xref: /linux-6.15/include/linux/percpu_counter.h (revision 2e4c77be) 
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 *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 */
150