PTHREAD_BARRIER(3) BSD Library Functions Manual PTHREAD_BARRIER(3)NAME
pthread_barrier — barrier interface
LIBRARY
POSIX Threads Library (libpthread, -lpthread)
SYNOPSIS
#include <pthread.h>
int
pthread_barrier_init(pthread_barrier_t * restrict barrier,
const pthread_barrierattr_t * restrict attr, unsigned int count);
int
pthread_barrier_destroy(pthread_barrier_t *barrier);
int
pthread_barrier_wait(pthread_barrier_t *barrier);
DESCRIPTION
The pthread_barrier_init() function creates a new barrier with attributes
attr and count. The count parameter indicates the number of threads
which will participate in the barrier. The pthread_barrierattr_init(3)
function may be used to specify the attributes supplied in attr. If attr
is NULL, the default attributes are used. Barriers are most commonly
used in the decomposition of parallel loops.
The pthread_barrier_destroy() function causes the resources allocated to
barrier to be released. No threads should be blocked on barrier.
The pthread_barrier_wait() function causes the current thread to wait on
the barrier specified. Once as many threads as specified by the count
parameter to the corresponding pthread_barrier_init() call have called
pthread_barrier_wait(), all threads will wake up, return from their
respective pthread_barrier_wait() calls and continue execution.
RETURN VALUES
If successful, pthread_barrier_init() will return zero and put the new
barrier id into barrier, otherwise an error number will be returned to
indicate the error.
If successful, pthread_barrier_destroy() will return zero. Otherwise an
error value will be returned.
If successful, pthread_barrier_wait() will return zero for all waiting
threads except for one. One thread will receive status
PTHREAD_BARRIER_SERIAL_THREAD, which is intended to indicate that this
thread may be used to update shared data. It is the responsibility of
this thread to insure the visibility and atomicity of any updates to
shared data with respect to the other threads participating in the bar‐
rier. In the case of failure, an error value will be returned.
ERRORS
The pthread_barrier_init() function may fail if:
[EINVAL] The value specified by count is zero or attr is
invalid.
The pthread_barrier_destroy() function may fail if:
[EBUSY] The barrier still has active threads associated with
it.
[EINVAL] The value specified by barrier is invalid.
The pthread_barrier_wait() function may fail if:
[EINVAL] The value specified by barrier is invalid.
SEE ALSOpthread_barrierattr(3), pthread_cond(3), pthread_mutex(3)STANDARDS
These functions conform to IEEE Std 1003.1-2001 (“POSIX.1”).
BSD July 8, 2010 BSD
