xref: /PHP-5.4/ext/sysvsem/sysvsem.c (revision c0d060f5)
1 /*
2    +----------------------------------------------------------------------+
3    | PHP Version 5                                                        |
4    +----------------------------------------------------------------------+
5    | Copyright (c) 1997-2014 The PHP Group                                |
6    +----------------------------------------------------------------------+
7    | This source file is subject to version 3.01 of the PHP license,      |
8    | that is bundled with this package in the file LICENSE, and is        |
9    | available through the world-wide-web at the following url:           |
10    | http://www.php.net/license/3_01.txt                                  |
11    | If you did not receive a copy of the PHP license and are unable to   |
12    | obtain it through the world-wide-web, please send a note to          |
13    | license@php.net so we can mail you a copy immediately.               |
14    +----------------------------------------------------------------------+
15    | Authors: Tom May <tom@go2net.com>                                    |
16    |          Gavin Sherry <gavin@linuxworld.com.au>                      |
17    +----------------------------------------------------------------------+
18  */
19 
20 /* $Id$ */
21 
22 /* Latest update build anc tested on Linux 2.2.14
23  *
24  * This has been built and tested on Solaris 2.6 and Linux 2.1.122.
25  * It may not compile or execute correctly on other systems.
26  *
27  * sas: Works for me on Linux 2.0.36 and FreeBSD 3.0-current
28  */
29 
30 #ifdef HAVE_CONFIG_H
31 #include "config.h"
32 #endif
33 
34 #include "php.h"
35 
36 #if HAVE_SYSVSEM
37 
38 #include <sys/types.h>
39 #include <sys/ipc.h>
40 #include <sys/sem.h>
41 #include <errno.h>
42 
43 #include "php_sysvsem.h"
44 
45 #if !HAVE_SEMUN
46 
47 union semun {
48 	int val;                    /* value for SETVAL */
49 	struct semid_ds *buf;       /* buffer for IPC_STAT, IPC_SET */
50 	unsigned short int *array;  /* array for GETALL, SETALL */
51 	struct seminfo *__buf;      /* buffer for IPC_INFO */
52 };
53 
54 #undef HAVE_SEMUN
55 #define HAVE_SEMUN 1
56 
57 #endif
58 
59 /* {{{ arginfo */
60 ZEND_BEGIN_ARG_INFO_EX(arginfo_sem_get, 0, 0, 1)
61 	ZEND_ARG_INFO(0, key)
62 	ZEND_ARG_INFO(0, max_acquire)
63 	ZEND_ARG_INFO(0, perm)
64 	ZEND_ARG_INFO(0, auto_release)
65 ZEND_END_ARG_INFO()
66 
67 ZEND_BEGIN_ARG_INFO_EX(arginfo_sem_acquire, 0, 0, 1)
68 	ZEND_ARG_INFO(0, sem_identifier)
69 ZEND_END_ARG_INFO()
70 
71 ZEND_BEGIN_ARG_INFO_EX(arginfo_sem_release, 0, 0, 1)
72 	ZEND_ARG_INFO(0, sem_identifier)
73 ZEND_END_ARG_INFO()
74 
75 ZEND_BEGIN_ARG_INFO_EX(arginfo_sem_remove, 0, 0, 1)
76 	ZEND_ARG_INFO(0, sem_identifier)
77 ZEND_END_ARG_INFO()
78 /* }}} */
79 
80 /* {{{ sysvsem_functions[]
81  */
82 const zend_function_entry sysvsem_functions[] = {
83 	PHP_FE(sem_get,			arginfo_sem_get)
84 	PHP_FE(sem_acquire,		arginfo_sem_acquire)
85 	PHP_FE(sem_release,		arginfo_sem_release)
86 	PHP_FE(sem_remove,		arginfo_sem_remove)
87 	PHP_FE_END
88 };
89 /* }}} */
90 
91 /* {{{ sysvsem_module_entry
92  */
93 zend_module_entry sysvsem_module_entry = {
94 	STANDARD_MODULE_HEADER,
95 	"sysvsem",
96 	sysvsem_functions,
97 	PHP_MINIT(sysvsem),
98 	NULL,
99 	NULL,
100 	NULL,
101 	NULL,
102 	NO_VERSION_YET,
103 	STANDARD_MODULE_PROPERTIES
104 };
105 /* }}} */
106 
107 #ifdef COMPILE_DL_SYSVSEM
ZEND_GET_MODULE(sysvsem)108 ZEND_GET_MODULE(sysvsem)
109 #endif
110 
111 
112 THREAD_LS sysvsem_module php_sysvsem_module;
113 
114 /* Semaphore functions using System V semaphores.  Each semaphore
115  * actually consists of three semaphores allocated as a unit under the
116  * same key.  Semaphore 0 (SYSVSEM_SEM) is the actual semaphore, it is
117  * initialized to max_acquire and decremented as processes acquire it.
118  * The value of semaphore 1 (SYSVSEM_USAGE) is a count of the number
119  * of processes using the semaphore.  After calling semget(), if a
120  * process finds that the usage count is 1, it will set the value of
121  * SYSVSEM_SEM to max_acquire.  This allows max_acquire to be set and
122  * track the PHP code without having a global init routine or external
123  * semaphore init code.  Except see the bug regarding a race condition
124  * php_sysvsem_get().  Semaphore 2 (SYSVSEM_SETVAL) serializes the
125  * calls to GETVAL SYSVSEM_USAGE and SETVAL SYSVSEM_SEM.  It can be
126  * acquired only when it is zero.
127  */
128 
129 #define SYSVSEM_SEM		0
130 #define SYSVSEM_USAGE	1
131 #define SYSVSEM_SETVAL	2
132 
133 /* {{{ release_sysvsem_sem
134  */
135 static void release_sysvsem_sem(zend_rsrc_list_entry *rsrc TSRMLS_DC)
136 {
137 	sysvsem_sem *sem_ptr = (sysvsem_sem *)rsrc->ptr;
138 	struct sembuf sop[2];
139 	int opcount = 1;
140 /*
141  * if count == -1, semaphore has been removed
142  * Need better way to handle this
143  */
144 
145 	if (sem_ptr->count == -1 || !sem_ptr->auto_release) {
146 		efree(sem_ptr);
147 		return;
148 	}
149 	/* Decrement the usage count. */
150 
151 	sop[0].sem_num = SYSVSEM_USAGE;
152 	sop[0].sem_op  = -1;
153 	sop[0].sem_flg = SEM_UNDO;
154 
155 	/* Release the semaphore if it has been acquired but not released. */
156 
157 	if (sem_ptr->count) {
158 
159 		sop[1].sem_num = SYSVSEM_SEM;
160 		sop[1].sem_op  = sem_ptr->count;
161 		sop[1].sem_flg = SEM_UNDO;
162 
163 		opcount++;
164 	}
165 
166 	semop(sem_ptr->semid, sop, opcount);
167 	efree(sem_ptr);
168 }
169 /* }}} */
170 
171 /* {{{ PHP_MINIT_FUNCTION
172  */
PHP_MINIT_FUNCTION(sysvsem)173 PHP_MINIT_FUNCTION(sysvsem)
174 {
175 	php_sysvsem_module.le_sem = zend_register_list_destructors_ex(release_sysvsem_sem, NULL, "sysvsem", module_number);
176 	return SUCCESS;
177 }
178 /* }}} */
179 
180 #define SETVAL_WANTS_PTR
181 
182 #if defined(_AIX)
183 #undef SETVAL_WANTS_PTR
184 #endif
185 
186 /* {{{ proto resource sem_get(int key [, int max_acquire [, int perm [, int auto_release]])
187    Return an id for the semaphore with the given key, and allow max_acquire (default 1) processes to acquire it simultaneously */
PHP_FUNCTION(sem_get)188 PHP_FUNCTION(sem_get)
189 {
190 	long key, max_acquire = 1, perm = 0666, auto_release = 1;
191 	int semid;
192 	struct sembuf sop[3];
193 	int count;
194 	sysvsem_sem *sem_ptr;
195 
196 	if (FAILURE == zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l|lll", &key, &max_acquire, &perm, &auto_release)) {
197 		RETURN_FALSE;
198 	}
199 
200 	/* Get/create the semaphore.  Note that we rely on the semaphores
201 	 * being zeroed when they are created.  Despite the fact that
202 	 * the(?)  Linux semget() man page says they are not initialized,
203 	 * the kernel versions 2.0.x and 2.1.z do in fact zero them.
204 	 */
205 
206 	semid = semget(key, 3, perm|IPC_CREAT);
207 	if (semid == -1) {
208 		php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for key 0x%lx: %s", key, strerror(errno));
209 		RETURN_FALSE;
210 	}
211 
212 	/* Find out how many processes are using this semaphore.  Note
213 	 * that on Linux (at least) there is a race condition here because
214 	 * semaphore undo on process exit is not atomic, so we could
215 	 * acquire SYSVSEM_SETVAL before a crashed process has decremented
216 	 * SYSVSEM_USAGE in which case count will be greater than it
217 	 * should be and we won't set max_acquire.  Fortunately this
218 	 * doesn't actually matter in practice.
219 	 */
220 
221 	/* Wait for sem 1 to be zero . . . */
222 
223 	sop[0].sem_num = SYSVSEM_SETVAL;
224 	sop[0].sem_op  = 0;
225 	sop[0].sem_flg = 0;
226 
227 	/* . . . and increment it so it becomes non-zero . . . */
228 
229 	sop[1].sem_num = SYSVSEM_SETVAL;
230 	sop[1].sem_op  = 1;
231 	sop[1].sem_flg = SEM_UNDO;
232 
233 	/* . . . and increment the usage count. */
234 
235 	sop[2].sem_num = SYSVSEM_USAGE;
236 	sop[2].sem_op  = 1;
237 	sop[2].sem_flg = SEM_UNDO;
238 	while (semop(semid, sop, 3) == -1) {
239 		if (errno != EINTR) {
240 			php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed acquiring SYSVSEM_SETVAL for key 0x%lx: %s", key, strerror(errno));
241 			break;
242 		}
243 	}
244 
245 	/* Get the usage count. */
246 	count = semctl(semid, SYSVSEM_USAGE, GETVAL, NULL);
247 	if (count == -1) {
248 		php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for key 0x%lx: %s", key, strerror(errno));
249 	}
250 
251 	/* If we are the only user, then take this opportunity to set the max. */
252 
253 	if (count == 1) {
254 #if HAVE_SEMUN
255 		/* This is correct for Linux which has union semun. */
256 		union semun semarg;
257 		semarg.val = max_acquire;
258 		if (semctl(semid, SYSVSEM_SEM, SETVAL, semarg) == -1) {
259 			php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for key 0x%lx: %s", key, strerror(errno));
260 		}
261 #elif defined(SETVAL_WANTS_PTR)
262 		/* This is correct for Solaris 2.6 which does not have union semun. */
263 		if (semctl(semid, SYSVSEM_SEM, SETVAL, &max_acquire) == -1) {
264 			php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for key 0x%lx: %s", key, strerror(errno));
265 		}
266 #else
267 		/* This works for i.e. AIX */
268 		if (semctl(semid, SYSVSEM_SEM, SETVAL, max_acquire) == -1) {
269 			php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for key 0x%lx: %s", key, strerror(errno));
270 		}
271 #endif
272 	}
273 
274 	/* Set semaphore 1 back to zero. */
275 
276 	sop[0].sem_num = SYSVSEM_SETVAL;
277 	sop[0].sem_op  = -1;
278 	sop[0].sem_flg = SEM_UNDO;
279 	while (semop(semid, sop, 1) == -1) {
280 		if (errno != EINTR) {
281 			php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed releasing SYSVSEM_SETVAL for key 0x%lx: %s", key, strerror(errno));
282 			break;
283 		}
284 	}
285 
286 	sem_ptr = (sysvsem_sem *) emalloc(sizeof(sysvsem_sem));
287 	sem_ptr->key   = key;
288 	sem_ptr->semid = semid;
289 	sem_ptr->count = 0;
290 	sem_ptr->auto_release = auto_release;
291 
292 	sem_ptr->id = ZEND_REGISTER_RESOURCE(return_value, sem_ptr, php_sysvsem_module.le_sem);
293 }
294 /* }}} */
295 
296 /* {{{ php_sysvsem_semop
