2 * Copyright 2010-2015 Samy Al Bahra.
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6 * modification, are permitted provided that the following conditions
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32 #include <ck_stdbool.h>
35 unsigned int sequence;
37 typedef struct ck_sequence ck_sequence_t;
39 #define CK_SEQUENCE_INITIALIZER { .sequence = 0 }
41 CK_CC_INLINE static void
42 ck_sequence_init(struct ck_sequence *sq)
45 ck_pr_store_uint(&sq->sequence, 0);
49 CK_CC_INLINE static unsigned int
50 ck_sequence_read_begin(const struct ck_sequence *sq)
55 version = ck_pr_load_uint(&sq->sequence);
58 * If a sequence is even then associated data may be in a
61 if (CK_CC_LIKELY((version & 1) == 0))
65 * If a sequence is odd then a thread is in the middle of an
66 * update. Retry the read to avoid operating on inconsistent
76 CK_CC_INLINE static bool
77 ck_sequence_read_retry(const struct ck_sequence *sq, unsigned int version)
81 * If the sequence number was updated then a read should be
85 return ck_pr_load_uint(&sq->sequence) != version;
88 #define CK_SEQUENCE_READ(seqlock, version) \
89 for (*(version) = 1; \
90 (*(version) != 0) && (*(version) = ck_sequence_read_begin(seqlock), 1); \
91 *(version) = ck_sequence_read_retry(seqlock, *(version)))
94 * This must be called after a successful mutex acquisition.
96 CK_CC_INLINE static void
97 ck_sequence_write_begin(struct ck_sequence *sq)
101 * Increment the sequence to an odd number to indicate
102 * the beginning of a write update.
104 ck_pr_store_uint(&sq->sequence, sq->sequence + 1);
110 * This must be called before mutex ownership is relinquished.
112 CK_CC_INLINE static void
113 ck_sequence_write_end(struct ck_sequence *sq)
117 * Increment the sequence to an even number to indicate
118 * completion of a write update.
121 ck_pr_store_uint(&sq->sequence, sq->sequence + 1);
125 #endif /* CK_SEQUENCE_H */