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apr_proc_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
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7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
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13  * See the License for the specific language governing permissions and
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15  */
16 
17 #ifndef APR_PROC_MUTEX_H
18 #define APR_PROC_MUTEX_H
19 
20 /**
21  * @file apr_proc_mutex.h
22  * @brief APR Process Locking Routines
23  */
24 
25 #include "apr.h"
26 #include "apr_pools.h"
27 #include "apr_errno.h"
28 
29 #ifdef __cplusplus
30 extern "C" {
31 #endif /* __cplusplus */
32 
33 /**
34  * @defgroup apr_proc_mutex Process Locking Routines
35  * @ingroup APR
36  * @{
37  */
38 
39 /**
40  * Enumerated potential types for APR process locking methods
41  * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
42  * APR_LOCK_foo. Only APR_LOCK_DEFAULT is portable.
43  */
44 typedef enum {
45  APR_LOCK_FCNTL, /**< fcntl() */
46  APR_LOCK_FLOCK, /**< flock() */
47  APR_LOCK_SYSVSEM, /**< System V Semaphores */
48  APR_LOCK_PROC_PTHREAD, /**< POSIX pthread process-based locking */
49  APR_LOCK_POSIXSEM, /**< POSIX semaphore process-based locking */
50  APR_LOCK_DEFAULT /**< Use the default process lock */
52 
53 /** Opaque structure representing a process mutex. */
55 
56 /* Function definitions */
57 
58 /**
59  * Create and initialize a mutex that can be used to synchronize processes.
60  * @param mutex the memory address where the newly created mutex will be
61  * stored.
62  * @param fname A file name to use if the lock mechanism requires one. This
63  * argument should always be provided. The lock code itself will
64  * determine if it should be used.
65  * @param mech The mechanism to use for the interprocess lock, if any; one of
66  * <PRE>
67  * APR_LOCK_FCNTL
68  * APR_LOCK_FLOCK
69  * APR_LOCK_SYSVSEM
70  * APR_LOCK_POSIXSEM
71  * APR_LOCK_PROC_PTHREAD
72  * APR_LOCK_DEFAULT pick the default mechanism for the platform
73  * </PRE>
74  * @param pool the pool from which to allocate the mutex.
75  * @see apr_lockmech_e
76  * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
77  * APR_LOCK_foo. Only APR_LOCK_DEFAULT is portable.
78  */
80  const char *fname,
81  apr_lockmech_e mech,
82  apr_pool_t *pool);
83 
84 /**
85  * Re-open a mutex in a child process.
86  * @param mutex The newly re-opened mutex structure.
87  * @param fname A file name to use if the mutex mechanism requires one. This
88  * argument should always be provided. The mutex code itself will
89  * determine if it should be used. This filename should be the
90  * same one that was passed to apr_proc_mutex_create().
91  * @param pool The pool to operate on.
92  * @remark This function must be called to maintain portability, even
93  * if the underlying lock mechanism does not require it.
94  */
96  const char *fname,
97  apr_pool_t *pool);
98 
99 /**
100  * Acquire the lock for the given mutex. If the mutex is already locked,
101  * the current thread will be put to sleep until the lock becomes available.
102  * @param mutex the mutex on which to acquire the lock.
103  */
105 
106 /**
107  * Attempt to acquire the lock for the given mutex. If the mutex has already
108  * been acquired, the call returns immediately with APR_EBUSY. Note: it
109  * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
110  * if the return value was APR_EBUSY, for portability reasons.
111  * @param mutex the mutex on which to attempt the lock acquiring.
112  */
114 
115 /**
116  * Release the lock for the given mutex.
117  * @param mutex the mutex from which to release the lock.
118  */
120 
121 /**
122  * Destroy the mutex and free the memory associated with the lock.
123  * @param mutex the mutex to destroy.
124  */
126 
127 /**
128  * Destroy the mutex and free the memory associated with the lock.
129  * @param mutex the mutex to destroy.
130  * @note This function is generally used to kill a cleanup on an already
131  * created mutex
132  */
134 
135 /**
136  * Return the name of the lockfile for the mutex, or NULL
137  * if the mutex doesn't use a lock file
138  */
139 
141 
142 /**
143  * Display the name of the mutex, as it relates to the actual method used.
144  * This matches the valid options for Apache's AcceptMutex directive
145  * @param mutex the name of the mutex
146  */
147 APR_DECLARE(const char *) apr_proc_mutex_name(apr_proc_mutex_t *mutex);
148 
149 /**
150  * Display the name of the default mutex: APR_LOCK_DEFAULT
151  */
152 APR_DECLARE(const char *) apr_proc_mutex_defname(void);
153 
154 /**
155  * Get the pool used by this proc_mutex.
156  * @return apr_pool_t the pool
157  */
158 APR_POOL_DECLARE_ACCESSOR(proc_mutex);
159 
160 /** @} */
161 
162 #ifdef __cplusplus
163 }
164 #endif
165 
166 #endif /* ! APR_PROC_MUTEX_H */