NAME

pthread_barrier_destroy, pthread_barrier_init, pthread_barrier_wait —

destroy, initialize or wait on a barrier object

LIBRARY

POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS

#include <pthread.h>

int
pthread_barrier_destroy(pthread_barrier_t *barrier);

int
pthread_barrier_init(pthread_barrier_t *restrict barrier, const pthread_barrierattr_t *attr, unsigned count);

int
pthread_barrier_wait(pthread_barrier_t *barrier);

DESCRIPTION

The pthread_barrier_init() function will initialize barrier with attributes specified in attr, or if it is NULL, with default attributes. The number of threads that must call pthread_barrier_wait() before any of the waiting threads can be released is specified by count. The pthread_barrier_destroy() function will destroy barrier and release any resources that may have been allocated on its behalf.

The pthread_barrier_wait() function will synchronize calling threads at barrier. The threads will be blocked from making further progress until a sufficient number of threads calls this function. The number of threads that must call it before any of them will be released is determined by the count argument to pthread_barrier_init(). Once the threads have been released the barrier will be reset.

IMPLEMENTATION NOTES

In 1:1 Threading Library (libthr, -lthr) the PTHREAD_BARRIER_SERIAL_THREAD return value will always be returned by the last thread to reach the barrier.

RETURN VALUES

If successful, both pthread_barrier_destroy() and pthread_barrier_init() will return zero. Otherwise, an error number will be returned to indicate the error. If the call to pthread_barrier_wait() is successful, all but one of the threads will return zero. That one thread will return PTHREAD_BARRIER_SERIAL_THREAD. Otherwise, an error number will be returned to indicate the error.

None of these functions will return EINTR.

ERRORS

The pthread_barrier_destroy() function will fail if:

[EBUSY]: An attempt was made to destroy barrier while it was in use.

The pthread_barrier_destroy() and pthread_barrier_wait() functions may fail if:

[EINVAL]: The value specified by barrier is invalid.

The pthread_barrier_init() function will fail if:

[EAGAIN]: The system lacks resources, other than memory, to initialize barrier.
[EINVAL]: The count argument is less than 1.
[ENOMEM]: Insufficient memory to initialize barrier.

HISTORY

The pthread_barrier_destroy(), pthread_barrier_init() and pthread_barrier_wait() functions first appeared in N:M Threading Library (libkse, -lkse) in FreeBSD 5.2, and in 1:1 Threading Library (libthr, -lthr) in FreeBSD 5.3.