/* 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/oom.h>
  #include <linux/rcupdate.h>

  #include <linux/export.h>

  #include <linux/bug.h>

  #include <linux/kthread.h>
  #include <linux/stop_machine.h>

  #include <linux/mutex.h>

  #include <linux/gfp.h>

  #include <linux/suspend.h>

  #include <linux/lockdep.h>

  #include <trace/events/power.h>

  #include "smpboot.h"

  #ifdef CONFIG_SMP

  /* Serializes the updates to cpu_online_mask, cpu_present_mask */

  static DEFINE_MUTEX(cpu_add_remove_lock);

  /*

   * The following two APIs (cpu_maps_update_begin/done) must be used when
   * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
   * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
   * hotplug callback (un)registration performed using __register_cpu_notifier()
   * or __unregister_cpu_notifier().

   */
  void cpu_maps_update_begin(void)
  {
  	mutex_lock(&cpu_add_remove_lock);
  }

  EXPORT_SYMBOL(cpu_notifier_register_begin);

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

  EXPORT_SYMBOL(cpu_notifier_register_done);

  static 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;

  #ifdef CONFIG_HOTPLUG_CPU

  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;

  	/* And allows lockless put_online_cpus(). */
  	atomic_t puts_pending;

  
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  	struct lockdep_map dep_map;
  #endif

  } cpu_hotplug = {
  	.active_writer = NULL,
  	.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
  	.refcount = 0,

  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  	.dep_map = {.name = "cpu_hotplug.lock" },
  #endif

  };

  /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
  #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)

  #define cpuhp_lock_acquire_tryread() \
  				  lock_map_acquire_tryread(&cpu_hotplug.dep_map)

  #define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
  #define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)

  void get_online_cpus(void)

  {

  	might_sleep();
  	if (cpu_hotplug.active_writer == current)

  		return;

  	cpuhp_lock_acquire_read();

  	mutex_lock(&cpu_hotplug.lock);
  	cpu_hotplug.refcount++;
  	mutex_unlock(&cpu_hotplug.lock);

  }

  EXPORT_SYMBOL_GPL(get_online_cpus);

  bool try_get_online_cpus(void)
  {
  	if (cpu_hotplug.active_writer == current)
  		return true;
  	if (!mutex_trylock(&cpu_hotplug.lock))
  		return false;
  	cpuhp_lock_acquire_tryread();
  	cpu_hotplug.refcount++;
  	mutex_unlock(&cpu_hotplug.lock);
  	return true;
  }
  EXPORT_SYMBOL_GPL(try_get_online_cpus);

  void put_online_cpus(void)

  {

  	if (cpu_hotplug.active_writer == current)

  		return;

  	if (!mutex_trylock(&cpu_hotplug.lock)) {
  		atomic_inc(&cpu_hotplug.puts_pending);
  		cpuhp_lock_release();
  		return;
  	}

  
  	if (WARN_ON(!cpu_hotplug.refcount))
  		cpu_hotplug.refcount++; /* try to fix things up */

  	if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
  		wake_up_process(cpu_hotplug.active_writer);

  	mutex_unlock(&cpu_hotplug.lock);

  	cpuhp_lock_release();

  }

  EXPORT_SYMBOL_GPL(put_online_cpus);

  /*
   * 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_hotplug_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

   * get_online_cpus() not an api which is called all that often.

   *
   */

  void cpu_hotplug_begin(void)

  {

  	cpu_hotplug.active_writer = current;

  	cpuhp_lock_acquire();

  	for (;;) {
  		mutex_lock(&cpu_hotplug.lock);

  		if (atomic_read(&cpu_hotplug.puts_pending)) {
  			int delta;
  
  			delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);
  			cpu_hotplug.refcount -= delta;
  		}

  		if (likely(!cpu_hotplug.refcount))
  			break;
  		__set_current_state(TASK_UNINTERRUPTIBLE);

  		mutex_unlock(&cpu_hotplug.lock);
  		schedule();

  	}

  }

  void cpu_hotplug_done(void)

  {
  	cpu_hotplug.active_writer = NULL;
  	mutex_unlock(&cpu_hotplug.lock);

  	cpuhp_lock_release();

  }

  /*
   * Wait for currently running CPU hotplug operations to complete (if any) and
   * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
   * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
   * hotplug path before performing hotplug operations. So acquiring that lock
   * guarantees mutual exclusion from any currently running hotplug operations.
   */
  void cpu_hotplug_disable(void)
  {
  	cpu_maps_update_begin();
  	cpu_hotplug_disabled = 1;
  	cpu_maps_update_done();
  }
  
  void cpu_hotplug_enable(void)
  {
  	cpu_maps_update_begin();
  	cpu_hotplug_disabled = 0;
  	cpu_maps_update_done();
  }

  #endif	/* CONFIG_HOTPLUG_CPU */

  /* Need to know about CPUs going up/down? */

  int __ref 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;

  }

  int __ref __register_cpu_notifier(struct notifier_block *nb)
  {
  	return raw_notifier_chain_register(&cpu_chain, nb);
  }

  static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
  			int *nr_calls)
  {

  	int ret;
  
  	ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,

  					nr_calls);

  
  	return notifier_to_errno(ret);

  }
  
  static int cpu_notify(unsigned long val, void *v)
  {
  	return __cpu_notify(val, v, -1, NULL);
  }

  #ifdef CONFIG_HOTPLUG_CPU

  static void cpu_notify_nofail(unsigned long val, void *v)
  {

  	BUG_ON(cpu_notify(val, v));

  }

  EXPORT_SYMBOL(register_cpu_notifier);

  EXPORT_SYMBOL(__register_cpu_notifier);

  void __ref 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);

  void __ref __unregister_cpu_notifier(struct notifier_block *nb)
  {
  	raw_notifier_chain_unregister(&cpu_chain, nb);
  }
  EXPORT_SYMBOL(__unregister_cpu_notifier);

  /**
   * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
   * @cpu: a CPU id
   *
   * This function walks all processes, finds a valid mm struct for each one and
   * then clears a corresponding bit in mm's cpumask.  While this all sounds
   * trivial, there are various non-obvious corner cases, which this function
   * tries to solve in a safe manner.
   *
   * Also note that the function uses a somewhat relaxed locking scheme, so it may
   * be called only for an already offlined CPU.
   */

  void clear_tasks_mm_cpumask(int cpu)
  {
  	struct task_struct *p;
  
  	/*
  	 * This function is called after the cpu is taken down and marked
  	 * offline, so its not like new tasks will ever get this cpu set in
  	 * their mm mask. -- Peter Zijlstra
  	 * Thus, we may use rcu_read_lock() here, instead of grabbing
  	 * full-fledged tasklist_lock.
  	 */

  	WARN_ON(cpu_online(cpu));

  	rcu_read_lock();
  	for_each_process(p) {
  		struct task_struct *t;

  		/*
  		 * Main thread might exit, but other threads may still have
  		 * a valid mm. Find one.
  		 */

  		t = find_lock_task_mm(p);
  		if (!t)
  			continue;
  		cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
  		task_unlock(t);
  	}
  	rcu_read_unlock();
  }

  static inline void check_for_tasks(int dead_cpu)

  {

  	struct task_struct *g, *p;

  	read_lock_irq(&tasklist_lock);
  	do_each_thread(g, p) {
  		if (!p->on_rq)
  			continue;
  		/*
  		 * We do the check with unlocked task_rq(p)->lock.
  		 * Order the reading to do not warn about a task,
  		 * which was running on this cpu in the past, and
  		 * it's just been woken on another cpu.
  		 */
  		rmb();
  		if (task_cpu(p) != dead_cpu)
  			continue;
  
  		pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)
  ",
  			p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
  	} while_each_thread(g, p);
  	read_unlock_irq(&tasklist_lock);

  }

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

  /* Take this CPU down. */

  static int __ref take_cpu_down(void *_param)

