thr_sem.c revision 173808 
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 173808 2007-11-21 06:01:02Z davidxu $
31 */
32
33#include "namespace.h"
34#include <sys/types.h>
35#include <sys/queue.h>
36#include <errno.h>
37#include <fcntl.h>
38#include <pthread.h>
39#include <semaphore.h>
40#include <stdlib.h>
41#include <time.h>
42#include <_semaphore.h>
43#include "un-namespace.h"
44
45#include "thr_private.h"
46
47
48__weak_reference(_sem_init, sem_init);
49__weak_reference(_sem_destroy, sem_destroy);
50__weak_reference(_sem_getvalue, sem_getvalue);
51__weak_reference(_sem_trywait, sem_trywait);
52__weak_reference(_sem_wait, sem_wait);
53__weak_reference(_sem_timedwait, sem_timedwait);
54__weak_reference(_sem_post, sem_post);
55
56
57static inline int
58sem_check_validity(sem_t *sem)
59{
60
61	if ((sem != NULL) && ((*sem)->magic == SEM_MAGIC))
62		return (0);
63	else {
64		errno = EINVAL;
65		return (-1);
66	}
67}
68
69static sem_t
70sem_alloc(unsigned int value, semid_t semid, int system_sem)
71{
72	sem_t sem;
73
74	if (value > SEM_VALUE_MAX) {
75		errno = EINVAL;
76		return (NULL);
77	}
78
79	sem = (sem_t)malloc(sizeof(struct sem));
80	if (sem == NULL) {
81		errno = ENOSPC;
82		return (NULL);
83	}
84	bzero(sem, sizeof(*sem));
85	/*
86	 * Fortunatly count and nwaiters are adjacency, so we can
87	 * use umtx_wait to wait on it, umtx_wait needs an address
88	 * can be accessed as a long interger.
89	 */
90	sem->count = (u_int32_t)value;
91	sem->nwaiters = 0;
92	sem->magic = SEM_MAGIC;
93	sem->semid = semid;
94	sem->syssem = system_sem;
95	return (sem);
96}
97
98int
99_sem_init(sem_t *sem, int pshared, unsigned int value)
100{
101	semid_t semid;
102
103	semid = (semid_t)SEM_USER;
104	if ((pshared != 0) && (ksem_init(&semid, value) != 0))
105		return (-1);
106
107	(*sem) = sem_alloc(value, semid, pshared);
108	if ((*sem) == NULL) {
109		if (pshared != 0)
110			ksem_destroy(semid);
111		return (-1);
112	}
113	return (0);
114}
115
116int
117_sem_destroy(sem_t *sem)
118{
119	int retval;
120
121	if (sem_check_validity(sem) != 0)
122		return (-1);
123
124	/*
125	 * If this is a system semaphore let the kernel track it otherwise
126	 * make sure there are no waiters.
