PTHREAD_BARRIER(3)					   BSD Library Functions Manual 					PTHREAD_BARRIER(3)

NAME

     pthread_barrier -- barrier interface

LIBRARY

     POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS

     #include <pthread.h>

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

     int
     pthread_barrier_destroy(pthread_barrier_t *barrier);

     int
     pthread_barrier_wait(pthread_barrier_t *barrier);

DESCRIPTION

     The pthread_barrier_init() function creates a new barrier with attributes attr and count.	The count parameter indicates the number of
     threads which will participate in the barrier.  The pthread_barrierattr_init(3) function may be used to specify the attributes supplied in
     attr.  If attr is NULL, the default attributes are used.  Barriers are most commonly used in the decomposition of parallel loops.

     The pthread_barrier_destroy() function causes the resources allocated to barrier to be released.  No threads should be blocked on barrier.

     The pthread_barrier_wait() function causes the current thread to wait on the barrier specified.  Once as many threads as specified by the
     count parameter to the corresponding pthread_barrier_init() call have called pthread_barrier_wait(), all threads will wake up, return from
     their respective pthread_barrier_wait() calls and continue execution.

RETURN VALUES

     If successful, pthread_barrier_init() will return zero and put the new barrier id into barrier, otherwise an error number will be returned to
     indicate the error.

     If successful, pthread_barrier_destroy() will return zero.  Otherwise an error value will be returned.

     If successful, pthread_barrier_wait() will return zero for all waiting threads except for one.  One thread will receive status
     PTHREAD_BARRIER_SERIAL_THREAD, which is intended to indicate that this thread may be used to update shared data.  It is the responsibility of
     this thread to insure the visibility and atomicity of any updates to shared data with respect to the other threads participating in the bar-
     rier.  In the case of failure, an error value will be returned.

ERRORS

     The pthread_barrier_init() function may fail if:

     [EINVAL]		The value specified by count is zero or attr is invalid.

     The pthread_barrier_destroy() function may fail if:

     [EBUSY]		The barrier still has active threads associated with it.

     [EINVAL]		The value specified by barrier is invalid.

     The pthread_barrier_wait() function may fail if:

     [EINVAL]		The value specified by barrier is invalid.

SEE ALSO

     pthread_barrierattr(3), pthread_cond(3), pthread_mutex(3)

STANDARDS

     These functions conform to IEEE Std 1003.1-2001 (``POSIX.1'').

BSD
								   July 8, 2010 							       BSD