xref: /linux-6.15/include/linux/percpu_counter.h (revision c819e2cf) 
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 
19 struct 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 
28 extern int percpu_counter_batch;
29 
30 int __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 
40 void percpu_counter_destroy(struct percpu_counter *fbc);
41 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
42 void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
43 s64 __percpu_counter_sum(struct percpu_counter *fbc);
44 int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs);
45 
46 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
47 {
48 	__percpu_counter_add(fbc, amount, percpu_counter_batch);
49 }
50 
51 static 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 
57 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
58 {
59 	return __percpu_counter_sum(fbc);
60 }
61 
62 static 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  */
72 static 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 
82 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
83 {
84 	return (fbc->counters != NULL);
85 }
86 
87 #else /* !CONFIG_SMP */
88 
89 struct percpu_counter {
90 	s64 count;
91 };
92 
93 static 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 
100 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
101 {
102 }
103 
104 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
105 {
106 	fbc->count = amount;
107 }
108 
109 static 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 
119 static inline void
120 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
121 {
122 	preempt_disable();
123 	fbc->count += amount;
124 	preempt_enable();
125 }
126 
127 static inline void
128 __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
129 {
130 	percpu_counter_add(fbc, amount);
131 }
132 
133 static 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  */
142 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
143 {
144 	return fbc->count;
145 }
146 
147 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
148 {
149 	return percpu_counter_read_positive(fbc);
150 }
151 
152 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
153 {
154 	return percpu_counter_read(fbc);
155 }
156 
157 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
158 {
159 	return 1;
160 }
161 
162 #endif	/* CONFIG_SMP */
163 
164 static inline void percpu_counter_inc(struct percpu_counter *fbc)
165 {
166 	percpu_counter_add(fbc, 1);
167 }
168 
169 static inline void percpu_counter_dec(struct percpu_counter *fbc)
170 {
171 	percpu_counter_add(fbc, -1);
172 }
173 
174 static 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 */
180