[linux-2.6-block.git] / kernel / smpboot.c

/*
 * Common SMP CPU bringup/teardown functions
 */
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/smp.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/export.h>
#include <linux/percpu.h>
#include <linux/kthread.h>
#include <linux/smpboot.h>

#include "smpboot.h"

#ifdef CONFIG_SMP

#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
/*
 * For the hotplug case we keep the task structs around and reuse
 * them.
 */
static DEFINE_PER_CPU(struct task_struct *, idle_threads);

struct task_struct *idle_thread_get(unsigned int cpu)
{
	struct task_struct *tsk = per_cpu(idle_threads, cpu);

	if (!tsk)
		return ERR_PTR(-ENOMEM);
	init_idle(tsk, cpu);
	return tsk;
}

void __init idle_thread_set_boot_cpu(void)
{
	per_cpu(idle_threads, smp_processor_id()) = current;
}

/**
 * idle_init - Initialize the idle thread for a cpu
 * @cpu:	The cpu for which the idle thread should be initialized
 *
 * Creates the thread if it does not exist.
 */
static inline void idle_init(unsigned int cpu)
{
	struct task_struct *tsk = per_cpu(idle_threads, cpu);

	if (!tsk) {
		tsk = fork_idle(cpu);
		if (IS_ERR(tsk))
			pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
		else
			per_cpu(idle_threads, cpu) = tsk;
	}
}

/**
 * idle_threads_init - Initialize idle threads for all cpus
 */
void __init idle_threads_init(void)
{
	unsigned int cpu, boot_cpu;

	boot_cpu = smp_processor_id();

	for_each_possible_cpu(cpu) {
		if (cpu != boot_cpu)
			idle_init(cpu);
	}
}
#endif

#endif /* #ifdef CONFIG_SMP */

static LIST_HEAD(hotplug_threads);
static DEFINE_MUTEX(smpboot_threads_lock);

struct smpboot_thread_data {
	unsigned int			cpu;
	unsigned int			status;
	struct smp_hotplug_thread	*ht;
};

enum {
	HP_THREAD_NONE = 0,
	HP_THREAD_ACTIVE,
	HP_THREAD_PARKED,
};

/**
 * smpboot_thread_fn - percpu hotplug thread loop function
 * @data:	thread data pointer
 *
 * Checks for thread stop and park conditions. Calls the necessary
 * setup, cleanup, park and unpark functions for the registered
 * thread.
 *
 * Returns 1 when the thread should exit, 0 otherwise.
 */
static int smpboot_thread_fn(void *data)
{
	struct smpboot_thread_data *td = data;
	struct smp_hotplug_thread *ht = td->ht;

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		preempt_disable();
		if (kthread_should_stop()) {
			__set_current_state(TASK_RUNNING);
			preempt_enable();
			if (ht->cleanup)
				ht->cleanup(td->cpu, cpu_online(td->cpu));
			kfree(td);
			return 0;
		}

		if (kthread_should_park()) {
			__set_current_state(TASK_RUNNING);
			preempt_enable();
			if (ht->park && td->status == HP_THREAD_ACTIVE) {
				BUG_ON(td->cpu != smp_processor_id());
				ht->park(td->cpu);
				td->status = HP_THREAD_PARKED;
			}
			kthread_parkme();
			/* We might have been woken for stop */
			continue;
		}

		BUG_ON(td->cpu != smp_processor_id());

		/* Check for state change setup */
		switch (td->status) {
		case HP_THREAD_NONE:
			__set_current_state(TASK_RUNNING);
			preempt_enable();
			if (ht->setup)
				ht->setup(td->cpu);
			td->status = HP_THREAD_ACTIVE;
			continue;

		case HP_THREAD_PARKED:
			__set_current_state(TASK_RUNNING);
			preempt_enable();
			if (ht->unpark)
				ht->unpark(td->cpu);
			td->status = HP_THREAD_ACTIVE;
			continue;
		}

		if (!ht->thread_should_run(td->cpu)) {
			preempt_enable_no_resched();
			schedule();
		} else {
			__set_current_state(TASK_RUNNING);
			preempt_enable();
			ht->thread_fn(td->cpu);
		}
	}
}

