pthread_mutex_init(3T)pthread_mutex_init(3T)NAMEpthread_mutex_init(), pthread_mutex_destroy() - initialize or destroy a
mutex
SYNOPSISPARAMETERS
mutex Pointer to the mutex to be initialized or destroyed.
attr Pointer to the attributes object that defines the
characteristics of the mutex to be initialized. If
the pointer is NULL, default attributes are used.
DESCRIPTION
The function initializes the mutex referenced by mutex with the
attributes attr. If the parameter attr is NULL, the default mutex
attributes are used. See pthread_mutexattr_init(3T) for a list of
default mutex attributes. After successful initialization, the mutex
is initialized, unlocked, and ready to be used in mutex operations. A
mutex should be initialized only once or the resulting behavior is
undefined. The function provides a way to ensure that a mutex is ini‐
tialized only once.
The macro can be used to initialize mutexes that are statically allo‐
cated. These mutexes will be initialized with default attributes. The
function does not need to be called for statically initialized mutexes.
If the process-shared attribute in the mutex attributes object refer‐
enced by attr is defined as the mutex must be allocated such that the
processes sharing the mutex have access to it. This may be done
through the memory-mapping functions (see mmap(2)) or the shared memory
functions (see shmget(2)).
The function destroys the mutex referenced by mutex. This function may
set mutex to an invalid value. The destroyed mutex can be reinitial‐
ized using the function If the mutex is used after destruction in any
mutex call, the resulting behavior is undefined.
A mutex should be destroyed only when it is unlocked. Destroying a
mutex that is currently being used results in undefined behavior.
RETURN VALUE
Upon successful completion, and return zero. Otherwise, an error num‐
ber is returned to indicate the error (the variable is not set).
ERRORS
If any of the following occur, the function returns the corresponding
error number:
The necessary resources (other than memory) to initialize
mutex were not available.
mutex is an already initialized mutex. However, get‐
ting for reinitializing the mutex cannot be
expected all the time since the behavior of
reinitializing the mutex is undefined.
mutex points to an illegal address.
The value specified by
mutex or attr is invalid.
There is insufficient memory available in which to initialize
mutex.
The caller does not have the necessary permission to perform the
mutex initialization.
If any of the following occur, the function returns the corresponding
error number:
mutex is currently locked or in use by another thread.
mutex is not a valid mutex.
WARNINGS
The space for the mutex must be allocated before calling Undefined
behavior will result if the process-shared attribute of attr is and the
space allocated for the mutex is not accessible to cooperating threads.
AUTHOR
and were derived from the IEEE POSIX P1003.1c standard.
SEE ALSOpthread_mutex_lock(3T), pthread_mutex_trylock(3T),
pthread_mutex_unlock(3T).
STANDARDS CONFORMANCE
Pthread Library pthread_mutex_init(3T)
