xref: /linux-6.15/include/linux/percpu_counter.h (revision e00a844a) 
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 
48 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
49 {
50 	return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
51 }
52 
53 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
54 {
55 	percpu_counter_add_batch(fbc, amount, percpu_counter_batch);
56 }
57 
58 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
59 {
60 	s64 ret = __percpu_counter_sum(fbc);
61 	return ret < 0 ? 0 : ret;
62 }
63 
64 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
65 {
66 	return __percpu_counter_sum(fbc);
67 }
68 
69 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
70 {
71 	return fbc->count;
72 }
73 
74 /*
75  * It is possible for the percpu_counter_read() to return a small negative
76  * number for some counter which should never be negative.
77  *
78  */
79 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
80 {
81 	s64 ret = fbc->count;
82 
83 	barrier();		/* Prevent reloads of fbc->count */
84 	if (ret >= 0)
85 		return ret;
86 	return 0;
87 }
88 
89 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
90 {
91 	return (fbc->counters != NULL);
92 }
93 
94 #else /* !CONFIG_SMP */
95 
96 struct percpu_counter {
97 	s64 count;
98 };
99 
100 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
101 				      gfp_t gfp)
102 {
103 	fbc->count = amount;
104 	return 0;
105 }
106 
107 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
108 {
109 }
110 
111 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
112 {
113 	fbc->count = amount;
114 }
115 
116 static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
117 {
118 	if (fbc->count > rhs)
119 		return 1;
120 	else if (fbc->count < rhs)
121 		return -1;
122 	else
123 		return 0;
124 }
125 
126 static inline int
127 __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
128 {
129 	return percpu_counter_compare(fbc, rhs);
130 }
131 
132 static inline void
133 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
134 {
135 	preempt_disable();
136 	fbc->count += amount;
137 	preempt_enable();
138 }
139 
140 static inline void
141 percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
142 {
143 	percpu_counter_add(fbc, amount);
144 }
145 
146 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
147 {
148 	return fbc->count;
149 }
150 
151 /*
152  * percpu_counter is intended to track positive numbers. In the UP case the
153  * number should never be negative.
154  */
155 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
156 {
157 	return fbc->count;
158 }
159 
160 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
161 {
162 	return percpu_counter_read_positive(fbc);
163 }
164 
165 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
166 {
167 	return percpu_counter_read(fbc);
168 }
169 
170 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
171 {
172 	return 1;
173 }
174 
175 #endif	/* CONFIG_SMP */
176 
177 static inline void percpu_counter_inc(struct percpu_counter *fbc)
178 {
179 	percpu_counter_add(fbc, 1);
180 }
181 
182 static inline void percpu_counter_dec(struct percpu_counter *fbc)
183 {
184 	percpu_counter_add(fbc, -1);
185 }
186 
187 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
188 {
189 	percpu_counter_add(fbc, -amount);
190 }
191 
192 #endif /* _LINUX_PERCPU_COUNTER_H */
193