int pthread_barrier_destroy(pthread_barrier_t *barrier);
int pthread_barrier_init(pthread_barrier_t *restrict barrier,
const pthread_barrierattr_t *restrict attr, unsigned count);
The pthread_barrier_destroy() function shall destroy the barrier referenced by barrier and release any resources used by the barrier. The effect of subsequent use of the barrier is undefined until the barrier is reinitialized by another call to pthread_barrier_init(). An implementation may use this function to set barrier to an invalid value. The results are undefined if pthread_barrier_destroy() is called when any thread is blocked on the barrier, or if this function is called with an uninitialized barrier.
The pthread_barrier_init() function shall allocate any resources required to use the barrier referenced by barrier and shall initialize the barrier with attributes referenced by attr. If attr is NULL, the default barrier attributes shall be used; the effect is the same as passing the address of a default barrier attributes object. The results are undefined if pthread_barrier_init() is called when any thread is blocked on the barrier (that is, has not returned from the pthread_barrier_wait() call). The results are undefined if a barrier is used without first being initialized. The results are undefined if pthread_barrier_init() is called specifying an already initialized barrier.
The count argument specifies the number of threads that must call pthread_barrier_wait() before any of them successfully return from the call. The value specified by count must be greater than zero.
If the pthread_barrier_init() function fails, the barrier shall not be initialized and the contents of barrier are undefined.
Only the object referenced by barrier may be used for performing synchronization. The result of referring to copies of that object in calls to pthread_barrier_destroy() or pthread_barrier_wait() is undefined.
Upon successful completion, these functions shall return zero; otherwise, an error number shall be returned to indicate the error.
The pthread_barrier_destroy() function may fail if:
- The implementation has detected an attempt to destroy a barrier while it is in use (for example, while being used in a pthread_barrier_wait() call) by another thread.
The value specified by barrier is invalid.
The pthread_barrier_init() function shall fail if:
- The system lacks the necessary resources to initialize another barrier.
- The value specified by count is equal to zero.
Insufficient memory exists to initialize the barrier.
The pthread_barrier_init() function may fail if:
- The implementation has detected an attempt to reinitialize a barrier while it is in use (for example, while being used in a pthread_barrier_wait() call) by another thread.
The value specified by attr is invalid.
These functions shall not return an error code of [EINTR].
The following sections are informative.
The pthread_barrier_destroy() and pthread_barrier_init() functions are part of the Barriers option and need not be provided on all implementations.
COPYRIGHTPortions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .