/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2000-2002 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Apache" and "Apache Software Foundation" must
* not be used to endorse or promote products derived from this
* software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* nor may "Apache" appear in their name, without prior written
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*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* .
*/
#include "apr_general.h"
#include "apr_lib.h"
#include "apr_strings.h"
#include "apr_portable.h"
#include "thread_rwlock.h"
#include "fileio.h"
#include
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)