mutex.c revision 362181 
1/*
2 * svn_mutex.c: routines for mutual exclusion.
3 *
4 * ====================================================================
5 *    Licensed to the Apache Software Foundation (ASF) under one
6 *    or more contributor license agreements.  See the NOTICE file
7 *    distributed with this work for additional information
8 *    regarding copyright ownership.  The ASF licenses this file
9 *    to you under the Apache License, Version 2.0 (the
10 *    "License"); you may not use this file except in compliance
11 *    with the License.  You may obtain a copy of the License at
12 *
13 *      http://www.apache.org/licenses/LICENSE-2.0
14 *
15 *    Unless required by applicable law or agreed to in writing,
16 *    software distributed under the License is distributed on an
17 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
18 *    KIND, either express or implied.  See the License for the
19 *    specific language governing permissions and limitations
20 *    under the License.
21 * ====================================================================
22 */
23
24#include <apr_portable.h>
25
26#include "svn_private_config.h"
27#include "private/svn_atomic.h"
28#include "private/svn_mutex.h"
29
30/* With CHECKED set to TRUE, LOCKED and OWNER must be set *after* acquiring
31 * the MUTEX and be reset *before* releasing it again.  This is sufficient
32 * because we only want to check whether the current thread already holds
33 * the lock.  And the current thread cannot be acquiring / releasing a lock
34 * *while* checking for recursion at the same time.
35 */
36struct svn_mutex__t
37{
38#if APR_HAS_THREADS
39
40  apr_thread_mutex_t *mutex;
41
42#else
43
44  /* Truly empty structs are not allowed. */
45  int dummy;
46
47#endif
48};
49
50svn_error_t *
51svn_mutex__init(svn_mutex__t **mutex_p,
52                svn_boolean_t mutex_required,
53                apr_pool_t *result_pool)
54{
55  /* always initialize the mutex pointer, even though it is not
56     strictly necessary if APR_HAS_THREADS has not been set */
57  *mutex_p = NULL;
58
59  if (mutex_required)
60    {
61      svn_mutex__t *mutex = apr_pcalloc(result_pool, sizeof(*mutex));
62
63#if APR_HAS_THREADS
64      apr_status_t status =
65          apr_thread_mutex_create(&mutex->mutex,
66                                  APR_THREAD_MUTEX_DEFAULT,
67                                  result_pool);
68      if (status)
69        return svn_error_wrap_apr(status, _("Can't create mutex"));
70#endif
71
72      *mutex_p = mutex;
73    }
74
75  return SVN_NO_ERROR;
76}
77
78svn_error_t *
79svn_mutex__lock(svn_mutex__t *mutex)
80{
81  if (mutex)
82    {
83#if APR_HAS_THREADS
84      apr_status_t status = apr_thread_mutex_lock(mutex->mutex);
85      if (status)
86        return svn_error_wrap_apr(status, _("Can't lock mutex"));
87#endif
88    }
89
90  return SVN_NO_ERROR;
91}
92
93svn_error_t *
94svn_mutex__unlock(svn_mutex__t *mutex,
95                  svn_error_t *err)
96{
97  if (mutex)
98    {
99#if APR_HAS_THREADS
100      apr_status_t status = apr_thread_mutex_unlock(mutex->mutex);
101      if (status && !err)
102        return svn_error_wrap_apr(status, _("Can't unlock mutex"));
103#endif
104    }
105
106  return err;
107}
108
109#if APR_HAS_THREADS
110
111apr_thread_mutex_t *
112svn_mutex__get(svn_mutex__t *mutex)
113{
114  return mutex->mutex;
115}
116
117#endif
118