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/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2000-2003 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
* permission of the Apache Software Foundation.
*
* 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,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* 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
* <http://www.apache.org/>.
*/
#include "apr.h"
#include "apr_private.h"
#include "apr_general.h"
#include "apr_strings.h"
#include "win32/apr_arch_thread_rwlock.h"
#include "apr_portable.h"
static apr_status_t thread_rwlock_cleanup(void *data)
{
return apr_thread_rwlock_destroy((apr_thread_rwlock_t *) data);
}
APR_DECLARE(apr_status_t)apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
apr_pool_t *pool)
{
*rwlock = apr_palloc(pool, sizeof(**rwlock));
(*rwlock)->pool = pool;
(*rwlock)->readers = 0;
if (! ((*rwlock)->read_event = CreateEvent(NULL, TRUE, FALSE, NULL))) {
*rwlock = NULL;
return apr_get_os_error();
}
if (! ((*rwlock)->write_mutex = CreateMutex(NULL, FALSE, NULL))) {
CloseHandle((*rwlock)->read_event);
*rwlock = NULL;
return apr_get_os_error();
}
apr_pool_cleanup_register(pool, *rwlock, thread_rwlock_cleanup,
apr_pool_cleanup_null);
return APR_SUCCESS;
}
static apr_status_t apr_thread_rwlock_rdlock_core(apr_thread_rwlock_t *rwlock,
DWORD milliseconds)
{
DWORD code = WaitForSingleObject(rwlock->write_mutex, milliseconds);
if (code == WAIT_FAILED || code == WAIT_TIMEOUT)
return APR_FROM_OS_ERROR(code);
/* We've successfully acquired the writer mutex, we can't be locked
* for write, so it's OK to add the reader lock. The writer mutex
* doubles as race condition protection for the readers counter.
*/
InterlockedIncrement(&rwlock->readers);
if (! ResetEvent(rwlock->read_event))
return apr_get_os_error();
if (! ReleaseMutex(rwlock->write_mutex))
return apr_get_os_error();
return APR_SUCCESS;
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock)
{
return apr_thread_rwlock_rdlock_core(rwlock, INFINITE);
}
APR_DECLARE(apr_status_t)
apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock)
{
return apr_thread_rwlock_rdlock_core(rwlock, 0);
}
static apr_status_t
apr_thread_rwlock_wrlock_core(apr_thread_rwlock_t *rwlock, DWORD milliseconds)
{
DWORD code = WaitForSingleObject(rwlock->write_mutex, milliseconds);
if (code == WAIT_FAILED || code == WAIT_TIMEOUT)
return APR_FROM_OS_ERROR(code);
/* 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) {
/* Must wait for readers to finish before returning, unless this
* is an trywrlock (milliseconds == 0):
*/
code = milliseconds
? WaitForSingleObject(rwlock->read_event, milliseconds)
: WAIT_TIMEOUT;
if (code == WAIT_FAILED || code == WAIT_TIMEOUT) {
/* Unable to wait for readers to finish, release write lock: */
if (! ReleaseMutex(rwlock->write_mutex))
return apr_get_os_error();
return APR_FROM_OS_ERROR(code);
}
}
return APR_SUCCESS;
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock)
{
return apr_thread_rwlock_wrlock_core(rwlock, INFINITE);
}
APR_DECLARE(apr_status_t)apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock)
{
return apr_thread_rwlock_wrlock_core(rwlock, 0);
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock)
{
apr_status_t rv = 0;
/* First, guess that we're unlocking a writer */
if (! ReleaseMutex(rwlock->write_mutex))
rv = apr_get_os_error();
if (rv == APR_FROM_OS_ERROR(ERROR_NOT_OWNER)) {
/* Nope, we must have a read lock */
if (rwlock->readers &&
! InterlockedDecrement(&rwlock->readers) &&
! SetEvent(rwlock->read_event)) {
rv = apr_get_os_error();
}
else {
rv = 0;
}
}
return rv;
}
APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock)
{
if (! CloseHandle(rwlock->read_event))
return apr_get_os_error();
if (! CloseHandle(rwlock->write_mutex))
return apr_get_os_error();
return APR_SUCCESS;
}
APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock)
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