pthread_barrier_destroy or pthread_barrier_init Subroutine

Purpose

Destroys or initializes a barrier object.

Syntax

#include <pthread.h>

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); 

Description

The pthread_barrier_destroy subroutine destroys the barrier referenced by the barrier parameter and releases 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 the pthread_barrier_init subroutine. An implementation can use this subroutine to set the barrier parameter to an invalid value. The results are undefined if the pthread_barrier_destroy subroutine is called when any thread is blocked on the barrier, or if this function is called with an uninitialized barrier.

The pthread_barrier_init subroutine allocates any resources required to use the barrier referenced by the barrier parameter and initializes the barrier with attributes referenced by the attr parameter. If the attr parameter is NULL, the default barrier attributes are used; the effect is the same as passing the address of a default barrier attributes object. The results are undefined if pthread_barrier_init subroutine 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 the pthread_barrier_init subroutine is called specifying an already initialized barrier.

The count argument specifies the number of threads that must call the pthread_barrier_wait subroutine before any of them successfully return from the call. The value specified by the count parameter must be greater than zero.

If the pthread_barrier_init subroutine fails, the barrier is not initialized and the contents of barrier are undefined.

Only the object referenced by the barrier parameter can be used for performing synchronization. The result of referring to copies of that object in calls to the pthread_barrier_destroy or pthread_barrier_wait subroutine is undefined.

Return Values

Upon successful completion, these functions shall return zero; otherwise, an error number shall be returned to indicate the error.

Error Codes