PTHREAD_BARRIER_WAIT(3P)                            POSIX Programmer's Manual                           PTHREAD_BARRIER_WAIT(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

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  bar-
       rier.

       When  the required number of threads have called pthread_barrier_wait() specifying the barrier, the constant PTHREAD_BAR-
       RIER_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 completed (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 com-
       pleted 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 eligible to use the same processing
       resources from eventually making forward progress in its execution.  Eligibility for processing resources shall be deter-
       mined by the scheduling policy.

RETURN VALUE
       Upon  successful  completion, the pthread_barrier_wait() function shall return PTHREAD_BARRIER_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 provided 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, Copy-
       right (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   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                      PTHREAD_BARRIER_WAIT(3P)