#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/thread_info.h>

  #include <linux/linkage.h>

  #include <linux/list.h>

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

    extern void add_preempt_count(int val);
    extern void sub_preempt_count(int val);

  #else
  # define add_preempt_count(val)	do { preempt_count() += (val); } while (0)
  # define sub_preempt_count(val)	do { preempt_count() -= (val); } while (0)
  #endif
  
  #define inc_preempt_count() add_preempt_count(1)
  #define dec_preempt_count() sub_preempt_count(1)
  
  #define preempt_count()	(current_thread_info()->preempt_count)
  
  #ifdef CONFIG_PREEMPT
  
  asmlinkage void preempt_schedule(void);
  
  #define preempt_disable() \
  do { \
  	inc_preempt_count(); \
  	barrier(); \
  } while (0)
  
  #define preempt_enable_no_resched() \
  do { \
  	barrier(); \
  	dec_preempt_count(); \
  } while (0)
  
  #define preempt_check_resched() \
  do { \
  	if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
  		preempt_schedule(); \
  } while (0)
  
  #define preempt_enable() \
  do { \
  	preempt_enable_no_resched(); \

  	barrier(); \

  	preempt_check_resched(); \
  } while (0)

  /* For debugging and tracer internals only! */
  #define add_preempt_count_notrace(val)			\
  	do { preempt_count() += (val); } while (0)
  #define sub_preempt_count_notrace(val)			\
  	do { preempt_count() -= (val); } while (0)
  #define inc_preempt_count_notrace() add_preempt_count_notrace(1)
  #define dec_preempt_count_notrace() sub_preempt_count_notrace(1)
  
  #define preempt_disable_notrace() \
  do { \
  	inc_preempt_count_notrace(); \
  	barrier(); \
  } while (0)
  
  #define preempt_enable_no_resched_notrace() \
  do { \
  	barrier(); \
  	dec_preempt_count_notrace(); \
  } while (0)
  
  /* preempt_check_resched is OK to trace */
  #define preempt_enable_notrace() \
  do { \
  	preempt_enable_no_resched_notrace(); \
  	barrier(); \
  	preempt_check_resched(); \
  } while (0)

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

  #define preempt_disable_notrace()		do { } while (0)
  #define preempt_enable_no_resched_notrace()	do { } while (0)
  #define preempt_enable_notrace()		do { } while (0)

  #endif

  #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 */