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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 #ifndef APR_GLOBAL_MUTEX_H
18 #define APR_GLOBAL_MUTEX_H
21 * @file apr_global_mutex.h
22 * @brief APR Global Locking Routines
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"
35 #endif /* __cplusplus */
38 * @defgroup APR_GlobalMutex Global Locking Routines
43 #if !APR_PROC_MUTEX_IS_GLOBAL || defined(DOXYGEN)
45 /** Opaque global mutex structure. */
46 typedef struct apr_global_mutex_t apr_global_mutex_t;
48 /* Function definitions */
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
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
67 * APR_LOCK_PROC_PTHREAD
68 * APR_LOCK_DEFAULT pick the default mechanism for the platform
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.
74 APR_DECLARE(apr_status_t) apr_global_mutex_create(apr_global_mutex_t **mutex,
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.
90 APR_DECLARE(apr_status_t) apr_global_mutex_child_init(
91 apr_global_mutex_t **mutex,
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.
100 APR_DECLARE(apr_status_t) apr_global_mutex_lock(apr_global_mutex_t *mutex);
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.
109 APR_DECLARE(apr_status_t) apr_global_mutex_trylock(apr_global_mutex_t *mutex);
112 * Release the lock for the given mutex.
113 * @param mutex the mutex from which to release the lock.
115 APR_DECLARE(apr_status_t) apr_global_mutex_unlock(apr_global_mutex_t *mutex);
118 * Destroy the mutex and free the memory associated with the lock.
119 * @param mutex the mutex to destroy.
121 APR_DECLARE(apr_status_t) apr_global_mutex_destroy(apr_global_mutex_t *mutex);
124 * Return the name of the lockfile for the mutex, or NULL
125 * if the mutex doesn't use a lock file
127 APR_DECLARE(const char *) apr_global_mutex_lockfile(apr_global_mutex_t *mutex);
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
135 APR_DECLARE(const char *) apr_global_mutex_name(apr_global_mutex_t *mutex);
138 * Get the pool used by this global_mutex.
139 * @return apr_pool_t the pool
141 APR_POOL_DECLARE_ACCESSOR(global_mutex);
143 #else /* APR_PROC_MUTEX_IS_GLOBAL */
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.
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
169 #endif /* ndef APR_GLOBAL_MUTEX_H */