Process Locking Routines

Overview

// typedefs

typedef struct apr_proc_mutex_t apr_proc_mutex_t;

// enums

enum apr_lockmech_e;

// global functions

apr_status_t
apr_proc_mutex_create(
    apr_proc_mutex_t** mutex,
    const char* fname,
    apr_lockmech_e mech,
    apr_pool_t* pool
);

apr_status_t
apr_proc_mutex_child_init(
    apr_proc_mutex_t** mutex,
    const char* fname,
    apr_pool_t* pool
);

apr_status_t
apr_proc_mutex_lock(apr_proc_mutex_t* mutex);

apr_status_t
apr_proc_mutex_trylock(apr_proc_mutex_t* mutex);

apr_status_t
apr_proc_mutex_unlock(apr_proc_mutex_t* mutex);

apr_status_t
apr_proc_mutex_destroy(apr_proc_mutex_t* mutex);

apr_status_t
apr_proc_mutex_cleanup(void* mutex);

const char*
apr_proc_mutex_lockfile(apr_proc_mutex_t* mutex);

const char*
apr_proc_mutex_name(apr_proc_mutex_t* mutex);

const char*
apr_proc_mutex_defname(void);

apr_pool_t*
apr_proc_mutex_pool_get(const apr_proc_mutex_t* theproc_mutex);

Detailed Documentation

Typedefs

typedef struct apr_proc_mutex_t apr_proc_mutex_t

Opaque structure representing a process mutex.

Global Functions

apr_status_t
apr_proc_mutex_create(
    apr_proc_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 processes.

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.

See also:

apr_lockmech_e

apr_status_t
apr_proc_mutex_child_init(
    apr_proc_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_proc_mutex_create().
pool	The pool to operate on.

apr_status_t
apr_proc_mutex_lock(apr_proc_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_proc_mutex_trylock(apr_proc_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_proc_mutex_unlock(apr_proc_mutex_t* mutex)

Release the lock for the given mutex.

Parameters:

mutex

the mutex from which to release the lock.

apr_status_t
apr_proc_mutex_destroy(apr_proc_mutex_t* mutex)

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

Parameters:

mutex

the mutex to destroy.

apr_status_t
apr_proc_mutex_cleanup(void* mutex)

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

Note

This function is generally used to kill a cleanup on an already created mutex

Parameters:

mutex

the mutex to destroy.

const char*
apr_proc_mutex_lockfile(apr_proc_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_proc_mutex_name(apr_proc_mutex_t* mutex)

Display the name of the mutex, as it relates to the actual method used. This matches the valid options for Apache’s AcceptMutex directive

Parameters:

mutex

the name of the mutex

const char*
apr_proc_mutex_defname(void)

Display the name of the default mutex: APR_LOCK_DEFAULT

apr_pool_t*
apr_proc_mutex_pool_get(const apr_proc_mutex_t* theproc_mutex)

Get the pool used by this proc_mutex.

Returns:

apr_pool_t the pool