pthread_mutex.c revision 1.1.2.11 1 /* $NetBSD: pthread_mutex.c,v 1.1.2.11 2002/04/26 17:45:57 nathanw Exp $ */
2
3 /*-
4 * Copyright (c) 2001 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Nathan J. Williams.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the NetBSD
21 * Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 * contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39 #include <assert.h>
40 #include <errno.h>
41 #include <sys/cdefs.h>
42
43 #include "pthread.h"
44 #include "pthread_int.h"
45
46
47 int
48 pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
49 {
50
51 #ifdef ERRORCHECK
52 if ((mutex == NULL) ||
53 (attr && (attr->ptma_magic != _PT_MUTEXATTR_MAGIC)))
54 return EINVAL;
55 #endif
56
57 mutex->ptm_magic = _PT_MUTEX_MAGIC;
58 mutex->ptm_owner = NULL;
59 pthread_lockinit(&mutex->ptm_lock);
60 pthread_lockinit(&mutex->ptm_interlock);
61 PTQ_INIT(&mutex->ptm_blocked);
62
63 return 0;
64 }
65
66
67 int
68 pthread_mutex_destroy(pthread_mutex_t *mutex)
69 {
70
71 #ifdef ERRORCHECK
72 if ((mutex == NULL) ||
73 (mutex->ptm_magic != _PT_MUTEX_MAGIC) ||
74 (mutex->ptm_lock != __SIMPLELOCK_UNLOCKED))
75 return EINVAL;
76 #endif
77
78 mutex->ptm_magic = _PT_MUTEX_DEAD;
79
80 return 0;
81 }
82
83
84 /*
85 * Note regarding memory visibility: Pthreads has rules about memory
86 * visibility and mutexes. Very roughly: Memory a thread can see when
87 * it unlocks a mutex can be seen by another thread that locks the
88 * same mutex.
89 *
90 * A memory barrier after a lock and before an unlock will provide
91 * this behavior. This code relies on __cpu_simple_lock_try() to issue
92 * a barrier after obtaining a lock, and on __cpu_simple_unlock() to
93 * issue a barrier before releasing a lock.
94 */
95
96 int
97 pthread_mutex_lock(pthread_mutex_t *mutex)
98 {
99 pthread_t self;
100
101 #ifdef ERRORCHECK
102 if ((mutex == NULL) || (mutex->ptm_magic != _PT_MUTEX_MAGIC))
103 return EINVAL;
104 #endif
105 self = pthread__self();
106
107 while (/*CONSTCOND*/1) {
108 if (__cpu_simple_lock_try(&mutex->ptm_lock))
109 break; /* got it! */
110
111 /* Okay, didn't look free. Get the interlock... */
112 pthread_spinlock(self, &mutex->ptm_interlock);
113 /* The mutex_unlock routine will get the interlock
114 * before looking at the list of sleepers, so if the
115 * lock is held we can safely put ourselves on the
116 * sleep queue. If it's not held, we can try taking it
117 * again.
118 */
119 if (mutex->ptm_lock == __SIMPLELOCK_LOCKED) {
120 PTQ_INSERT_TAIL(&mutex->ptm_blocked, self, pt_sleep);
121 /* Locking a mutex is not a cancellation
122 * point, so we don't need to do the
123 * test-cancellation dance. We may get woken
124 * up spuriously by pthread_cancel, though,
125 * but it's okay since we're just going to
126 * retry.
127 */
128 pthread_spinlock(self, &self->pt_statelock);
129 self->pt_state = PT_STATE_BLOCKED_QUEUE;
130 self->pt_sleepobj = mutex;
131 self->pt_sleepq = &mutex->ptm_blocked;
132 self->pt_sleeplock = &mutex->ptm_interlock;
133 pthread_spinunlock(self, &self->pt_statelock);
134
135 pthread__block(self, &mutex->ptm_interlock);
136 /* interlock is not held when we return */
137 } else {
138 pthread_spinunlock(self, &mutex->ptm_interlock);
139 }
140 /* Go around for another try. */
141 }
142
143 /* We have the lock! */
144 #ifdef ERRORCHECK
145 mutex->ptm_owner = self;
146 #endif
147 return 0;
148 }
149
150
151 int
152 pthread_mutex_trylock(pthread_mutex_t *mutex)
153 {
154
155 #ifdef ERRORCHECK
156 if ((mutex == NULL) || (mutex->ptm_magic != _PT_MUTEX_MAGIC))
157 return EINVAL;
158 #endif
159
160 if (__cpu_simple_lock_try(&mutex->ptm_lock) == 0)
161 return EBUSY;
162
163 #ifdef ERRORCHECK
164 mutex->ptm_owner = pthread__self();
165 #endif
166 return 0;
167 }
168
169
170 int
171 pthread_mutex_unlock(pthread_mutex_t *mutex)
172 {
173 pthread_t self, blocked;
174
175 self = pthread__self();
176
177 #ifdef ERRORCHECK
178 if ((mutex == NULL) || (mutex->ptm_magic != _PT_MUTEX_MAGIC))
179 return EINVAL;
180
181 if (mutex->ptm_lock != __SIMPLELOCK_LOCKED)
182 return EPERM; /* Not exactly the right error. */
183
184 /* One is only permitted to unlock one's own mutexes. */
185 if (mutex->ptm_owner != self)
186 return EPERM;
187 #endif
188
189 pthread_spinlock(self, &mutex->ptm_interlock);
190 blocked = PTQ_FIRST(&mutex->ptm_blocked);
191 if (blocked)
192 PTQ_REMOVE(&mutex->ptm_blocked, blocked, pt_sleep);
193 #ifdef ERRORCHECK
194 mutex->ptm_owner = NULL;
195 #endif
196 __cpu_simple_unlock(&mutex->ptm_lock);
197 pthread_spinunlock(self, &mutex->ptm_interlock);
198
199 /* Give the head of the blocked queue another try. */
200 if (blocked)
201 pthread__sched(self, blocked);
202
203 return 0;
204 }
205
206 int
207 pthread_mutexattr_init(pthread_mutexattr_t *attr)
208 {
209
210 #ifdef ERRORCHECK
211 if (attr == NULL)
212 return EINVAL;
213 #endif
214
215 attr->ptma_magic = _PT_MUTEXATTR_MAGIC;
216
217 return 0;
218 }
219
220
221 int
222 pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
223 {
224
225 #ifdef ERRORCHECK
226 if ((attr == NULL) ||
227 (attr->ptma_magic != _PT_MUTEXATTR_MAGIC))
228 return EINVAL;
229 #endif
230
231 attr->ptma_magic = _PT_MUTEXATTR_DEAD;
232
233 return 0;
234 }
235
236
237 int
238 pthread_once(pthread_once_t *once_control, void (*routine)(void))
239 {
240
241 if (once_control->pto_done == 0) {
242 pthread_mutex_lock(&once_control->pto_mutex);
243 if (once_control->pto_done == 0) {
244 routine();
245 once_control->pto_done = 1;
246 }
247 pthread_mutex_unlock(&once_control->pto_mutex);
248 }
249
250 return 0;
251 }
252