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PTHREAD_BARRIER_WAIT(P) 	    POSIX Programmer's Manual		  PTHREAD_BARRIER_WAIT(P)

NAME
       pthread_barrier_wait - synchronize at a barrier (ADVANCED REALTIME THREADS)

SYNOPSIS
       #include <pthread.h>

       int pthread_barrier_wait(pthread_barrier_t *barrier);

DESCRIPTION
       The pthread_barrier_wait() function shall synchronize participating threads at the barrier
       referenced by barrier.  The calling thread  shall  block  until	the  required  number  of
       threads have called pthread_barrier_wait() specifying the barrier.

       When the required number of threads have called pthread_barrier_wait() specifying the bar-
       rier, the constant PTHREAD_BARRIER_SERIAL_THREAD shall  be  returned  to  one  unspecified
       thread  and  zero  shall  be returned to each of the remaining threads. At this point, the
       barrier shall be reset to the state it had as a result of  the  most  recent  pthread_bar-
       rier_init() function that referenced it.

       The  constant  PTHREAD_BARRIER_SERIAL_THREAD is defined in <pthread.h> and its value shall
       be distinct from any other value returned by pthread_barrier_wait().

       The results are undefined if this function is called with an uninitialized barrier.

       If a signal is delivered to a thread blocked on a barrier, upon	return	from  the  signal
       handler	the  thread  shall resume waiting at the barrier if the barrier wait has not com-
       pleted (that is, if the required number of threads have not arrived at the barrier  during
       the  execution of the signal handler); otherwise, the thread shall continue as normal from
       the completed barrier wait. Until the thread in the signal handler returns from it, it  is
       unspecified  whether other threads may proceed past the barrier once they have all reached
       it.

       A thread that has blocked on a barrier shall not prevent any unblocked thread that is eli-
       gible  to use the same processing resources from eventually making forward progress in its
       execution.  Eligibility for processing resources shall be  determined  by  the  scheduling
       policy.

RETURN VALUE
       Upon  successful completion, the pthread_barrier_wait() function shall return PTHREAD_BAR-
       RIER_SERIAL_THREAD for a single (arbitrary) thread synchronized at the  barrier	and  zero
       for  each  of  the other threads. Otherwise, an error number shall be returned to indicate
       the error.

ERRORS
       The pthread_barrier_wait() function may fail if:

       EINVAL The value specified by barrier does not refer to an initialized barrier object.

       This function shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Applications using this function may be subject to priority inversion, as discussed in the
       Base Definitions volume of IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.

       The  pthread_barrier_wait()  function  is part of the Barriers option and need not be pro-
       vided on all implementations.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       pthread_barrier_destroy()  ,  the  Base	Definitions   volume   of   IEEE Std 1003.1-2001,
       <pthread.h>

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003			  PTHREAD_BARRIER_WAIT(P)
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