163 lines
4.7 KiB
Groff
163 lines
4.7 KiB
Groff
.\" $NetBSD: pthread_barrier.3,v 1.4 2010/07/09 18:07:20 jruoho Exp $
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.\"
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.\" Copyright (c) 2002, 2010 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" ----------------------------------------------------------------------------
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.Dd July 8, 2010
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.Dt PTHREAD_BARRIER 3
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.Os
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.Sh NAME
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.Nm pthread_barrier
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.Nd barrier interface
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.Sh LIBRARY
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.Lb libpthread
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.Sh SYNOPSIS
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.In pthread.h
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.Ft int
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.Fn pthread_barrier_init "pthread_barrier_t * restrict barrier" \
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"const pthread_barrierattr_t * restrict attr" "unsigned int count"
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.Ft int
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.Fn pthread_barrier_destroy "pthread_barrier_t *barrier"
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.Ft int
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.Fn pthread_barrier_wait "pthread_barrier_t *barrier"
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.\" ----------------------------------------------------------------------------
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.Sh DESCRIPTION
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The
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.Fn pthread_barrier_init
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function creates a new barrier with attributes
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.Fa attr
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and
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.Fa count .
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The
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.Fa count
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parameter indicates the number of threads
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which will participate in the barrier.
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The
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.Xr pthread_barrierattr_init 3
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function may be used to specify the attributes supplied in
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.Fa attr .
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If
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.Fa attr
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is
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.Dv NULL ,
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the default attributes are used.
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Barriers are most commonly used in the decomposition of parallel loops.
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.Pp
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.\" -----
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The
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.Fn pthread_barrier_destroy
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function causes the resources allocated to
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.Fa barrier
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to be released.
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No threads should be blocked on
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.Fa barrier .
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.Pp
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.\" -----
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The
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.Fn pthread_barrier_wait
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function causes the current thread to wait on the barrier specified.
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Once as many threads as specified by the
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.Fa count
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parameter to the corresponding
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.Fn pthread_barrier_init
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call have called
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.Fn pthread_barrier_wait ,
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all threads will wake up, return from their respective
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.Fn pthread_barrier_wait
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calls and continue execution.
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.\" ----------------------------------------------------------------------------
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.Sh RETURN VALUES
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If successful,
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.Fn pthread_barrier_init
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will return zero and put the new barrier id into
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.Fa barrier ,
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otherwise an error number will be returned to indicate the error.
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.Pp
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.\" -----
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If successful,
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.Fn pthread_barrier_destroy
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will return zero.
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Otherwise an error value will be returned.
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.Pp
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.\" -----
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If successful,
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.Fn pthread_barrier_wait
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will return zero for all waiting threads except for one.
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One thread will receive status
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.Dv PTHREAD_BARRIER_SERIAL_THREAD ,
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which is intended to indicate that this thread may be used to update
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shared data.
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It is the responsibility of this thread to insure the visibility
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and atomicity of any updates to shared data with respect to the
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other threads participating in the barrier.
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In the case of failure, an error value will be returned.
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.\" ----------------------------------------------------------------------------
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.Sh ERRORS
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The
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.Fn pthread_barrier_init
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function may fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The value specified by
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.Fa count
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is zero or
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.Fa attr
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is invalid.
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.El
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.Pp
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.\" -----
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The
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.Fn pthread_barrier_destroy
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function may fail if:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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The
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.Fa barrier
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still has active threads associated with it.
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.It Bq Er EINVAL
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The value specified by
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.Fa barrier
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is invalid.
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.El
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.Pp
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.\" -----
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The
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.Fn pthread_barrier_wait
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function may fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The value specified by
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.Fa barrier
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is invalid.
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.El
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.\" ---------------------------------------------------------------------------
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.Sh SEE ALSO
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.Xr pthread_barrierattr 3 ,
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.Xr pthread_cond 3 ,
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.Xr pthread_mutex 3
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.Sh STANDARDS
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These functions conform to
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.St -p1003.1-2001 .
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