xref: /freebsd/lib/libc/gen/sem_new.c (revision 1f4bcc459a76b7aa664f3fd557684cd0ba6da352) 
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 				ni = NULL;
182 				goto error;
183 			}
184 			if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT |
185 			    O_EXCL) || ni->dev != sb.st_dev ||
186 			    ni->ino != sb.st_ino) {
187 				ni->name = NULL;
188 				ni = NULL;
189 				break;
190 			}
191 			ni->open_count++;
192 			sem = ni->sem;
193 			_pthread_mutex_unlock(&sem_llock);
194 			_close(fd);
195 			return (sem);
196 		}
197 	}
198 
199 	len = sizeof(*ni) + strlen(name) + 1;
200 	ni = (struct sem_nameinfo *)malloc(len);
201 	if (ni == NULL) {
202 		errno = ENOSPC;
203 		goto error;
204 	}
205 
206 	ni->name = (char *)(ni+1);
207 	strcpy(ni->name, name);
208 
209 	if (fd == -1) {
210 		fd = _open(path, flags | O_RDWR | O_CLOEXEC | O_EXLOCK, mode);
211 		if (fd == -1 || _fstat(fd, &sb) == -1)
212 			goto error;
213 	}
214 	if (sb.st_size < sizeof(sem_t)) {
215 		sem_t tmp;
216 
217 		tmp._magic = SEM_MAGIC;
218 		tmp._kern._count = value;
219 		tmp._kern._flags = USYNC_PROCESS_SHARED | SEM_NAMED;
220 		if (_write(fd, &tmp, sizeof(tmp)) != sizeof(tmp))
221 			goto error;
222 	}
223 	flock(fd, LOCK_UN);
224 	sem = (sem_t *)mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE,
225 		MAP_SHARED|MAP_NOSYNC, fd, 0);
226 	if (sem == MAP_FAILED) {
227 		sem = NULL;
228 		if (errno == ENOMEM)
229 			errno = ENOSPC;
230 		goto error;
231 	}
232 	if (sem->_magic != SEM_MAGIC) {
233 		errno = EINVAL;
234 		goto error;
235 	}
236 	ni->open_count = 1;
237 	ni->sem = sem;
238 	ni->dev = sb.st_dev;
239 	ni->ino = sb.st_ino;
240 	LIST_INSERT_HEAD(&sem_list, ni, next);
241 	_close(fd);
242 	_pthread_mutex_unlock(&sem_llock);
243 	return (sem);
244 
245 error:
246 	errsave = errno;
247 	if (fd != -1)
248 		_close(fd);
249 	if (sem != NULL)
250 		munmap(sem, sizeof(sem_t));
251 	free(ni);
252 	_pthread_mutex_unlock(&sem_llock);
253 	errno = errsave;
254 	return (SEM_FAILED);
255 }
256 
257 int
258 _sem_close(sem_t *sem)
259 {
260 	struct sem_nameinfo *ni;
261 
262 	if (sem_check_validity(sem) != 0)
263 		return (-1);
264 
265 	if (!(sem->_kern._flags & SEM_NAMED)) {
266 		errno = EINVAL;
267 		return (-1);
268 	}
269 
270 	_pthread_once(&once, sem_module_init);
271 
272 	_pthread_mutex_lock(&sem_llock);
273 	LIST_FOREACH(ni, &sem_list, next) {
274 		if (sem == ni->sem) {
275 			if (--ni->open_count > 0) {
276 				_pthread_mutex_unlock(&sem_llock);
277 				return (0);
278 			}
279 			else
280 				break;
281 		}
282 	}
283 
284 	if (ni) {
285 		LIST_REMOVE(ni, next);
286 		_pthread_mutex_unlock(&sem_llock);
287 		munmap(sem, sizeof(*sem));
288 		free(ni);
289 		return (0);
290 	}
291 	_pthread_mutex_unlock(&sem_llock);
292 	errno = EINVAL;
293 	return (-1);
294 }
295 
296 int
297 _sem_unlink(const char *name)
298 {
299 	char path[PATH_MAX];
300 
301 	if (name[0] != '/') {
302 		errno = ENOENT;
303 		return -1;
304 	}
305 	name++;
306 	strcpy(path, SEM_PREFIX);
307 	if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
308 		errno = ENAMETOOLONG;
309 		return (-1);
310 	}
311 
312 	return (unlink(path));