static int
__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
{
	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
	struct smpboot_thread_data *td;

	if (tsk)
		return 0;

	td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
	if (!td)
		return -ENOMEM;
	td->cpu = cpu;
	td->ht = ht;

	tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
				    ht->thread_comm);
	if (IS_ERR(tsk)) {
		kfree(td);
		return PTR_ERR(tsk);
	}
	get_task_struct(tsk);
	*per_cpu_ptr(ht->store, cpu) = tsk;
	if (ht->create) {
		/*
		 * Make sure that the task has actually scheduled out
		 * into park position, before calling the create
		 * callback. At least the migration thread callback
		 * requires that the task is off the runqueue.
		 */
		if (!wait_task_inactive(tsk, TASK_PARKED))
			WARN_ON(1);
		else
			ht->create(cpu);
	}
	return 0;
}

int smpboot_create_threads(unsigned int cpu)
{
	struct smp_hotplug_thread *cur;
	int ret = 0;

	mutex_lock(&smpboot_threads_lock);
	list_for_each_entry(cur, &hotplug_threads, list) {
		ret = __smpboot_create_thread(cur, cpu);
		if (ret)
			break;
	}
	mutex_unlock(&smpboot_threads_lock);
	return ret;
}

static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
{
	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);

	if (ht->pre_unpark)
		ht->pre_unpark(cpu);
	kthread_unpark(tsk);
}

void smpboot_unpark_threads(unsigned int cpu)
{
	struct smp_hotplug_thread *cur;

	mutex_lock(&smpboot_threads_lock);
	list_for_each_entry(cur, &hotplug_threads, list)
		smpboot_unpark_thread(cur, cpu);
	mutex_unlock(&smpboot_threads_lock);
}

static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
{
	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);

	if (tsk && !ht->selfparking)
		kthread_park(tsk);
}

void smpboot_park_threads(unsigned int cpu)
{
	struct smp_hotplug_thread *cur;

	mutex_lock(&smpboot_threads_lock);
	list_for_each_entry_reverse(cur, &hotplug_threads, list)
		smpboot_park_thread(cur, cpu);
	mutex_unlock(&smpboot_threads_lock);
}

static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
{
	unsigned int cpu;

	/* We need to destroy also the parked threads of offline cpus */
	for_each_possible_cpu(cpu) {
		struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);

		if (tsk) {
			kthread_stop(tsk);
			put_task_struct(tsk);
			*per_cpu_ptr(ht->store, cpu) = NULL;
		}
	}
}

/**
 * smpboot_register_percpu_thread - Register a per_cpu thread related to hotplug
 * @plug_thread:	Hotplug thread descriptor
 *
 * Creates and starts the threads on all online cpus.
 */
int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
{
	unsigned int cpu;
	int ret = 0;

	get_online_cpus();
	mutex_lock(&smpboot_threads_lock);
	for_each_online_cpu(cpu) {
		ret = __smpboot_create_thread(plug_thread, cpu);
		if (ret) {
			smpboot_destroy_threads(plug_thread);
			goto out;
		}
		smpboot_unpark_thread(plug_thread, cpu);
	}
	list_add(&plug_thread->list, &hotplug_threads);
out:
	mutex_unlock(&smpboot_threads_lock);
	put_online_cpus();
	return ret;
}
EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);

/**
 * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
 * @plug_thread:	Hotplug thread descriptor
 *
 * Stops all threads on all possible cpus.
 */
void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
{
	get_online_cpus();
	mutex_lock(&smpboot_threads_lock);
	list_del(&plug_thread->list);
	smpboot_destroy_threads(plug_thread);
	mutex_unlock(&smpboot_threads_lock);
	put_online_cpus();
}
EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);

static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);

/*
 * Called to poll specified CPU's state, for example, when waiting for
 * a CPU to come online.
 */
int cpu_report_state(int cpu)
{
	return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
}

