preempt.h

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

#else /* !CONFIG_PREEMPT */

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

#endif /* CONFIG_PREEMPT */


#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)

/* 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 /* !CONFIG_PREEMPT_COUNT */

#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 /* CONFIG_PREEMPT_COUNT */

#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 /* __LINUX_PREEMPT_H */