  {

  	struct take_cpu_down_param *param = _param;

  	int err;

  	/* Ensure this CPU doesn't handle any more interrupts. */
  	err = __cpu_disable();
  	if (err < 0)

  		return err;

  	cpu_notify(CPU_DYING | param->mod, param->hcpu);

  	/* Park the stopper thread */
  	kthread_park(current);

  	return 0;

  }

  /* Requires cpu_add_remove_lock to be held */

  static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)

  {

  	int err, nr_calls = 0;

  	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();

  	err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);

  	if (err) {

  		nr_calls--;

  		__cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);

  		pr_warn("%s: attempt to take down CPU %u failed
  ",
  			__func__, cpu);

  		goto out_release;

  	}

  	/*
  	 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
  	 * and RCU users of this state to go away such that all new such users
  	 * will observe it.
  	 *
  	 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
  	 * not imply sync_sched(), so explicitly call both.

  	 *
  	 * Do sync before park smpboot threads to take care the rcu boost case.

  	 */
  #ifdef CONFIG_PREEMPT
  	synchronize_sched();
  #endif
  	synchronize_rcu();

  	smpboot_park_threads(cpu);

  	/*
  	 * So now all preempt/rcu users must observe !cpu_active().
  	 */

  	err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));

  	if (err) {

  		/* CPU didn't die: tell everyone.  Can't complain. */

  		smpboot_unpark_threads(cpu);

  		cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);

  		goto out_release;

  	}

  	BUG_ON(cpu_online(cpu));

  	/*
  	 * The migration_call() CPU_DYING callback will have removed all
  	 * runnable tasks from the cpu, there's only the idle task left now
  	 * that the migration thread is done doing the stop_machine thing.

  	 *
  	 * Wait for the stop thread to go away.

  	 */

  	while (!idle_cpu(cpu))
  		cpu_relax();

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

  	/* CPU is completely dead: tell everyone.  Too late to complain. */

  	cpu_notify_nofail(CPU_DEAD | mod, hcpu);

  
  	check_for_tasks(cpu);

  out_release:

  	cpu_hotplug_done();

  	if (!err)
  		cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);

  	return err;
  }

  int __ref cpu_down(unsigned int cpu)

  {

  	int err;

  	cpu_maps_update_begin();

  
  	if (cpu_hotplug_disabled) {

  		err = -EBUSY;

  		goto out;
  	}

  	err = _cpu_down(cpu, 0);

  out:

  	cpu_maps_update_done();

  	return err;
  }

  EXPORT_SYMBOL(cpu_down);

  #endif /*CONFIG_HOTPLUG_CPU*/

  /* Requires cpu_add_remove_lock to be held */

  static int _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;

  	struct task_struct *idle;

  	cpu_hotplug_begin();

  	if (cpu_online(cpu) || !cpu_present(cpu)) {
  		ret = -EINVAL;
  		goto out;
  	}

  	idle = idle_thread_get(cpu);
  	if (IS_ERR(idle)) {
  		ret = PTR_ERR(idle);

  		goto out;

  	}

  	ret = smpboot_create_threads(cpu);
  	if (ret)
  		goto out;

  	ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);

  	if (ret) {

  		nr_calls--;

  		pr_warn("%s: attempt to bring up CPU %u failed
  ",
  			__func__, cpu);

  		goto out_notify;
  	}
  
  	/* Arch-specific enabling code. */

  	ret = __cpu_up(cpu, idle);

  	if (ret != 0)
  		goto out_notify;

  	BUG_ON(!cpu_online(cpu));

  	/* Wake the per cpu threads */
  	smpboot_unpark_threads(cpu);

  	/* Now call notifier in preparation. */

  	cpu_notify(CPU_ONLINE | mod, hcpu);

  
  out_notify:
  	if (ret != 0)

  		__cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);

  out:

  	cpu_hotplug_done();

  
  	return ret;
  }

  int cpu_up(unsigned int cpu)