/*
 * If CPU has died properly, set its state to CPU_UP_PREPARE and
 * return success.  Otherwise, return -EBUSY if the CPU died after
 * cpu_wait_death() timed out.  And yet otherwise again, return -EAGAIN
 * if cpu_wait_death() timed out and the CPU still hasn't gotten around
 * to dying.  In the latter two cases, the CPU might not be set up
 * properly, but it is up to the arch-specific code to decide.
 * Finally, -EIO indicates an unanticipated problem.
 *
 * Note that it is permissible to omit this call entirely, as is
 * done in architectures that do no CPU-hotplug error checking.
 */
int cpu_check_up_prepare(int cpu)
{
	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
		atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
		return 0;
	}

	switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {

	case CPU_POST_DEAD:

		/* The CPU died properly, so just start it up again. */
		atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
		return 0;

	case CPU_DEAD_FROZEN:

		/*
		 * Timeout during CPU death, so let caller know.
		 * The outgoing CPU completed its processing, but after
		 * cpu_wait_death() timed out and reported the error. The
		 * caller is free to proceed, in which case the state
		 * will be reset properly by cpu_set_state_online().
		 * Proceeding despite this -EBUSY return makes sense
		 * for systems where the outgoing CPUs take themselves
		 * offline, with no post-death manipulation required from
		 * a surviving CPU.
		 */
		return -EBUSY;

	case CPU_BROKEN:

		/*
		 * The most likely reason we got here is that there was
		 * a timeout during CPU death, and the outgoing CPU never
		 * did complete its processing.  This could happen on
		 * a virtualized system if the outgoing VCPU gets preempted
		 * for more than five seconds, and the user attempts to
		 * immediately online that same CPU.  Trying again later
		 * might return -EBUSY above, hence -EAGAIN.
		 */
		return -EAGAIN;

	default:

		/* Should not happen.  Famous last words. */
		return -EIO;
	}
}

/*
 * Mark the specified CPU online.
 *
 * Note that it is permissible to omit this call entirely, as is
 * done in architectures that do no CPU-hotplug error checking.
 */
void cpu_set_state_online(int cpu)
{
	(void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
}

#ifdef CONFIG_HOTPLUG_CPU

/*
 * Wait for the specified CPU to exit the idle loop and die.
 */
bool cpu_wait_death(unsigned int cpu, int seconds)
{
	int jf_left = seconds * HZ;
	int oldstate;
	bool ret = true;
	int sleep_jf = 1;

	might_sleep();

	/* The outgoing CPU will normally get done quite quickly. */
	if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
		goto update_state;
	udelay(5);

	/* But if the outgoing CPU dawdles, wait increasingly long times. */
	while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
		schedule_timeout_uninterruptible(sleep_jf);
		jf_left -= sleep_jf;
		if (jf_left <= 0)
			break;
		sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
	}
update_state:
	oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
	if (oldstate == CPU_DEAD) {
		/* Outgoing CPU died normally, update state. */
		smp_mb(); /* atomic_read() before update. */
		atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
	} else {
		/* Outgoing CPU still hasn't died, set state accordingly. */
		if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
				   oldstate, CPU_BROKEN) != oldstate)
			goto update_state;
		ret = false;
	}
	return ret;
}

/*
 * Called by the outgoing CPU to report its successful death.  Return
 * false if this report follows the surviving CPU's timing out.
 *
 * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
 * timed out.  This approach allows architectures to omit calls to
 * cpu_check_up_prepare() and cpu_set_state_online() without defeating
 * the next cpu_wait_death()'s polling loop.
 */
bool cpu_report_death(void)
{
	int oldstate;
	int newstate;
	int cpu = smp_processor_id();

	do {
		oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
		if (oldstate != CPU_BROKEN)
			newstate = CPU_DEAD;
		else
			newstate = CPU_DEAD_FROZEN;
	} while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
				oldstate, newstate) != oldstate);
	return newstate == CPU_DEAD;
}

