/* 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/export.h>

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

  #include <linux/mutex.h>

  #include <linux/gfp.h>

  #include <linux/suspend.h>

  #ifdef CONFIG_SMP

  /* Serializes the updates to cpu_online_mask, cpu_present_mask */

  static DEFINE_MUTEX(cpu_add_remove_lock);

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

  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;

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

  void get_online_cpus(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(get_online_cpus);

  void put_online_cpus(void)

  {

  	if (cpu_hotplug.active_writer == current)

  		return;

  	mutex_lock(&cpu_hotplug.lock);

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

  	mutex_unlock(&cpu_hotplug.lock);

  }

  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.

   *
   */
  static void cpu_hotplug_begin(void)
  {

  	cpu_hotplug.active_writer = current;

  
  	for (;;) {
  		mutex_lock(&cpu_hotplug.lock);
  		if (likely(!cpu_hotplug.refcount))
  			break;
  		__set_current_state(TASK_UNINTERRUPTIBLE);

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

  	}

  }
  
  static void cpu_hotplug_done(void)
  {
  	cpu_hotplug.active_writer = NULL;
  	mutex_unlock(&cpu_hotplug.lock);
  }

  
  #else /* #if CONFIG_HOTPLUG_CPU */
  static void cpu_hotplug_begin(void) {}
  static void cpu_hotplug_done(void) {}

  #endif	/* #else #if 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;

  }

  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);

  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);

  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 && p->state == TASK_RUNNING &&

  		    (p->utime || p->stime))

  			printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
  				"(state = %ld, flags = %x)
  ",
  				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 __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);

  	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);

  		printk("%s: attempt to take down CPU %u failed
  ",

  				__func__, cpu);

  		goto out_release;

  	}

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

  	if (err) {

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

  		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 __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();

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

  	if (ret) {

  		nr_calls--;

  		printk(KERN_WARNING "%s: attempt to bring up CPU %u failed
  ",

  				__func__, cpu);

  		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. */

  	cpu_notify(CPU_ONLINE | mod, hcpu);

  
  out_notify:
  	if (ret != 0)

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

  	cpu_hotplug_done();

  
  	return ret;
  }

  int __cpuinit cpu_up(unsigned int cpu)

  {
  	int err = 0;

  
  #ifdef	CONFIG_MEMORY_HOTPLUG
  	int nid;
  	pg_data_t	*pgdat;
  #endif

  	if (!cpu_possible(cpu)) {

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

  #if defined(CONFIG_IA64)

  		printk(KERN_ERR "please check additional_cpus= boot "
  				"parameter
  ");
  #endif
  		return -EINVAL;
  	}

  #ifdef	CONFIG_MEMORY_HOTPLUG
  	nid = cpu_to_node(cpu);
  	if (!node_online(nid)) {
  		err = mem_online_node(nid);
  		if (err)
  			return err;
  	}
  
  	pgdat = NODE_DATA(nid);
  	if (!pgdat) {
  		printk(KERN_ERR
  			"Can't online cpu %d due to NULL pgdat
  ", cpu);
  		return -ENOMEM;
  	}

  	if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
  		mutex_lock(&zonelists_mutex);

  		build_all_zonelists(NULL);

  		mutex_unlock(&zonelists_mutex);
  	}

  #endif

  	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;

  void __weak arch_disable_nonboot_cpus_begin(void)
  {
  }
  
  void __weak arch_disable_nonboot_cpus_end(void)
  {
  }

  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);

  	arch_disable_nonboot_cpus_begin();

  	printk("Disabling non-boot CPUs ...
  ");
  	for_each_online_cpu(cpu) {
  		if (cpu == first_cpu)
  			continue;

  		error = _cpu_down(cpu, 1);

  		if (!error)

  			cpumask_set_cpu(cpu, frozen_cpus);

  		else {

  			printk(KERN_ERR "Error taking CPU%d down: %d
  ",
  				cpu, error);
  			break;
  		}
  	}

  	arch_disable_nonboot_cpus_end();

  	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
  ");

  	}

  	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;

  	printk(KERN_INFO "Enabling non-boot CPUs ...
  ");

  
  	arch_enable_nonboot_cpus_begin();

  	for_each_cpu(cpu, frozen_cpus) {

  		error = _cpu_up(cpu, 1);

  		if (!error) {

  			printk(KERN_INFO "CPU%d is up
  ", cpu);

  			continue;
  		}

  		printk(KERN_WARNING "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);

  
  /*
   * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU
   * hotplug when tasks are about to be frozen. Also, don't allow the freezer
   * to continue until any currently running CPU hotplug operation gets
   * completed.
   * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the
   * 'cpu_add_remove_lock'. And this same lock is also taken by the regular
   * CPU hotplug path and released only after it is complete. Thus, we
   * (and hence the freezer) will block here until any currently running CPU
   * hotplug operation gets completed.
   */
  void cpu_hotplug_disable_before_freeze(void)
  {
  	cpu_maps_update_begin();
  	cpu_hotplug_disabled = 1;
  	cpu_maps_update_done();
  }
  
  
  /*
   * When tasks have been thawed, re-enable regular CPU hotplug (which had been
   * disabled while beginning to freeze tasks).
   */
  void cpu_hotplug_enable_after_thaw(void)
  {
  	cpu_maps_update_begin();
  	cpu_hotplug_disabled = 0;
  	cpu_maps_update_done();
  }
  
  /*
   * 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_before_freeze();
  		break;
  
  	case PM_POST_SUSPEND:
  	case PM_POST_HIBERNATION:
  		cpu_hotplug_enable_after_thaw();
  		break;
  
  	default:
  		return NOTIFY_DONE;
  	}
  
  	return NOTIFY_OK;
  }

  static int __init cpu_hotplug_pm_sync_init(void)

  {
  	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 __cpuinit 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));
  	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);
  }