thr_pspinlock.c revision 144518 
1/*-
2 * Copyright (c) 2003 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, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: head/lib/libthr/thread/thr_pspinlock.c 144518 2005-04-02 01:20:00Z davidxu $
27 */
28
29#include <errno.h>
30#include <stdlib.h>
31#include <pthread.h>
32#include "thr_private.h"
33
34#define SPIN_COUNT 100000
35
36__weak_reference(_pthread_spin_init, pthread_spin_init);
37__weak_reference(_pthread_spin_destroy, pthread_spin_destroy);
38__weak_reference(_pthread_spin_trylock, pthread_spin_trylock);
39__weak_reference(_pthread_spin_lock, pthread_spin_lock);
40__weak_reference(_pthread_spin_unlock, pthread_spin_unlock);
41
42int
43_pthread_spin_init(pthread_spinlock_t *lock, int pshared)
44{
45	struct pthread_spinlock	*lck;
46	int ret;
47
48	if (lock == NULL || pshared != PTHREAD_PROCESS_PRIVATE)
49		ret = EINVAL;
50	else if ((lck = malloc(sizeof(struct pthread_spinlock))) == NULL)
51		ret = ENOMEM;
52	else {
53		_thr_umtx_init(&lck->s_lock);
54		*lock = lck;
55		ret = 0;
56	}
57
58	return (ret);
59}
60
61int
62_pthread_spin_destroy(pthread_spinlock_t *lock)
63{
64	int ret;
65
66	if (lock == NULL || *lock == NULL)
67		ret = EINVAL;
68	else {
69		free(*lock);
70		*lock = NULL;
71		ret = 0;
72	}
73
74	return (ret);
75}
76
77int
78_pthread_spin_trylock(pthread_spinlock_t *lock)
79{
80	struct pthread *curthread = _get_curthread();
81	struct pthread_spinlock	*lck;
82	int ret;
83
84	if (lock == NULL || (lck = *lock) == NULL)
85		ret = EINVAL;
86	else
87		ret = THR_UMTX_TRYLOCK(curthread, &lck->s_lock);
88	return (ret);
89}
90
91int
92_pthread_spin_lock(pthread_spinlock_t *lock)
93{
94	struct pthread *curthread = _get_curthread();
95	struct pthread_spinlock	*lck;
96	int ret, count;
97
98	if (lock == NULL || (lck = *lock) == NULL)
99		ret = EINVAL;
100	else {
101		count = SPIN_COUNT;
102		while ((ret = THR_UMTX_TRYLOCK(curthread, &lck->s_lock)) != 0) {
103			while (lck->s_lock) {
104#ifdef __i386__
105				/* tell cpu we are spinning */
106				__asm __volatile("pause");
107#endif
108				if (--count <= 0) {
109					count = SPIN_COUNT;
110					_pthread_yield();
111				}
112			}
113		}
114		ret = 0;
115	}
116
117	return (ret);
118}
119
120int
121_pthread_spin_unlock(pthread_spinlock_t *lock)
122{
123	struct pthread *curthread = _get_curthread();
124	struct pthread_spinlock	*lck;
125	int ret;
126
127	if (lock == NULL || (lck = *lock) == NULL)
128		ret = EINVAL;
129	else {
130		ret = THR_UMTX_UNLOCK(curthread, &lck->s_lock);
131	}
132	return (ret);
133}
134