#endif /* #ifdef CONFIG_HOTPLUG_CPU */
Commit	Line	Data
38498a67 TG	1	/*
	2	* Common SMP CPU bringup/teardown functions
	3	*/
f97f8f06	4	#include <linux/cpu.h>
29d5e047 TG	5	#include <linux/err.h>
29d5e047 TG	6	#include <linux/smp.h>
8038dad7	7	#include <linux/delay.h>
38498a67	8	#include <linux/init.h>
f97f8f06 TG	9	#include <linux/list.h>
f97f8f06 TG	10	#include <linux/slab.h>
29d5e047	11	#include <linux/sched.h>
f97f8f06	12	#include <linux/export.h>
29d5e047	13	#include <linux/percpu.h>
f97f8f06 TG	14	#include <linux/kthread.h>
f97f8f06 TG	15	#include <linux/smpboot.h>
38498a67 TG	16
	17	#include "smpboot.h"
	18
3180d89b PM	19	#ifdef CONFIG_SMP
3180d89b PM	20
29d5e047	21	#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
29d5e047 TG	22	/*
	23	* For the hotplug case we keep the task structs around and reuse
	24	* them.
	25	*/
	26	static DEFINE_PER_CPU(struct task_struct *, idle_threads);
	27
0db0628d	28	struct task_struct *idle_thread_get(unsigned int cpu)
29d5e047 TG	29	{
	30	struct task_struct *tsk = per_cpu(idle_threads, cpu);
	31
	32	if (!tsk)
3bb5d2ee	33	return ERR_PTR(-ENOMEM);
29d5e047 TG	34	init_idle(tsk, cpu);
	35	return tsk;
	36	}
	37
3bb5d2ee	38	void __init idle_thread_set_boot_cpu(void)
29d5e047	39	{
3bb5d2ee	40	per_cpu(idle_threads, smp_processor_id()) = current;
29d5e047 TG	41	}
29d5e047 TG	42
4a70d2d9 SB	43	/**
	44	* idle_init - Initialize the idle thread for a cpu
	45	* @cpu: The cpu for which the idle thread should be initialized
	46	*
	47	* Creates the thread if it does not exist.
	48	*/
3bb5d2ee	49	static inline void idle_init(unsigned int cpu)
29d5e047	50	{
3bb5d2ee SS	51	struct task_struct *tsk = per_cpu(idle_threads, cpu);
	52
	53	if (!tsk) {
	54	tsk = fork_idle(cpu);
	55	if (IS_ERR(tsk))
	56	pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
	57	else
	58	per_cpu(idle_threads, cpu) = tsk;
	59	}
29d5e047 TG	60	}
	61
	62	/**
4a70d2d9	63	* idle_threads_init - Initialize idle threads for all cpus
29d5e047	64	*/
3bb5d2ee	65	void __init idle_threads_init(void)
29d5e047	66	{
ee74d132 SB	67	unsigned int cpu, boot_cpu;
	68
	69	boot_cpu = smp_processor_id();
29d5e047	70
3bb5d2ee	71	for_each_possible_cpu(cpu) {
ee74d132	72	if (cpu != boot_cpu)
3bb5d2ee	73	idle_init(cpu);
29d5e047	74	}
29d5e047	75	}
29d5e047	76	#endif
f97f8f06	77
3180d89b PM	78	#endif /* #ifdef CONFIG_SMP */
3180d89b PM	79
f97f8f06 TG	80	static LIST_HEAD(hotplug_threads);
	81	static DEFINE_MUTEX(smpboot_threads_lock);
	82
	83	struct smpboot_thread_data {
	84	unsigned int cpu;
	85	unsigned int status;
	86	struct smp_hotplug_thread *ht;
	87	};
	88
	89	enum {
	90	HP_THREAD_NONE = 0,
	91	HP_THREAD_ACTIVE,
	92	HP_THREAD_PARKED,
	93	};
	94
	95	/**
	96	* smpboot_thread_fn - percpu hotplug thread loop function
	97	* @data: thread data pointer
	98	*
	99	* Checks for thread stop and park conditions. Calls the necessary
	100	* setup, cleanup, park and unpark functions for the registered
	101	* thread.
	102	*
	103	* Returns 1 when the thread should exit, 0 otherwise.
	104	*/
	105	static int smpboot_thread_fn(void *data)
	106	{
	107	struct smpboot_thread_data *td = data;
	108	struct smp_hotplug_thread *ht = td->ht;
	109
	110	while (1) {
	111	set_current_state(TASK_INTERRUPTIBLE);
	112	preempt_disable();
	113	if (kthread_should_stop()) {
7d4d2696	114	__set_current_state(TASK_RUNNING);
f97f8f06 TG	115	preempt_enable();
	116	if (ht->cleanup)
	117	ht->cleanup(td->cpu, cpu_online(td->cpu));
	118	kfree(td);
	119	return 0;
	120	}
	121
	122	if (kthread_should_park()) {
