONFIG_S390)
		printk(KERN_ERR "please check additional_cpus= boot "
				"parameter\n");
#endif
		return -EINVAL;
	}

	cpu_maps_update_begin();
	if (cpu_hotplug_disabled)
		err = -EBUSY;
	else
		err = _cpu_up(cpu, 0);

	cpu_maps_update_done();
	return err;
}

#ifdef CONFIG_PM_SLEEP_SMP
static cpumask_t frozen_cpus;

int disable_nonboot_cpus(void)
{
	int cpu, first_cpu, error = 0;

	cpu_maps_update_begin();
	first_cpu = first_cpu(cpu_online_map);
	/* We take down all of the non-boot CPUs in one shot to avoid races
	 * with the userspace trying to use the CPU hotplug at the same time
	 */
	cpus_clear(frozen_cpus);
	printk("Disabling non-boot CPUs ...\n");
	for_each_online_cpu(cpu) {
		if (cpu == first_cpu)
			continue;
		error = _cpu_down(cpu, 1);
		if (!error) {
			cpu_set(cpu, frozen_cpus);
			printk("CPU%d is down\n", cpu);
		} else {
			printk(KERN_ERR "Error taking CPU%d down: %d\n",
				cpu, error);
			break;
		}
	}
	if (!error) {
		BUG_ON(num_online_cpus() > 1);
		/* Make sure the CPUs won't be enabled by someone else */
		cpu_hotplug_disabled = 1;
	} else {
		printk(KERN_ERR "Non-boot CPUs are not disabled\n");
	}
	cpu_maps_update_done();
	return error;
}

void enable_nonboot_cpus(void)
{
	int cpu, error;

	/* Allow everyone to use the CPU hotplug again */
	cpu_maps_update_begin();
	cpu_hotplug_disabled = 0;
	if (cpus_empty(frozen_cpus))
		goto out;

	printk("Enabling non-boot CPUs ...\n");
	for_each_cpu_mask(cpu, frozen_cpus) {
		error = _cpu_up(cpu, 1);
		if (!error) {
			printk("CPU%d is up\n", cpu);
			continue;
		}
		printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
	}
	cpus_clear(frozen_cpus);
out:
	cpu_maps_update_done();
}
#endif /* CONFIG_PM_SLEEP_SMP */
Commit	Line	Data
1da177e4 LT	1	/* CPU control.
	2	* (C) 2001, 2002, 2003, 2004 Rusty Russell
	3	*
	4	* This code is licenced under the GPL.
	5	*/
	6	#include <linux/proc_fs.h>
	7	#include <linux/smp.h>
	8	#include <linux/init.h>
	9	#include <linux/notifier.h>
	10	#include <linux/sched.h>
	11	#include <linux/unistd.h>
	12	#include <linux/cpu.h>
	13	#include <linux/module.h>
	14	#include <linux/kthread.h>
	15	#include <linux/stop_machine.h>
81615b62	16	#include <linux/mutex.h>
1da177e4	17
d221938c	18	/* Serializes the updates to cpu_online_map, cpu_present_map */
aa953877	19	static DEFINE_MUTEX(cpu_add_remove_lock);
1da177e4	20
bd5349cf	21	static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
1da177e4	22
e3920fb4 RW	23	/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
	24	* Should always be manipulated under cpu_add_remove_lock
	25	*/
	26	static int cpu_hotplug_disabled;
	27
d221938c GS	28	static struct {
	29	struct task_struct *active_writer;
	30	struct mutex lock; /* Synchronizes accesses to refcount, */
	31	/*
	32	* Also blocks the new readers during
	33	* an ongoing cpu hotplug operation.
	34	*/
	35	int refcount;
	36	wait_queue_head_t writer_queue;
	37	} cpu_hotplug;
90d45d17	38
d221938c GS	39	#define writer_exists() (cpu_hotplug.active_writer != NULL)
	40
	41	void __init cpu_hotplug_init(void)
	42	{
	43	cpu_hotplug.active_writer = NULL;
	44	mutex_init(&cpu_hotplug.lock);
	45	cpu_hotplug.refcount = 0;
	46	init_waitqueue_head(&cpu_hotplug.writer_queue);
	47	}
	48
	49	#ifdef CONFIG_HOTPLUG_CPU
90d45d17	50
a9d9baa1 AR	51	void lock_cpu_hotplug(void)
a9d9baa1 AR	52	{
d221938c GS	53	might_sleep();
d221938c GS	54	if (cpu_hotplug.active_writer == current)
aa953877	55	return;
d221938c GS	56	mutex_lock(&cpu_hotplug.lock);
	57	cpu_hotplug.refcount++;
	58	mutex_unlock(&cpu_hotplug.lock);
	59
a9d9baa1 AR	60	}
a9d9baa1 AR	61	EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
90d45d17	62
a9d9baa1 AR	63	void unlock_cpu_hotplug(void)
a9d9baa1 AR	64	{
d221938c	65	if (cpu_hotplug.active_writer == current)
aa953877	66	return;
d221938c GS	67	mutex_lock(&cpu_hotplug.lock);
	68	cpu_hotplug.refcount--;
	69
	70	if (unlikely(writer_exists()) && !cpu_hotplug.refcount)
	71	wake_up(&cpu_hotplug.writer_queue);
	72
	73	mutex_unlock(&cpu_hotplug.lock);
	74
a9d9baa1 AR	75	}
	76	EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
	77
a9d9baa1	78	#endif /* CONFIG_HOTPLUG_CPU */
90d45d17	79
d221938c GS	80	/*
	81	* The following two API's must be used when attempting
	82	* to serialize the updates to cpu_online_map, cpu_present_map.
	83	*/
	84	void cpu_maps_update_begin(void)
	85	{
	86	mutex_lock(&cpu_add_remove_lock);
	87	}
	88
	89	void cpu_maps_update_done(void)
	90	{
	91	mutex_unlock(&cpu_add_remove_lock);
	92	}
	93
	94	/*
	95	* This ensures that the hotplug operation can begin only when the
	96	* refcount goes to zero.
	97	*
	98	* Note that during a cpu-hotplug operation, the new readers, if any,
	99	* will be blocked by the cpu_hotplug.lock
	100	*
	101	* Since cpu_maps_update_begin is always called after invoking
	102	* cpu_maps_update_begin, we can be sure that only one writer is active.
	103	*
	104	* Note that theoretically, there is a possibility of a livelock:
	105	* - Refcount goes to zero, last reader wakes up the sleeping
	106	* writer.
	107	* - Last reader unlocks the cpu_hotplug.lock.
	108	* - A new reader arrives at this moment, bumps up the refcount.
	109	* - The writer acquires the cpu_hotplug.lock finds the refcount
	110	* non zero and goes to sleep again.
	111	*
	112	* However, this is very difficult to achieve in practice since
	113	* lock_cpu_hotplug() not an api which is called all that often.
