| /* Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| /*Read/Write locking implementation based on the MultiLock code from |
| * Stephen Beaulieu <hippo@be.com> |
| */ |
| |
| #include "apr_arch_thread_rwlock.h" |
| #include "apr_strings.h" |
| #include "apr_portable.h" |
| |
| #define BIG_NUM 100000 |
| |
| static apr_status_t _thread_rw_cleanup(void * data) |
| { |
| apr_thread_rwlock_t *mutex = (apr_thread_rwlock_t*)data; |
| |
| if (mutex->ReadCount != 0) { |
| while (atomic_add(&mutex->ReadCount , -1) > 1){ |
| release_sem (mutex->Read); |
| } |
| } |
| if (mutex->WriteCount != 0) { |
| while (atomic_add(&mutex->WriteCount , -1) > 1){ |
| release_sem (mutex->Write); |
| } |
| } |
| if (mutex->LockCount != 0) { |
| while (atomic_add(&mutex->LockCount , -1) > 1){ |
| release_sem (mutex->Lock); |
| } |
| } |
| |
| delete_sem(mutex->Read); |
| delete_sem(mutex->Write); |
| delete_sem(mutex->Lock); |
| return APR_SUCCESS; |
| } |
| |
| APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock, |
| apr_pool_t *pool) |
| { |
| apr_thread_rwlock_t *new; |
| |
| new = (apr_thread_rwlock_t *)apr_pcalloc(pool, sizeof(apr_thread_rwlock_t)); |
| if (new == NULL){ |
| return APR_ENOMEM; |
| } |
| |
| new->pool = pool; |
| /* we need to make 3 locks... */ |
| new->ReadCount = 0; |
| new->WriteCount = 0; |
| new->LockCount = 0; |
| new->Read = create_sem(0, "APR_ReadLock"); |
| new->Write = create_sem(0, "APR_WriteLock"); |
| new->Lock = create_sem(0, "APR_Lock"); |
| |
| if (new->Lock < 0 || new->Read < 0 || new->Write < 0) { |
| _thread_rw_cleanup(new); |
| return -1; |
| } |
| |
| apr_pool_cleanup_register(new->pool, (void *)new, _thread_rw_cleanup, |
| apr_pool_cleanup_null); |
| (*rwlock) = new; |
| return APR_SUCCESS; |
| } |
| |
| APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock) |
| { |
| int32 rv = APR_SUCCESS; |
| |
| if (find_thread(NULL) == rwlock->writer) { |
| /* we're the writer - no problem */ |
| rwlock->Nested++; |
| } else { |
| /* we're not the writer */ |
| int32 r = atomic_add(&rwlock->ReadCount, 1); |
| if (r < 0) { |
| /* Oh dear, writer holds lock, wait for sem */ |
| rv = acquire_sem_etc(rwlock->Read, 1, B_DO_NOT_RESCHEDULE, |
| B_INFINITE_TIMEOUT); |
| } |
| } |
| |
| return rv; |
| } |
| |
| APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock) |
| { |
| return APR_ENOTIMPL; |
| } |
| |
| APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock) |
| { |
| int rv = APR_SUCCESS; |
| |
| if (find_thread(NULL) == rwlock->writer) { |
| rwlock->Nested++; |
| } else { |
| /* we're not the writer... */ |
| if (atomic_add(&rwlock->LockCount, 1) >= 1) { |
| /* we're locked - acquire the sem */ |
| rv = acquire_sem_etc(rwlock->Lock, 1, B_DO_NOT_RESCHEDULE, |
| B_INFINITE_TIMEOUT); |
| } |
| if (rv == APR_SUCCESS) { |
| /* decrement the ReadCount to a large -ve number so that |
| * we block on new readers... |
| */ |
| int32 readers = atomic_add(&rwlock->ReadCount, -BIG_NUM); |
| if (readers > 0) { |
| /* readers are holding the lock */ |
| rv = acquire_sem_etc(rwlock->Write, readers, B_DO_NOT_RESCHEDULE, |
| B_INFINITE_TIMEOUT); |
| } |
| if (rv == APR_SUCCESS) |
| rwlock->writer = find_thread(NULL); |
| } |
| } |
| |
| return rv; |
| } |
| |
| APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock) |
| { |
| return APR_ENOTIMPL; |
| } |
| |
| APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock) |
| { |
| apr_status_t rv = APR_SUCCESS; |
| int32 readers; |
| |
| /* we know we hold the lock, so don't check it :) */ |
| if (find_thread(NULL) == rwlock->writer) { |
| /* we know we hold the lock, so don't check it :) */ |
| if (rwlock->Nested > 1) { |
| /* we're recursively locked */ |
| rwlock->Nested--; |
| return APR_SUCCESS; |
| } |
| /* OK so we need to release the sem if we have it :) */ |
| readers = atomic_add(&rwlock->ReadCount, BIG_NUM) + BIG_NUM; |
| if (readers > 0) { |
| rv = release_sem_etc(rwlock->Read, readers, B_DO_NOT_RESCHEDULE); |
| } |
| if (rv == APR_SUCCESS) { |
| rwlock->writer = -1; |
| if (atomic_add(&rwlock->LockCount, -1) > 1) { |
| rv = release_sem_etc(rwlock->Lock, 1, B_DO_NOT_RESCHEDULE); |
| } |
| } |
| } else { |
| /* We weren't the Writer, so just release the ReadCount... */ |
| if (atomic_add(&rwlock->ReadCount, -1) < 0) { |
| /* we have a writer waiting for the lock, so release it */ |
| rv = release_sem_etc(rwlock->Write, 1, B_DO_NOT_RESCHEDULE); |
| } |
| } |
| |
| return rv; |
| } |
| |
| APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock) |
| { |
| apr_status_t stat; |
| if ((stat = _thread_rw_cleanup(rwlock)) == APR_SUCCESS) { |
| apr_pool_cleanup_kill(rwlock->pool, rwlock, _thread_rw_cleanup); |
| return APR_SUCCESS; |
| } |
| return stat; |
| } |
| |
| APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock) |
| |