xref: /freebsd/lib/libc/gen/sem_new.c (revision a3422d96bd4c08d07bb6c1984c86578b67ee6a41) 
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_clockwait_np, sem_clockwait_np);
60 __weak_reference(_sem_trywait, sem_trywait);
61 __weak_reference(_sem_unlink, sem_unlink);
62 __weak_reference(_sem_wait, sem_wait);
63 
64 #define SEM_PREFIX	"/tmp/SEMD"
65 #define SEM_MAGIC	((u_int32_t)0x73656d32)
66 
67 _Static_assert(SEM_VALUE_MAX <= USEM_MAX_COUNT, "SEM_VALUE_MAX too large");
68 
69 struct sem_nameinfo {
70 	int open_count;
71 	char *name;
72 	dev_t dev;
73 	ino_t ino;
74 	sem_t *sem;
75 	LIST_ENTRY(sem_nameinfo) next;
76 };
77 
78 static pthread_once_t once = PTHREAD_ONCE_INIT;
79 static pthread_mutex_t sem_llock;
80 static LIST_HEAD(,sem_nameinfo) sem_list = LIST_HEAD_INITIALIZER(sem_list);
81 
82 static void
83 sem_prefork()
84 {
85 
86 	_pthread_mutex_lock(&sem_llock);
87 }
88 
89 static void
90 sem_postfork()
91 {
92 	_pthread_mutex_unlock(&sem_llock);
93 }
94 
95 static void
96 sem_child_postfork()
97 {
98 	_pthread_mutex_unlock(&sem_llock);
99 }
100 
101 static void
102 sem_module_init(void)
103 {
104 	pthread_mutexattr_t ma;
105 
106 	_pthread_mutexattr_init(&ma);
107 	_pthread_mutexattr_settype(&ma,  PTHREAD_MUTEX_RECURSIVE);
108 	_pthread_mutex_init(&sem_llock, &ma);
109 	_pthread_mutexattr_destroy(&ma);
110 	_pthread_atfork(sem_prefork, sem_postfork, sem_child_postfork);
111 }
112 
113 static inline int
114 sem_check_validity(sem_t *sem)
115 {
116 
117 	if (sem->_magic == SEM_MAGIC)
118 		return (0);
119 	else {
120 		errno = EINVAL;
121 		return (-1);
122 	}
123 }
124 
125 int
126 _sem_init(sem_t *sem, int pshared, unsigned int value)
127 {
128 
129 	if (value > SEM_VALUE_MAX) {
130 		errno = EINVAL;
131 		return (-1);
132 	}
133 
134 	bzero(sem, sizeof(sem_t));
135 	sem->_magic = SEM_MAGIC;
136 	sem->_kern._count = (u_int32_t)value;
137 	sem->_kern._flags = pshared ? USYNC_PROCESS_SHARED : 0;
138 	return (0);
139 }
140 
141 sem_t *
142 _sem_open(const char *name, int flags, ...)
143 {
144 	char path[PATH_MAX];
145 
146 	struct stat sb;
147 	va_list ap;
148 	struct sem_nameinfo *ni = NULL;
149 	sem_t *sem = NULL;
150 	int fd = -1, mode, len, errsave;
151 	int value = 0;
152 
153 	if (name[0] != '/') {
154 		errno = EINVAL;
155 		return (SEM_FAILED);
156 	}
157 	name++;
158 	strcpy(path, SEM_PREFIX);
159 	if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
160 		errno = ENAMETOOLONG;
161 		return (SEM_FAILED);
162 	}
163 	if (flags & ~(O_CREAT|O_EXCL)) {
164 		errno = EINVAL;
165 		return (SEM_FAILED);
166 	}
167 	if ((flags & O_CREAT) != 0) {
168 		va_start(ap, flags);
169 		mode = va_arg(ap, int);
170 		value = va_arg(ap, int);
171 		va_end(ap);
172 	}
173 	fd = -1;
174 	_pthread_once(&once, sem_module_init);
175 
176 	_pthread_mutex_lock(&sem_llock);
177 	LIST_FOREACH(ni, &sem_list, next) {
178 		if (ni->name != NULL && strcmp(name, ni->name) == 0) {
179 			fd = _open(path, flags | O_RDWR | O_CLOEXEC |
180 			    O_EXLOCK, mode);
181 			if (fd == -1 || _fstat(fd, &sb) == -1) {
182 				ni = NULL;
183 				goto error;
184 			}
185 			if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT |
186 			    O_EXCL) || ni->dev != sb.st_dev ||
187 			    ni->ino != sb.st_ino) {
188 				ni->name = NULL;
