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.
NAMEpthread_barrier_wait — synchronize at a barrier
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
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 POSIX.1‐2008, Section
3.287, Priority Inversion.
RATIONALE
If an implementation detects that the value specified by the barrier
argument to pthread_barrier_wait() does not refer to an initialized
barrier object, it is recommended that the function should fail and
report an [EINVAL] error.
FUTURE DIRECTIONS
None.
SEE ALSOpthread_barrier_destroy()
The Base Definitions volume of POSIX.1‐2008, Section 3.287, Priority
Inversion, Section 4.11, Memory Synchronization, <pthread.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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.ker‐
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IEEE/The Open Group 2013 PTHREAD_BARRIER_WAIT(3P)
