xref: /freebsd/lib/libc/gen/sem_new.c (revision 6ae1554a5d9b318f8ad53ccc39fa5a961403da73) 
1 /*
2  * Copyright (C) 2010 David Xu <davidxu@freebsd.org>.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice(s), this list of conditions and the following disclaimer as
10  *    the first lines of this file unmodified other than the possible
11  *    addition of one or more copyright notices.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice(s), this list of conditions and the following disclaimer in
14  *    the documentation and/or other materials provided with the
15  *    distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
20  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
21  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
24  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
25  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
26  * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
27  * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28  *
29  * $FreeBSD$
30  */
31 
32 #include "namespace.h"
33 #include <sys/types.h>
34 #include <sys/queue.h>
35 #include <sys/mman.h>
36 #include <sys/stat.h>
37 #include <errno.h>
38 #include <machine/atomic.h>
39 #include <sys/umtx.h>
40 #include <limits.h>
41 #include <fcntl.h>
42 #include <pthread.h>
43 #include <stdarg.h>
44 #include <stdlib.h>
45 #include <string.h>
46 #include <time.h>
47 #include <semaphore.h>
48 #include <unistd.h>
49 #include "un-namespace.h"
50 #include "libc_private.h"
51 
52 __weak_reference(_sem_close, sem_close);
53 __weak_reference(_sem_destroy, sem_destroy);
54 __weak_reference(_sem_getvalue, sem_getvalue);
55 __weak_reference(_sem_init, sem_init);
56 __weak_reference(_sem_open, sem_open);
57 __weak_reference(_sem_post, sem_post);
58 __weak_reference(_sem_timedwait, sem_timedwait);
59 __weak_reference(_sem_trywait, sem_trywait);
60 __weak_reference(_sem_unlink, sem_unlink);
61 __weak_reference(_sem_wait, sem_wait);
62 
63 #define SEM_PREFIX	"/tmp/SEMD"
64 #define SEM_MAGIC	((u_int32_t)0x73656d32)
65 
66 _Static_assert(SEM_VALUE_MAX <= USEM_MAX_COUNT, "SEM_VALUE_MAX too large");
67 
68 struct sem_nameinfo {
69 	int open_count;
70 	char *name;
71 	dev_t dev;
72 	ino_t ino;
73 	sem_t *sem;
74 	LIST_ENTRY(sem_nameinfo) next;
75 };
76 
77 static pthread_once_t once = PTHREAD_ONCE_INIT;
78 static pthread_mutex_t sem_llock;
79 static LIST_HEAD(,sem_nameinfo) sem_list = LIST_HEAD_INITIALIZER(sem_list);
80 
81 static void
82 sem_prefork()
83 {
84 
85 	_pthread_mutex_lock(&sem_llock);
86 }
87 
88 static void
89 sem_postfork()
90 {
91 	_pthread_mutex_unlock(&sem_llock);
92 }
93 
94 static void
95 sem_child_postfork()
96 {
97 	_pthread_mutex_unlock(&sem_llock);
98 }
99 
100 static void
101 sem_module_init(void)
102 {
103 	pthread_mutexattr_t ma;
104 
105 	_pthread_mutexattr_init(&ma);
106 	_pthread_mutexattr_settype(&ma,  PTHREAD_MUTEX_RECURSIVE);
107 	_pthread_mutex_init(&sem_llock, &ma);
108 	_pthread_mutexattr_destroy(&ma);
109 	_pthread_atfork(sem_prefork, sem_postfork, sem_child_postfork);
110 }
111 
112 static inline int
113 sem_check_validity(sem_t *sem)
114 {
115 
116 	if (sem->_magic == SEM_MAGIC)
117 		return (0);
118 	else {
119 		errno = EINVAL;
120 		return (-1);
121 	}
122 }
123 
124 int
125 _sem_init(sem_t *sem, int pshared, unsigned int value)
126 {
127 
128 	if (value > SEM_VALUE_MAX) {
129 		errno = EINVAL;
130 		return (-1);
131 	}
132 
133 	bzero(sem, sizeof(sem_t));
134 	sem->_magic = SEM_MAGIC;
135 	sem->_kern._count = (u_int32_t)value;
136 	sem->_kern._flags = pshared ? USYNC_PROCESS_SHARED : 0;
137 	return (0);
138 }
139 
140 sem_t *
141 _sem_open(const char *name, int flags, ...)
