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apr_global_mutex.h
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2  * contributor license agreements. See the NOTICE file distributed with
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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
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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,
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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
34 extern "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. */
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  */
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  */
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  */
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  */
110 
111 /**
112  * Release the lock for the given mutex.
113  * @param mutex the mutex from which to release the lock.
114  */
116 
117 /**
118  * Destroy the mutex and free the memory associated with the lock.
119  * @param mutex the mutex to destroy.
120  */
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  */
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  */
136 
137 /**
138  * Get the pool used by this global_mutex.
139  * @return apr_pool_t the pool
140  */
141 APR_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 */