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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 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 *counters;
25};
26
27#if NR_CPUS >= 16
28#define FBC_BATCH (NR_CPUS*2)
29#else
30#define FBC_BATCH (NR_CPUS*4)
31#endif
32
33void percpu_counter_init(struct percpu_counter *fbc, s64 amount);
34void percpu_counter_destroy(struct percpu_counter *fbc);
35void percpu_counter_mod(struct percpu_counter *fbc, s32 amount);
36s64 percpu_counter_sum(struct percpu_counter *fbc);
37
38static inline s64 percpu_counter_read(struct percpu_counter *fbc)
39{
40 return fbc->count;
41}
42
43/*
44 * It is possible for the percpu_counter_read() to return a small negative
45 * number for some counter which should never be negative.
46 *
47 */
48static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
49{
50 s64 ret = fbc->count;
51
52 barrier(); /* Prevent reloads of fbc->count */
53 if (ret >= 0)
54 return ret;
55 return 1;
56}
57
58#else
59
60struct percpu_counter {
61 s64 count;
62};
63
64static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
65{
66 fbc->count = amount;
67}
68
69static inline void percpu_counter_destroy(struct percpu_counter *fbc)
70{
71}
72
73static inline void
74percpu_counter_mod(struct percpu_counter *fbc, s32 amount)
75{
76 preempt_disable();
77 fbc->count += amount;
78 preempt_enable();
79}
80
81static inline s64 percpu_counter_read(struct percpu_counter *fbc)
82{
83 return fbc->count;
84}
85
86static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
87{
88 return fbc->count;
89}
90
91static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
92{
93 return percpu_counter_read_positive(fbc);
94}
95
96#endif /* CONFIG_SMP */
97
98static inline void percpu_counter_inc(struct percpu_counter *fbc)
99{
100 percpu_counter_mod(fbc, 1);
101}
102
103static inline void percpu_counter_dec(struct percpu_counter *fbc)
104{
105 percpu_counter_mod(fbc, -1);
106}
107
108#endif /* _LINUX_PERCPU_COUNTER_H */