1
2 /*
3 * Copyright (C) Igor Sysoev
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 static void ngx_shmtx_wakeup(ngx_shmtx_t *mtx);
16
17
18 ngx_int_t
ngx_shmtx_create(ngx_shmtx_t * mtx,ngx_shmtx_sh_t * addr,u_char * name)19 ngx_shmtx_create(ngx_shmtx_t *mtx, ngx_shmtx_sh_t *addr, u_char *name)
20 {
21 mtx->lock = &addr->lock;
22
23 if (mtx->spin == (ngx_uint_t) -1) {
24 return NGX_OK;
25 }
26
27 mtx->spin = 2048;
28
29 #if (NGX_HAVE_POSIX_SEM)
30
31 mtx->wait = &addr->wait;
32
33 if (sem_init(&mtx->sem, 1, 0) == -1) {
34 ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
35 "sem_init() failed");
36 } else {
37 mtx->semaphore = 1;
38 }
39
40 #endif
41
42 return NGX_OK;
43 }
44
45
46 void
ngx_shmtx_destroy(ngx_shmtx_t * mtx)47 ngx_shmtx_destroy(ngx_shmtx_t *mtx)
48 {
49 #if (NGX_HAVE_POSIX_SEM)
50
51 if (mtx->semaphore) {
52 if (sem_destroy(&mtx->sem) == -1) {
53 ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
54 "sem_destroy() failed");
55 }
56 }
57
58 #endif
59 }
60
61
62 ngx_uint_t
ngx_shmtx_trylock(ngx_shmtx_t * mtx)63 ngx_shmtx_trylock(ngx_shmtx_t *mtx)
64 {
65 return (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid));
66 }
67
68
69 void
ngx_shmtx_lock(ngx_shmtx_t * mtx)70 ngx_shmtx_lock(ngx_shmtx_t *mtx)
71 {
72 ngx_uint_t i, n;
73
74 ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, "shmtx lock");
75
76 for ( ;; ) {
77
78 if (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid)) {
79 return;
80 }
81
82 if (ngx_ncpu > 1) {
83
84 for (n = 1; n < mtx->spin; n <<= 1) {
85
86 for (i = 0; i < n; i++) {
87 ngx_cpu_pause();
88 }
89
90 if (*mtx->lock == 0
91 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid))
92 {
93 return;
94 }
95 }
96 }
97
98 #if (NGX_HAVE_POSIX_SEM)
99
100 if (mtx->semaphore) {
101 (void) ngx_atomic_fetch_add(mtx->wait, 1);
102
103 if (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid)) {
104 (void) ngx_atomic_fetch_add(mtx->wait, -1);
105 return;
106 }
107
108 ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
109 "shmtx wait %uA", *mtx->wait);
110
111 while (sem_wait(&mtx->sem) == -1) {
112 ngx_err_t err;
113
114 err = ngx_errno;
115
116 if (err != NGX_EINTR) {
117 ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, err,
118 "sem_wait() failed while waiting on shmtx");
119 break;
120 }
121 }
122
123 ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
124 "shmtx awoke");
125
126 continue;
127 }
128
129 #endif
130
131 ngx_sched_yield();
132 }
133 }
134
135
136 void
ngx_shmtx_unlock(ngx_shmtx_t * mtx)137 ngx_shmtx_unlock(ngx_shmtx_t *mtx)
138 {
139 if (mtx->spin != (ngx_uint_t) -1) {
140 ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, "shmtx unlock");
141 }
142
143 if (ngx_atomic_cmp_set(mtx->lock, ngx_pid, 0)) {
144 ngx_shmtx_wakeup(mtx);
145 }
146 }
147
148
149 ngx_uint_t
ngx_shmtx_force_unlock(ngx_shmtx_t * mtx,ngx_pid_t pid)150 ngx_shmtx_force_unlock(ngx_shmtx_t *mtx, ngx_pid_t pid)
151 {
152 ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
153 "shmtx forced unlock");
154
155 if (ngx_atomic_cmp_set(mtx->lock, pid, 0)) {
