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NetBSD 6.1.5 - man page for pthread_barrier (netbsd section 3)

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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 speci-
     fied.  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 barrier.  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
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