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

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 *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 deter‐
     mined by the count argument to pthread_barrier_init().  Once the threads
     have been released the barrier will be reset.

IMPLEMENTATION NOTES
     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 indi‐
     cate 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 ini‐
			tialize barrier.

     [EINVAL]		The count argument is less than 1.

     [ENOMEM]		Insufficient memory to initialize barrier.

SEE ALSO
     pthread_barrierattr(3)

BSD				 July 10, 2009				   BSD

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