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_destroy, pthread_barrier_init — destroy and initialize a barrier object

SYNOPSIS

       #include <pthread.h>

       int pthread_barrier_destroy(pthread_barrier_t *barrier);
       int pthread_barrier_init(pthread_barrier_t *restrict barrier,
           const pthread_barrierattr_t *restrict attr, unsigned count);

DESCRIPTION

       The pthread_barrier_destroy() function shall destroy the barrier referenced by barrier and
       release any resources used by the barrier. The effect of subsequent use of the barrier  is
       undefined  until  the  barrier is reinitialized by another call to pthread_barrier_init().
       An implementation may use this function to set barrier to an invalid  value.  The  results
       are  undefined  if  pthread_barrier_destroy()  is called when any thread is blocked on the
       barrier, or if this function is called with an uninitialized barrier.

       The pthread_barrier_init() function shall allocate  any  resources  required  to  use  the
       barrier  referenced by barrier and shall initialize the barrier with attributes referenced
       by attr.  If attr is NULL, the default barrier attributes shall be used; the effect is the
       same  as  passing  the  address  of  a  default barrier attributes object. The results are
       undefined if pthread_barrier_init() is called when any thread is blocked  on  the  barrier
       (that  is,  has  not  returned  from  the  pthread_barrier_wait()  call).  The results are
       undefined if a barrier is used without first being initialized. The results are  undefined
       if pthread_barrier_init() is called specifying an already initialized barrier.

       The  count  argument specifies the number of threads that must call pthread_barrier_wait()
       before any of them successfully return from the call. The value specified by count must be
       greater than zero.

       If the pthread_barrier_init() function fails, the barrier shall not be initialized and the
       contents of barrier are undefined.

       See Section 2.9.9, Synchronization Object Copies  and  Alternative  Mappings  for  further
       requirements.

RETURN VALUE

       Upon  successful completion, these functions shall return zero; otherwise, an error number
       shall be returned to indicate the error.

ERRORS

       The pthread_barrier_init() function shall fail if:

       EAGAIN The system lacks the necessary resources to initialize another barrier.

       EINVAL The value specified by count is equal to zero.

       ENOMEM Insufficient memory exists to initialize the barrier.

       These functions shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       If an implementation  detects  that  the  value  specified  by  the  barrier  argument  to
       pthread_barrier_destroy()  does  not  refer  to  an  initialized  barrier  object,  it  is
       recommended that the function should fail and report an [EINVAL] error.

       If  an  implementation  detects  that  the  value  specified  by  the  attr  argument   to
       pthread_barrier_init()  does  not refer to an initialized barrier attributes object, it is
       recommended that the function should fail and report an [EINVAL] error.

       If an implementation  detects  that  the  value  specified  by  the  barrier  argument  to
       pthread_barrier_destroy()  or  pthread_barrier_init()  refers  to a barrier that is in use
       (for example, in a pthread_barrier_wait() call) by another thread,  or  detects  that  the
       value  specified  by  the  barrier argument to pthread_barrier_init() refers to an already
       initialized barrier object, it is recommended that the function should fail and report  an
       [EBUSY] error.

FUTURE DIRECTIONS

       None.

SEE ALSO

       pthread_barrier_wait()

       The Base Definitions volume of POSIX.1‐2017, <pthread.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .