#ifndef _LINUX_STOP_MACHINE
  #define _LINUX_STOP_MACHINE

  #include <linux/cpu.h>

  #include <linux/cpumask.h>

  #include <linux/smp.h>

  #include <linux/list.h>

  /*
   * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
   * monopolization mechanism.  The caller can specify a non-sleeping
   * function to be executed on a single or multiple cpus preempting all
   * other processes and monopolizing those cpus until it finishes.
   *
   * Resources for this mechanism are preallocated when a cpu is brought
   * up and requests are guaranteed to be served as long as the target
   * cpus are online.
   */

  typedef int (*cpu_stop_fn_t)(void *arg);

  #ifdef CONFIG_SMP

  struct cpu_stop_work {
  	struct list_head	list;		/* cpu_stopper->works */
  	cpu_stop_fn_t		fn;
  	void			*arg;
  	struct cpu_stop_done	*done;
  };
  
  int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);

  int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);

  void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
  			 struct cpu_stop_work *work_buf);
  int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
  int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);

  void stop_machine_park(int cpu);

  void stop_machine_unpark(int cpu);

  #else	/* CONFIG_SMP */
  
  #include <linux/workqueue.h>
  
  struct cpu_stop_work {
  	struct work_struct	work;
  	cpu_stop_fn_t		fn;
  	void			*arg;
  };
  
  static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
  {
  	int ret = -ENOENT;
  	preempt_disable();
  	if (cpu == smp_processor_id())
  		ret = fn(arg);
  	preempt_enable();
  	return ret;
  }
  
  static void stop_one_cpu_nowait_workfn(struct work_struct *work)
  {
  	struct cpu_stop_work *stwork =
  		container_of(work, struct cpu_stop_work, work);
  	preempt_disable();
  	stwork->fn(stwork->arg);
  	preempt_enable();
  }
  
  static inline void stop_one_cpu_nowait(unsigned int cpu,
  				       cpu_stop_fn_t fn, void *arg,
  				       struct cpu_stop_work *work_buf)
  {
  	if (cpu == smp_processor_id()) {
  		INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
  		work_buf->fn = fn;
  		work_buf->arg = arg;
  		schedule_work(&work_buf->work);
  	}
  }
  
  static inline int stop_cpus(const struct cpumask *cpumask,
  			    cpu_stop_fn_t fn, void *arg)
  {
  	if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
  		return stop_one_cpu(raw_smp_processor_id(), fn, arg);
  	return -ENOENT;
  }
  
  static inline int try_stop_cpus(const struct cpumask *cpumask,
  				cpu_stop_fn_t fn, void *arg)
  {
  	return stop_cpus(cpumask, fn, arg);
  }
  
  #endif	/* CONFIG_SMP */

  /*
   * stop_machine "Bogolock": stop the entire machine, disable
   * interrupts.  This is a very heavy lock, which is equivalent to
   * grabbing every spinlock (and more).  So the "read" side to such a

   * lock is anything which disables preemption.

   */

  #if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)

  /**

   * stop_machine: freeze the machine on all CPUs and run this function

   * @fn: the function to run
   * @data: the data ptr for the @fn()

   * @cpus: the cpus to run the @fn() on (NULL = any online cpu)

   *

   * Description: This causes a thread to be scheduled on every cpu,

   * each of which disables interrupts.  The result is that no one is

   * holding a spinlock or inside any other preempt-disabled region when
   * @fn() runs.

   *
   * This can be thought of as a very heavy write lock, equivalent to
   * grabbing every spinlock in the kernel. */

  int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);

  int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,

  				   const struct cpumask *cpus);

  #else	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */

  static inline int stop_machine(cpu_stop_fn_t fn, void *data,

  				 const struct cpumask *cpus)

  {

  	unsigned long flags;

  	int ret;

  	local_irq_save(flags);

  	ret = fn(data);

  	local_irq_restore(flags);

  	return ret;
  }

  static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,

  						 const struct cpumask *cpus)
  {

  	return stop_machine(fn, data, cpus);

  }

  #endif	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */

  #endif	/* _LINUX_STOP_MACHINE */