189 				ni = NULL;
190 				break;
191 			}
192 			ni->open_count++;
193 			sem = ni->sem;
194 			_pthread_mutex_unlock(&sem_llock);
195 			_close(fd);
196 			return (sem);
197 		}
198 	}
199 
200 	len = sizeof(*ni) + strlen(name) + 1;
201 	ni = (struct sem_nameinfo *)malloc(len);
202 	if (ni == NULL) {
203 		errno = ENOSPC;
204 		goto error;
205 	}
206 
207 	ni->name = (char *)(ni+1);
208 	strcpy(ni->name, name);
209 
210 	if (fd == -1) {
211 		fd = _open(path, flags | O_RDWR | O_CLOEXEC | O_EXLOCK, mode);
212 		if (fd == -1 || _fstat(fd, &sb) == -1)
213 			goto error;
214 	}
215 	if (sb.st_size < sizeof(sem_t)) {
216 		sem_t tmp;
217 
218 		tmp._magic = SEM_MAGIC;
219 		tmp._kern._count = value;
220 		tmp._kern._flags = USYNC_PROCESS_SHARED | SEM_NAMED;
221 		if (_write(fd, &tmp, sizeof(tmp)) != sizeof(tmp))
222 			goto error;
223 	}
224 	flock(fd, LOCK_UN);
225 	sem = (sem_t *)mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE,
226 		MAP_SHARED|MAP_NOSYNC, fd, 0);
227 	if (sem == MAP_FAILED) {
228 		sem = NULL;
229 		if (errno == ENOMEM)
230 			errno = ENOSPC;
231 		goto error;
232 	}
233 	if (sem->_magic != SEM_MAGIC) {
234 		errno = EINVAL;
235 		goto error;
236 	}
237 	ni->open_count = 1;
238 	ni->sem = sem;
239 	ni->dev = sb.st_dev;
240 	ni->ino = sb.st_ino;
241 	LIST_INSERT_HEAD(&sem_list, ni, next);
242 	_close(fd);
243 	_pthread_mutex_unlock(&sem_llock);
244 	return (sem);
245 
246 error:
247 	errsave = errno;
248 	if (fd != -1)
249 		_close(fd);
250 	if (sem != NULL)
251 		munmap(sem, sizeof(sem_t));
252 	free(ni);
253 	_pthread_mutex_unlock(&sem_llock);
254 	errno = errsave;
255 	return (SEM_FAILED);
256 }
257 
258 int
259 _sem_close(sem_t *sem)
260 {
261 	struct sem_nameinfo *ni;
262 
263 	if (sem_check_validity(sem) != 0)
264 		return (-1);
265 
266 	if (!(sem->_kern._flags & SEM_NAMED)) {
267 		errno = EINVAL;
268 		return (-1);
269 	}
270 
271 	_pthread_once(&once, sem_module_init);
272 
273 	_pthread_mutex_lock(&sem_llock);
274 	LIST_FOREACH(ni, &sem_list, next) {
275 		if (sem == ni->sem) {
276 			if (--ni->open_count > 0) {
277 				_pthread_mutex_unlock(&sem_llock);
278 				return (0);
279 			}
280 			else
281 				break;
282 		}
283 	}
284 
285 	if (ni) {
286 		LIST_REMOVE(ni, next);
287 		_pthread_mutex_unlock(&sem_llock);
288 		munmap(sem, sizeof(*sem));
289 		free(ni);
290 		return (0);
291 	}
292 	_pthread_mutex_unlock(&sem_llock);
293 	errno = EINVAL;
294 	return (-1);
295 }
296 
297 int
298 _sem_unlink(const char *name)
299 {
300 	char path[PATH_MAX];
301 
302 	if (name[0] != '/') {
303 		errno = ENOENT;
304 		return -1;
305 	}
306 	name++;
307 	strcpy(path, SEM_PREFIX);
308 	if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
309 		errno = ENAMETOOLONG;
310 		return (-1);
311 	}
312 
313 	return (unlink(path));
314 }
315 
316 int
317 _sem_destroy(sem_t *sem)
318 {
319 
320 	if (sem_check_validity(sem) != 0)
321 		return (-1);
322 
323 	if (sem->_kern._flags & SEM_NAMED) {
324 		errno = EINVAL;
325 		return (-1);
326 	}
327 	sem->_magic = 0;
328 	return (0);
329 }
330 
331 int
332 _sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
333 {
334 
335 	if (sem_check_validity(sem) != 0)
336 		return (-1);
337 
338 	*sval = (int)USEM_COUNT(sem->_kern._count);
339 	return (0);
340 }
