xref: /linux-6.15/include/linux/percpu_counter.h (revision c8ea0d67) 
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_PERCPU_COUNTER_H
3 #define _LINUX_PERCPU_COUNTER_H
4 /*
5  * A simple "approximate counter" for use in ext2 and ext3 superblocks.
6  *
7  * WARNING: these things are HUGE.  4 kbytes per counter on 32-way P4.
8  */
9 
10 #include <linux/spinlock.h>
11 #include <linux/smp.h>
12 #include <linux/list.h>
13 #include <linux/threads.h>
14 #include <linux/percpu.h>
15 #include <linux/types.h>
16 #include <linux/gfp.h>
17 
18 #ifdef CONFIG_SMP
19 
20 struct percpu_counter {
21 	raw_spinlock_t lock;
22 	s64 count;
23 #ifdef CONFIG_HOTPLUG_CPU
24 	struct list_head list;	/* All percpu_counters are on a list */
25 #endif
26 	s32 __percpu *counters;
27 };
28 
29 extern int percpu_counter_batch;
30 
31 int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp,
32 			  struct lock_class_key *key);
33 
34 #define percpu_counter_init(fbc, value, gfp)				\
35 	({								\
36 		static struct lock_class_key __key;			\
37 									\
38 		__percpu_counter_init(fbc, value, gfp, &__key);		\
39 	})
40 
41 void percpu_counter_destroy(struct percpu_counter *fbc);
42 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
43 void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount,
44 			      s32 batch);
45 s64 __percpu_counter_sum(struct percpu_counter *fbc);
46 int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch);
47 void percpu_counter_sync(struct percpu_counter *fbc);
48 
49 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
50 {
51 	return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
52 }
53 
54 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
55 {
56 	percpu_counter_add_batch(fbc, amount, percpu_counter_batch);
57 }
58 
59 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
60 {
61 	s64 ret = __percpu_counter_sum(fbc);
62 	return ret < 0 ? 0 : ret;
63 }
64 
65 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
66 {
67 	return __percpu_counter_sum(fbc);
68 }
69 
70 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
71 {
72 	return fbc->count;
73 }
74 
75 /*
76  * It is possible for the percpu_counter_read() to return a small negative
77  * number for some counter which should never be negative.
78  *
79  */
80 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
81 {
82 	/* Prevent reloads of fbc->count */
83 	s64 ret = READ_ONCE(fbc->count);
84 
85 	if (ret >= 0)
86 		return ret;
87 	return 0;
88 }
89 
90 static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
91 {
92 	return (fbc->counters != NULL);
93 }
94 
95 #else /* !CONFIG_SMP */
96 
97 struct percpu_counter {
98 	s64 count;
99 };
100 
101 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
102 				      gfp_t gfp)
103 {
104 	fbc->count = amount;
105 	return 0;
106 }
107 
108 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
109 {
110 }
111 
112 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
113 {
114 	fbc->count = amount;
115 }
116 
117 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
118 {
119 	if (fbc->count > rhs)
120 		return 1;
121 	else if (fbc->count < rhs)
122 		return -1;
123 	else
124 		return 0;
125 }
126 
127 static inline int
128 __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
129 {
130 	return percpu_counter_compare(fbc, rhs);
131 }
132 
133 static inline void
134 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
135 {
136 	preempt_disable();
137 	fbc->count += amount;
138 	preempt_enable();
139 }
140 
141 static inline void
142 percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
143 {
144 	percpu_counter_add(fbc, amount);
145 }
146 
147 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
148 {
149 	return fbc->count;
150 }
151 
152 /*
153  * percpu_counter is intended to track positive numbers. In the UP case the
154  * number should never be negative.
155  */
156 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
157 {
158 	return fbc->count;
159 }
160 
161 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
162 {
163 	return percpu_counter_read_positive(fbc);
164 }
165 
166 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
167 {
168 	return percpu_counter_read(fbc);
169 }
170 
171 static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
172 {
173 	return true;
174 }
175 
176 static inline void percpu_counter_sync(struct percpu_counter *fbc)
177 {
178 }
179 #endif	/* CONFIG_SMP */
180 
181 static inline void percpu_counter_inc(struct percpu_counter *fbc)
182 {
183 	percpu_counter_add(fbc, 1);
184 }
185 
186 static inline void percpu_counter_dec(struct percpu_counter *fbc)
187 {
188 	percpu_counter_add(fbc, -1);
189 }
190 
191 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
192 {
193 	percpu_counter_add(fbc, -amount);
194 }
195 
196 #endif /* _LINUX_PERCPU_COUNTER_H */
197