	123	__set_current_state(TASK_RUNNING);
	124	preempt_enable();
	125	if (ht->park && td->status == HP_THREAD_ACTIVE) {
	126	BUG_ON(td->cpu != smp_processor_id());
	127	ht->park(td->cpu);
	128	td->status = HP_THREAD_PARKED;
	129	}
	130	kthread_parkme();
	131	/* We might have been woken for stop */
	132	continue;
	133	}
	134
dc893e19	135	BUG_ON(td->cpu != smp_processor_id());
f97f8f06 TG	136
	137	/* Check for state change setup */
	138	switch (td->status) {
	139	case HP_THREAD_NONE:
7d4d2696	140	__set_current_state(TASK_RUNNING);
f97f8f06 TG	141	preempt_enable();
	142	if (ht->setup)
	143	ht->setup(td->cpu);
	144	td->status = HP_THREAD_ACTIVE;
7d4d2696 PZ	145	continue;
7d4d2696 PZ	146
f97f8f06	147	case HP_THREAD_PARKED:
7d4d2696	148	__set_current_state(TASK_RUNNING);
f97f8f06 TG	149	preempt_enable();
	150	if (ht->unpark)
	151	ht->unpark(td->cpu);
	152	td->status = HP_THREAD_ACTIVE;
7d4d2696	153	continue;
f97f8f06 TG	154	}
	155
	156	if (!ht->thread_should_run(td->cpu)) {
7d4d2696	157	preempt_enable_no_resched();
f97f8f06 TG	158	schedule();
f97f8f06 TG	159	} else {
7d4d2696	160	__set_current_state(TASK_RUNNING);
f97f8f06 TG	161	preempt_enable();
	162	ht->thread_fn(td->cpu);
	163	}
	164	}
	165	}
	166
	167	static int
	168	__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
	169	{
	170	struct task_struct tsk = per_cpu_ptr(ht->store, cpu);
	171	struct smpboot_thread_data *td;
	172
	173	if (tsk)
	174	return 0;
	175
	176	td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
	177	if (!td)
	178	return -ENOMEM;
	179	td->cpu = cpu;
	180	td->ht = ht;
	181
	182	tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
	183	ht->thread_comm);
	184	if (IS_ERR(tsk)) {
	185	kfree(td);
	186	return PTR_ERR(tsk);
	187	}
f97f8f06 TG	188	get_task_struct(tsk);
f97f8f06 TG	189	*per_cpu_ptr(ht->store, cpu) = tsk;
f2530dc7 TG	190	if (ht->create) {
	191	/*
	192	* Make sure that the task has actually scheduled out
	193	* into park position, before calling the create
	194	* callback. At least the migration thread callback
	195	* requires that the task is off the runqueue.
	196	*/
	197	if (!wait_task_inactive(tsk, TASK_PARKED))
	198	WARN_ON(1);
	199	else
	200	ht->create(cpu);
	201	}
f97f8f06 TG	202	return 0;
	203	}
	204
	205	int smpboot_create_threads(unsigned int cpu)
	206	{
	207	struct smp_hotplug_thread *cur;
	208	int ret = 0;
	209
	210	mutex_lock(&smpboot_threads_lock);
	211	list_for_each_entry(cur, &hotplug_threads, list) {
	212	ret = __smpboot_create_thread(cur, cpu);
	213	if (ret)
	214	break;
	215	}
	216	mutex_unlock(&smpboot_threads_lock);
	217	return ret;
	218	}
	219
	220	static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
	221	{
	222	struct task_struct tsk = per_cpu_ptr(ht->store, cpu);
	223
46c498c2 TG	224	if (ht->pre_unpark)
46c498c2 TG	225	ht->pre_unpark(cpu);
f97f8f06 TG	226	kthread_unpark(tsk);
	227	}
	228
	229	void smpboot_unpark_threads(unsigned int cpu)
	230	{
	231	struct smp_hotplug_thread *cur;
	232
	233	mutex_lock(&smpboot_threads_lock);
	234	list_for_each_entry(cur, &hotplug_threads, list)
	235	smpboot_unpark_thread(cur, cpu);
	236	mutex_unlock(&smpboot_threads_lock);
	237	}
	238
	239	static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
	240	{
	241	struct task_struct tsk = per_cpu_ptr(ht->store, cpu);
	242
7d7e499f	243	if (tsk && !ht->selfparking)
f97f8f06 TG	244	kthread_park(tsk);
	245	}
	246
	247	void smpboot_park_threads(unsigned int cpu)
	248	{
	249	struct smp_hotplug_thread *cur;
	250
	251	mutex_lock(&smpboot_threads_lock);
