#ifndef __LINUX_PREEMPT_H
  #define __LINUX_PREEMPT_H
  
  /*
   * include/linux/preempt.h - macros for accessing and manipulating
   * preempt_count (used for kernel preemption, interrupt count, etc.)
   */

  #include <linux/linkage.h>

  #include <linux/list.h>

  /*
   * We use the MSB mostly because its available; see <linux/preempt_mask.h> for
   * the other bits -- can't include that header due to inclusion hell.
   */
  #define PREEMPT_NEED_RESCHED	0x80000000

  #include <asm/preempt.h>

  #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)

  extern void preempt_count_add(int val);
  extern void preempt_count_sub(int val);
  #define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); })

  #else

  #define preempt_count_add(val)	__preempt_count_add(val)
  #define preempt_count_sub(val)	__preempt_count_sub(val)
  #define preempt_count_dec_and_test() __preempt_count_dec_and_test()

  #endif

  #define __preempt_count_inc() __preempt_count_add(1)
  #define __preempt_count_dec() __preempt_count_sub(1)

  #define preempt_count_inc() preempt_count_add(1)
  #define preempt_count_dec() preempt_count_sub(1)

  
  #ifdef CONFIG_PREEMPT_COUNT

  #define preempt_disable() \
  do { \

  	preempt_count_inc(); \

  	barrier(); \
  } while (0)

  #define sched_preempt_enable_no_resched() \

  do { \
  	barrier(); \

  	preempt_count_dec(); \

  } while (0)

  #define preempt_enable_no_resched() sched_preempt_enable_no_resched()

  #ifdef CONFIG_PREEMPT

  #define preempt_enable() \
  do { \

  	barrier(); \
  	if (unlikely(preempt_count_dec_and_test())) \

  		__preempt_schedule(); \

  } while (0)

  #define preempt_check_resched() \
  do { \
  	if (should_resched()) \

  		__preempt_schedule(); \

  } while (0)
  
  #else

  #define preempt_enable() \
  do { \
  	barrier(); \
  	preempt_count_dec(); \
  } while (0)

  #define preempt_check_resched() do { } while (0)
  #endif

  
  #define preempt_disable_notrace() \
  do { \

  	__preempt_count_inc(); \

  	barrier(); \
  } while (0)
  
  #define preempt_enable_no_resched_notrace() \
  do { \
  	barrier(); \

  	__preempt_count_dec(); \

  } while (0)

  #ifdef CONFIG_PREEMPT

  #ifndef CONFIG_CONTEXT_TRACKING
  #define __preempt_schedule_context() __preempt_schedule()

  #endif

  #define preempt_enable_notrace() \
  do { \

  	barrier(); \
  	if (unlikely(__preempt_count_dec_and_test())) \

  		__preempt_schedule_context(); \

  } while (0)

  #else

  #define preempt_enable_notrace() \
  do { \
  	barrier(); \
  	__preempt_count_dec(); \
  } while (0)

  #endif

  #else /* !CONFIG_PREEMPT_COUNT */

  /*
   * Even if we don't have any preemption, we need preempt disable/enable
   * to be barriers, so that we don't have things like get_user/put_user
   * that can cause faults and scheduling migrate into our preempt-protected
   * region.
   */

  #define preempt_disable()			barrier()

  #define sched_preempt_enable_no_resched()	barrier()

  #define preempt_enable_no_resched()		barrier()
  #define preempt_enable()			barrier()
  #define preempt_check_resched()			do { } while (0)

  
  #define preempt_disable_notrace()		barrier()
  #define preempt_enable_no_resched_notrace()	barrier()
  #define preempt_enable_notrace()		barrier()

  #endif /* CONFIG_PREEMPT_COUNT */

  #ifdef MODULE
  /*
   * Modules have no business playing preemption tricks.
   */
  #undef sched_preempt_enable_no_resched
  #undef preempt_enable_no_resched
  #undef preempt_enable_no_resched_notrace
  #undef preempt_check_resched
  #endif

  #define preempt_set_need_resched() \
  do { \
  	set_preempt_need_resched(); \
  } while (0)
  #define preempt_fold_need_resched() \
  do { \
  	if (tif_need_resched()) \
  		set_preempt_need_resched(); \
  } while (0)

  #ifdef CONFIG_PREEMPT_NOTIFIERS
  
  struct preempt_notifier;
  
  /**
   * preempt_ops - notifiers called when a task is preempted and rescheduled
   * @sched_in: we're about to be rescheduled:
   *    notifier: struct preempt_notifier for the task being scheduled
   *    cpu:  cpu we're scheduled on
   * @sched_out: we've just been preempted
   *    notifier: struct preempt_notifier for the task being preempted
   *    next: the task that's kicking us out

   *
   * Please note that sched_in and out are called under different
   * contexts.  sched_out is called with rq lock held and irq disabled
   * while sched_in is called without rq lock and irq enabled.  This
   * difference is intentional and depended upon by its users.

   */
  struct preempt_ops {
  	void (*sched_in)(struct preempt_notifier *notifier, int cpu);
  	void (*sched_out)(struct preempt_notifier *notifier,
  			  struct task_struct *next);
  };
  
  /**
   * preempt_notifier - key for installing preemption notifiers
   * @link: internal use
   * @ops: defines the notifier functions to be called
   *
   * Usually used in conjunction with container_of().
   */
  struct preempt_notifier {
  	struct hlist_node link;
  	struct preempt_ops *ops;
  };
  
  void preempt_notifier_register(struct preempt_notifier *notifier);
  void preempt_notifier_unregister(struct preempt_notifier *notifier);
  
  static inline void preempt_notifier_init(struct preempt_notifier *notifier,
  				     struct preempt_ops *ops)
  {
  	INIT_HLIST_NODE(&notifier->link);
  	notifier->ops = ops;
  }
  
  #endif

  #endif /* __LINUX_PREEMPT_H */