percpu: add __percpu sparse annotations to core kernel subsystems
[linux-2.6.git] / include / linux / percpu_counter.h
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         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
44 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
45 {
46         __percpu_counter_add(fbc, amount, percpu_counter_batch);
47 }
48
49 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
50 {
51         s64 ret = __percpu_counter_sum(fbc);
52         return ret < 0 ? 0 : ret;
53 }
54
55 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
56 {
57         return __percpu_counter_sum(fbc);
58 }
59
60 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
61 {
62         return fbc->count;
63 }
64
65 /*
66  * It is possible for the percpu_counter_read() to return a small negative
67  * number for some counter which should never be negative.
68  *
69  */
70 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
71 {
72         s64 ret = fbc->count;
73
74         barrier();              /* Prevent reloads of fbc->count */
75         if (ret >= 0)
76                 return ret;
77         return 1;
78 }
79
80 #else
81
82 struct percpu_counter {
83         s64 count;
84 };
85
86 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
87 {
88         fbc->count = amount;
89         return 0;
90 }
91
92 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
93 {
94 }
95
96 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
97 {
98         fbc->count = amount;
99 }
100
101 #define __percpu_counter_add(fbc, amount, batch) \
102         percpu_counter_add(fbc, amount)
103
104 static inline void
105 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
106 {
107         preempt_disable();
108         fbc->count += amount;
109         preempt_enable();
110 }
111
112 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
113 {
114         return fbc->count;
115 }
116
117 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
118 {
119         return fbc->count;
120 }
121
122 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
123 {
124         return percpu_counter_read_positive(fbc);
125 }
126
127 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
128 {
129         return percpu_counter_read(fbc);
130 }
131
132 #endif  /* CONFIG_SMP */
133
134 static inline void percpu_counter_inc(struct percpu_counter *fbc)
135 {
136         percpu_counter_add(fbc, 1);
137 }
138
139 static inline void percpu_counter_dec(struct percpu_counter *fbc)
140 {
141         percpu_counter_add(fbc, -1);
142 }
143
144 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
145 {
146         percpu_counter_add(fbc, -amount);
147 }
148
149 #endif /* _LINUX_PERCPU_COUNTER_H */