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_init
7. percpu_counter_destroy
8. percpu_counter_set
9. percpu_counter_add
10. percpu_counter_read
11. percpu_counter_read_positive
12. percpu_counter_sum_positive
13. percpu_counter_sum
14. percpu_counter_inc
15. percpu_counter_dec
16. 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>

#ifdef CONFIG_SMP

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

#if NR_CPUS >= 16
#define FBC_BATCH       (NR_CPUS*2)
#else
#define FBC_BATCH       (NR_CPUS*4)
#endif

int percpu_counter_init(struct percpu_counter *fbc, s64 amount);
int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount);
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);

static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
        __percpu_counter_add(fbc, amount, FBC_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 1;
}

#else

struct percpu_counter {
        s64 count;
};

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

#define percpu_counter_init_irq percpu_counter_init

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;
}

#define __percpu_counter_add(fbc, amount, batch) \
        percpu_counter_add(fbc, amount)

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

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

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);
}

#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 */