142 {
143 	char path[PATH_MAX];
144 
145 	struct stat sb;
146 	va_list ap;
147 	struct sem_nameinfo *ni = NULL;
148 	sem_t *sem = NULL;
149 	int fd = -1, mode, len, errsave;
150 	int value = 0;
151 
152 	if (name[0] != '/') {
153 		errno = EINVAL;
154 		return (SEM_FAILED);
155 	}
156 	name++;
157 	strcpy(path, SEM_PREFIX);
158 	if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
159 		errno = ENAMETOOLONG;
160 		return (SEM_FAILED);
161 	}
162 	if (flags & ~(O_CREAT|O_EXCL)) {
163 		errno = EINVAL;
164 		return (SEM_FAILED);
165 	}
166 	if ((flags & O_CREAT) != 0) {
167 		va_start(ap, flags);
168 		mode = va_arg(ap, int);
169 		value = va_arg(ap, int);
170 		va_end(ap);
171 	}
172 	fd = -1;
173 	_pthread_once(&once, sem_module_init);
174 
175 	_pthread_mutex_lock(&sem_llock);
176 	LIST_FOREACH(ni, &sem_list, next) {
177 		if (ni->name != NULL && strcmp(name, ni->name) == 0) {
178 			fd = _open(path, flags | O_RDWR | O_CLOEXEC |
179 			    O_EXLOCK, mode);
180 			if (fd == -1 || _fstat(fd, &sb) == -1)
181 				goto error;
182 			if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT |
183 			    O_EXCL) || ni->dev != sb.st_dev ||
184 			    ni->ino != sb.st_ino) {
185 				ni->name = NULL;
186 				ni = NULL;
187 				break;
188 			}
189 			ni->open_count++;
190 			sem = ni->sem;
191 			_pthread_mutex_unlock(&sem_llock);
192 			_close(fd);
193 			return (sem);
194 		}
195 	}
196 
197 	len = sizeof(*ni) + strlen(name) + 1;
198 	ni = (struct sem_nameinfo *)malloc(len);
199 	if (ni == NULL) {
200 		errno = ENOSPC;
201 		goto error;
202 	}
203 
204 	ni->name = (char *)(ni+1);
205 	strcpy(ni->name, name);
206 
207 	if (fd == -1) {
208 		fd = _open(path, flags | O_RDWR | O_CLOEXEC | O_EXLOCK, mode);
209 		if (fd == -1 || _fstat(fd, &sb) == -1)
210 			goto error;
211 	}
212 	if (sb.st_size < sizeof(sem_t)) {
213 		sem_t tmp;
214 
215 		tmp._magic = SEM_MAGIC;
216 		tmp._kern._count = value;
217 		tmp._kern._flags = USYNC_PROCESS_SHARED | SEM_NAMED;
218 		if (_write(fd, &tmp, sizeof(tmp)) != sizeof(tmp))
219 			goto error;
220 	}
221 	flock(fd, LOCK_UN);
222 	sem = (sem_t *)mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE,
223 		MAP_SHARED|MAP_NOSYNC, fd, 0);
224 	if (sem == MAP_FAILED) {
225 		sem = NULL;
226 		if (errno == ENOMEM)
227 			errno = ENOSPC;
228 		goto error;
229 	}
230 	if (sem->_magic != SEM_MAGIC) {
231 		errno = EINVAL;
232 		goto error;
233 	}
234 	ni->open_count = 1;
235 	ni->sem = sem;
236 	ni->dev = sb.st_dev;
237 	ni->ino = sb.st_ino;
238 	LIST_INSERT_HEAD(&sem_list, ni, next);
239 	_close(fd);
240 	_pthread_mutex_unlock(&sem_llock);
241 	return (sem);
242 
243 error:
244 	errsave = errno;
245 	if (fd != -1)
246 		_close(fd);
247 	if (sem != NULL)
248 		munmap(sem, sizeof(sem_t));
249 	free(ni);
250 	_pthread_mutex_unlock(&sem_llock);
251 	errno = errsave;
252 	return (SEM_FAILED);
253 }
254 
255 int
256 _sem_close(sem_t *sem)
257 {
258 	struct sem_nameinfo *ni;
259 
260 	if (sem_check_validity(sem) != 0)
261 		return (-1);
262 
263 	if (!(sem->_kern._flags & SEM_NAMED)) {
264 		errno = EINVAL;
265 		return (-1);
266 	}
267 
268 	_pthread_once(&once, sem_module_init);
269 
270 	_pthread_mutex_lock(&sem_llock);
271 	LIST_FOREACH(ni, &sem_list, next) {
272 		if (sem == ni->sem) {
273 			if (--ni->open_count > 0) {
274 				_pthread_mutex_unlock(&sem_llock);
275 				return (0);
276 			}
277 			else
278 				break;
279 		}
280 	}
281 
282 	if (ni) {
283 		LIST_REMOVE(ni, next);
284 		_pthread_mutex_unlock(&sem_llock);
285 		munmap(sem, sizeof(*sem));
286 		free(ni);
287 		return (0);
288 	}
