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: src/lib/libpthread/thread/thr_pspinlock.c,v 1.2 2003/11/04 19:56:12 deischen Exp $
27  * $DragonFly: src/lib/libthread_xu/thread/thr_pspinlock.c,v 1.2 2005/03/29 19:26:20 joerg Exp $
28  */
29 
30 #include <machine/tls.h>
31 
32 #include <errno.h>
33 #include <stdlib.h>
34 #include <pthread.h>
35 #include "thr_private.h"
36 
37 #define SPIN_COUNT 100000
38 
39 __weak_reference(_pthread_spin_init, pthread_spin_init);
40 __weak_reference(_pthread_spin_destroy, pthread_spin_destroy);
41 __weak_reference(_pthread_spin_trylock, pthread_spin_trylock);
42 __weak_reference(_pthread_spin_lock, pthread_spin_lock);
43 __weak_reference(_pthread_spin_unlock, pthread_spin_unlock);
44 
45 int
46 _pthread_spin_init(pthread_spinlock_t *lock, int pshared)
47 {
48 	struct pthread_spinlock	*lck;
49 	int ret;
50 
51 	if (lock == NULL || pshared != PTHREAD_PROCESS_PRIVATE)
52 		ret = EINVAL;
53 	else if ((lck = malloc(sizeof(struct pthread_spinlock))) == NULL)
54 		ret = ENOMEM;
55 	else {
56 		_thr_umtx_init(&lck->s_lock);
57 		*lock = lck;
58 		ret = 0;
59 	}
60 
61 	return (ret);
62 }
63 
64 int
65 _pthread_spin_destroy(pthread_spinlock_t *lock)
66 {
67 	int ret;
68 
69 	if (lock == NULL || *lock == NULL)
70 		ret = EINVAL;
71 	else {
72 		free(*lock);
73 		*lock = NULL;
74 		ret = 0;
75 	}
76 
77 	return (ret);
78 }
79 
80 int
81 _pthread_spin_trylock(pthread_spinlock_t *lock)
82 {
83 	struct pthread *curthread = tls_get_curthread();
84 	struct pthread_spinlock	*lck;
85 	int ret;
86 
87 	if (lock == NULL || (lck = *lock) == NULL)
88 		ret = EINVAL;
89 	else
90 		ret = THR_UMTX_TRYLOCK(curthread, &lck->s_lock);
91 	return (ret);
92 }
93 
94 int
95 _pthread_spin_lock(pthread_spinlock_t *lock)
96 {
97 	struct pthread *curthread = tls_get_curthread();
98 	struct pthread_spinlock	*lck;
99 	int ret, count;
100 
101 	if (lock == NULL || (lck = *lock) == NULL)
102 		ret = EINVAL;
103 	else {
104 		count = SPIN_COUNT;
105 		while ((ret = THR_UMTX_TRYLOCK(curthread, &lck->s_lock)) != 0) {
106 			while (lck->s_lock) {
107 #ifdef __i386__
108 				/* tell cpu we are spinning */
109 				__asm __volatile("pause");
110 #endif
111 				if (--count <= 0) {
112 					count = SPIN_COUNT;
113 					_pthread_yield();
114 				}
115 			}
116 		}
117 		ret = 0;
118 	}
119 
120 	return (ret);
121 }
122 
123 int
124 _pthread_spin_unlock(pthread_spinlock_t *lock)
125 {
126 	struct pthread *curthread = tls_get_curthread();
127 	struct pthread_spinlock	*lck;
128 	int ret;
129 
130 	if (lock == NULL || (lck = *lock) == NULL)
131 		ret = EINVAL;
132 	else {
133 		ret = THR_UMTX_UNLOCK(curthread, &lck->s_lock);
134 	}
135 	return (ret);
136 }
137