297  */
php_sysvsem_semop(INTERNAL_FUNCTION_PARAMETERS,int acquire)298 static void php_sysvsem_semop(INTERNAL_FUNCTION_PARAMETERS, int acquire)
299 {
300 	zval *arg_id;
301 	sysvsem_sem *sem_ptr;
302 	struct sembuf sop;
303 
304 	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "r", &arg_id) == FAILURE) {
305 		return;
306 	}
307 
308 	ZEND_FETCH_RESOURCE(sem_ptr, sysvsem_sem *, &arg_id, -1, "SysV semaphore", php_sysvsem_module.le_sem);
309 
310 	if (!acquire && sem_ptr->count == 0) {
311 		php_error_docref(NULL TSRMLS_CC, E_WARNING, "SysV semaphore %ld (key 0x%x) is not currently acquired", Z_LVAL_P(arg_id), sem_ptr->key);
312 		RETURN_FALSE;
313 	}
314 
315 	sop.sem_num = SYSVSEM_SEM;
316 	sop.sem_op  = acquire ? -1 : 1;
317 	sop.sem_flg = SEM_UNDO;
318 
319 	while (semop(sem_ptr->semid, &sop, 1) == -1) {
320 		if (errno != EINTR) {
321 			php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed to %s key 0x%x: %s", acquire ? "acquire" : "release", sem_ptr->key, strerror(errno));
322 			RETURN_FALSE;
323 		}
324 	}
325 
326 	sem_ptr->count -= acquire ? -1 : 1;
327 	RETURN_TRUE;
328 }
329 /* }}} */
330 
331 /* {{{ proto bool sem_acquire(resource id)
332    Acquires the semaphore with the given id, blocking if necessary */
PHP_FUNCTION(sem_acquire)333 PHP_FUNCTION(sem_acquire)
334 {
335 	php_sysvsem_semop(INTERNAL_FUNCTION_PARAM_PASSTHRU, 1);
336 }
337 /* }}} */
338 
339 /* {{{ proto bool sem_release(resource id)
340    Releases the semaphore with the given id */
PHP_FUNCTION(sem_release)341 PHP_FUNCTION(sem_release)
342 {
343 	php_sysvsem_semop(INTERNAL_FUNCTION_PARAM_PASSTHRU, 0);
344 }
345 /* }}} */
346 
347 /* {{{ proto bool sem_remove(resource id)
348    Removes semaphore from Unix systems */
349 
350 /*
351  * contributed by Gavin Sherry gavin@linuxworld.com.au
352  * Fri Mar 16 00:50:13 EST 2001
353  */
354 
PHP_FUNCTION(sem_remove)355 PHP_FUNCTION(sem_remove)
356 {
357 	zval *arg_id;
358 	sysvsem_sem *sem_ptr;
359 #if HAVE_SEMUN
360 	union semun un;
361 	struct semid_ds buf;
362 #endif
363 
364 	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "r", &arg_id) == FAILURE) {
365 		return;
366 	}
367 
368 	ZEND_FETCH_RESOURCE(sem_ptr, sysvsem_sem *, &arg_id, -1, "SysV semaphore", php_sysvsem_module.le_sem);
369 
370 #if HAVE_SEMUN
371 	un.buf = &buf;
372 	if (semctl(sem_ptr->semid, 0, IPC_STAT, un) < 0) {
373 #else
374 	if (semctl(sem_ptr->semid, 0, IPC_STAT, NULL) < 0) {
375 #endif
376 		php_error_docref(NULL TSRMLS_CC, E_WARNING, "SysV semaphore %ld does not (any longer) exist", Z_LVAL_P(arg_id));
377 		RETURN_FALSE;
378 	}
379 
380 #if HAVE_SEMUN
381 	if (semctl(sem_ptr->semid, 0, IPC_RMID, un) < 0) {
382 #else
383 	if (semctl(sem_ptr->semid, 0, IPC_RMID, NULL) < 0) {
384 #endif
385 		php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for SysV sempphore %ld: %s", Z_LVAL_P(arg_id), strerror(errno));
386 		RETURN_FALSE;
387 	}
388 
389 	/* let release_sysvsem_sem know we have removed
390 	 * the semaphore to avoid issues with releasing.
391 	 */
392 
393 	sem_ptr->count = -1;
394 	RETURN_TRUE;
395 }
396 
397 /* }}} */
398 
399 #endif /* HAVE_SYSVSEM */
400 
401 /*
402  * Local variables:
403  * tab-width: 4
404  * c-basic-offset: 4
405  * End:
406  * vim600: sw=4 ts=4 fdm=marker
407  * vim<600: sw=4 ts=4
408  */
409