thr_pspinlock.c revision 119909 
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 119909 2003-09-09 06:57:51Z davidxu $
27 */
28
29#include <errno.h>
30#include <stdlib.h>
31#include <pthread.h>
32#include <atomic_ops.h>
33#include "thr_private.h"
34
35#define SPIN_COUNT 10000
36
37int
38pthread_spin_init(pthread_spinlock_t *lock, int pshared)
39{
40	struct pthread_spinlock	*lck;
41	int ret;
42
43	if (lock == NULL || pshared != PTHREAD_PROCESS_PRIVATE)
44		ret = EINVAL;
45	else if ((lck = malloc(sizeof(struct pthread_spinlock))) == NULL)
46		ret = ENOMEM;
47	else {
48		lck->s_lock = 0;
49		lck->s_owner= NULL;
50		*lock = lck;
51		ret = 0;
52	}
53
54	return (ret);
55}
56
57int
58pthread_spin_destroy(pthread_spinlock_t *lock)
59{
60	int ret;
61
62	if (lock == NULL || *lock == NULL)
63		ret = EINVAL;
64	else if ((*lock)->s_owner != NULL)
65		ret = EBUSY;
66	else {
67		free(*lock);
68		*lock = NULL;
69		ret = 0;
70	}
71
72	return (ret);
73}
74
75int
76pthread_spin_trylock(pthread_spinlock_t *lock)
77{
78	struct pthread_spinlock	*lck;
79	struct pthread *self = _pthread_self();
80	int oldval, ret;
81
82	if (lock == NULL || (lck = *lock) == NULL)
83		ret = EINVAL;
84	else if (lck->s_owner == self)
85		ret = EDEADLK;
86	else if (lck->s_lock != 0)
87		ret = EBUSY;
88	else {
89		atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
90		if (oldval)
91			ret = EBUSY;
92		else {
93			lck->s_owner = _pthread_self();
94			ret = 0;
95		}
96	}
97	return (ret);
98}
99
100int
101pthread_spin_lock(pthread_spinlock_t *lock)
102{
103	struct pthread_spinlock	*lck;
104	struct pthread *self = _pthread_self();
105	int count, oldval, ret;
106
107	if (lock == NULL || (lck = *lock) == NULL)
108		ret = EINVAL;
109	else if (lck->s_owner == self)
110		ret = EDEADLK;
111	else {
112		do {
113			count = SPIN_COUNT;
114			while (lck->s_lock) {
115#ifdef __i386__
116				/* tell cpu we are spinning */
117				__asm __volatile("pause");
118#endif
119				if (--count <= 0) {
120					count = SPIN_COUNT;
121					_pthread_yield();
122				}
123			}
124			atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
125		} while (oldval);
126
127		lck->s_owner = self;
128		ret = 0;
129	}
130
131	return (ret);
132}
133
134int
135pthread_spin_unlock(pthread_spinlock_t *lock)
136{
137	struct pthread_spinlock	*lck;
138	int ret;
139
140	if (lock == NULL || (lck = *lock) == NULL)
141		ret = EINVAL;
142	else {
143		if (lck->s_owner != _pthread_self())
144			ret = EPERM;
145		else {
146			lck->s_owner = NULL;
147			atomic_swap_int((int *)&lck->s_lock, 0, &ret);
148			ret = 0;
149		}
150	}
151
152	return (ret);
153}
154
155