313 }
314 
315 int
316 _sem_destroy(sem_t *sem)
317 {
318 
319 	if (sem_check_validity(sem) != 0)
320 		return (-1);
321 
322 	if (sem->_kern._flags & SEM_NAMED) {
323 		errno = EINVAL;
324 		return (-1);
325 	}
326 	sem->_magic = 0;
327 	return (0);
328 }
329 
330 int
331 _sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
332 {
333 
334 	if (sem_check_validity(sem) != 0)
335 		return (-1);
336 
337 	*sval = (int)USEM_COUNT(sem->_kern._count);
338 	return (0);
339 }
340 
341 static __inline int
342 usem_wake(struct _usem2 *sem)
343 {
344 	return _umtx_op(sem, UMTX_OP_SEM2_WAKE, 0, NULL, NULL);
345 }
346 
347 static __inline int
348 usem_wait(struct _usem2 *sem, const struct timespec *abstime)
349 {
350 	struct _umtx_time *tm_p, timeout;
351 	size_t tm_size;
352 
353 	if (abstime == NULL) {
354 		tm_p = NULL;
355 		tm_size = 0;
356 	} else {
357 		timeout._clockid = CLOCK_REALTIME;
358 		timeout._flags = UMTX_ABSTIME;
359 		timeout._timeout = *abstime;
360 		tm_p = &timeout;
361 		tm_size = sizeof(timeout);
362 	}
363 	return _umtx_op(sem, UMTX_OP_SEM2_WAIT, 0,
364 		    (void *)tm_size, __DECONST(void*, tm_p));
365 }
366 
367 int
368 _sem_trywait(sem_t *sem)
369 {
370 	int val;
371 
372 	if (sem_check_validity(sem) != 0)
373 		return (-1);
374 
375 	while (USEM_COUNT(val = sem->_kern._count) > 0) {
376 		if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
377 			return (0);
378 	}
379 	errno = EAGAIN;
380 	return (-1);
381 }
382 
383 int
384 _sem_timedwait(sem_t * __restrict sem,
385 	const struct timespec * __restrict abstime)
386 {
387 	int val, retval;
388 
389 	if (sem_check_validity(sem) != 0)
390 		return (-1);
391 
392 	retval = 0;
393 	_pthread_testcancel();
394 	for (;;) {
395 		while (USEM_COUNT(val = sem->_kern._count) > 0) {
396 			if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
397 				return (0);
398 		}
399 
400 		if (retval) {
401 			_pthread_testcancel();
402 			break;
403 		}
404 
405 		/*
406 		 * The timeout argument is only supposed to
407 		 * be checked if the thread would have blocked.
408 		 */
409 		if (abstime != NULL) {
410 			if (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0) {
411 				errno = EINVAL;
412 				return (-1);
413 			}
414 		}
415 		_pthread_cancel_enter(1);
416 		retval = usem_wait(&sem->_kern, abstime);
417 		_pthread_cancel_leave(0);
418 	}
419 	return (retval);
420 }
421 
422 int
423 _sem_wait(sem_t *sem)
424 {
425 	return _sem_timedwait(sem, NULL);
426 }
427 
428 /*
429  * POSIX:
430  * The sem_post() interface is reentrant with respect to signals and may be
431  * invoked from a signal-catching function.
432  * The implementation does not use lock, so it should be safe.
433  */
434 int
435 _sem_post(sem_t *sem)
436 {
437 	unsigned int count;
438 
439 	if (sem_check_validity(sem) != 0)
440 		return (-1);
441 
442 	do {
443 		count = sem->_kern._count;
444 		if (USEM_COUNT(count) + 1 > SEM_VALUE_MAX) {
445 			errno = EOVERFLOW;
446 			return (-1);
447 		}
448 	} while (!atomic_cmpset_rel_int(&sem->_kern._count, count, count + 1));
449 	if (count & USEM_HAS_WAITERS)
450 		usem_wake(&sem->_kern);
451 	return (0);
452 }
453