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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 (consult 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_bar-
       rier_wait() specifying the barrier.
       When the required number of threads have called  pthread_barrier_wait()
       specifying  the  barrier,  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 uninitial-
       ized 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  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 eligible to use the same processing resources from even-
       tually  making forward progress in its execution.  Eligibility for pro-
       cessing resources shall be determined 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,  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 original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003             PTHREAD_BARRIER_WAIT(3P)