thr_pspinlock.c revision 149691 
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/libkse/thread/thr_pspinlock.c 149691 2005-09-01 15:21:23Z stefanf $
27 */
28
29#include <sys/types.h>
30#include <errno.h>
31#include <pthread.h>
32#include <stdint.h>
33#include <stdlib.h>
34
35#include "atomic_ops.h"
36#include "thr_private.h"
37
38#define SPIN_COUNT 10000
39
40__weak_reference(_pthread_spin_init, pthread_spin_init);
41__weak_reference(_pthread_spin_destroy, pthread_spin_destroy);
42__weak_reference(_pthread_spin_trylock, pthread_spin_trylock);
43__weak_reference(_pthread_spin_lock, pthread_spin_lock);
44__weak_reference(_pthread_spin_unlock, pthread_spin_unlock);
45
46int
47_pthread_spin_init(pthread_spinlock_t *lock, int pshared)
48{
49	struct pthread_spinlock	*lck;
50	int ret;
51
52	if (lock == NULL || pshared != PTHREAD_PROCESS_PRIVATE)
53		ret = EINVAL;
54	else if ((lck = malloc(sizeof(struct pthread_spinlock))) == NULL)
55		ret = ENOMEM;
56	else {
57		lck->s_lock = 0;
58		lck->s_owner= NULL;
59		*lock = lck;
60		ret = 0;
61	}
62
63	return (ret);
64}
65
66int
67_pthread_spin_destroy(pthread_spinlock_t *lock)
68{
69	int ret;
70
71	if (lock == NULL || *lock == NULL)
72		ret = EINVAL;
73	else if ((*lock)->s_owner != NULL)
74		ret = EBUSY;
75	else {
76		free(*lock);
77		*lock = NULL;
78		ret = 0;
79	}
80
81	return (ret);
82}
83
84int
85_pthread_spin_trylock(pthread_spinlock_t *lock)
86{
87	struct pthread_spinlock	*lck;
88	struct pthread *self = _pthread_self();
89	int oldval, ret;
90
91	if (lock == NULL || (lck = *lock) == NULL)
92		ret = EINVAL;
93	else if (lck->s_owner == self)
94		ret = EDEADLK;
95	else if (lck->s_lock != 0)
96		ret = EBUSY;
97	else {
98		atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
99		if (oldval)
100			ret = EBUSY;
101		else {
102			lck->s_owner = _pthread_self();
103			ret = 0;
104		}
105	}
106	return (ret);
107}
108
109int
110_pthread_spin_lock(pthread_spinlock_t *lock)
111{
112	struct pthread_spinlock	*lck;
113	struct pthread *self = _pthread_self();
114	int count, oldval, ret;
115
116	if (lock == NULL || (lck = *lock) == NULL)
117		ret = EINVAL;
118	else if (lck->s_owner == self)
119		ret = EDEADLK;
120	else {
121		do {
122			count = SPIN_COUNT;
123			while (lck->s_lock) {
124#ifdef __i386__
125				/* tell cpu we are spinning */
126				__asm __volatile("pause");
127#endif
128				if (--count <= 0) {
129					count = SPIN_COUNT;
130					_pthread_yield();
131				}
132			}
133			atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
134		} while (oldval);
135
136		lck->s_owner = self;
137		ret = 0;
138	}
139
140	return (ret);
141}
142
143int
144_pthread_spin_unlock(pthread_spinlock_t *lock)
145{
146	struct pthread_spinlock	*lck;
147	int ret;
148
149	if (lock == NULL || (lck = *lock) == NULL)
150		ret = EINVAL;
151	else {
152		if (lck->s_owner != _pthread_self())
153			ret = EPERM;
154		else {
155			lck->s_owner = NULL;
156			atomic_swap_int((int *)&lck->s_lock, 0, &ret);
157			ret = 0;
158		}
159	}
160
161	return (ret);
162}
163
164