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 #include <linux/gfp.h>
  16
  17 #ifdef CONFIG_SMP
  18
  19 struct percpu_counter {
  20         raw_spinlock_t lock;
  21         s64 count;
  22 #ifdef CONFIG_HOTPLUG_CPU
  23         struct list_head list;  /* All percpu_counters are on a list */
  24 #endif
  25         s32 __percpu *counters;
  26 };
  27
  28 extern int percpu_counter_batch;
  29
  30 int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp,
  31                           struct lock_class_key *key);
  32
  33 #define percpu_counter_init(fbc, value, gfp)                            \
  34         ({                                                              \
  35                 static struct lock_class_key __key;                     \
  36                                                                         \
  37                 __percpu_counter_init(fbc, value, gfp, &__key);         \
  38         })
  39
  40 void percpu_counter_destroy(struct percpu_counter *fbc);
  41 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
  42 void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount,
  43                               s32 batch);
  44 s64 __percpu_counter_sum(struct percpu_counter *fbc);
  45 int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch);
  46
  47 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
  48 {
  49         return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
  50 }
  51
  52 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
  53 {
  54         percpu_counter_add_batch(fbc, amount, percpu_counter_batch);
  55 }
  56
  57 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
  58 {
  59         s64 ret = __percpu_counter_sum(fbc);
  60         return ret < 0 ? 0 : ret;
  61 }
  62
  63 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
  64 {
  65         return __percpu_counter_sum(fbc);
  66 }
  67
  68 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
  69 {
  70         return fbc->count;
  71 }
  72
  73 /*
  74  * It is possible for the percpu_counter_read() to return a small negative
  75  * number for some counter which should never be negative.
  76  *
  77  */
  78 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
  79 {
  80         s64 ret = fbc->count;
  81
  82         barrier();              /* Prevent reloads of fbc->count */
  83         if (ret >= 0)
  84                 return ret;
  85         return 0;
  86 }
  87
  88 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
  89 {
  90         return (fbc->counters != NULL);
  91 }
  92
  93 #else /* !CONFIG_SMP */
  94
  95 struct percpu_counter {
  96         s64 count;
  97 };
  98
  99 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
 100                                       gfp_t gfp)
 101 {
 102         fbc->count = amount;
 103         return 0;
 104 }
 105
 106 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
 107 {
 108 }
 109
 110 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
 111 {
 112         fbc->count = amount;
 113 }
 114
 115 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
 116 {
 117         if (fbc->count > rhs)
 118                 return 1;
 119         else if (fbc->count < rhs)
 120                 return -1;
 121         else
 122                 return 0;
 123 }
 124
 125 static inline int
 126 __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
 127 {
 128         return percpu_counter_compare(fbc, rhs);
 129 }
 130
 131 static inline void
 132 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
 133 {
 134         preempt_disable();
 135         fbc->count += amount;
 136         preempt_enable();
 137 }
 138
 139 static inline void
 140 percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
 141 {
 142         percpu_counter_add(fbc, amount);
 143 }
 144
 145 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
 146 {
 147         return fbc->count;
 148 }
 149
 150 /*
 151  * percpu_counter is intended to track positive numbers. In the UP case the
 152  * number should never be negative.
 153  */
 154 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
 155 {
 156         return fbc->count;
 157 }
 158
 159 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
 160 {
 161         return percpu_counter_read_positive(fbc);
 162 }
 163
 164 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
 165 {
 166         return percpu_counter_read(fbc);
 167 }
 168
 169 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
 170 {
 171         return 1;
 172 }
 173
 174 #endif  /* CONFIG_SMP */
 175
 176 static inline void percpu_counter_inc(struct percpu_counter *fbc)
 177 {
 178         percpu_counter_add(fbc, 1);
 179 }
 180
 181 static inline void percpu_counter_dec(struct percpu_counter *fbc)
 182 {
 183         percpu_counter_add(fbc, -1);
 184 }
 185
 186 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
 187 {
 188         percpu_counter_add(fbc, -amount);
 189 }
 190
 191 #endif /* _LINUX_PERCPU_COUNTER_H */