	114	*
	115	*/
	116	static void cpu_hotplug_begin(void)
	117	{
	118	DECLARE_WAITQUEUE(wait, current);
	119
	120	mutex_lock(&cpu_hotplug.lock);
	121
	122	cpu_hotplug.active_writer = current;
	123	add_wait_queue_exclusive(&cpu_hotplug.writer_queue, &wait);
	124	while (cpu_hotplug.refcount) {
	125	set_current_state(TASK_UNINTERRUPTIBLE);
	126	mutex_unlock(&cpu_hotplug.lock);
	127	schedule();
	128	mutex_lock(&cpu_hotplug.lock);
	129	}
	130	remove_wait_queue_locked(&cpu_hotplug.writer_queue, &wait);
	131	}
	132
	133	static void cpu_hotplug_done(void)
	134	{
	135	cpu_hotplug.active_writer = NULL;
	136	mutex_unlock(&cpu_hotplug.lock);
	137	}
1da177e4	138	/* Need to know about CPUs going up/down? */
65edc68c	139	int __cpuinit register_cpu_notifier(struct notifier_block *nb)
1da177e4	140	{
bd5349cf	141	int ret;
d221938c	142	cpu_maps_update_begin();
bd5349cf	143	ret = raw_notifier_chain_register(&cpu_chain, nb);
d221938c	144	cpu_maps_update_done();
bd5349cf	145	return ret;
1da177e4	146	}
65edc68c CS	147
	148	#ifdef CONFIG_HOTPLUG_CPU
	149
1da177e4 LT	150	EXPORT_SYMBOL(register_cpu_notifier);
	151
	152	void unregister_cpu_notifier(struct notifier_block *nb)
	153	{
d221938c	154	cpu_maps_update_begin();
bd5349cf	155	raw_notifier_chain_unregister(&cpu_chain, nb);
d221938c	156	cpu_maps_update_done();
1da177e4 LT	157	}
	158	EXPORT_SYMBOL(unregister_cpu_notifier);
	159
1da177e4 LT	160	static inline void check_for_tasks(int cpu)
	161	{
	162	struct task_struct *p;
	163
	164	write_lock_irq(&tasklist_lock);
	165	for_each_process(p) {
	166	if (task_cpu(p) == cpu &&
	167	(!cputime_eq(p->utime, cputime_zero) \|\|
	168	!cputime_eq(p->stime, cputime_zero)))
	169	printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
e7407dcc	170	(state = %ld, flags = %x) \n",
ba25f9dc PE	171	p->comm, task_pid_nr(p), cpu,
ba25f9dc PE	172	p->state, p->flags);
1da177e4 LT	173	}
	174	write_unlock_irq(&tasklist_lock);
	175	}
	176
db912f96 AK	177	struct take_cpu_down_param {
	178	unsigned long mod;
	179	void *hcpu;
	180	};
	181
1da177e4	182	/* Take this CPU down. */
db912f96	183	static int take_cpu_down(void *_param)
1da177e4	184	{
db912f96	185	struct take_cpu_down_param *param = _param;
1da177e4 LT	186	int err;
1da177e4 LT	187
db912f96 AK	188	raw_notifier_call_chain(&cpu_chain, CPU_DYING \| param->mod,
db912f96 AK	189	param->hcpu);
1da177e4 LT	190	/* Ensure this CPU doesn't handle any more interrupts. */
	191	err = __cpu_disable();
	192	if (err < 0)
f3705136	193	return err;
1da177e4	194
f3705136 ZM	195	/* Force idle task to run as soon as we yield: it should
	196	immediately notice cpu is offline and die quickly. */
	197	sched_idle_next();
	198	return 0;
1da177e4 LT	199	}
1da177e4 LT	200
e3920fb4	201	/* Requires cpu_add_remove_lock to be held */
8bb78442	202	static int _cpu_down(unsigned int cpu, int tasks_frozen)
1da177e4	203	{
e7407dcc	204	int err, nr_calls = 0;
1da177e4 LT	205	struct task_struct *p;
1da177e4 LT	206	cpumask_t old_allowed, tmp;
e7407dcc	207	void hcpu = (void )(long)cpu;
8bb78442	208	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
db912f96 AK	209	struct take_cpu_down_param tcd_param = {
	210	.mod = mod,
	211	.hcpu = hcpu,
	212	};
1da177e4	213
e3920fb4 RW	214	if (num_online_cpus() == 1)
e3920fb4 RW	215	return -EBUSY;
1da177e4	216
e3920fb4 RW	217	if (!cpu_online(cpu))
e3920fb4 RW	218	return -EINVAL;
1da177e4	219
d221938c	220	cpu_hotplug_begin();
e7407dcc	221	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
8bb78442	222	err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE \| mod,
e7407dcc	223	hcpu, -1, &nr_calls);
1da177e4	224	if (err == NOTIFY_BAD) {
a0d8cdb6	225	nr_calls--;
8bb78442 RW	226	__raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED \| mod,
8bb78442 RW	227	hcpu, nr_calls, NULL);
1da177e4 LT	228	printk("%s: attempt to take down CPU %u failed\n",
1da177e4 LT	229	__FUNCTION__, cpu);
baaca49f GS	230	err = -EINVAL;
baaca49f GS	231	goto out_release;
1da177e4 LT	232	}
	233
	234	/* Ensure that we are not runnable on dying cpu */
	235	old_allowed = current->cpus_allowed;
	236	tmp = CPU_MASK_ALL;
	237	cpu_clear(cpu, tmp);
	238	set_cpus_allowed(current, tmp);
	239
db912f96	240	p = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
aa953877	241
8fa1d7d3	242	if (IS_ERR(p) \|\| cpu_online(cpu)) {
1da177e4	243	/* CPU didn't die: tell everyone. Can't complain. */
8bb78442	244	if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED \| mod,
e7407dcc	245	hcpu) == NOTIFY_BAD)
1da177e4 LT	246	BUG();
1da177e4 LT	247
8fa1d7d3 ST	248	if (IS_ERR(p)) {
	249	err = PTR_ERR(p);
	250	goto out_allowed;
	251	}
1da177e4	252	goto out_thread;
8fa1d7d3	253	}
1da177e4 LT	254
	255	/* Wait for it to sleep (leaving idle task). */
	256	while (!idle_cpu(cpu))
	257	yield();
	258
	259	/* This actually kills the CPU. */
	260	__cpu_die(cpu);
	261
1da177e4	262	/* CPU is completely dead: tell everyone. Too late to complain. */
8bb78442 RW	263	if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD \| mod,
8bb78442 RW	264	hcpu) == NOTIFY_BAD)
1da177e4 LT	265	BUG();
	266
	267	check_for_tasks(cpu);
	268
	269	out_thread:
	270	err = kthread_stop(p);
	271	out_allowed:
	272	set_cpus_allowed(current, old_allowed);
baaca49f	273	out_release:
8bb78442	274	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
d221938c	275	cpu_hotplug_done();
e3920fb4 RW	276	return err;
	277	}
	278
	279	int cpu_down(unsigned int cpu)
	280	{
	281	int err = 0;
	282
d221938c	283	cpu_maps_update_begin();
e3920fb4 RW	284	if (cpu_hotplug_disabled)
	285	err = -EBUSY;
	286	else
8bb78442	287	err = _cpu_down(cpu, 0);
e3920fb4	288
d221938c	289	cpu_maps_update_done();
1da177e4 LT	290	return err;
	291	}
	292	#endif /CONFIG_HOTPLUG_CPU/
	293
e3920fb4	294	/* Requires cpu_add_remove_lock to be held */
8bb78442	295	static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
1da177e4	296	{
baaca49f	297	int ret, nr_calls = 0;
1da177e4	298	void hcpu = (void )(long)cpu;
8bb78442	299	unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
1da177e4	300
e3920fb4 RW	301	if (cpu_online(cpu) \|\| !cpu_present(cpu))
e3920fb4 RW	302	return -EINVAL;
90d45d17	303
d221938c	304	cpu_hotplug_begin();
baaca49f	305	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
8bb78442	306	ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE \| mod, hcpu,
baaca49f	307	-1, &nr_calls);
1da177e4	308	if (ret == NOTIFY_BAD) {
a0d8cdb6	309	nr_calls--;
1da177e4 LT	310	printk("%s: attempt to bring up CPU %u failed\n",
	311	__FUNCTION__, cpu);
	312	ret = -EINVAL;
	313	goto out_notify;
