Global Locking Routines

Overview

// typedefs

typedef struct apr_global_mutex_t apr_global_mutex_t;

// global functions

apr_status_t
apr_global_mutex_create(
    apr_global_mutex_t** mutex,
    const char* fname,
    apr_lockmech_e mech,
    apr_pool_t* pool
);

apr_status_t
apr_global_mutex_child_init(
    apr_global_mutex_t** mutex,
    const char* fname,
    apr_pool_t* pool
);

apr_status_t
apr_global_mutex_lock(apr_global_mutex_t* mutex);

apr_status_t
apr_global_mutex_trylock(apr_global_mutex_t* mutex);

apr_status_t
apr_global_mutex_unlock(apr_global_mutex_t* mutex);

apr_status_t
apr_global_mutex_destroy(apr_global_mutex_t* mutex);

const char*
apr_global_mutex_lockfile(apr_global_mutex_t* mutex);

const char*
apr_global_mutex_name(apr_global_mutex_t* mutex);

apr_pool_t*
apr_global_mutex_pool_get(const apr_global_mutex_t* theglobal_mutex);

Detailed Documentation

Typedefs

typedef struct apr_global_mutex_t apr_global_mutex_t

Opaque global mutex structure.

Global Functions

apr_status_t
apr_global_mutex_create(
    apr_global_mutex_t** mutex,
    const char* fname,
    apr_lockmech_e mech,
    apr_pool_t* pool
)

Create and initialize a mutex that can be used to synchronize both processes and threads. Note: There is considerable overhead in using this API if only cross-process or cross-thread mutual exclusion is required. See apr_proc_mutex.h and apr_thread_mutex.h for more specialized lock routines.

Warning

Check APR_HAS_foo_SERIALIZE defines to see if the platform supports APR_LOCK_foo. Only APR_LOCK_DEFAULT is portable.

Parameters:

mutex	the memory address where the newly created mutex will be stored.
fname	A file name to use if the lock mechanism requires one. This argument should always be provided. The lock code itself will determine if it should be used.
mech	The mechanism to use for the interprocess lock, if any; one of APR_LOCK_FCNTL APR_LOCK_FLOCK APR_LOCK_SYSVSEM APR_LOCK_POSIXSEM APR_LOCK_PROC_PTHREAD APR_LOCK_DEFAULT pick the default mechanism for the platform
pool	the pool from which to allocate the mutex.

apr_status_t
apr_global_mutex_child_init(
    apr_global_mutex_t** mutex,
    const char* fname,
    apr_pool_t* pool
)

Re-open a mutex in a child process. This function must be called to maintain portability, even if the underlying lock mechanism does not require it.

Parameters:

mutex	The newly re-opened mutex structure.
fname	A file name to use if the mutex mechanism requires one. This argument should always be provided. The mutex code itself will determine if it should be used. This filename should be the same one that was passed to apr_global_mutex_create().
pool	The pool to operate on.

apr_status_t
apr_global_mutex_lock(apr_global_mutex_t* mutex)

Acquire the lock for the given mutex. If the mutex is already locked, the current thread will be put to sleep until the lock becomes available.

Parameters:

mutex

the mutex on which to acquire the lock.

apr_status_t
apr_global_mutex_trylock(apr_global_mutex_t* mutex)

Attempt to acquire the lock for the given mutex. If the mutex has already been acquired, the call returns immediately with APR_EBUSY. Note: it is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine if the return value was APR_EBUSY, for portability reasons.

Parameters:

mutex

the mutex on which to attempt the lock acquiring.

apr_status_t
apr_global_mutex_unlock(apr_global_mutex_t* mutex)

Release the lock for the given mutex.

Parameters:

mutex

the mutex from which to release the lock.

apr_status_t
apr_global_mutex_destroy(apr_global_mutex_t* mutex)

Destroy the mutex and free the memory associated with the lock.

Parameters:

mutex

the mutex to destroy.

const char*
apr_global_mutex_lockfile(apr_global_mutex_t* mutex)

Return the name of the lockfile for the mutex, or NULL if the mutex doesn’t use a lock file

const char*
apr_global_mutex_name(apr_global_mutex_t* mutex)

Display the name of the mutex, as it relates to the actual method used for the underlying apr_proc_mutex_t, if any. NULL is returned if there is no underlying apr_proc_mutex_t.

Parameters:

mutex

the name of the mutex

apr_pool_t*
apr_global_mutex_pool_get(const apr_global_mutex_t* theglobal_mutex)

Get the pool used by this global_mutex.

Returns:

apr_pool_t the pool