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Linux/include/linux/percpu_counter.h

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  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 */
192 

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