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----------------------------------------------------------------------------
.Dd July 8, 2010 .Dt PTHREAD_BARRIER 3 .Os .Sh NAME .Nm pthread_barrier .Nd barrier interface .Sh LIBRARY .Lb libpthread .Sh SYNOPSIS n pthread.h .Ft int .Fn pthread_barrier_init "pthread_barrier_t * restrict barrier" \ "const pthread_barrierattr_t * restrict attr" "unsigned int count" .Ft int .Fn pthread_barrier_destroy "pthread_barrier_t *barrier" .Ft int .Fn pthread_barrier_wait "pthread_barrier_t *barrier" ----------------------------------------------------------------------------
.Sh DESCRIPTION The .Fn pthread_barrier_init function creates a new barrier, with attributes specified with .Fa attr and .Fa count . The .Fa count parameter indicates the number of threads which will participate in the barrier. If .Fa attr is NULL the default attributes are used. Barriers are most commonly used in the decomposition of parallel loops.
p
-----
The
.Fn pthread_barrier_destroy
function causes the resources allocated to
.Fa barrier
to be released.
No threads should be blocked on
.Fa barrier .
p
-----
The
.Fn pthread_barrier_wait
function causes the current thread to wait on the barrier specified.
Once as many threads as specified by the
.Fa count
parameter to the corresponding
.Fn pthread_barrier_init
call have called
.Fn pthread_barrier_wait ,
all threads will wake up, return from their respective
.Fn pthread_barrier_wait
calls and continue execution.
----------------------------------------------------------------------------
.Sh RETURN VALUES
If successful,
.Fn pthread_barrier_init
will return zero and put the new barrier id into
.Fa barrier ,
otherwise an error number will be returned to indicate the error.
p
-----
If successful,
.Fn pthread_barrier_destroy
will return zero.
Otherwise an error value will be returned.
p
-----
If successful,
.Fn pthread_barrier_wait
will return zero for all waiting threads except for one.
One thread will receive status
.Dv 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 barrier.
In the case of failure, an error value will be returned.
----------------------------------------------------------------------------
.Sh ERRORS
.Fn pthread_barrier_init
may fail if:
l -tag -width Er t Bq Er EAGAIN The system lacks the resources to initialize another barrier.
t Bq Er EINVAL The value specified by
.Fa count
is zero or
.Fa attr
is invalid.
t Bq Er ENOMEM Insufficient memory exists to initialize the barrier.
t Bq Er EBUSY The barrier structure has been initialized already.
.El
p
-----
.Fn pthread_barrier_destroy
may fail if:
l -tag -width Er t Bq Er EBUSY The
.Fa barrier
still has active threads associated with it.
t Bq Er EINVAL The value specified by
.Fa barrier
is invalid.
.El
p
-----
.Fn pthread_barrier_wait
may fail if:
l -tag -width Er t Bq Er EINVAL The value specified by
.Fa barrier
is invalid.
.El
----------------------------------------------------------------------------
.Sh SEE ALSO
.Xr pthread 3 ,
.Xr pthread_barrierattr 3 ,
.Xr pthread_cond 3
.Xr pthread_mutex 3 ,
.Xr pthread_rwlock 3 ,
.Xr pthread_spin 3
.Sh STANDARDS
These functions conform to
.St -p1003.1-2001 .
Indexes created Tue Sep 30 17:09:57 GMT 2025