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    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 #include "apr_time.h"
   33 
   34 #ifdef __cplusplus
   35 extern "C" {
   36 #endif /* __cplusplus */
   37 
   38 /**
   39  * @defgroup APR_GlobalMutex Global Locking Routines
   40  * @ingroup APR 
   41  * @{
   42  */
   43 
   44 #if !APR_PROC_MUTEX_IS_GLOBAL || defined(DOXYGEN)
   45 
   46 /** Opaque global mutex structure. */
   47 typedef struct apr_global_mutex_t apr_global_mutex_t;
   48 
   49 /*   Function definitions */
   50 
   51 /**
   52  * Create and initialize a mutex that can be used to synchronize both
   53  * processes and threads. Note: There is considerable overhead in using
   54  * this API if only cross-process or cross-thread mutual exclusion is
   55  * required. See apr_proc_mutex.h and apr_thread_mutex.h for more
   56  * specialized lock routines.
   57  * @param mutex the memory address where the newly created mutex will be
   58  *        stored.
   59  * @param fname A file name to use if the lock mechanism requires one.  This
   60  *        argument should always be provided.  The lock code itself will
   61  *        determine if it should be used.
   62  * @param mech The mechanism to use for the interprocess lock, if any; one of
   63  * <PRE>
   64  *            APR_LOCK_FCNTL
   65  *            APR_LOCK_FLOCK
   66  *            APR_LOCK_SYSVSEM
   67  *            APR_LOCK_POSIXSEM
   68  *            APR_LOCK_PROC_PTHREAD
   69  *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
   70  *            APR_LOCK_DEFAULT_TIMED pick the default timed mechanism
   71  * </PRE>
   72  * @param pool the pool from which to allocate the mutex.
   73  * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
   74  *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
   75  */
   76 APR_DECLARE(apr_status_t) apr_global_mutex_create(apr_global_mutex_t **mutex,
   77                                                   const char *fname,
   78                                                   apr_lockmech_e mech,
   79                                                   apr_pool_t *pool);
   80 
   81 /**
   82  * Re-open a mutex in a child process.
   83  * @param mutex The newly re-opened mutex structure.
   84  * @param fname A file name to use if the mutex mechanism requires one.  This
   85  *              argument should always be provided.  The mutex code itself will
   86  *              determine if it should be used.  This filename should be the 
   87  *              same one that was passed to apr_global_mutex_create().
   88  * @param pool The pool to operate on.
   89  * @remark This function must be called to maintain portability, even
   90  *         if the underlying lock mechanism does not require it.
   91  */
   92 APR_DECLARE(apr_status_t) apr_global_mutex_child_init(
   93                               apr_global_mutex_t **mutex,
   94                               const char *fname,
   95                               apr_pool_t *pool);
   96 
   97 /**
   98  * Acquire the lock for the given mutex. If the mutex is already locked,
   99  * the current thread will be put to sleep until the lock becomes available.
  100  * @param mutex the mutex on which to acquire the lock.
  101  */
  102 APR_DECLARE(apr_status_t) apr_global_mutex_lock(apr_global_mutex_t *mutex);
  103 
  104 /**
  105  * Attempt to acquire the lock for the given mutex. If the mutex has already
  106  * been acquired, the call returns immediately with APR_EBUSY. Note: it
  107  * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
  108  * if the return value was APR_EBUSY, for portability reasons.
  109  * @param mutex the mutex on which to attempt the lock acquiring.
  110  */
  111 APR_DECLARE(apr_status_t) apr_global_mutex_trylock(apr_global_mutex_t *mutex);
  112 
  113 /**
  114  * Attempt to acquire the lock for the given mutex until timeout expires.
  115  * If the acquisition time outs, the call returns with APR_TIMEUP.
  116  * @param mutex the mutex on which to attempt the lock acquiring.
  117  * @param timeout the relative timeout (microseconds).
  118  * @note A negative or nul timeout means immediate attempt, returning
  119  *       APR_TIMEUP without blocking if it the lock is already acquired.
  120  */
  121 APR_DECLARE(apr_status_t) apr_global_mutex_timedlock(apr_global_mutex_t *mutex,
  122                                                  apr_interval_time_t timeout);
  123 
  124 /**
  125  * Release the lock for the given mutex.
  126  * @param mutex the mutex from which to release the lock.
  127  */
  128 APR_DECLARE(apr_status_t) apr_global_mutex_unlock(apr_global_mutex_t *mutex);
  129 
  130 /**
  131  * Destroy the mutex and free the memory associated with the lock.
  132  * @param mutex the mutex to destroy.
  133  */
  134 APR_DECLARE(apr_status_t) apr_global_mutex_destroy(apr_global_mutex_t *mutex);
  135 
  136 /**
  137  * Return the name of the lockfile for the mutex, or NULL
  138  * if the mutex doesn't use a lock file
  139  */
  140 APR_DECLARE(const char *) apr_global_mutex_lockfile(apr_global_mutex_t *mutex);
  141 
  142 /**
  143  * Get the mechanism of the mutex, as it relates to the actual method
  144  * used for the underlying apr_proc_mutex_t.
  145  * @param mutex the mutex to get the mechanism from.
  146  */
  147 APR_DECLARE(apr_lockmech_e) apr_global_mutex_mech(apr_global_mutex_t *mutex);
  148 
  149 /**
  150  * Get the mechanism's name of the mutex, as it relates to the actual method
  151  * used for the underlying apr_proc_mutex_t.
  152  * @param mutex the mutex to get the mechanism's name from.
  153  */
  154 APR_DECLARE(const char *) apr_global_mutex_name(apr_global_mutex_t *mutex);
  155 
  156 /**
  157  * Set mutex permissions.
  158  */
  159 APR_PERMS_SET_IMPLEMENT(global_mutex);
  160 
  161 /**
  162  * Get the pool used by this global_mutex.
  163  * @return apr_pool_t the pool
  164  */
  165 APR_POOL_DECLARE_ACCESSOR(global_mutex);
  166 
  167 #else /* APR_PROC_MUTEX_IS_GLOBAL */
  168 
  169 /* Some platforms [e.g. Win32] have cross process locks that are truly
  170  * global locks, since there isn't the concept of cross-process locks.
  171  * Define these platforms in terms of an apr_proc_mutex_t.
  172  */
  173 
  174 #define apr_global_mutex_t          apr_proc_mutex_t
  175 #define apr_global_mutex_create     apr_proc_mutex_create
  176 #define apr_global_mutex_child_init apr_proc_mutex_child_init
  177 #define apr_global_mutex_lock       apr_proc_mutex_lock
  178 #define apr_global_mutex_trylock    apr_proc_mutex_trylock
  179 #define apr_global_mutex_unlock     apr_proc_mutex_unlock
  180 #define apr_global_mutex_destroy    apr_proc_mutex_destroy
  181 #define apr_global_mutex_lockfile   apr_proc_mutex_lockfile
  182 #define apr_global_mutex_mech       apr_proc_mutex_mech
  183 #define apr_global_mutex_name       apr_proc_mutex_name
  184 #define apr_global_mutex_perms_set  apr_proc_mutex_perms_set
  185 #define apr_global_mutex_pool_get   apr_proc_mutex_pool_get
  186 
  187 #endif
  188 
  189 /** @} */
  190 
  191 #ifdef __cplusplus
  192 }
  193 #endif
  194 
  195 #endif  /* ndef APR_GLOBAL_MUTEX_H */