1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements. See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License. You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 /*Read/Write locking implementation based on the MultiLock code from
18 * Stephen Beaulieu <hippo@be.com>
21 #include "beos/apr_arch_thread_rwlock.h"
22 #include "apr_strings.h"
23 #include "apr_portable.h"
25 #define BIG_NUM 100000
27 static apr_status_t _thread_rw_cleanup(void * data)
29 apr_thread_rwlock_t *mutex = (apr_thread_rwlock_t*)data;
31 if (mutex->ReadCount != 0) {
32 while (atomic_add(&mutex->ReadCount , -1) > 1){
33 release_sem (mutex->Read);
36 if (mutex->WriteCount != 0) {
37 while (atomic_add(&mutex->WriteCount , -1) > 1){
38 release_sem (mutex->Write);
41 if (mutex->LockCount != 0) {
42 while (atomic_add(&mutex->LockCount , -1) > 1){
43 release_sem (mutex->Lock);
47 delete_sem(mutex->Read);
48 delete_sem(mutex->Write);
49 delete_sem(mutex->Lock);
53 APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
56 apr_thread_rwlock_t *new;
58 new = (apr_thread_rwlock_t *)apr_pcalloc(pool, sizeof(apr_thread_rwlock_t));
64 /* we need to make 3 locks... */
68 new->Read = create_sem(0, "APR_ReadLock");
69 new->Write = create_sem(0, "APR_WriteLock");
70 new->Lock = create_sem(0, "APR_Lock");
72 if (new->Lock < 0 || new->Read < 0 || new->Write < 0) {
73 _thread_rw_cleanup(new);
77 apr_pool_cleanup_register(new->pool, (void *)new, _thread_rw_cleanup,
78 apr_pool_cleanup_null);
83 APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock)
85 int32 rv = APR_SUCCESS;
87 if (find_thread(NULL) == rwlock->writer) {
88 /* we're the writer - no problem */
91 /* we're not the writer */
92 int32 r = atomic_add(&rwlock->ReadCount, 1);
94 /* Oh dear, writer holds lock, wait for sem */
95 rv = acquire_sem_etc(rwlock->Read, 1, B_DO_NOT_RESCHEDULE,
103 APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock)
108 APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock)
110 int rv = APR_SUCCESS;
112 if (find_thread(NULL) == rwlock->writer) {
115 /* we're not the writer... */
116 if (atomic_add(&rwlock->LockCount, 1) >= 1) {
117 /* we're locked - acquire the sem */
118 rv = acquire_sem_etc(rwlock->Lock, 1, B_DO_NOT_RESCHEDULE,
121 if (rv == APR_SUCCESS) {
122 /* decrement the ReadCount to a large -ve number so that
123 * we block on new readers...
125 int32 readers = atomic_add(&rwlock->ReadCount, -BIG_NUM);
127 /* readers are holding the lock */
128 rv = acquire_sem_etc(rwlock->Write, readers, B_DO_NOT_RESCHEDULE,
131 if (rv == APR_SUCCESS)
132 rwlock->writer = find_thread(NULL);
139 APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock)
144 APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock)
146 apr_status_t rv = APR_SUCCESS;
149 /* we know we hold the lock, so don't check it :) */
150 if (find_thread(NULL) == rwlock->writer) {
151 /* we know we hold the lock, so don't check it :) */
152 if (rwlock->Nested > 1) {
153 /* we're recursively locked */
157 /* OK so we need to release the sem if we have it :) */
158 readers = atomic_add(&rwlock->ReadCount, BIG_NUM) + BIG_NUM;
160 rv = release_sem_etc(rwlock->Read, readers, B_DO_NOT_RESCHEDULE);
162 if (rv == APR_SUCCESS) {
164 if (atomic_add(&rwlock->LockCount, -1) > 1) {
165 rv = release_sem_etc(rwlock->Lock, 1, B_DO_NOT_RESCHEDULE);
169 /* We weren't the Writer, so just release the ReadCount... */
170 if (atomic_add(&rwlock->ReadCount, -1) < 0) {
171 /* we have a writer waiting for the lock, so release it */
172 rv = release_sem_etc(rwlock->Write, 1, B_DO_NOT_RESCHEDULE);
179 APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock)
182 if ((stat = _thread_rw_cleanup(rwlock)) == APR_SUCCESS) {
183 apr_pool_cleanup_kill(rwlock->pool, rwlock, _thread_rw_cleanup);
189 APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock)