Mercurial > hg > nginx-quic
annotate src/core/ngx_rwlock.c @ 6826:d0404c9a7675
Slab: simplified allocation from slots.
Removed code that would cause an endless loop, and removed condition
check that is always false. The first page in the slot list is
guaranteed to satisfy an allocation.
author | Ruslan Ermilov <ru@nginx.com> |
---|---|
date | Wed, 07 Dec 2016 22:25:37 +0300 |
parents | e769cc88f996 |
children | 12efcdcb8a4b |
rev | line source |
---|---|
6101 | 1 |
2 /* | |
3 * Copyright (C) Ruslan Ermilov | |
4 * Copyright (C) Nginx, Inc. | |
5 */ | |
6 | |
7 | |
8 #include <ngx_config.h> | |
9 #include <ngx_core.h> | |
10 | |
11 | |
12 #if (NGX_HAVE_ATOMIC_OPS) | |
13 | |
14 | |
15 #define NGX_RWLOCK_SPIN 2048 | |
16 #define NGX_RWLOCK_WLOCK ((ngx_atomic_uint_t) -1) | |
17 | |
18 | |
19 void | |
20 ngx_rwlock_wlock(ngx_atomic_t *lock) | |
21 { | |
22 ngx_uint_t i, n; | |
23 | |
24 for ( ;; ) { | |
25 | |
26 if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { | |
27 return; | |
28 } | |
29 | |
30 if (ngx_ncpu > 1) { | |
31 | |
32 for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { | |
33 | |
34 for (i = 0; i < n; i++) { | |
35 ngx_cpu_pause(); | |
36 } | |
37 | |
38 if (*lock == 0 | |
39 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) | |
40 { | |
41 return; | |
42 } | |
43 } | |
44 } | |
45 | |
46 ngx_sched_yield(); | |
47 } | |
48 } | |
49 | |
50 | |
51 void | |
52 ngx_rwlock_rlock(ngx_atomic_t *lock) | |
53 { | |
54 ngx_uint_t i, n; | |
55 ngx_atomic_uint_t readers; | |
56 | |
57 for ( ;; ) { | |
58 readers = *lock; | |
59 | |
60 if (readers != NGX_RWLOCK_WLOCK | |
61 && ngx_atomic_cmp_set(lock, readers, readers + 1)) | |
62 { | |
63 return; | |
64 } | |
65 | |
66 if (ngx_ncpu > 1) { | |
67 | |
68 for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { | |
69 | |
70 for (i = 0; i < n; i++) { | |
71 ngx_cpu_pause(); | |
72 } | |
73 | |
74 readers = *lock; | |
75 | |
76 if (readers != NGX_RWLOCK_WLOCK | |
77 && ngx_atomic_cmp_set(lock, readers, readers + 1)) | |
78 { | |
79 return; | |
80 } | |
81 } | |
82 } | |
83 | |
84 ngx_sched_yield(); | |
85 } | |
86 } | |
87 | |
88 | |
89 void | |
90 ngx_rwlock_unlock(ngx_atomic_t *lock) | |
91 { | |
92 ngx_atomic_uint_t readers; | |
93 | |
94 readers = *lock; | |
95 | |
96 if (readers == NGX_RWLOCK_WLOCK) { | |
97 *lock = 0; | |
98 return; | |
99 } | |
100 | |
101 for ( ;; ) { | |
102 | |
103 if (ngx_atomic_cmp_set(lock, readers, readers - 1)) { | |
104 return; | |
105 } | |
106 | |
107 readers = *lock; | |
108 } | |
109 } | |
110 | |
111 | |
6103
79ddb0bdb273
Upstream: the "zone" directive.
Ruslan Ermilov <ru@nginx.com>
parents:
6101
diff
changeset
|
112 #else |
79ddb0bdb273
Upstream: the "zone" directive.
Ruslan Ermilov <ru@nginx.com>
parents:
6101
diff
changeset
|
113 |
6270
e769cc88f996
Core: read/write locks are also required by the Stream module.
Piotr Sikora <piotrsikora@google.com>
parents:
6103
diff
changeset
|
114 #if (NGX_HTTP_UPSTREAM_ZONE || NGX_STREAM_UPSTREAM_ZONE) |
6103
79ddb0bdb273
Upstream: the "zone" directive.
Ruslan Ermilov <ru@nginx.com>
parents:
6101
diff
changeset
|
115 |
79ddb0bdb273
Upstream: the "zone" directive.
Ruslan Ermilov <ru@nginx.com>
parents:
6101
diff
changeset
|
116 #error ngx_atomic_cmp_set() is not defined! |
79ddb0bdb273
Upstream: the "zone" directive.
Ruslan Ermilov <ru@nginx.com>
parents:
6101
diff
changeset
|
117 |
6101 | 118 #endif |
6103
79ddb0bdb273
Upstream: the "zone" directive.
Ruslan Ermilov <ru@nginx.com>
parents:
6101
diff
changeset
|
119 |
79ddb0bdb273
Upstream: the "zone" directive.
Ruslan Ermilov <ru@nginx.com>
parents:
6101
diff
changeset
|
120 #endif |