/* 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>

  /*
   * Represents all cpu's present in the system
   * In systems capable of hotplug, this map could dynamically grow
   * as new cpu's are detected in the system via any platform specific
   * method, such as ACPI for e.g.
   */
  cpumask_t cpu_present_map __read_mostly;
  EXPORT_SYMBOL(cpu_present_map);
  
  #ifndef CONFIG_SMP
  
  /*
   * Represents all cpu's that are currently online.
   */
  cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
  EXPORT_SYMBOL(cpu_online_map);
  
  cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
  EXPORT_SYMBOL(cpu_possible_map);
  
  #else /* CONFIG_SMP */

  /* 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;

  } cpu_hotplug;

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

  }

  cpumask_t cpu_active_map;

  #ifdef CONFIG_HOTPLUG_CPU

  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);

  #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_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);
  }

  /* 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;

  }

  
  #ifdef CONFIG_HOTPLUG_CPU

  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 &&
  		    (!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) 
  ",

  				 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;

  	raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
  				param->hcpu);

  	/* 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 __ref _cpu_down(unsigned int cpu, int tasks_frozen)

  {

  	int err, nr_calls = 0;

  	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();

  	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
  ",

  				__func__, cpu);

  		err = -EINVAL;
  		goto out_release;

  	}
  
  	/* Ensure that we are not runnable on dying cpu */
  	old_allowed = current->cpus_allowed;

  	cpus_setall(tmp);

  	cpu_clear(cpu, tmp);

  	set_cpus_allowed_ptr(current, &tmp);

  	tmp = cpumask_of_cpu(cpu);

  	err = __stop_machine(take_cpu_down, &tcd_param, &tmp);

  	if (err) {

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

  		if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,

  					    hcpu) == NOTIFY_BAD)

  			BUG();

  		goto out_allowed;

  	}

  	BUG_ON(cpu_online(cpu));

  
  	/* 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_allowed:

  	set_cpus_allowed_ptr(current, &old_allowed);

  out_release:

  	cpu_hotplug_done();

  	if (!err) {
  		if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
  					    hcpu) == NOTIFY_BAD)
  			BUG();
  	}

  	return err;
  }

  int __ref cpu_down(unsigned int cpu)

  {
  	int err = 0;

  	cpu_maps_update_begin();

  
  	if (cpu_hotplug_disabled) {

  		err = -EBUSY;

  		goto out;
  	}
  
  	cpu_clear(cpu, cpu_active_map);

  	/*
  	 * Make sure the all cpus did the reschedule and are not
  	 * using stale version of the cpu_active_map.
  	 * This is not strictly necessary becuase stop_machine()
  	 * that we run down the line already provides the required
  	 * synchronization. But it's really a side effect and we do not
  	 * want to depend on the innards of the stop_machine here.
  	 */
  	synchronize_sched();

  	err = _cpu_down(cpu, 0);

  	if (cpu_online(cpu))
  		cpu_set(cpu, cpu_active_map);
  
  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 = __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
  ",

  				__func__, 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));

  	cpu_set(cpu, cpu_active_map);

  	/* 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);

  	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
  ", cpu);

  #if defined(CONFIG_IA64) || defined(CONFIG_X86_64)

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

  	cpu_maps_update_begin();

  
  	if (cpu_hotplug_disabled) {

  		err = -EBUSY;

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

  out:

  	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 ...
  ");
  	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
  ", cpu);
  		} else {
  			printk(KERN_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 {

  		printk(KERN_ERR "Non-boot CPUs are not disabled
  ");

  	}

  	cpu_maps_update_done();

  	return error;
  }

  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 (cpus_empty(frozen_cpus))

  		goto out;

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

  	for_each_cpu_mask_nr(cpu, frozen_cpus) {

  		error = _cpu_up(cpu, 1);

  		if (!error) {
  			printk("CPU%d is up
  ", cpu);
  			continue;
  		}

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

  	}
  	cpus_clear(frozen_cpus);

  out:

  	cpu_maps_update_done();

  }

  #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 (cpu_isset(cpu, frozen_cpus))
  		val = CPU_STARTING_FROZEN;
  #endif /* CONFIG_PM_SLEEP_SMP */
  	raw_notifier_call_chain(&cpu_chain, 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_cpu() 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);