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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_arch_thread_mutex.h"
#define APR_WANT_MEMFUNC
#include "apr_want.h"
#if APR_HAS_THREADS
static apr_status_t thread_mutex_cleanup(void *data)
{
apr_thread_mutex_t *mutex = data;
apr_status_t rv;
rv = pthread_mutex_destroy(&mutex->mutex);
#ifdef PTHREAD_SETS_ERRNO
if (rv) {
rv = errno;
}
#endif
return rv;
}
APR_DECLARE(apr_status_t) apr_thread_mutex_create(apr_thread_mutex_t **mutex,
unsigned int flags,
apr_pool_t *pool)
{
apr_thread_mutex_t *new_mutex;
apr_status_t rv;
new_mutex = apr_pcalloc(pool, sizeof(apr_thread_mutex_t));
new_mutex->pool = pool;
/* Optimal default is APR_THREAD_MUTEX_UNNESTED,
* no additional checks required for either flag.
*/
new_mutex->nested = flags & APR_THREAD_MUTEX_NESTED;
if ((rv = pthread_mutex_init(&new_mutex->mutex, NULL))) {
#ifdef PTHREAD_SETS_ERRNO
rv = errno;
#endif
return rv;
}
apr_pool_cleanup_register(new_mutex->pool,
new_mutex, thread_mutex_cleanup,
apr_pool_cleanup_null);
*mutex = new_mutex;
return APR_SUCCESS;
}
APR_DECLARE(apr_status_t) apr_thread_mutex_lock(apr_thread_mutex_t *mutex)
{
apr_status_t rv;
if (mutex->nested) {
/*
* Although threadsafe, this test is NOT reentrant.
* The thread's main and reentrant attempts will both mismatch
* testing the mutex is owned by this thread, so a deadlock is expected.
*/
if (apr_os_thread_equal(mutex->owner, apr_os_thread_current())) {
apr_atomic_inc(&mutex->owner_ref);
return APR_SUCCESS;
}
rv = pthread_mutex_lock(&mutex->mutex);
if (rv) {
#ifdef PTHREAD_SETS_ERRNO
rv = errno;
#endif
return rv;
}
if (apr_atomic_cas(&mutex->owner_ref, 1, 0) != 0) {
/* The owner_ref should be zero when the lock is not held,
* if owner_ref was non-zero we have a mutex reference bug.
* XXX: so now what?
*/
mutex->owner_ref = 1;
}
/* Note; do not claim ownership until the owner_ref has been
* incremented; limits a subtle race in reentrant code.
*/
mutex->owner = apr_os_thread_current();
return rv;
}
else {
rv = pthread_mutex_lock(&mutex->mutex);
#ifdef PTHREAD_SETS_ERRNO
if (rv) {
rv = errno;
}
#endif
return rv;
}
}
APR_DECLARE(apr_status_t) apr_thread_mutex_trylock(apr_thread_mutex_t *mutex)
{
apr_status_t rv;
if (mutex->nested) {
/*
* Although threadsafe, this test is NOT reentrant.
* The thread's main and reentrant attempts will both mismatch
* testing the mutex is owned by this thread, so one will fail
* the trylock.
*/
if (apr_os_thread_equal(mutex->owner, apr_os_thread_current())) {
apr_atomic_inc(&mutex->owner_ref);
return APR_SUCCESS;
}
rv = pthread_mutex_trylock(&mutex->mutex);
if (rv) {
#ifdef PTHREAD_SETS_ERRNO
rv = errno;
#endif
return (rv == EBUSY) ? APR_EBUSY : rv;
}
if (apr_atomic_cas(&mutex->owner_ref, 1, 0) != 0) {
/* The owner_ref should be zero when the lock is not held,
* if owner_ref was non-zero we have a mutex reference bug.
* XXX: so now what?
*/
mutex->owner_ref = 1;
}
/* Note; do not claim ownership until the owner_ref has been
* incremented; limits a subtle race in reentrant code.
*/
mutex->owner = apr_os_thread_current();
}
else {
rv = pthread_mutex_trylock(&mutex->mutex);
if (rv) {
#ifdef PTHREAD_SETS_ERRNO
rv = errno;
#endif
return (rv == EBUSY) ? APR_EBUSY : rv;
}
}
return rv;
}
APR_DECLARE(apr_status_t) apr_thread_mutex_unlock(apr_thread_mutex_t *mutex)
{
apr_status_t status;
if (mutex->nested) {
/*
* The code below is threadsafe and reentrant.
*/
if (apr_os_thread_equal(mutex->owner, apr_os_thread_current())) {
/*
* This should never occur, and indicates an application error
*/
if (mutex->owner_ref == 0) {
return APR_EINVAL;
}
if (apr_atomic_dec(&mutex->owner_ref) != 0)
return APR_SUCCESS;
mutex->owner = 0;
}
/*
* This should never occur, and indicates an application error
*/
else {
return APR_EINVAL;
}
}
status = pthread_mutex_unlock(&mutex->mutex);
#ifdef PTHREAD_SETS_ERRNO
if (status) {
status = errno;
}
#endif
return status;
}
APR_DECLARE(apr_status_t) apr_thread_mutex_destroy(apr_thread_mutex_t *mutex)
{
return apr_pool_cleanup_run(mutex->pool, mutex, thread_mutex_cleanup);
}
APR_POOL_IMPLEMENT_ACCESSOR(thread_mutex)
#endif /* APR_HAS_THREADS */
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