  {
  	int err = 0;

  	if (!cpu_possible(cpu)) {

  		pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time
  ",
  		       cpu);

  #if defined(CONFIG_IA64)

  		pr_err("please check additional_cpus= boot parameter
  ");

  #endif
  		return -EINVAL;
  	}

  	err = try_online_node(cpu_to_node(cpu));
  	if (err)
  		return err;

  	cpu_maps_update_begin();

  
  	if (cpu_hotplug_disabled) {

  		err = -EBUSY;

  		goto out;
  	}
  
  	err = _cpu_up(cpu, 0);

  out:

  	cpu_maps_update_done();

  	return err;
  }

  EXPORT_SYMBOL_GPL(cpu_up);

  #ifdef CONFIG_PM_SLEEP_SMP

  static cpumask_var_t frozen_cpus;

  
  int disable_nonboot_cpus(void)
  {

  	int cpu, first_cpu, error = 0;

  	cpu_maps_update_begin();

  	first_cpu = cpumask_first(cpu_online_mask);

  	/*
  	 * 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
  	 */

  	cpumask_clear(frozen_cpus);

  	pr_info("Disabling non-boot CPUs ...
  ");

  	for_each_online_cpu(cpu) {
  		if (cpu == first_cpu)
  			continue;

  		trace_suspend_resume(TPS("CPU_OFF"), cpu, true);

  		error = _cpu_down(cpu, 1);

  		trace_suspend_resume(TPS("CPU_OFF"), cpu, false);

  		if (!error)

  			cpumask_set_cpu(cpu, frozen_cpus);

  		else {

  			pr_err("Error taking CPU%d down: %d
  ", 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 {

  		pr_err("Non-boot CPUs are not disabled
  ");

  	}

  	cpu_maps_update_done();

  	return error;
  }

  void __weak arch_enable_nonboot_cpus_begin(void)
  {
  }
  
  void __weak arch_enable_nonboot_cpus_end(void)
  {
  }

  void __ref enable_nonboot_cpus(void)

  {
  	int cpu, error;
  
  	/* Allow everyone to use the CPU hotplug again */

  	cpu_maps_update_begin();

  	cpu_hotplug_disabled = 0;

  	if (cpumask_empty(frozen_cpus))

  		goto out;

  	pr_info("Enabling non-boot CPUs ...
  ");

  
  	arch_enable_nonboot_cpus_begin();

  	for_each_cpu(cpu, frozen_cpus) {

  		trace_suspend_resume(TPS("CPU_ON"), cpu, true);

  		error = _cpu_up(cpu, 1);

  		trace_suspend_resume(TPS("CPU_ON"), cpu, false);

  		if (!error) {

  			pr_info("CPU%d is up
  ", cpu);

  			continue;
  		}

  		pr_warn("Error taking CPU%d up: %d
  ", cpu, error);

  	}

  
  	arch_enable_nonboot_cpus_end();

  	cpumask_clear(frozen_cpus);

  out:

  	cpu_maps_update_done();

  }

  static int __init alloc_frozen_cpus(void)

  {
  	if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
  		return -ENOMEM;
  	return 0;
  }
  core_initcall(alloc_frozen_cpus);

  
  /*

   * When callbacks for CPU hotplug notifications are being executed, we must
   * ensure that the state of the system with respect to the tasks being frozen
   * or not, as reported by the notification, remains unchanged *throughout the
   * duration* of the execution of the callbacks.
   * Hence we need to prevent the freezer from racing with regular CPU hotplug.
   *
   * This synchronization is implemented by mutually excluding regular CPU
   * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
   * Hibernate notifications.
   */
  static int
  cpu_hotplug_pm_callback(struct notifier_block *nb,
  			unsigned long action, void *ptr)
  {
  	switch (action) {
  
  	case PM_SUSPEND_PREPARE:
  	case PM_HIBERNATION_PREPARE:

  		cpu_hotplug_disable();

  		break;
  
  	case PM_POST_SUSPEND:
  	case PM_POST_HIBERNATION:

  		cpu_hotplug_enable();

  		break;
  
  	default:
  		return NOTIFY_DONE;
  	}
  
  	return NOTIFY_OK;
  }

  static int __init cpu_hotplug_pm_sync_init(void)

