kernel/smpboot.c - kernel/msm-4.9 - Gitiles

 /*
  * Common SMP CPU bringup/teardown functions
  */
 #include <linux/cpu.h>
 #include <linux/err.h>
 #include <linux/smp.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;

 	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);
 	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);
	/*
	* Common SMP CPU bringup/teardown functions
	*/
	#include <linux/cpu.h>
	#include <linux/err.h>
	#include <linux/smp.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;

	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);
	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);