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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_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 #include "apr_perms_set.h"
   29 #include "apr_time.h"
   30 
   31 #ifdef __cplusplus
   32 extern "C" {
   33 #endif /* __cplusplus */
   34 
   35 /**
   36  * @defgroup apr_proc_mutex Process Locking Routines
   37  * @ingroup APR 
   38  * @{
   39  */
   40 
   41 /** 
   42  * Enumerated potential types for APR process locking methods
   43  * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
   44  *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
   45  */
   46 typedef enum {
   47     APR_LOCK_FCNTL,         /**< fcntl() */
   48     APR_LOCK_FLOCK,         /**< flock() */
   49     APR_LOCK_SYSVSEM,       /**< System V Semaphores */
   50     APR_LOCK_PROC_PTHREAD,  /**< POSIX pthread process-based locking */
   51     APR_LOCK_POSIXSEM,      /**< POSIX semaphore process-based locking */
   52     APR_LOCK_DEFAULT,       /**< Use the default process lock */
   53     APR_LOCK_DEFAULT_TIMED  /**< Use the default process timed lock */
   54 } apr_lockmech_e;
   55 
   56 /** Opaque structure representing a process mutex. */
   57 typedef struct apr_proc_mutex_t apr_proc_mutex_t;
   58 
   59 /*   Function definitions */
   60 
   61 /**
   62  * Create and initialize a mutex that can be used to synchronize processes.
   63  * @param mutex the memory address where the newly created mutex will be
   64  *        stored.
   65  * @param fname A file name to use if the lock mechanism requires one.  This
   66  *        argument should always be provided.  The lock code itself will
   67  *        determine if it should be used.
   68  * @param mech The mechanism to use for the interprocess lock, if any; one of
   69  * <PRE>
   70  *            APR_LOCK_FCNTL
   71  *            APR_LOCK_FLOCK
   72  *            APR_LOCK_SYSVSEM
   73  *            APR_LOCK_POSIXSEM
   74  *            APR_LOCK_PROC_PTHREAD
   75  *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
   76  * </PRE>
   77  * @param pool the pool from which to allocate the mutex.
   78  * @see apr_lockmech_e
   79  * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
   80  *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
   81  */
   82 APR_DECLARE(apr_status_t) apr_proc_mutex_create(apr_proc_mutex_t **mutex,
   83                                                 const char *fname,
   84                                                 apr_lockmech_e mech,
   85                                                 apr_pool_t *pool);
   86 
   87 /**
   88  * Re-open a mutex in a child process.
   89  * @param mutex The newly re-opened mutex structure.
   90  * @param fname A file name to use if the mutex mechanism requires one.  This
   91  *              argument should always be provided.  The mutex code itself will
   92  *              determine if it should be used.  This filename should be the 
   93  *              same one that was passed to apr_proc_mutex_create().
   94  * @param pool The pool to operate on.
   95  * @remark This function must be called to maintain portability, even
   96  *         if the underlying lock mechanism does not require it.
   97  */
   98 APR_DECLARE(apr_status_t) apr_proc_mutex_child_init(apr_proc_mutex_t **mutex,
   99                                                     const char *fname,
  100                                                     apr_pool_t *pool);
  101 
  102 /**
  103  * Acquire the lock for the given mutex. If the mutex is already locked,
  104  * the current thread will be put to sleep until the lock becomes available.
  105  * @param mutex the mutex on which to acquire the lock.
  106  */
  107 APR_DECLARE(apr_status_t) apr_proc_mutex_lock(apr_proc_mutex_t *mutex);
  108 
  109 /**
  110  * Attempt to acquire the lock for the given mutex. If the mutex has already
  111  * been acquired, the call returns immediately with APR_EBUSY. Note: it
  112  * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
  113  * if the return value was APR_EBUSY, for portability reasons.
  114  * @param mutex the mutex on which to attempt the lock acquiring.
  115  */
  116 APR_DECLARE(apr_status_t) apr_proc_mutex_trylock(apr_proc_mutex_t *mutex);
  117 
  118 /**
  119  * Attempt to acquire the lock for the given mutex until timeout expires.
  120  * If the acquisition time outs, the call returns with APR_TIMEUP.
  121  * @param mutex the mutex on which to attempt the lock acquiring.
  122  * @param timeout the relative timeout (microseconds).
  123  * @note A negative or nul timeout means immediate attempt, returning
  124  *       APR_TIMEUP without blocking if it the lock is already acquired.
  125  */
  126 APR_DECLARE(apr_status_t) apr_proc_mutex_timedlock(apr_proc_mutex_t *mutex,
  127                                                apr_interval_time_t timeout);
  128 
  129 /**
  130  * Release the lock for the given mutex.
  131  * @param mutex the mutex from which to release the lock.
  132  */
  133 APR_DECLARE(apr_status_t) apr_proc_mutex_unlock(apr_proc_mutex_t *mutex);
  134 
  135 /**
  136  * Destroy the mutex and free the memory associated with the lock.
  137  * @param mutex the mutex to destroy.
  138  */
  139 APR_DECLARE(apr_status_t) apr_proc_mutex_destroy(apr_proc_mutex_t *mutex);
  140 
  141 /**
  142  * Destroy the mutex and free the memory associated with the lock.
  143  * @param mutex the mutex to destroy.
  144  * @note This function is generally used to kill a cleanup on an already
  145  *       created mutex
  146  */
  147 APR_DECLARE(apr_status_t) apr_proc_mutex_cleanup(void *mutex);
  148 
  149 /**
  150  * Return the name of the lockfile for the mutex, or NULL
  151  * if the mutex doesn't use a lock file
  152  */
  153 
  154 APR_DECLARE(const char *) apr_proc_mutex_lockfile(apr_proc_mutex_t *mutex);
  155 
  156 /**
  157  * Get the mechanism of the mutex, as it relates to the actual method
  158  * used for the underlying apr_proc_mutex_t.
  159  * @param mutex the mutex to get the mechanism from.
  160  */
  161 APR_DECLARE(apr_lockmech_e) apr_proc_mutex_mech(apr_proc_mutex_t *mutex);
  162 
  163 /**
  164  * Get the mechanism's name of the mutex, as it relates to the actual method
  165  * used for the underlying apr_proc_mutex_t.
  166  * @param mutex the mutex to get the mechanism's name from.
  167  */
  168 APR_DECLARE(const char *) apr_proc_mutex_name(apr_proc_mutex_t *mutex);
  169 
  170 /**
  171  * Display the name of the default mutex: APR_LOCK_DEFAULT
  172  */
  173 APR_DECLARE(const char *) apr_proc_mutex_defname(void);
  174 
  175 /**
  176  * Set mutex permissions.
  177  */
  178 APR_PERMS_SET_IMPLEMENT(proc_mutex);
  179 
  180 /**
  181  * Get the pool used by this proc_mutex.
  182  * @return apr_pool_t the pool
  183  */
  184 APR_POOL_DECLARE_ACCESSOR(proc_mutex);
  185 
  186 /** @} */
  187 
  188 #ifdef __cplusplus
  189 }
  190 #endif
  191 
  192 #endif  /* ! APR_PROC_MUTEX_H */