341 
342 static __inline int
343 usem_wake(struct _usem2 *sem)
344 {
345 	return _umtx_op(sem, UMTX_OP_SEM2_WAKE, 0, NULL, NULL);
346 }
347 
348 static __inline int
349 usem_wait(struct _usem2 *sem, clockid_t clock_id, int flags,
350     const struct timespec *rqtp, struct timespec *rmtp)
351 {
352 	struct {
353 		struct _umtx_time timeout;
354 		struct timespec remain;
355 	} tms;
356 	void *tm_p;
357 	size_t tm_size;
358 	int retval;
359 
360 	if (rqtp == NULL) {
361 		tm_p = NULL;
362 		tm_size = 0;
363 	} else {
364 		tms.timeout._clockid = clock_id;
365 		tms.timeout._flags = (flags & TIMER_ABSTIME) ? UMTX_ABSTIME : 0;
366 		tms.timeout._timeout = *rqtp;
367 		tm_p = &tms;
368 		tm_size = sizeof(tms);
369 	}
370 	retval = _umtx_op(sem, UMTX_OP_SEM2_WAIT, 0, (void *)tm_size, tm_p);
371 	if (retval == -1 && errno == EINTR && (flags & TIMER_ABSTIME) == 0 &&
372 	    rqtp != NULL && rmtp != NULL) {
373 		*rmtp = tms.remain;
374 	}
375 
376 	return (retval);
377 }
378 
379 int
380 _sem_trywait(sem_t *sem)
381 {
382 	int val;
383 
384 	if (sem_check_validity(sem) != 0)
385 		return (-1);
386 
387 	while (USEM_COUNT(val = sem->_kern._count) > 0) {
388 		if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
389 			return (0);
390 	}
391 	errno = EAGAIN;
392 	return (-1);
393 }
394 
395 int
396 _sem_clockwait_np(sem_t * __restrict sem, clockid_t clock_id, int flags,
397 	const struct timespec *rqtp, struct timespec *rmtp)
398 {
399 	int val, retval;
400 
401 	if (sem_check_validity(sem) != 0)
402 		return (-1);
403 
404 	retval = 0;
405 	_pthread_testcancel();
406 	for (;;) {
407 		while (USEM_COUNT(val = sem->_kern._count) > 0) {
408 			if (atomic_cmpset_acq_int(&sem->_kern._count, val,
409 			    val - 1))
410 				return (0);
411 		}
412 
413 		if (retval) {
414 			_pthread_testcancel();
415 			break;
416 		}
417 
418 		/*
419 		 * The timeout argument is only supposed to
420 		 * be checked if the thread would have blocked.
421 		 */
422 		if (rqtp != NULL) {
423 			if (rqtp->tv_nsec >= 1000000000 || rqtp->tv_nsec < 0) {
424 				errno = EINVAL;
425 				return (-1);
426 			}
427 		}
428 		_pthread_cancel_enter(1);
429 		retval = usem_wait(&sem->_kern, clock_id, flags, rqtp, rmtp);
430 		_pthread_cancel_leave(0);
431 	}
432 	return (retval);
433 }
434 
435 int
436 _sem_timedwait(sem_t * __restrict sem,
437 	const struct timespec * __restrict abstime)
438 {
439 	return (_sem_clockwait_np(sem, CLOCK_REALTIME, TIMER_ABSTIME, abstime,
440 	    NULL));
441 };
442 
443 int
444 _sem_wait(sem_t *sem)
445 {
446 	return _sem_timedwait(sem, NULL);
447 }
448 
449 /*
450  * POSIX:
451  * The sem_post() interface is reentrant with respect to signals and may be
452  * invoked from a signal-catching function.
453  * The implementation does not use lock, so it should be safe.
454  */
455 int
456 _sem_post(sem_t *sem)
457 {
458 	unsigned int count;
459 
460 	if (sem_check_validity(sem) != 0)
461 		return (-1);
462 
463 	do {
464 		count = sem->_kern._count;
465 		if (USEM_COUNT(count) + 1 > SEM_VALUE_MAX) {
466 			errno = EOVERFLOW;
467 			return (-1);
468 		}
469 	} while (!atomic_cmpset_rel_int(&sem->_kern._count, count, count + 1));
470 	if (count & USEM_HAS_WAITERS)
471 		usem_wake(&sem->_kern);
472 	return (0);
473 }
474