127	 */
128	if ((*sem)->syssem != 0)
129		retval = ksem_destroy((*sem)->semid);
130	else {
131		retval = 0;
132		(*sem)->magic = 0;
133	}
134	if (retval == 0)
135		free(*sem);
136	return (retval);
137}
138
139int
140_sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
141{
142	int retval;
143
144	if (sem_check_validity(sem) != 0)
145		return (-1);
146
147	if ((*sem)->syssem != 0)
148		retval = ksem_getvalue((*sem)->semid, sval);
149        else {
150		*sval = (int)(*sem)->count;
151		retval = 0;
152	}
153	return (retval);
154}
155
156int
157_sem_trywait(sem_t *sem)
158{
159	int val;
160
161	if (sem_check_validity(sem) != 0)
162		return (-1);
163
164	if ((*sem)->syssem != 0)
165 		return (ksem_trywait((*sem)->semid));
166
167	while ((val = (*sem)->count) > 0) {
168		if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
169			return (0);
170	}
171	errno = EAGAIN;
172	return (-1);
173}
174
175static void
176sem_cancel_handler(void *arg)
177{
178	sem_t *sem = arg;
179
180	atomic_add_int(&(*sem)->nwaiters, -1);
181}
182
183int
184_sem_wait(sem_t *sem)
185{
186	struct pthread *curthread;
187	int val, retval;
188
189	if (sem_check_validity(sem) != 0)
190		return (-1);
191
192	curthread = _get_curthread();
193	if ((*sem)->syssem != 0) {
194		_thr_cancel_enter(curthread);
195		retval = ksem_wait((*sem)->semid);
196		_thr_cancel_leave(curthread);
197		return (retval);
198	}
199
200	_pthread_testcancel();
201	do {
202		atomic_add_int(&(*sem)->nwaiters, 1);
203		while ((val = (*sem)->count) > 0) {
204			if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1)) {
205				atomic_add_int(&(*sem)->nwaiters, -1);
206				return (0);
207			}
208		}
209		THR_CLEANUP_PUSH(curthread, sem_cancel_handler, sem);
210		_thr_cancel_enter(curthread);
211		retval = _thr_umtx_wait_uint(&(*sem)->count, 0, NULL);
212		atomic_add_int(&(*sem)->nwaiters, -1);
213		_thr_cancel_leave(curthread);
214		THR_CLEANUP_POP(curthread, 0);
215	} while (retval == 0);
216	errno = retval;
217	return (-1);
218}
219
220int
221_sem_timedwait(sem_t * __restrict sem,
222    const struct timespec * __restrict abstime)
223{
224	struct timespec ts, ts2;
225	struct pthread *curthread;
226	int val, retval;
227
228	if (sem_check_validity(sem) != 0)
229		return (-1);
230
231	curthread = _get_curthread();
232	if ((*sem)->syssem != 0) {
233		_thr_cancel_enter(curthread);
234		retval = ksem_timedwait((*sem)->semid, abstime);
235		_thr_cancel_leave(curthread);
236		return (retval);
237	}
238
239	/*
240	 * The timeout argument is only supposed to
241	 * be checked if the thread would have blocked.
242	 */
243	_pthread_testcancel();
244	do {
245		atomic_add_int(&(*sem)->nwaiters, 1);
246		while ((val = (*sem)->count) > 0) {
247			if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1)) {
248				atomic_add_int(&(*sem)->nwaiters, -1);
249				return (0);
250			}
251		}
252		if (abstime == NULL) {
253			atomic_add_int(&(*sem)->nwaiters, -1);
254			errno = EINVAL;
255			return (-1);
256		}
257		THR_CLEANUP_PUSH(curthread, sem_cancel_handler, sem);
258		clock_gettime(CLOCK_REALTIME, &ts);
259		TIMESPEC_SUB(&ts2, abstime, &ts);
260		_thr_cancel_enter(curthread);
261		retval = _thr_umtx_wait_uint(&(*sem)->count, 0, &ts2);
262		atomic_add_int(&(*sem)->nwaiters, -1);
263		_thr_cancel_leave(curthread);
264		THR_CLEANUP_POP(curthread, 0);
265	} while (retval == 0);
266	errno = retval;
267	return (-1);
268}
269
270int
271_sem_post(sem_t *sem)
272{
273	int val, retval = 0;
274
275	if (sem_check_validity(sem) != 0)
276		return (-1);
277
278	if ((*sem)->syssem != 0)
279		return (ksem_post((*sem)->semid));
280
281	/*
282	 * sem_post() is required to be safe to call from within
283	 * signal handlers, these code should work as that.
284	 */
285	do {
286		val = (*sem)->count;
287	} while (!atomic_cmpset_rel_int(&(*sem)->count, val, val + 1));
288
289	if ((*sem)->nwaiters) {
290		retval = _thr_umtx_wake(&(*sem)->count, val + 1);
291		if (retval > 0)
292			retval = 0;
293	}
294	return (retval);
295}
296