root/include/linux/percpu_counter.h

INCLUDED FROM

DEFINITIONS

1. percpu_counter_add
2. percpu_counter_sum_positive
3. percpu_counter_sum
4. percpu_counter_read
5. percpu_counter_read_positive
6. percpu_counter_initialized
7. percpu_counter_init
8. percpu_counter_destroy
9. percpu_counter_set
10. percpu_counter_compare
11. percpu_counter_add
12. __percpu_counter_add
13. percpu_counter_read
14. percpu_counter_read_positive
15. percpu_counter_sum_positive
16. percpu_counter_sum
17. percpu_counter_initialized
18. percpu_counter_inc
19. percpu_counter_dec
20. percpu_counter_sub

#ifndef _LINUX_PERCPU_COUNTER_H
#define _LINUX_PERCPU_COUNTER_H
/*
 * A simple "approximate counter" for use in ext2 and ext3 superblocks.
 *
 * WARNING: these things are HUGE.  4 kbytes per counter on 32-way P4.
 */

#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/list.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>
#include <linux/gfp.h>

#ifdef CONFIG_SMP

struct percpu_counter {
        raw_spinlock_t lock;
        s64 count;
#ifdef CONFIG_HOTPLUG_CPU
        struct list_head list;  /* All percpu_counters are on a list */
#endif
        s32 __percpu *counters;
};

extern int percpu_counter_batch;

int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp,
                          struct lock_class_key *key);

#define percpu_counter_init(fbc, value, gfp)                            \
        ({                                                              \
                static struct lock_class_key __key;                     \
                                                                        \
                __percpu_counter_init(fbc, value, gfp, &__key);         \
        })

void percpu_counter_destroy(struct percpu_counter *fbc);
void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
s64 __percpu_counter_sum(struct percpu_counter *fbc);
int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs);

static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
        __percpu_counter_add(fbc, amount, percpu_counter_batch);
}

static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
{
        s64 ret = __percpu_counter_sum(fbc);
        return ret < 0 ? 0 : ret;
}

static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
        return __percpu_counter_sum(fbc);
}

static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
        return fbc->count;
}

/*
 * It is possible for the percpu_counter_read() to return a small negative
 * number for some counter which should never be negative.
 *
 */
static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
        s64 ret = fbc->count;

        barrier();              /* Prevent reloads of fbc->count */
        if (ret >= 0)
                return ret;
        return 0;
}

static inline int percpu_counter_initialized(struct percpu_counter *fbc)
{
        return (fbc->counters != NULL);
}

#else /* !CONFIG_SMP */

struct percpu_counter {
        s64 count;
};

static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
                                      gfp_t gfp)
{
        fbc->count = amount;
        return 0;
}

static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
}

static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
{
        fbc->count = amount;
}

static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
{
        if (fbc->count > rhs)
                return 1;
        else if (fbc->count < rhs)
                return -1;
        else
                return 0;
}

static inline void
percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
        preempt_disable();
        fbc->count += amount;
        preempt_enable();
}

static inline void
__percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
{
        percpu_counter_add(fbc, amount);
}

static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
        return fbc->count;
}

/*
 * percpu_counter is intended to track positive numbers. In the UP case the
 * number should never be negative.
 */
static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
        return fbc->count;
}

static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
{
        return percpu_counter_read_positive(fbc);
}

static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
        return percpu_counter_read(fbc);
}

static inline int percpu_counter_initialized(struct percpu_counter *fbc)
{
        return 1;
}

#endif  /* CONFIG_SMP */

static inline void percpu_counter_inc(struct percpu_counter *fbc)
{
        percpu_counter_add(fbc, 1);
}

static inline void percpu_counter_dec(struct percpu_counter *fbc)
{
        percpu_counter_add(fbc, -1);
}

static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
{
        percpu_counter_add(fbc, -amount);
}

#endif /* _LINUX_PERCPU_COUNTER_H */