289 	_pthread_mutex_unlock(&sem_llock);
290 	errno = EINVAL;
291 	return (-1);
292 }
293 
294 int
295 _sem_unlink(const char *name)
296 {
297 	char path[PATH_MAX];
298 
299 	if (name[0] != '/') {
300 		errno = ENOENT;
301 		return -1;
302 	}
303 	name++;
304 	strcpy(path, SEM_PREFIX);
305 	if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
306 		errno = ENAMETOOLONG;
307 		return (-1);
308 	}
309 
310 	return (unlink(path));
311 }
312 
313 int
314 _sem_destroy(sem_t *sem)
315 {
316 
317 	if (sem_check_validity(sem) != 0)
318 		return (-1);
319 
320 	if (sem->_kern._flags & SEM_NAMED) {
321 		errno = EINVAL;
322 		return (-1);
323 	}
324 	sem->_magic = 0;
325 	return (0);
326 }
327 
328 int
329 _sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
330 {
331 
332 	if (sem_check_validity(sem) != 0)
333 		return (-1);
334 
335 	*sval = (int)USEM_COUNT(sem->_kern._count);
336 	return (0);
337 }
338 
339 static __inline int
340 usem_wake(struct _usem2 *sem)
341 {
342 	return _umtx_op(sem, UMTX_OP_SEM2_WAKE, 0, NULL, NULL);
343 }
344 
345 static __inline int
346 usem_wait(struct _usem2 *sem, const struct timespec *abstime)
347 {
348 	struct _umtx_time *tm_p, timeout;
349 	size_t tm_size;
350 
351 	if (abstime == NULL) {
352 		tm_p = NULL;
353 		tm_size = 0;
354 	} else {
355 		timeout._clockid = CLOCK_REALTIME;
356 		timeout._flags = UMTX_ABSTIME;
357 		timeout._timeout = *abstime;
358 		tm_p = &timeout;
359 		tm_size = sizeof(timeout);
360 	}
361 	return _umtx_op(sem, UMTX_OP_SEM2_WAIT, 0,
362 		    (void *)tm_size, __DECONST(void*, tm_p));
363 }
364 
365 int
366 _sem_trywait(sem_t *sem)
367 {
368 	int val;
369 
370 	if (sem_check_validity(sem) != 0)
371 		return (-1);
372 
373 	while (USEM_COUNT(val = sem->_kern._count) > 0) {
374 		if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
375 			return (0);
376 	}
377 	errno = EAGAIN;
378 	return (-1);
379 }
380 
381 int
382 _sem_timedwait(sem_t * __restrict sem,
383 	const struct timespec * __restrict abstime)
384 {
385 	int val, retval;
386 
387 	if (sem_check_validity(sem) != 0)
388 		return (-1);
389 
390 	retval = 0;
391 	_pthread_testcancel();
392 	for (;;) {
393 		while (USEM_COUNT(val = sem->_kern._count) > 0) {
394 			if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
395 				return (0);
396 		}
397 
398 		if (retval) {
399 			_pthread_testcancel();
400 			break;
401 		}
402 
403 		/*
404 		 * The timeout argument is only supposed to
405 		 * be checked if the thread would have blocked.
406 		 */
407 		if (abstime != NULL) {
408 			if (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0) {
409 				errno = EINVAL;
410 				return (-1);
411 			}
412 		}
413 		_pthread_cancel_enter(1);
414 		retval = usem_wait(&sem->_kern, abstime);
415 		_pthread_cancel_leave(0);
416 	}
417 	return (retval);
418 }
419 
420 int
421 _sem_wait(sem_t *sem)
422 {
423 	return _sem_timedwait(sem, NULL);
424 }
425 
426 /*
427  * POSIX:
428  * The sem_post() interface is reentrant with respect to signals and may be
429  * invoked from a signal-catching function.
430  * The implementation does not use lock, so it should be safe.
431  */
432 int
433 _sem_post(sem_t *sem)
434 {
435 	unsigned int count;
436 
437 	if (sem_check_validity(sem) != 0)
438 		return (-1);
439 
440 	do {
441 		count = sem->_kern._count;
442 		if (USEM_COUNT(count) + 1 > SEM_VALUE_MAX) {
443 			errno = EOVERFLOW;
444 			return (-1);
445 		}
446 	} while (!atomic_cmpset_rel_int(&sem->_kern._count, count, count + 1));
447 	if (count & USEM_HAS_WAITERS)
448 		usem_wake(&sem->_kern);
449 	return (0);
450 }
451