LXR linux/include/linux/percpu

   1#ifndef _LINUX_PERCPU_COUNTER_H
   2#define _LINUX_PERCPU_COUNTER_H
   3/*
   4 * A simple "approximate counter" for use in ext2 and ext3 superblocks.
   5 *
   6 * WARNING: these things are HUGE.  4 kbytes per counter on 32-way P4.
   7 */
   8
   9#include <linux/spinlock.h>
  10#include <linux/smp.h>
  11#include <linux/list.h>
  12#include <linux/threads.h>
  13#include <linux/percpu.h>
  14#include <linux/types.h>
  15
  16#ifdef CONFIG_SMP
  17
  18struct percpu_counter {
  19        spinlock_t lock;
  20        s64 count;
  21#ifdef CONFIG_HOTPLUG_CPU
  22        struct list_head list;  /* All percpu_counters are on a list */
  23#endif
  24        s32 *counters;
  25};
  26
  27#if NR_CPUS >= 16
  28#define FBC_BATCH       (NR_CPUS*2)
  29#else
  30#define FBC_BATCH       (NR_CPUS*4)
  31#endif
  32
  33int percpu_counter_init(struct percpu_counter *fbc, s64 amount);
  34int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount);
  35void percpu_counter_destroy(struct percpu_counter *fbc);
  36void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
  37void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
  38s64 __percpu_counter_sum(struct percpu_counter *fbc);
  39
  40static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
  41{
  42        __percpu_counter_add(fbc, amount, FBC_BATCH);
  43}
  44
  45static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
  46{
  47        s64 ret = __percpu_counter_sum(fbc);
  48        return ret < 0 ? 0 : ret;
  49}
  50
  51static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
  52{
  53        return __percpu_counter_sum(fbc);
  54}
  55
  56static inline s64 percpu_counter_read(struct percpu_counter *fbc)
  57{
  58        return fbc->count;
  59}
  60
  61/*
  62 * It is possible for the percpu_counter_read() to return a small negative
  63 * number for some counter which should never be negative.
  64 *
  65 */
  66static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
  67{
  68        s64 ret = fbc->count;
  69
  70        barrier();              /* Prevent reloads of fbc->count */
  71        if (ret >= 0)
  72                return ret;
  73        return 1;
  74}
  75
  76#else
  77
  78struct percpu_counter {
  79        s64 count;
  80};
  81
  82static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
  83{
  84        fbc->count = amount;
  85        return 0;
  86}
  87
  88#define percpu_counter_init_irq percpu_counter_init
  89
  90static inline void percpu_counter_destroy(struct percpu_counter *fbc)
  91{
  92}
  93
  94static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
  95{
  96        fbc->count = amount;
  97}
  98
  99#define __percpu_counter_add(fbc, amount, batch) \
 100        percpu_counter_add(fbc, amount)
 101
 102static inline void
 103percpu_counter_add(struct percpu_counter *fbc, s64 amount)
 104{
 105        preempt_disable();
 106        fbc->count += amount;
 107        preempt_enable();
 108}
 109
 110static inline s64 percpu_counter_read(struct percpu_counter *fbc)
 111{
 112        return fbc->count;
 113}
 114
 115static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
 116{
 117        return fbc->count;
 118}
 119
 120static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
 121{
 122        return percpu_counter_read_positive(fbc);
 123}
 124
 125static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
 126{
 127        return percpu_counter_read(fbc);
 128}
 129
 130#endif  /* CONFIG_SMP */
 131
 132static inline void percpu_counter_inc(struct percpu_counter *fbc)
 133{
 134        percpu_counter_add(fbc, 1);
 135}
 136
 137static inline void percpu_counter_dec(struct percpu_counter *fbc)
 138{
 139        percpu_counter_add(fbc, -1);
 140}
 141
 142static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
 143{
 144        percpu_counter_add(fbc, -amount);
 145}
 146
 147#endif /* _LINUX_PERCPU_COUNTER_H */
 148