include/linux/preempt.h


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#ifndef __LINUX_PREEMPT_H
#define __LINUX_PREEMPT_H


#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_check_resched() \
do { \
	if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
		preempt_schedule(); \
} while (0)

#else 

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

#endif 


#ifdef CONFIG_PREEMPT_COUNT

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

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

#define preempt_enable_no_resched()	sched_preempt_enable_no_resched()

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

#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)

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

#else 

#define preempt_disable()		do { } while (0)
#define sched_preempt_enable_no_resched()	do { } while (0)
#define preempt_enable_no_resched()	do { } while (0)
#define preempt_enable()		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;

struct preempt_ops {
	void (*sched_in)(struct preempt_notifier *notifier, int cpu);
	void (*sched_out)(struct preempt_notifier *notifier,
			  struct task_struct *next);
};

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