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/* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
* applicable.
*
* Licensed 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.
*/
#include "apr_general.h"
#include "apr_lib.h"
#include "apr_strings.h"
#include "apr_portable.h"
#include "apr_arch_thread_rwlock.h"
#include "apr_arch_file_io.h"
#include <string.h>
static apr_status_t thread_rwlock_cleanup(void *therwlock)
{
apr_thread_rwlock_t *rwlock = therwlock;
return apr_thread_rwlock_destroy(rwlock);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
apr_pool_t *pool)
{
apr_thread_rwlock_t *new_rwlock;
ULONG rc;
new_rwlock = (apr_thread_rwlock_t *)apr_palloc(pool, sizeof(apr_thread_rwlock_t));
new_rwlock->pool = pool;
new_rwlock->readers = 0;
rc = DosCreateMutexSem(NULL, &(new_rwlock->write_lock), 0, FALSE);
if (rc)
return APR_FROM_OS_ERROR(rc);
rc = DosCreateEventSem(NULL, &(new_rwlock->read_done), 0, FALSE);
if (rc)
return APR_FROM_OS_ERROR(rc);
*rwlock = new_rwlock;
if (!rc)
apr_pool_cleanup_register(pool, new_rwlock, thread_rwlock_cleanup,
apr_pool_cleanup_null);
return APR_FROM_OS_ERROR(rc);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock)
{
ULONG rc, posts;
rc = DosRequestMutexSem(rwlock->write_lock, SEM_INDEFINITE_WAIT);
if (rc)
return APR_FROM_OS_ERROR(rc);
/* We've successfully acquired the writer mutex so we can't be locked
* for write which means it's ok to add a reader lock. The writer mutex
* doubles as race condition protection for the readers counter.
*/
rwlock->readers++;
DosResetEventSem(rwlock->read_done, &posts);
rc = DosReleaseMutexSem(rwlock->write_lock);
return APR_FROM_OS_ERROR(rc);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock)
{
/* As above but with different wait time */
ULONG rc, posts;
rc = DosRequestMutexSem(rwlock->write_lock, SEM_IMMEDIATE_RETURN);
if (rc)
return APR_FROM_OS_ERROR(rc);
rwlock->readers++;
DosResetEventSem(rwlock->read_done, &posts);
rc = DosReleaseMutexSem(rwlock->write_lock);
return APR_FROM_OS_ERROR(rc);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock)
{
ULONG rc;
rc = DosRequestMutexSem(rwlock->write_lock, SEM_INDEFINITE_WAIT);
if (rc)
return APR_FROM_OS_ERROR(rc);
/* We've got the writer lock but we have to wait for all readers to
* unlock before it's ok to use it
*/
if (rwlock->readers) {
rc = DosWaitEventSem(rwlock->read_done, SEM_INDEFINITE_WAIT);
if (rc)
DosReleaseMutexSem(rwlock->write_lock);
}
return APR_FROM_OS_ERROR(rc);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock)
{
ULONG rc;
rc = DosRequestMutexSem(rwlock->write_lock, SEM_IMMEDIATE_RETURN);
if (rc)
return APR_FROM_OS_ERROR(rc);
/* We've got the writer lock but we have to wait for all readers to
* unlock before it's ok to use it
*/
if (rwlock->readers) {
/* There are readers active, give up */
DosReleaseMutexSem(rwlock->write_lock);
rc = ERROR_TIMEOUT;
}
return APR_FROM_OS_ERROR(rc);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock)
{
ULONG rc;
/* First, guess that we're unlocking a writer */
rc = DosReleaseMutexSem(rwlock->write_lock);
if (rc == ERROR_NOT_OWNER) {
/* Nope, we must have a read lock */
if (rwlock->readers) {
DosEnterCritSec();
rwlock->readers--;
if (rwlock->readers == 0) {
DosPostEventSem(rwlock->read_done);
}
DosExitCritSec();
rc = 0;
}
}
return APR_FROM_OS_ERROR(rc);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock)
{
ULONG rc;
if (rwlock->write_lock == 0)
return APR_SUCCESS;
while (DosReleaseMutexSem(rwlock->write_lock) == 0);
rc = DosCloseMutexSem(rwlock->write_lock);
if (!rc) {
rwlock->write_lock = 0;
DosCloseEventSem(rwlock->read_done);
return APR_SUCCESS;
}
return APR_FROM_OS_ERROR(rc);
}
APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock)
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