	252	list_for_each_entry_reverse(cur, &hotplug_threads, list)
	253	smpboot_park_thread(cur, cpu);
	254	mutex_unlock(&smpboot_threads_lock);
	255	}
	256
	257	static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
	258	{
	259	unsigned int cpu;
	260
	261	/* We need to destroy also the parked threads of offline cpus */
	262	for_each_possible_cpu(cpu) {
	263	struct task_struct tsk = per_cpu_ptr(ht->store, cpu);
	264
	265	if (tsk) {
	266	kthread_stop(tsk);
	267	put_task_struct(tsk);
	268	*per_cpu_ptr(ht->store, cpu) = NULL;
	269	}
	270	}
	271	}
	272
	273	/**
	274	* smpboot_register_percpu_thread - Register a per_cpu thread related to hotplug
	275	* @plug_thread: Hotplug thread descriptor
	276	*
	277	* Creates and starts the threads on all online cpus.
	278	*/
	279	int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
	280	{
	281	unsigned int cpu;
	282	int ret = 0;
	283
4bee9686	284	get_online_cpus();
f97f8f06 TG	285	mutex_lock(&smpboot_threads_lock);
	286	for_each_online_cpu(cpu) {
	287	ret = __smpboot_create_thread(plug_thread, cpu);
	288	if (ret) {
	289	smpboot_destroy_threads(plug_thread);
	290	goto out;
	291	}
	292	smpboot_unpark_thread(plug_thread, cpu);
	293	}
	294	list_add(&plug_thread->list, &hotplug_threads);
	295	out:
	296	mutex_unlock(&smpboot_threads_lock);
4bee9686	297	put_online_cpus();
f97f8f06 TG	298	return ret;
	299	}
	300	EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
	301
	302	/**
	303	* smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
	304	* @plug_thread: Hotplug thread descriptor
	305	*
	306	* Stops all threads on all possible cpus.
	307	*/
	308	void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
	309	{
	310	get_online_cpus();
	311	mutex_lock(&smpboot_threads_lock);
	312	list_del(&plug_thread->list);
	313	smpboot_destroy_threads(plug_thread);
	314	mutex_unlock(&smpboot_threads_lock);
	315	put_online_cpus();
	316	}
	317	EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
8038dad7 PM	318
	319	static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
	320
	321	/*
	322	* Called to poll specified CPU's state, for example, when waiting for
	323	* a CPU to come online.
	324	*/
	325	int cpu_report_state(int cpu)
	326	{
	327	return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
	328	}
	329
	330	/*
	331	* If CPU has died properly, set its state to CPU_UP_PREPARE and
	332	* return success. Otherwise, return -EBUSY if the CPU died after
	333	* cpu_wait_death() timed out. And yet otherwise again, return -EAGAIN
	334	* if cpu_wait_death() timed out and the CPU still hasn't gotten around
	335	* to dying. In the latter two cases, the CPU might not be set up
	336	* properly, but it is up to the arch-specific code to decide.
	337	* Finally, -EIO indicates an unanticipated problem.
	338	*
	339	* Note that it is permissible to omit this call entirely, as is
	340	* done in architectures that do no CPU-hotplug error checking.
	341	*/
	342	int cpu_check_up_prepare(int cpu)
	343	{
	344	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
	345	atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
	346	return 0;
	347	}
	348
	349	switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
	350
	351	case CPU_POST_DEAD:
	352
	353	/* The CPU died properly, so just start it up again. */
	354	atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
	355	return 0;
	356
	357	case CPU_DEAD_FROZEN:
	358
	359	/*
	360	* Timeout during CPU death, so let caller know.
	361	* The outgoing CPU completed its processing, but after
	362	* cpu_wait_death() timed out and reported the error. The
	363	* caller is free to proceed, in which case the state
	364	* will be reset properly by cpu_set_state_online().
	365	* Proceeding despite this -EBUSY return makes sense
	366	* for systems where the outgoing CPUs take themselves
	367	* offline, with no post-death manipulation required from
	368	* a surviving CPU.
	369	*/
	370	return -EBUSY;
	371
	372	case CPU_BROKEN:
	373
	374	/*
	375	* The most likely reason we got here is that there was
	376	* a timeout during CPU death, and the outgoing CPU never
	377	* did complete its processing. This could happen on
	378	* a virtualized system if the outgoing VCPU gets preempted
	379	* for more than five seconds, and the user attempts to
	380	* immediately online that same CPU. Trying again later
	381	* might return -EBUSY above, hence -EAGAIN.
382	*/
383	return -EAGAIN;
384
385	default:
386
387	/* Should not happen. Famous last words. */
388	return -EIO;
389	}
390	}
391
392	/*
393	* Mark the specified CPU online.
394	*
395	* Note that it is permissible to omit this call entirely, as is
396	* done in architectures that do no CPU-hotplug error checking.
397	*/
398	void cpu_set_state_online(int cpu)
399	{
400	(void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
401	}
402
403	#ifdef CONFIG_HOTPLUG_CPU
404
405	/*
406	* Wait for the specified CPU to exit the idle loop and die.
407	*/
408	bool cpu_wait_death(unsigned int cpu, int seconds)
409	{
410	int jf_left = seconds * HZ;
411	int oldstate;
412	bool ret = true;
413	int sleep_jf = 1;
414
415	might_sleep();
416
417	/* The outgoing CPU will normally get done quite quickly. */
418	if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
419	goto update_state;
420	udelay(5);
421
422	/* But if the outgoing CPU dawdles, wait increasingly long times. */
423	while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
424	schedule_timeout_uninterruptible(sleep_jf);
425	jf_left -= sleep_jf;
426	if (jf_left <= 0)
427	break;
428	sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
429	}
430	update_state:
431	oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
432	if (oldstate == CPU_DEAD) {
433	/* Outgoing CPU died normally, update state. */
434	smp_mb(); /* atomic_read() before update. */
435	atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
436	} else {
437	/* Outgoing CPU still hasn't died, set state accordingly. */
438	if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
439	oldstate, CPU_BROKEN) != oldstate)
440	goto update_state;
441	ret = false;
442	}
443	return ret;
444	}
445
446	/*
447	* Called by the outgoing CPU to report its successful death. Return
448	* false if this report follows the surviving CPU's timing out.
449	*
450	* A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
451	* timed out. This approach allows architectures to omit calls to
452	* cpu_check_up_prepare() and cpu_set_state_online() without defeating
453	* the next cpu_wait_death()'s polling loop.
454	*/
455	bool cpu_report_death(void)
456	{
457	int oldstate;
458	int newstate;
459	int cpu = smp_processor_id();
460
461	do {
462	oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
463	if (oldstate != CPU_BROKEN)
464	newstate = CPU_DEAD;
465	else
466	newstate = CPU_DEAD_FROZEN;
467	} while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
468	oldstate, newstate) != oldstate);
469	return newstate == CPU_DEAD;
470	}
471
472	#endif /* #ifdef CONFIG_HOTPLUG_CPU */