156 ngx_shmtx_wakeup(mtx);
157 return 1;
158 }
159
160 return 0;
161 }
162
163
164 static void
ngx_shmtx_wakeup(ngx_shmtx_t * mtx)165 ngx_shmtx_wakeup(ngx_shmtx_t *mtx)
166 {
167 #if (NGX_HAVE_POSIX_SEM)
168 ngx_atomic_uint_t wait;
169
170 if (!mtx->semaphore) {
171 return;
172 }
173
174 for ( ;; ) {
175
176 wait = *mtx->wait;
177
178 if ((ngx_atomic_int_t) wait <= 0) {
179 return;
180 }
181
182 if (ngx_atomic_cmp_set(mtx->wait, wait, wait - 1)) {
183 break;
184 }
185 }
186
187 ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
188 "shmtx wake %uA", wait);
189
190 if (sem_post(&mtx->sem) == -1) {
191 ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
192 "sem_post() failed while wake shmtx");
193 }
194
195 #endif
196 }
197
198
199 #else
200
201
202 ngx_int_t
ngx_shmtx_create(ngx_shmtx_t * mtx,ngx_shmtx_sh_t * addr,u_char * name)203 ngx_shmtx_create(ngx_shmtx_t *mtx, ngx_shmtx_sh_t *addr, u_char *name)
204 {
205 if (mtx->name) {
206
207 if (ngx_strcmp(name, mtx->name) == 0) {
208 mtx->name = name;
209 return NGX_OK;
210 }
211
212 ngx_shmtx_destroy(mtx);
213 }
214
215 mtx->fd = ngx_open_file(name, NGX_FILE_RDWR, NGX_FILE_CREATE_OR_OPEN,
216 NGX_FILE_DEFAULT_ACCESS);
217
218 if (mtx->fd == NGX_INVALID_FILE) {
219 ngx_log_error(NGX_LOG_EMERG, ngx_cycle->log, ngx_errno,
220 ngx_open_file_n " \"%s\" failed", name);
221 return NGX_ERROR;
222 }
223
224 if (ngx_delete_file(name) == NGX_FILE_ERROR) {
225 ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
226 ngx_delete_file_n " \"%s\" failed", name);
227 }
228
229 mtx->name = name;
230
231 return NGX_OK;
232 }
233
234
235 void
ngx_shmtx_destroy(ngx_shmtx_t * mtx)236 ngx_shmtx_destroy(ngx_shmtx_t *mtx)
237 {
238 if (ngx_close_file(mtx->fd) == NGX_FILE_ERROR) {
239 ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
240 ngx_close_file_n " \"%s\" failed", mtx->name);
241 }
242 }
243
244
245 ngx_uint_t
ngx_shmtx_trylock(ngx_shmtx_t * mtx)246 ngx_shmtx_trylock(ngx_shmtx_t *mtx)
247 {
248 ngx_err_t err;
249
250 err = ngx_trylock_fd(mtx->fd);
251
252 if (err == 0) {
253 return 1;
254 }
255
256 if (err == NGX_EAGAIN) {
257 return 0;
258 }
259
260 #if __osf__ /* Tru64 UNIX */
261
262 if (err == NGX_EACCES) {
263 return 0;
264 }
265
266 #endif
267
268 ngx_log_abort(err, ngx_trylock_fd_n " %s failed", mtx->name);
269
270 return 0;
271 }
272
273
274 void
ngx_shmtx_lock(ngx_shmtx_t * mtx)275 ngx_shmtx_lock(ngx_shmtx_t *mtx)
276 {
277 ngx_err_t err;
278
279 err = ngx_lock_fd(mtx->fd);
280
281 if (err == 0) {
282 return;
283 }
284
285 ngx_log_abort(err, ngx_lock_fd_n " %s failed", mtx->name);
286 }
287
288
289 void
ngx_shmtx_unlock(ngx_shmtx_t * mtx)290 ngx_shmtx_unlock(ngx_shmtx_t *mtx)
291 {
292 ngx_err_t err;
293
294 err = ngx_unlock_fd(mtx->fd);
295
296 if (err == 0) {
297 return;
298 }
299
300 ngx_log_abort(err, ngx_unlock_fd_n " %s failed", mtx->name);
301 }
302
303
304 ngx_uint_t
ngx_shmtx_force_unlock(ngx_shmtx_t * mtx,ngx_pid_t pid)305 ngx_shmtx_force_unlock(ngx_shmtx_t *mtx, ngx_pid_t pid)
306 {
307 return 0;
308 }
309
310 #endif
311