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c6bb62bc JA |
1 | #ifndef FIO_SEQLOCK_H |
2 | #define FIO_SEQLOCK_H | |
3 | ||
64dbaa7e | 4 | #include "types.h" |
c6bb62bc JA |
5 | #include "../arch/arch.h" |
6 | ||
7 | struct seqlock { | |
33ab6905 KC |
8 | #ifdef __cplusplus |
9 | std::atomic<unsigned int> sequence; | |
10 | #else | |
ecba19b6 | 11 | volatile unsigned int sequence; |
33ab6905 | 12 | #endif |
c6bb62bc JA |
13 | }; |
14 | ||
15 | static inline void seqlock_init(struct seqlock *s) | |
16 | { | |
17 | s->sequence = 0; | |
18 | } | |
19 | ||
20 | static inline unsigned int read_seqlock_begin(struct seqlock *s) | |
21 | { | |
22 | unsigned int seq; | |
23 | ||
24 | do { | |
5fa0c063 | 25 | seq = atomic_load_acquire(&s->sequence); |
c6bb62bc JA |
26 | if (!(seq & 1)) |
27 | break; | |
28 | nop; | |
29 | } while (1); | |
30 | ||
c6bb62bc JA |
31 | return seq; |
32 | } | |
33 | ||
34 | static inline bool read_seqlock_retry(struct seqlock *s, unsigned int seq) | |
35 | { | |
36 | read_barrier(); | |
37 | return s->sequence != seq; | |
38 | } | |
39 | ||
40 | static inline void write_seqlock_begin(struct seqlock *s) | |
41 | { | |
5fa0c063 | 42 | s->sequence = atomic_load_acquire(&s->sequence) + 1; |
c6bb62bc JA |
43 | } |
44 | ||
45 | static inline void write_seqlock_end(struct seqlock *s) | |
46 | { | |
5fa0c063 | 47 | atomic_store_release(&s->sequence, s->sequence + 1); |
c6bb62bc JA |
48 | } |
49 | ||
50 | #endif |