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pthread_barrier_destroy, pthread_barrier_init — destroy and initialize a barrier object
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_init() function shall fail if:
- The system lacks the necessary resources to initialize another barrier.
- The value specified by count is equal to zero.
These functions shall not return an error code of [EINTR].
The following sections are informative.
If an implementation detects that the value specified by the barrier argument to pthread_barrier_destroy() does not refer to an initialized barrier object, it is recommended that the function should fail and report an [EINVAL] error.
If an implementation detects that the value specified by the attr argument to pthread_barrier_init() does not refer to an initialized barrier attributes object, it is recommended that the function should fail and report an [EINVAL] error.
If an implementation detects that the value specified by the barrier argument to pthread_barrier_destroy() or pthread_barrier_init() refers to a barrier that is in use (for example, in a pthread_barrier_wait() call) by another thread, or detects that the value specified by the barrier argument to pthread_barrier_init() refers to an already initialized barrier object, it is recommended that the function should fail and report an [EBUSY] error.
The Base Definitions volume of POSIX.1‐2008, <pthread.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
- Insufficient memory exists to initialize the barrier.
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