xref: /linux-6.15/include/linux/percpu_counter.h (revision 0bdede8a) 
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, s32 batch);
45 
46 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
47 {
48 	return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
49 }
50 
51 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
52 {
53 	__percpu_counter_add(fbc, amount, percpu_counter_batch);
54 }
55 
56 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
57 {
58 	s64 ret = __percpu_counter_sum(fbc);
59 	return ret < 0 ? 0 : ret;
60 }
61 
62 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
63 {
64 	return __percpu_counter_sum(fbc);
65 }
66 
67 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
68 {
69 	return fbc->count;
70 }
71 
72 /*
73  * It is possible for the percpu_counter_read() to return a small negative
74  * number for some counter which should never be negative.
75  *
76  */
77 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
78 {
79 	s64 ret = fbc->count;
80 
81 	barrier();		/* Prevent reloads of fbc->count */
82 	if (ret >= 0)
83 		return ret;
84 	return 0;
85 }
86 
87 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
88 {
89 	return (fbc->counters != NULL);
90 }
91 
92 #else /* !CONFIG_SMP */
93 
94 struct percpu_counter {
95 	s64 count;
96 };
97 
98 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
99 				      gfp_t gfp)
100 {
101 	fbc->count = amount;
102 	return 0;
103 }
104 
105 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
106 {
107 }
108 
109 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
110 {
111 	fbc->count = amount;
112 }
113 
114 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
115 {
116 	if (fbc->count > rhs)
117 		return 1;
118 	else if (fbc->count < rhs)
119 		return -1;
120 	else
121 		return 0;
122 }
123 
124 static inline int
125 __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
126 {
127 	return percpu_counter_compare(fbc, rhs);
128 }
129 
130 static inline void
131 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
132 {
133 	preempt_disable();
134 	fbc->count += amount;
135 	preempt_enable();
136 }
137 
138 static inline void
139 __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
140 {
141 	percpu_counter_add(fbc, amount);
142 }
143 
144 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
145 {
146 	return fbc->count;
147 }
148 
149 /*
150  * percpu_counter is intended to track positive numbers. In the UP case the
151  * number should never be negative.
152  */
153 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
154 {
155 	return fbc->count;
156 }
157 
158 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
159 {
160 	return percpu_counter_read_positive(fbc);
161 }
162 
163 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
164 {
165 	return percpu_counter_read(fbc);
166 }
167 
168 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
169 {
170 	return 1;
171 }
172 
173 #endif	/* CONFIG_SMP */
174 
175 static inline void percpu_counter_inc(struct percpu_counter *fbc)
176 {
177 	percpu_counter_add(fbc, 1);
178 }
179 
180 static inline void percpu_counter_dec(struct percpu_counter *fbc)
181 {
182 	percpu_counter_add(fbc, -1);
183 }
184 
185 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
186 {
187 	percpu_counter_add(fbc, -amount);
188 }
189 
190 #endif /* _LINUX_PERCPU_COUNTER_H */
191