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