thr_sem.c revision 144518 
1/*
2 * Copyright (C) 2005 David Xu <davidxu@freebsd.org>.
3 * Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice(s), this list of conditions and the following disclaimer as
11 *    the first lines of this file unmodified other than the possible
12 *    addition of one or more copyright notices.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice(s), this list of conditions and the following disclaimer in
15 *    the documentation and/or other materials provided with the
16 *    distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
22 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
25 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
26 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
27 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
28 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 * $FreeBSD: head/lib/libthr/thread/thr_sem.c 144518 2005-04-02 01:20:00Z davidxu $
31 */
32
33#include "namespace.h"
34#include <sys/queue.h>
35#include <errno.h>
36#include <fcntl.h>
37#include <pthread.h>
38#include <semaphore.h>
39#include <stdlib.h>
40#include <time.h>
41#include <_semaphore.h>
42#include "un-namespace.h"
43
44#include "thr_private.h"
45
46
47__weak_reference(_sem_init, sem_init);
48__weak_reference(_sem_destroy, sem_destroy);
49__weak_reference(_sem_getvalue, sem_getvalue);
50__weak_reference(_sem_trywait, sem_trywait);
51__weak_reference(_sem_wait, sem_wait);
52__weak_reference(_sem_timedwait, sem_timedwait);
53__weak_reference(_sem_post, sem_post);
54
55
56static inline int
57sem_check_validity(sem_t *sem)
58{
59
60	if ((sem != NULL) && ((*sem)->magic == SEM_MAGIC))
61		return (0);
62	else {
63		errno = EINVAL;
64		return (-1);
65	}
66}
67
68static sem_t
69sem_alloc(unsigned int value, semid_t semid, int system_sem)
70{
71	sem_t sem;
72
73	if (value > SEM_VALUE_MAX) {
74		errno = EINVAL;
75		return (NULL);
76	}
77
78	sem = (sem_t)malloc(sizeof(struct sem));
79	if (sem == NULL) {
80		errno = ENOSPC;
81		return (NULL);
82	}
83	_thr_umtx_init((umtx_t *)&sem->lock);
84	/*
85	 * Fortunatly count and nwaiters are adjacency, so we can
86	 * use umtx_wait to wait on it, umtx_wait needs an address
87	 * can be accessed as a long interger.
88	 */
89	sem->count = (u_int32_t)value;
90	sem->nwaiters = 0;
91	sem->magic = SEM_MAGIC;
92	sem->semid = semid;
93	sem->syssem = system_sem;
94	return (sem);
95}
96
97int
98_sem_init(sem_t *sem, int pshared, unsigned int value)
99{
100	semid_t semid;
101
102	semid = (semid_t)SEM_USER;
103	if ((pshared != 0) && (ksem_init(&semid, value) != 0))
104		return (-1);
105
106	(*sem) = sem_alloc(value, semid, pshared);
107	if ((*sem) == NULL) {
108		if (pshared != 0)
109			ksem_destroy(semid);
110		return (-1);
111	}
112	return (0);
113}
114
115int
116_sem_destroy(sem_t *sem)
117{
118	int retval;
119
120	if (sem_check_validity(sem) != 0)
121		return (-1);
122
123	/*
124	 * If this is a system semaphore let the kernel track it otherwise
125	 * make sure there are no waiters.
126	 */
127	if ((*sem)->syssem != 0)
128		retval = ksem_destroy((*sem)->semid);
129	else {
130		retval = 0;
131		(*sem)->magic = 0;
132	}
133	if (retval == 0)
134		free(*sem);
135	return (retval);
136}
137
138int
139_sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
140{
141	int retval;
142
143	if (sem_check_validity(sem) != 0)
144		return (-1);
145
146	if ((*sem)->syssem != 0)
147		retval = ksem_getvalue((*sem)->semid, sval);
148        else {
149		*sval = (int)(*sem)->count;
150		retval = 0;
151	}
152	return (retval);
153}
154
155int
156_sem_trywait(sem_t *sem)
157{
158	int val;
159
160	if (sem_check_validity(sem) != 0)
161		return (-1);
162
163	if ((*sem)->syssem != 0)
164 		return (ksem_trywait((*sem)->semid));
165
166	while ((val = (*sem)->count) > 0) {
167		if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
168			return (0);
169	}
170	errno = EAGAIN;
171	return (-1);
172}
173
174int
175_sem_wait(sem_t *sem)
176{
177	struct pthread *curthread;
178	int val, oldcancel, retval;
179
180	if (sem_check_validity(sem) != 0)
181		return (-1);
182
183	curthread = _get_curthread();
184	if ((*sem)->syssem != 0) {
185		oldcancel = _thr_cancel_enter(curthread);
186		retval = ksem_wait((*sem)->semid);
187		_thr_cancel_leave(curthread, oldcancel);
188		return (retval);
189	}
190
191	_pthread_testcancel();
192	do {
193		while ((val = (*sem)->count) > 0) {
194			if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
195				return (0);
196		}
197		oldcancel = _thr_cancel_enter(curthread);
198		retval = _thr_umtx_wait((umtx_t *)&(*sem)->count, 0, NULL);
199		_thr_cancel_leave(curthread, oldcancel);
200	} while (retval == 0);
201	errno = retval;
202	return (-1);
203}
204
205int
206_sem_timedwait(sem_t * __restrict sem, struct timespec * __restrict abstime)
207{
208	struct timespec ts, ts2;
209	struct pthread *curthread;
210	int val, oldcancel, retval;
211
212	if (sem_check_validity(sem) != 0)
213		return (-1);
214
215	curthread = _get_curthread();
216	if ((*sem)->syssem != 0) {
217		oldcancel = _thr_cancel_enter(curthread);
218		retval = ksem_timedwait((*sem)->semid, abstime);
219		_thr_cancel_leave(curthread, oldcancel);
220		return (retval);
221	}
222
223	/*
224	 * The timeout argument is only supposed to
225	 * be checked if the thread would have blocked.
226	 */
227	_pthread_testcancel();
228	do {
229		while ((val = (*sem)->count) > 0) {
230			if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
231				return (0);
232		}
233		if (abstime == NULL) {
234			errno = EINVAL;
235			return (-1);
236		}
237		clock_gettime(CLOCK_REALTIME, &ts);
238		TIMESPEC_SUB(&ts2, abstime, &ts);
239		oldcancel = _thr_cancel_enter(curthread);
240		retval = _thr_umtx_wait((umtx_t *)&(*sem)->count, 0, &ts2);
241		_thr_cancel_leave(curthread, oldcancel);
242	} while (retval == 0);
243	errno = retval;
244	return (-1);
245}
246
247int
248_sem_post(sem_t *sem)
249{
250	int val, retval;
251
252	if (sem_check_validity(sem) != 0)
253		return (-1);
254
255	if ((*sem)->syssem != 0)
256		return (ksem_post((*sem)->semid));
257
258	/*
259	 * sem_post() is required to be safe to call from within
260	 * signal handlers, these code should work as that.
261	 */
262	do {
263		val = (*sem)->count;
264	} while (!atomic_cmpset_acq_int(&(*sem)->count, val, val + 1));
265	retval = _thr_umtx_wake((umtx_t *)&(*sem)->count, val + 1);
266	if (retval > 0)
267		retval = 0;
268	return (retval);
269}
270