apr_global_mutex.h revision 251875 
1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef APR_GLOBAL_MUTEX_H
18#define APR_GLOBAL_MUTEX_H
19
20/**
21 * @file apr_global_mutex.h
22 * @brief APR Global Locking Routines
23 */
24
25#include "apr.h"
26#include "apr_proc_mutex.h"    /* only for apr_lockmech_e */
27#include "apr_pools.h"
28#include "apr_errno.h"
29#if APR_PROC_MUTEX_IS_GLOBAL
30#include "apr_proc_mutex.h"
31#endif
32
33#ifdef __cplusplus
34extern "C" {
35#endif /* __cplusplus */
36
37/**
38 * @defgroup APR_GlobalMutex Global Locking Routines
39 * @ingroup APR
40 * @{
41 */
42
43#if !APR_PROC_MUTEX_IS_GLOBAL || defined(DOXYGEN)
44
45/** Opaque global mutex structure. */
46typedef struct apr_global_mutex_t apr_global_mutex_t;
47
48/*   Function definitions */
49
50/**
51 * Create and initialize a mutex that can be used to synchronize both
52 * processes and threads. Note: There is considerable overhead in using
53 * this API if only cross-process or cross-thread mutual exclusion is
54 * required. See apr_proc_mutex.h and apr_thread_mutex.h for more
55 * specialized lock routines.
56 * @param mutex the memory address where the newly created mutex will be
57 *        stored.
58 * @param fname A file name to use if the lock mechanism requires one.  This
59 *        argument should always be provided.  The lock code itself will
60 *        determine if it should be used.
61 * @param mech The mechanism to use for the interprocess lock, if any; one of
62 * <PRE>
63 *            APR_LOCK_FCNTL
64 *            APR_LOCK_FLOCK
65 *            APR_LOCK_SYSVSEM
66 *            APR_LOCK_POSIXSEM
67 *            APR_LOCK_PROC_PTHREAD
68 *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
69 * </PRE>
70 * @param pool the pool from which to allocate the mutex.
71 * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
72 *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
73 */
74APR_DECLARE(apr_status_t) apr_global_mutex_create(apr_global_mutex_t **mutex,
75                                                  const char *fname,
76                                                  apr_lockmech_e mech,
77                                                  apr_pool_t *pool);
78
79/**
80 * Re-open a mutex in a child process.
81 * @param mutex The newly re-opened mutex structure.
82 * @param fname A file name to use if the mutex mechanism requires one.  This
83 *              argument should always be provided.  The mutex code itself will
84 *              determine if it should be used.  This filename should be the
85 *              same one that was passed to apr_global_mutex_create().
86 * @param pool The pool to operate on.
87 * @remark This function must be called to maintain portability, even
88 *         if the underlying lock mechanism does not require it.
89 */
90APR_DECLARE(apr_status_t) apr_global_mutex_child_init(
91                              apr_global_mutex_t **mutex,
92                              const char *fname,
93                              apr_pool_t *pool);
94
95/**
96 * Acquire the lock for the given mutex. If the mutex is already locked,
97 * the current thread will be put to sleep until the lock becomes available.
98 * @param mutex the mutex on which to acquire the lock.
99 */
100APR_DECLARE(apr_status_t) apr_global_mutex_lock(apr_global_mutex_t *mutex);
101
102/**
103 * Attempt to acquire the lock for the given mutex. If the mutex has already
104 * been acquired, the call returns immediately with APR_EBUSY. Note: it
105 * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
106 * if the return value was APR_EBUSY, for portability reasons.
107 * @param mutex the mutex on which to attempt the lock acquiring.
108 */
109APR_DECLARE(apr_status_t) apr_global_mutex_trylock(apr_global_mutex_t *mutex);
110
111/**
112 * Release the lock for the given mutex.
113 * @param mutex the mutex from which to release the lock.
114 */
115APR_DECLARE(apr_status_t) apr_global_mutex_unlock(apr_global_mutex_t *mutex);
116
117/**
118 * Destroy the mutex and free the memory associated with the lock.
119 * @param mutex the mutex to destroy.
120 */
121APR_DECLARE(apr_status_t) apr_global_mutex_destroy(apr_global_mutex_t *mutex);
122
123/**
124 * Return the name of the lockfile for the mutex, or NULL
125 * if the mutex doesn't use a lock file
126 */
127APR_DECLARE(const char *) apr_global_mutex_lockfile(apr_global_mutex_t *mutex);
128
129/**
130 * Display the name of the mutex, as it relates to the actual method used
131 * for the underlying apr_proc_mutex_t, if any.  NULL is returned if
132 * there is no underlying apr_proc_mutex_t.
133 * @param mutex the name of the mutex
134 */
135APR_DECLARE(const char *) apr_global_mutex_name(apr_global_mutex_t *mutex);
136
137/**
138 * Get the pool used by this global_mutex.
139 * @return apr_pool_t the pool
140 */
141APR_POOL_DECLARE_ACCESSOR(global_mutex);
142
143#else /* APR_PROC_MUTEX_IS_GLOBAL */
144
145/* Some platforms [e.g. Win32] have cross process locks that are truly
146 * global locks, since there isn't the concept of cross-process locks.
147 * Define these platforms in terms of an apr_proc_mutex_t.
148 */
149
150#define apr_global_mutex_t          apr_proc_mutex_t
151#define apr_global_mutex_create     apr_proc_mutex_create
152#define apr_global_mutex_child_init apr_proc_mutex_child_init
153#define apr_global_mutex_lock       apr_proc_mutex_lock
154#define apr_global_mutex_trylock    apr_proc_mutex_trylock
155#define apr_global_mutex_unlock     apr_proc_mutex_unlock
156#define apr_global_mutex_destroy    apr_proc_mutex_destroy
157#define apr_global_mutex_lockfile   apr_proc_mutex_lockfile
158#define apr_global_mutex_name       apr_proc_mutex_name
159#define apr_global_mutex_pool_get   apr_proc_mutex_pool_get
160
161#endif
162
163/** @} */
164
165#ifdef __cplusplus
166}
167#endif
168
169#endif  /* ndef APR_GLOBAL_MUTEX_H */
170