xref: /linux-6.15/include/linux/percpu_counter.h (revision 71ccc212) 
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 int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs);
44 
45 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
46 {
47 	__percpu_counter_add(fbc, amount, percpu_counter_batch);
48 }
49 
50 static 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 
56 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
57 {
58 	return __percpu_counter_sum(fbc);
59 }
60 
61 static 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  */
71 static 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 1;
79 }
80 
81 #else
82 
83 struct percpu_counter {
84 	s64 count;
85 };
86 
87 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
88 {
89 	fbc->count = amount;
90 	return 0;
91 }
92 
93 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
94 {
95 }
96 
97 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
98 {
99 	fbc->count = amount;
100 }
101 
102 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
103 {
104 	if (fbc->count > rhs)
105 		return 1;
106 	else if (fbc->count < rhs)
107 		return -1;
108 	else
109 		return 0;
110 }
111 
112 static inline void
113 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
114 {
115 	preempt_disable();
116 	fbc->count += amount;
117 	preempt_enable();
118 }
119 
120 static inline void
121 __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
122 {
123 	percpu_counter_add(fbc, amount);
124 }
125 
126 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
127 {
128 	return fbc->count;
129 }
130 
131 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
132 {
133 	return fbc->count;
134 }
135 
136 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
137 {
138 	return percpu_counter_read_positive(fbc);
139 }
140 
141 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
142 {
143 	return percpu_counter_read(fbc);
144 }
145 
146 #endif	/* CONFIG_SMP */
147 
148 static inline void percpu_counter_inc(struct percpu_counter *fbc)
149 {
150 	percpu_counter_add(fbc, 1);
151 }
152 
153 static inline void percpu_counter_dec(struct percpu_counter *fbc)
154 {
155 	percpu_counter_add(fbc, -1);
156 }
157 
158 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
159 {
160 	percpu_counter_add(fbc, -amount);
161 }
162 
163 #endif /* _LINUX_PERCPU_COUNTER_H */
164