xref: /linux-6.15/include/linux/percpu_counter.h (revision bbb03029) 
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_batch(struct percpu_counter *fbc, s64 amount,
43 			      s32 batch);
44 s64 __percpu_counter_sum(struct percpu_counter *fbc);
45 int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch);
46 
47 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
48 {
49 	return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
50 }
51 
52 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
53 {
54 	percpu_counter_add_batch(fbc, amount, percpu_counter_batch);
55 }
56 
57 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
58 {
59 	s64 ret = __percpu_counter_sum(fbc);
60 	return ret < 0 ? 0 : ret;
61 }
62 
63 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
64 {
65 	return __percpu_counter_sum(fbc);
66 }
67 
68 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
69 {
70 	return fbc->count;
71 }
72 
73 /*
74  * It is possible for the percpu_counter_read() to return a small negative
75  * number for some counter which should never be negative.
76  *
77  */
78 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
79 {
80 	s64 ret = fbc->count;
81 
82 	barrier();		/* Prevent reloads of fbc->count */
83 	if (ret >= 0)
84 		return ret;
85 	return 0;
86 }
87 
88 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
89 {
90 	return (fbc->counters != NULL);
91 }
92 
93 #else /* !CONFIG_SMP */
94 
95 struct percpu_counter {
96 	s64 count;
97 };
98 
99 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
100 				      gfp_t gfp)
101 {
102 	fbc->count = amount;
103 	return 0;
104 }
105 
106 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
107 {
108 }
109 
110 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
111 {
112 	fbc->count = amount;
113 }
114 
115 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
116 {
117 	if (fbc->count > rhs)
118 		return 1;
119 	else if (fbc->count < rhs)
120 		return -1;
121 	else
122 		return 0;
123 }
124 
125 static inline int
126 __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
127 {
128 	return percpu_counter_compare(fbc, rhs);
129 }
130 
131 static inline void
132 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
133 {
134 	preempt_disable();
135 	fbc->count += amount;
136 	preempt_enable();
137 }
138 
139 static inline void
140 percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
141 {
142 	percpu_counter_add(fbc, amount);
143 }
144 
145 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
146 {
147 	return fbc->count;
148 }
149 
150 /*
151  * percpu_counter is intended to track positive numbers. In the UP case the
152  * number should never be negative.
153  */
154 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
155 {
156 	return fbc->count;
157 }
158 
159 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
160 {
161 	return percpu_counter_read_positive(fbc);
162 }
163 
164 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
165 {
166 	return percpu_counter_read(fbc);
167 }
168 
169 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
170 {
171 	return 1;
172 }
173 
174 #endif	/* CONFIG_SMP */
175 
176 static inline void percpu_counter_inc(struct percpu_counter *fbc)
177 {
178 	percpu_counter_add(fbc, 1);
179 }
180 
181 static inline void percpu_counter_dec(struct percpu_counter *fbc)
182 {
183 	percpu_counter_add(fbc, -1);
184 }
185 
186 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
187 {
188 	percpu_counter_add(fbc, -amount);
189 }
190 
191 #endif /* _LINUX_PERCPU_COUNTER_H */
192