thr_pspinlock.c revision 122071 
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 122071 2003-11-04 19:56:12Z deischen $
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
37__weak_reference(_pthread_spin_init, pthread_spin_init);
38__weak_reference(_pthread_spin_destroy, pthread_spin_destroy);
39__weak_reference(_pthread_spin_trylock, pthread_spin_trylock);
40__weak_reference(_pthread_spin_lock, pthread_spin_lock);
41__weak_reference(_pthread_spin_unlock, pthread_spin_unlock);
42
43int
44_pthread_spin_init(pthread_spinlock_t *lock, int pshared)
45{
46	struct pthread_spinlock	*lck;
47	int ret;
48
49	if (lock == NULL || pshared != PTHREAD_PROCESS_PRIVATE)
50		ret = EINVAL;
51	else if ((lck = malloc(sizeof(struct pthread_spinlock))) == NULL)
52		ret = ENOMEM;
53	else {
54		lck->s_lock = 0;
55		lck->s_owner= NULL;
56		*lock = lck;
57		ret = 0;
58	}
59
60	return (ret);
61}
62
63int
64_pthread_spin_destroy(pthread_spinlock_t *lock)
65{
66	int ret;
67
68	if (lock == NULL || *lock == NULL)
69		ret = EINVAL;
70	else if ((*lock)->s_owner != NULL)
71		ret = EBUSY;
72	else {
73		free(*lock);
74		*lock = NULL;
75		ret = 0;
76	}
77
78	return (ret);
79}
80
81int
82_pthread_spin_trylock(pthread_spinlock_t *lock)
83{
84	struct pthread_spinlock	*lck;
85	struct pthread *self = _pthread_self();
86	int oldval, ret;
87
88	if (lock == NULL || (lck = *lock) == NULL)
89		ret = EINVAL;
90	else if (lck->s_owner == self)
91		ret = EDEADLK;
92	else if (lck->s_lock != 0)
93		ret = EBUSY;
94	else {
95		atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
96		if (oldval)
97			ret = EBUSY;
98		else {
99			lck->s_owner = _pthread_self();
100			ret = 0;
101		}
102	}
103	return (ret);
104}
105
106int
107_pthread_spin_lock(pthread_spinlock_t *lock)
108{
109	struct pthread_spinlock	*lck;
110	struct pthread *self = _pthread_self();
111	int count, oldval, ret;
112
113	if (lock == NULL || (lck = *lock) == NULL)
114		ret = EINVAL;
115	else if (lck->s_owner == self)
116		ret = EDEADLK;
117	else {
118		do {
119			count = SPIN_COUNT;
120			while (lck->s_lock) {
121#ifdef __i386__
122				/* tell cpu we are spinning */
123				__asm __volatile("pause");
124#endif
125				if (--count <= 0) {
126					count = SPIN_COUNT;
127					_pthread_yield();
128				}
129			}
130			atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
131		} while (oldval);
132
133		lck->s_owner = self;
134		ret = 0;
135	}
136
137	return (ret);
138}
139
140int
141_pthread_spin_unlock(pthread_spinlock_t *lock)
142{
143	struct pthread_spinlock	*lck;
144	int ret;
145
146	if (lock == NULL || (lck = *lock) == NULL)
147		ret = EINVAL;
148	else {
149		if (lck->s_owner != _pthread_self())
150			ret = EPERM;
151		else {
152			lck->s_owner = NULL;
153			atomic_swap_int((int *)&lck->s_lock, 0, &ret);
154			ret = 0;
155		}
156	}
157
158	return (ret);
159}
160
161