1ck_brlock(3)             BSD Library Functions Manual             ck_brlock(3)
2

NAME

4     ck_brlock_init, ck_brlock_write_lock, ck_brlock_write_unlock,
5     ck_brlock_write_trylock, ck_brlock_read_register,
6     ck_brlock_read_unregister, ck_brlock_read_lock, ck_brlock_read_trylock,
7     ck_brlock_read_unlock — big-reader locks
8

LIBRARY

10     Concurrency Kit (libck, -lck)
11

SYNOPSIS

13     #include <ck_brlock.h>
14
15     ck_brlock_t brlock = CK_BRLOCK_INITIALIZER;
16
17     ck_brlock_reader_t reader = CK_BRLOCK_READER_INITIALIZER;
18
19     void
20     ck_brlock_init(ck_brlock_t *br);
21
22     void
23     ck_brlock_write_lock(ck_brlock_t *br);
24
25     void
26     ck_brlock_write_unlock(ck_brlock_t *br);
27
28     bool
29     ck_brlock_write_trylock(ck_brlock_t *br, unsigned int factor);
30
31     void
32     ck_brlock_read_register(ck_brlock_t *br, ck_brlock_reader_t *reader);
33
34     void
35     ck_brlock_read_unregister(ck_brlock_t *br, ck_brlock_reader_t *reader);
36
37     void
38     ck_brlock_read_lock(ck_brlock_t *br, ck_brlock_reader_t *reader);
39
40     bool
41     ck_brlock_read_trylock(ck_brlock_t *br, ck_brlock_reader_t *reader,
42         unsigned int factor);
43
44     void
45     ck_brlock_read_unlock(ck_brlock_reader_t *reader);
46

DESCRIPTION

48     Big reader locks are distributed reader-writer locks with low latency
49     constant time reader acquisition (with respect to number of concurrent
50     readers). On the other hand, writer acquisitions are a relatively expen‐
51     sive O(n) operation. This is a write-biased lock.
52

EXAMPLE

54           static ck_brlock_t lock = CK_BRLOCK_INITIALIZER;
55           static __thread ck_brlock_reader_t reader;
56
57           static void
58           reader(void)
59           {
60
61                   /* Add our thread as a lock participant. */
62                   ck_brlock_read_register(&lock, &reader);
63
64                   for (;;) {
65                           ck_brlock_read_lock(&lock, &reader);
66                           /* Read-side critical section. */
67                           ck_brlock_read_unlock(&reader);
68
69                           if (ck_brlock_read_trylock(&lock, &reader, 1) == true) {
70                                   /* Read-side critical section. */
71                                   ck_brlock_read_unlock(&reader);
72                           }
73                   }
74
75                   return;
76           }
77
78           static void
79           writer(void)
80           {
81
82                   for (;;) {
83                           ck_brlock_write_lock(&lock);
84                           /* Write-side critical section. */
85                           ck_brlock_write_unlock(&lock);
86
87                           if (ck_brlock_write_trylock(&lock, 1) == true) {
88                                   /* Write-side critical section. */
89                                   ck_brlock_write_unlock(&lock);
90                           }
91                   }
92
93                   return;
94           }
95

SEE ALSO

97     ck_bytelock(3), ck_rwlock(3)
98
99     Additional information available at http://concurrencykit.org/
100
101                                July 26, 2013.