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
percpu_counter_add(struct percpu_counter * fbc,s64 amount)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
percpu_counter_sum_positive(struct percpu_counter * fbc)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
percpu_counter_sum(struct percpu_counter * fbc)56 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
57 {
58 return __percpu_counter_sum(fbc);
59 }
60
percpu_counter_read(struct percpu_counter * fbc)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 */
percpu_counter_read_positive(struct percpu_counter * fbc)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
percpu_counter_initialized(struct percpu_counter * fbc)81 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
82 {
83 return (fbc->counters != NULL);
84 }
85
86 #else
87
88 struct percpu_counter {
89 s64 count;
90 };
91
percpu_counter_init(struct percpu_counter * fbc,s64 amount)92 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
93 {
94 fbc->count = amount;
95 return 0;
96 }
97
percpu_counter_destroy(struct percpu_counter * fbc)98 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
99 {
100 }
101
percpu_counter_set(struct percpu_counter * fbc,s64 amount)102 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
103 {
104 fbc->count = amount;
105 }
106
percpu_counter_compare(struct percpu_counter * fbc,s64 rhs)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
percpu_counter_add(struct percpu_counter * fbc,s64 amount)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
__percpu_counter_add(struct percpu_counter * fbc,s64 amount,s32 batch)126 __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
127 {
128 percpu_counter_add(fbc, amount);
129 }
130
percpu_counter_read(struct percpu_counter * fbc)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 */
percpu_counter_read_positive(struct percpu_counter * fbc)140 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
141 {
142 return fbc->count;
143 }
144
percpu_counter_sum_positive(struct percpu_counter * fbc)145 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
146 {
147 return percpu_counter_read_positive(fbc);
148 }
149
percpu_counter_sum(struct percpu_counter * fbc)150 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
151 {
152 return percpu_counter_read(fbc);
153 }
154
percpu_counter_initialized(struct percpu_counter * fbc)155 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
156 {
157 return 1;
158 }
159
160 #endif /* CONFIG_SMP */
161
percpu_counter_inc(struct percpu_counter * fbc)162 static inline void percpu_counter_inc(struct percpu_counter *fbc)
163 {
164 percpu_counter_add(fbc, 1);
165 }
166
percpu_counter_dec(struct percpu_counter * fbc)167 static inline void percpu_counter_dec(struct percpu_counter *fbc)
168 {
169 percpu_counter_add(fbc, -1);
170 }
171
percpu_counter_sub(struct percpu_counter * fbc,s64 amount)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 */
178