  {

  	/*
  	 * cpu_hotplug_pm_callback has higher priority than x86
  	 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
  	 * to disable cpu hotplug to avoid cpu hotplug race.
  	 */

  	pm_notifier(cpu_hotplug_pm_callback, 0);
  	return 0;
  }
  core_initcall(cpu_hotplug_pm_sync_init);

  #endif /* CONFIG_PM_SLEEP_SMP */

  /**
   * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
   * @cpu: cpu that just started
   *
   * This function calls the cpu_chain notifiers with CPU_STARTING.
   * It must be called by the arch code on the new cpu, before the new cpu
   * enables interrupts and before the "boot" cpu returns from __cpu_up().
   */

  void notify_cpu_starting(unsigned int cpu)

  {
  	unsigned long val = CPU_STARTING;
  
  #ifdef CONFIG_PM_SLEEP_SMP

  	if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))

  		val = CPU_STARTING_FROZEN;
  #endif /* CONFIG_PM_SLEEP_SMP */

  	cpu_notify(val, (void *)(long)cpu);

  }

  #endif /* CONFIG_SMP */

  /*
   * cpu_bit_bitmap[] is a special, "compressed" data structure that
   * represents all NR_CPUS bits binary values of 1<<nr.
   *

   * It is used by cpumask_of() to get a constant address to a CPU

   * mask value that has a single bit set only.
   */

  /* cpu_bit_bitmap[0] is empty - so we can back into it */

  #define MASK_DECLARE_1(x)	[x+1][0] = (1UL << (x))

  #define MASK_DECLARE_2(x)	MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
  #define MASK_DECLARE_4(x)	MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
  #define MASK_DECLARE_8(x)	MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)

  const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
  
  	MASK_DECLARE_8(0),	MASK_DECLARE_8(8),
  	MASK_DECLARE_8(16),	MASK_DECLARE_8(24),
  #if BITS_PER_LONG > 32
  	MASK_DECLARE_8(32),	MASK_DECLARE_8(40),
  	MASK_DECLARE_8(48),	MASK_DECLARE_8(56),

  #endif
  };

  EXPORT_SYMBOL_GPL(cpu_bit_bitmap);

  
  const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
  EXPORT_SYMBOL(cpu_all_bits);

  
  #ifdef CONFIG_INIT_ALL_POSSIBLE
  static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
  	= CPU_BITS_ALL;
  #else
  static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
  #endif
  const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
  EXPORT_SYMBOL(cpu_possible_mask);
  
  static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
  const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
  EXPORT_SYMBOL(cpu_online_mask);
  
  static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
  const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
  EXPORT_SYMBOL(cpu_present_mask);
  
  static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
  const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
  EXPORT_SYMBOL(cpu_active_mask);

  
  void set_cpu_possible(unsigned int cpu, bool possible)
  {
  	if (possible)
  		cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
  	else
  		cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
  }
  
  void set_cpu_present(unsigned int cpu, bool present)
  {
  	if (present)
  		cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
  	else
  		cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
  }
  
  void set_cpu_online(unsigned int cpu, bool online)
  {

  	if (online) {

  		cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));

  		cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
  	} else {

  		cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));

  	}

  }
  
  void set_cpu_active(unsigned int cpu, bool active)
  {
  	if (active)
  		cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
  	else
  		cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
  }
  
  void init_cpu_present(const struct cpumask *src)
  {
  	cpumask_copy(to_cpumask(cpu_present_bits), src);
  }
  
  void init_cpu_possible(const struct cpumask *src)
  {
  	cpumask_copy(to_cpumask(cpu_possible_bits), src);
  }
  
  void init_cpu_online(const struct cpumask *src)
  {
  	cpumask_copy(to_cpumask(cpu_online_bits), src);
  }