include/linux/percpu_counter.h

   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
  18 struct 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 extern int percpu_counter_batch;
  28
  29 int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
  30                           struct lock_class_key *key);
  31
  32 #define percpu_counter_init(fbc, value)                                 \
  33         ({                                                              \
  34                 static struct lock_class_key __key;                     \
  35                                                                         \
  36                 __percpu_counter_init(fbc, value, &__key);              \
  37         })
  38
  39 void percpu_counter_destroy(struct percpu_counter *fbc);
  40 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
  41 void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
  42 s64 __percpu_counter_sum(struct percpu_counter *fbc);
  43
  44 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
  45 {
  46         __percpu_counter_add(fbc, amount, percpu_counter_batch);
  47 }
  48
  49 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
  50 {
  51         s64 ret = __percpu_counter_sum(fbc);
  52         return ret < 0 ? 0 : ret;
  53 }
  54
  55 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
  56 {
  57         return __percpu_counter_sum(fbc);
  58 }
  59
  60 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
  61 {
  62         return fbc->count;
  63 }
  64
  65 /*
  66  * It is possible for the percpu_counter_read() to return a small negative
  67  * number for some counter which should never be negative.
  68  *
  69  */
  70 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
  71 {
  72         s64 ret = fbc->count;
  73
  74         barrier();              /* Prevent reloads of fbc->count */
  75         if (ret >= 0)
  76                 return ret;
  77         return 1;
  78 }
  79
  80 #else
  81
  82 struct percpu_counter {
  83         s64 count;
  84 };
  85
  86 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
  87 {
  88         fbc->count = amount;
  89         return 0;
  90 }
  91
  92 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
  93 {
  94 }
  95
  96 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
  97 {
  98         fbc->count = amount;
  99 }
 100
 101 #define __percpu_counter_add(fbc, amount, batch) \
 102         percpu_counter_add(fbc, amount)
 103
 104 static inline void
 105 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
 106 {
 107         preempt_disable();
 108         fbc->count += amount;
 109         preempt_enable();
 110 }
 111
 112 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
 113 {
 114         return fbc->count;
 115 }
 116
 117 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
 118 {
 119         return fbc->count;
 120 }
 121
 122 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
 123 {
 124         return percpu_counter_read_positive(fbc);
 125 }
 126
 127 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
 128 {
 129         return percpu_counter_read(fbc);
 130 }
 131
 132 #endif  /* CONFIG_SMP */
 133
 134 static inline void percpu_counter_inc(struct percpu_counter *fbc)
 135 {
 136         percpu_counter_add(fbc, 1);
 137 }
 138
 139 static inline void percpu_counter_dec(struct percpu_counter *fbc)
 140 {
 141         percpu_counter_add(fbc, -1);
 142 }
 143
 144 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
 145 {
 146         percpu_counter_add(fbc, -amount);
 147 }
 148
 149 #endif /* _LINUX_PERCPU_COUNTER_H */