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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
16#ifdef CONFIG_SMP
17
18struct 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
27extern int percpu_counter_batch;
28
29int __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
39void percpu_counter_destroy(struct percpu_counter *fbc);
40void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
41void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
42s64 __percpu_counter_sum(struct percpu_counter *fbc);
43int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs);
44
45static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
46{
47 __percpu_counter_add(fbc, amount, percpu_counter_batch);
48}
49
50static 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
56static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
57{
58 return __percpu_counter_sum(fbc);
59}
60
61static 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 */
71static 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
81static inline int percpu_counter_initialized(struct percpu_counter *fbc)
82{
83 return (fbc->counters != NULL);
84}
85
86#else
87
88struct percpu_counter {
89 s64 count;
90};
91
92static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
93{
94 fbc->count = amount;
95 return 0;
96}
97
98static inline void percpu_counter_destroy(struct percpu_counter *fbc)
99{
100}
101
102static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
103{
104 fbc->count = amount;
105}
106
107static 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
117static inline void
118percpu_counter_add(struct percpu_counter *fbc, s64 amount)
119{
120 preempt_disable();
121 fbc->count += amount;
122 preempt_enable();
123}
124
125static inline void
126__percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
127{
128 percpu_counter_add(fbc, amount);
129}
130
131static 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 */
140static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
141{
142 return fbc->count;
143}
144
145static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
146{
147 return percpu_counter_read_positive(fbc);
148}
149
150static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
151{
152 return percpu_counter_read(fbc);
153}
154
155static inline int percpu_counter_initialized(struct percpu_counter *fbc)
156{
157 return 1;
158}
159
160#endif /* CONFIG_SMP */
161
162static inline void percpu_counter_inc(struct percpu_counter *fbc)
163{
164 percpu_counter_add(fbc, 1);
165}
166
167static inline void percpu_counter_dec(struct percpu_counter *fbc)
168{
169 percpu_counter_add(fbc, -1);
170}
171
172static 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 */