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/* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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#include "apr_general.h"
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#include "apr_strings.h"
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#include "apr_portable.h"
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#include "apr_arch_thread_rwlock.h"
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#include "apr_arch_file_io.h"
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static apr_status_t thread_rwlock_cleanup(void *therwlock)
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apr_thread_rwlock_t *rwlock = therwlock;
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return apr_thread_rwlock_destroy(rwlock);
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APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
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apr_thread_rwlock_t *new_rwlock;
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new_rwlock = (apr_thread_rwlock_t *)apr_palloc(pool, sizeof(apr_thread_rwlock_t));
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new_rwlock->pool = pool;
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new_rwlock->readers = 0;
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rc = DosCreateMutexSem(NULL, &(new_rwlock->write_lock), 0, FALSE);
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return APR_FROM_OS_ERROR(rc);
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rc = DosCreateEventSem(NULL, &(new_rwlock->read_done), 0, FALSE);
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return APR_FROM_OS_ERROR(rc);
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apr_pool_cleanup_register(pool, new_rwlock, thread_rwlock_cleanup,
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apr_pool_cleanup_null);
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return APR_FROM_OS_ERROR(rc);
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APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock)
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rc = DosRequestMutexSem(rwlock->write_lock, SEM_INDEFINITE_WAIT);
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return APR_FROM_OS_ERROR(rc);
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/* We've successfully acquired the writer mutex so we can't be locked
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* for write which means it's ok to add a reader lock. The writer mutex
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* doubles as race condition protection for the readers counter.
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DosResetEventSem(rwlock->read_done, &posts);
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rc = DosReleaseMutexSem(rwlock->write_lock);
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return APR_FROM_OS_ERROR(rc);
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APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock)
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/* As above but with different wait time */
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rc = DosRequestMutexSem(rwlock->write_lock, SEM_IMMEDIATE_RETURN);
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return APR_FROM_OS_ERROR(rc);
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DosResetEventSem(rwlock->read_done, &posts);
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rc = DosReleaseMutexSem(rwlock->write_lock);
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return APR_FROM_OS_ERROR(rc);
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APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock)
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rc = DosRequestMutexSem(rwlock->write_lock, SEM_INDEFINITE_WAIT);
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return APR_FROM_OS_ERROR(rc);
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/* We've got the writer lock but we have to wait for all readers to
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* unlock before it's ok to use it
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if (rwlock->readers) {
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rc = DosWaitEventSem(rwlock->read_done, SEM_INDEFINITE_WAIT);
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DosReleaseMutexSem(rwlock->write_lock);
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return APR_FROM_OS_ERROR(rc);
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APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock)
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rc = DosRequestMutexSem(rwlock->write_lock, SEM_IMMEDIATE_RETURN);
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return APR_FROM_OS_ERROR(rc);
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/* We've got the writer lock but we have to wait for all readers to
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* unlock before it's ok to use it
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if (rwlock->readers) {
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/* There are readers active, give up */
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DosReleaseMutexSem(rwlock->write_lock);
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return APR_FROM_OS_ERROR(rc);
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APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock)
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/* First, guess that we're unlocking a writer */
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rc = DosReleaseMutexSem(rwlock->write_lock);
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if (rc == ERROR_NOT_OWNER) {
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/* Nope, we must have a read lock */
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if (rwlock->readers) {
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if (rwlock->readers == 0) {
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DosPostEventSem(rwlock->read_done);
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return APR_FROM_OS_ERROR(rc);
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APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock)
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if (rwlock->write_lock == 0)
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while (DosReleaseMutexSem(rwlock->write_lock) == 0);
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rc = DosCloseMutexSem(rwlock->write_lock);
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rwlock->write_lock = 0;
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DosCloseEventSem(rwlock->read_done);
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return APR_FROM_OS_ERROR(rc);
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APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock)