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         raw_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 __percpu *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 int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs);
  44
  45 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
  46 {
  47         __percpu_counter_add(fbc, amount, percpu_counter_batch);
  48 }
  49
  50 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
  51 {
  52         s64 ret = __percpu_counter_sum(fbc);
  53         return ret < 0 ? 0 : ret;
  54 }
  55
  56 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
  57 {
  58         return __percpu_counter_sum(fbc);
  59 }
  60
  61 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
  62 {
  63         return fbc->count;
  64 }
  65
  66 /*
  67  * It is possible for the percpu_counter_read() to return a small negative
  68  * number for some counter which should never be negative.
  69  *
  70  */
  71 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
  72 {
  73         s64 ret = fbc->count;
  74
  75         barrier();              /* Prevent reloads of fbc->count */
  76         if (ret >= 0)
  77                 return ret;
  78         return 0;
  79 }
  80
  81 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
  82 {
  83         return (fbc->counters != NULL);
  84 }
  85
  86 #else /* !CONFIG_SMP */
  87
  88 struct percpu_counter {
  89         s64 count;
  90 };
  91
  92 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
  93 {
  94         fbc->count = amount;
  95         return 0;
  96 }
  97
  98 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
  99 {
 100 }
 101
 102 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
 103 {
 104         fbc->count = amount;
 105 }
 106
 107 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
 108 {
 109         if (fbc->count > rhs)
 110                 return 1;
 111         else if (fbc->count < rhs)
 112                 return -1;
 113         else
 114                 return 0;
 115 }
 116
 117 static inline void
 118 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
 119 {
 120         preempt_disable();
 121         fbc->count += amount;
 122         preempt_enable();
 123 }
 124
 125 static inline void
 126 __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
 127 {
 128         percpu_counter_add(fbc, amount);
 129 }
 130
 131 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
 132 {
 133         return fbc->count;
 134 }
 135
 136 /*
 137  * percpu_counter is intended to track positive numbers. In the UP case the
 138  * number should never be negative.
 139  */
 140 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
 141 {
 142         return fbc->count;
 143 }
 144
 145 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
 146 {
 147         return percpu_counter_read_positive(fbc);
 148 }
 149
 150 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
 151 {
 152         return percpu_counter_read(fbc);
 153 }
 154
 155 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
 156 {
 157         return 1;
 158 }
 159
 160 #endif  /* CONFIG_SMP */
 161
 162 static inline void percpu_counter_inc(struct percpu_counter *fbc)
 163 {
 164         percpu_counter_add(fbc, 1);
 165 }
 166
 167 static inline void percpu_counter_dec(struct percpu_counter *fbc)
 168 {
 169         percpu_counter_add(fbc, -1);
 170 }
 171
 172 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
 173 {
 174         percpu_counter_add(fbc, -amount);
 175 }
 176
 177 #endif /* _LINUX_PERCPU_COUNTER_H */