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