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Viewing changes to srclib/apr/locks/win32/thread_rwlock.c

  • Committer: Bazaar Package Importer
  • Author(s): Andreas Barth
  • Date: 2006-12-09 21:05:45 UTC
  • mfrom: (0.6.1 upstream)
  • Revision ID: james.westby@ubuntu.com-20061209210545-h70s0xaqc2v8vqr2
Tags: 2.2.3-3.2
http://bugs.debian.org/396265
* Non-maintainer upload.
* 043_ajp_connection_reuse: Patch from upstream Bugzilla, fixing a critical
  issue with regard to connection reuse in mod_proxy_ajp.
  Closes: #396265

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srclib/apr/locks/win32/thread_rwlock.c
 
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/* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
 
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 * applicable.
 
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 *
 
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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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 *
 
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 *     http://www.apache.org/licenses/LICENSE-2.0
 
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 *
 
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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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 */
 
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#include "apr.h"
 
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#include "apr_private.h"
 
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#include "apr_general.h"
 
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#include "apr_strings.h"
 
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#include "win32/apr_arch_thread_rwlock.h"
 
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#include "apr_portable.h"
 
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static apr_status_t thread_rwlock_cleanup(void *data)
 
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{
 
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    apr_thread_rwlock_t *rwlock = data;
 
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    if (! CloseHandle(rwlock->read_event))
 
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        return apr_get_os_error();
 
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    if (! CloseHandle(rwlock->write_mutex))
 
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        return apr_get_os_error();
 
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    return APR_SUCCESS;
 
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}
 
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APR_DECLARE(apr_status_t)apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
 
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                                                  apr_pool_t *pool)
 
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{
 
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    *rwlock = apr_palloc(pool, sizeof(**rwlock));
 
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    (*rwlock)->pool        = pool;
 
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    (*rwlock)->readers     = 0;
 
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    if (! ((*rwlock)->read_event = CreateEvent(NULL, TRUE, FALSE, NULL))) {
 
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        *rwlock = NULL;
 
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        return apr_get_os_error();
 
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    }
 
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    if (! ((*rwlock)->write_mutex = CreateMutex(NULL, FALSE, NULL))) {
 
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        CloseHandle((*rwlock)->read_event);
 
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        *rwlock = NULL;
 
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        return apr_get_os_error();
 
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    }
 
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    apr_pool_cleanup_register(pool, *rwlock, thread_rwlock_cleanup,
 
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                              apr_pool_cleanup_null);
 
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    return APR_SUCCESS;
 
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}
 
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static apr_status_t apr_thread_rwlock_rdlock_core(apr_thread_rwlock_t *rwlock,
 
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                                                  DWORD  milliseconds)
 
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{
 
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    DWORD   code = WaitForSingleObject(rwlock->write_mutex, milliseconds);
 
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    if (code == WAIT_FAILED || code == WAIT_TIMEOUT)
 
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        return APR_FROM_OS_ERROR(code);
 
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    /* We've successfully acquired the writer mutex, we can't be locked
 
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     * for write, so it's OK to add the reader lock.  The writer mutex
 
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     * doubles as race condition protection for the readers counter.   
 
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     */
 
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    InterlockedIncrement(&rwlock->readers);
 
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    if (! ResetEvent(rwlock->read_event))
 
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        return apr_get_os_error();
 
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    if (! ReleaseMutex(rwlock->write_mutex))
 
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        return apr_get_os_error();
 
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    return APR_SUCCESS;
 
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}
 
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APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock)
 
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{
 
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    return apr_thread_rwlock_rdlock_core(rwlock, INFINITE);
 
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}
 
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APR_DECLARE(apr_status_t) 
 
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apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock)
 
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{
 
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    return apr_thread_rwlock_rdlock_core(rwlock, 0);
 
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}
 
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static apr_status_t 
 
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apr_thread_rwlock_wrlock_core(apr_thread_rwlock_t *rwlock, DWORD milliseconds)
 
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{
 
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    DWORD   code = WaitForSingleObject(rwlock->write_mutex, milliseconds);
 
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    if (code == WAIT_FAILED || code == WAIT_TIMEOUT)
 
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        return APR_FROM_OS_ERROR(code);
 
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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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     */
 
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    if (rwlock->readers) {
 
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        /* Must wait for readers to finish before returning, unless this
 
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         * is an trywrlock (milliseconds == 0):
 
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         */
 
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        code = milliseconds
 
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          ? WaitForSingleObject(rwlock->read_event, milliseconds)
 
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          : WAIT_TIMEOUT;
 
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        if (code == WAIT_FAILED || code == WAIT_TIMEOUT) {
 
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            /* Unable to wait for readers to finish, release write lock: */
 
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            if (! ReleaseMutex(rwlock->write_mutex))
 
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                return apr_get_os_error();
 
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            return APR_FROM_OS_ERROR(code);
 
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        }
 
122
    }
 
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    return APR_SUCCESS;
 
125
}
 
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APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock)
 
128
{
 
129
    return apr_thread_rwlock_wrlock_core(rwlock, INFINITE);
 
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}
 
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APR_DECLARE(apr_status_t)apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock)
 
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{
 
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    return apr_thread_rwlock_wrlock_core(rwlock, 0);
 
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}
 
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APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock)
 
138
{
 
139
    apr_status_t rv = 0;
 
140
 
 
141
    /* First, guess that we're unlocking a writer */
 
142
    if (! ReleaseMutex(rwlock->write_mutex))
 
143
        rv = apr_get_os_error();
 
144
    
 
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    if (rv == APR_FROM_OS_ERROR(ERROR_NOT_OWNER)) {
 
146
        /* Nope, we must have a read lock */
 
147
        if (rwlock->readers &&
 
148
            ! InterlockedDecrement(&rwlock->readers) &&
 
149
            ! SetEvent(rwlock->read_event)) {
 
150
            rv = apr_get_os_error();
 
151
        }
 
152
        else {
 
153
            rv = 0;
 
154
        }
 
155
    }
 
156
 
 
157
    return rv;
 
158
}
 
159
 
 
160
APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock)
 
161
{
 
162
    return apr_pool_cleanup_run(rwlock->pool, rwlock, thread_rwlock_cleanup);
 
163
}
 
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APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock)