root/include/linux/preempt.h

INCLUDED FROM

DEFINITIONS

1. preempt_notifier_init

#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
 */
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 */