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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
17/* percpu_counter batch for local add or sub */
18#define PERCPU_COUNTER_LOCAL_BATCH INT_MAX
19
20#ifdef CONFIG_SMP
21
22struct percpu_counter {
23 raw_spinlock_t lock;
24 s64 count;
25#ifdef CONFIG_HOTPLUG_CPU
26 struct list_head list; /* All percpu_counters are on a list */
27#endif
28 s32 __percpu *counters;
29};
30
31extern int percpu_counter_batch;
32
33int __percpu_counter_init_many(struct percpu_counter *fbc, s64 amount,
34 gfp_t gfp, u32 nr_counters,
35 struct lock_class_key *key);
36
37#define percpu_counter_init_many(fbc, value, gfp, nr_counters) \
38 ({ \
39 static struct lock_class_key __key; \
40 \
41 __percpu_counter_init_many(fbc, value, gfp, nr_counters,\
42 &__key); \
43 })
44
45
46#define percpu_counter_init(fbc, value, gfp) \
47 percpu_counter_init_many(fbc, value, gfp, 1)
48
49void percpu_counter_destroy_many(struct percpu_counter *fbc, u32 nr_counters);
50static inline void percpu_counter_destroy(struct percpu_counter *fbc)
51{
52 percpu_counter_destroy_many(fbc, nr_counters: 1);
53}
54
55void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
56void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount,
57 s32 batch);
58s64 __percpu_counter_sum(struct percpu_counter *fbc);
59int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch);
60bool __percpu_counter_limited_add(struct percpu_counter *fbc, s64 limit,
61 s64 amount, s32 batch);
62void percpu_counter_sync(struct percpu_counter *fbc);
63
64static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
65{
66 return __percpu_counter_compare(fbc, rhs, batch: percpu_counter_batch);
67}
68
69static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
70{
71 percpu_counter_add_batch(fbc, amount, batch: percpu_counter_batch);
72}
73
74static inline bool
75percpu_counter_limited_add(struct percpu_counter *fbc, s64 limit, s64 amount)
76{
77 return __percpu_counter_limited_add(fbc, limit, amount,
78 batch: percpu_counter_batch);
79}
80
81/*
82 * With percpu_counter_add_local() and percpu_counter_sub_local(), counts
83 * are accumulated in local per cpu counter and not in fbc->count until
84 * local count overflows PERCPU_COUNTER_LOCAL_BATCH. This makes counter
85 * write efficient.
86 * But percpu_counter_sum(), instead of percpu_counter_read(), needs to be
87 * used to add up the counts from each CPU to account for all the local
88 * counts. So percpu_counter_add_local() and percpu_counter_sub_local()
89 * should be used when a counter is updated frequently and read rarely.
90 */
91static inline void
92percpu_counter_add_local(struct percpu_counter *fbc, s64 amount)
93{
94 percpu_counter_add_batch(fbc, amount, PERCPU_COUNTER_LOCAL_BATCH);
95}
96
97static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
98{
99 s64 ret = __percpu_counter_sum(fbc);
100 return ret < 0 ? 0 : ret;
101}
102
103static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
104{
105 return __percpu_counter_sum(fbc);
106}
107
108static inline s64 percpu_counter_read(struct percpu_counter *fbc)
109{
110 return fbc->count;
111}
112
113/*
114 * It is possible for the percpu_counter_read() to return a small negative
115 * number for some counter which should never be negative.
116 *
117 */
118static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
119{
120 /* Prevent reloads of fbc->count */
121 s64 ret = READ_ONCE(fbc->count);
122
123 if (ret >= 0)
124 return ret;
125 return 0;
126}
127
128static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
129{
130 return (fbc->counters != NULL);
131}
132
133#else /* !CONFIG_SMP */
134
135struct percpu_counter {
136 s64 count;
137};
138
139static inline int percpu_counter_init_many(struct percpu_counter *fbc,
140 s64 amount, gfp_t gfp,
141 u32 nr_counters)
142{
143 u32 i;
144
145 for (i = 0; i < nr_counters; i++)
146 fbc[i].count = amount;
147
148 return 0;
149}
150
151static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
152 gfp_t gfp)
153{
154 return percpu_counter_init_many(fbc, amount, gfp, 1);
155}
156
157static inline void percpu_counter_destroy_many(struct percpu_counter *fbc,
158 u32 nr_counters)
159{
160}
161
162static inline void percpu_counter_destroy(struct percpu_counter *fbc)
163{
164}
165
166static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
167{
168 fbc->count = amount;
169}
170
171static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
172{
173 if (fbc->count > rhs)
174 return 1;
175 else if (fbc->count < rhs)
176 return -1;
177 else
178 return 0;
179}
180
181static inline int
182__percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
183{
184 return percpu_counter_compare(fbc, rhs);
185}
186
187static inline void
188percpu_counter_add(struct percpu_counter *fbc, s64 amount)
189{
190 unsigned long flags;
191
192 local_irq_save(flags);
193 fbc->count += amount;
194 local_irq_restore(flags);
195}
196
197static inline bool
198percpu_counter_limited_add(struct percpu_counter *fbc, s64 limit, s64 amount)
199{
200 unsigned long flags;
201 bool good = false;
202 s64 count;
203
204 if (amount == 0)
205 return true;
206
207 local_irq_save(flags);
208 count = fbc->count + amount;
209 if ((amount > 0 && count <= limit) ||
210 (amount < 0 && count >= limit)) {
211 fbc->count = count;
212 good = true;
213 }
214 local_irq_restore(flags);
215 return good;
216}
217
218/* non-SMP percpu_counter_add_local is the same with percpu_counter_add */
219static inline void
220percpu_counter_add_local(struct percpu_counter *fbc, s64 amount)
221{
222 percpu_counter_add(fbc, amount);
223}
224
225static inline void
226percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
227{
228 percpu_counter_add(fbc, amount);
229}
230
231static inline s64 percpu_counter_read(struct percpu_counter *fbc)
232{
233 return fbc->count;
234}
235
236/*
237 * percpu_counter is intended to track positive numbers. In the UP case the
238 * number should never be negative.
239 */
240static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
241{
242 return fbc->count;
243}
244
245static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
246{
247 return percpu_counter_read_positive(fbc);
248}
249
250static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
251{
252 return percpu_counter_read(fbc);
253}
254
255static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
256{
257 return true;
258}
259
260static inline void percpu_counter_sync(struct percpu_counter *fbc)
261{
262}
263#endif /* CONFIG_SMP */
264
265static inline void percpu_counter_inc(struct percpu_counter *fbc)
266{
267 percpu_counter_add(fbc, amount: 1);
268}
269
270static inline void percpu_counter_dec(struct percpu_counter *fbc)
271{
272 percpu_counter_add(fbc, amount: -1);
273}
274
275static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
276{
277 percpu_counter_add(fbc, amount: -amount);
278}
279
280static inline void
281percpu_counter_sub_local(struct percpu_counter *fbc, s64 amount)
282{
283 percpu_counter_add_local(fbc, amount: -amount);
284}
285
286#endif /* _LINUX_PERCPU_COUNTER_H */
287

source code of linux/include/linux/percpu_counter.h