	314	}
	315
	316	/* Arch-specific enabling code. */
	317	ret = __cpu_up(cpu);
	318	if (ret != 0)
	319	goto out_notify;
6978c705	320	BUG_ON(!cpu_online(cpu));
1da177e4 LT	321
1da177e4 LT	322	/* Now call notifier in preparation. */
8bb78442	323	raw_notifier_call_chain(&cpu_chain, CPU_ONLINE \| mod, hcpu);
1da177e4 LT	324
	325	out_notify:
	326	if (ret != 0)
baaca49f	327	__raw_notifier_call_chain(&cpu_chain,
8bb78442	328	CPU_UP_CANCELED \| mod, hcpu, nr_calls, NULL);
baaca49f	329	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
d221938c	330	cpu_hotplug_done();
e3920fb4 RW	331
	332	return ret;
	333	}
	334
b282b6f8	335	int __cpuinit cpu_up(unsigned int cpu)
e3920fb4 RW	336	{
e3920fb4 RW	337	int err = 0;
73e753a5 KH	338	if (!cpu_isset(cpu, cpu_possible_map)) {
	339	printk(KERN_ERR "can't online cpu %d because it is not "
	340	"configured as may-hotadd at boot time\n", cpu);
	341	#if defined(CONFIG_IA64) \|\| defined(CONFIG_X86_64) \|\| defined(CONFIG_S390)
	342	printk(KERN_ERR "please check additional_cpus= boot "
	343	"parameter\n");
	344	#endif
	345	return -EINVAL;
	346	}
e3920fb4	347
d221938c	348	cpu_maps_update_begin();
e3920fb4 RW	349	if (cpu_hotplug_disabled)
	350	err = -EBUSY;
	351	else
8bb78442	352	err = _cpu_up(cpu, 0);
e3920fb4	353
d221938c	354	cpu_maps_update_done();
e3920fb4 RW	355	return err;
	356	}
	357
f3de4be9	358	#ifdef CONFIG_PM_SLEEP_SMP
e3920fb4 RW	359	static cpumask_t frozen_cpus;
	360
	361	int disable_nonboot_cpus(void)
	362	{
e1d9fd2e	363	int cpu, first_cpu, error = 0;
e3920fb4	364
d221938c	365	cpu_maps_update_begin();
1d64b9cb	366	first_cpu = first_cpu(cpu_online_map);
e3920fb4 RW	367	/* We take down all of the non-boot CPUs in one shot to avoid races
	368	* with the userspace trying to use the CPU hotplug at the same time
	369	*/
	370	cpus_clear(frozen_cpus);
	371	printk("Disabling non-boot CPUs ...\n");
	372	for_each_online_cpu(cpu) {
	373	if (cpu == first_cpu)
	374	continue;
8bb78442	375	error = _cpu_down(cpu, 1);
e3920fb4 RW	376	if (!error) {
	377	cpu_set(cpu, frozen_cpus);
	378	printk("CPU%d is down\n", cpu);
	379	} else {
	380	printk(KERN_ERR "Error taking CPU%d down: %d\n",
	381	cpu, error);
	382	break;
	383	}
	384	}
	385	if (!error) {
	386	BUG_ON(num_online_cpus() > 1);
	387	/* Make sure the CPUs won't be enabled by someone else */
	388	cpu_hotplug_disabled = 1;
	389	} else {
e1d9fd2e	390	printk(KERN_ERR "Non-boot CPUs are not disabled\n");
e3920fb4	391	}
d221938c	392	cpu_maps_update_done();
e3920fb4 RW	393	return error;
	394	}
	395
	396	void enable_nonboot_cpus(void)
	397	{
	398	int cpu, error;
	399
	400	/* Allow everyone to use the CPU hotplug again */
d221938c	401	cpu_maps_update_begin();
e3920fb4	402	cpu_hotplug_disabled = 0;
ed746e3b	403	if (cpus_empty(frozen_cpus))
1d64b9cb	404	goto out;
e3920fb4 RW	405
	406	printk("Enabling non-boot CPUs ...\n");
	407	for_each_cpu_mask(cpu, frozen_cpus) {
8bb78442	408	error = _cpu_up(cpu, 1);
e3920fb4 RW	409	if (!error) {
	410	printk("CPU%d is up\n", cpu);
	411	continue;
	412	}
1d64b9cb	413	printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
e3920fb4 RW	414	}
e3920fb4 RW	415	cpus_clear(frozen_cpus);
1d64b9cb	416	out:
d221938c	417	cpu_maps_update_done();
1da177e4	418	}
f3de4be9	419	#endif /* CONFIG_PM_SLEEP_SMP */