183 lines
4.1 KiB
Groff
183 lines
4.1 KiB
Groff
.\" $NetBSD: cnd.3,v 1.2 2019/04/27 10:57:11 wiz Exp $
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.\"
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.\" Copyright (c) 2016 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Kamil Rytarowski.
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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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.Dd October 16, 2016
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.Dt CND 3
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.Os
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.Sh NAME
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.Nm cnd
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.Nd condition variable functions
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.Sh LIBRARY
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.Lb libpthread
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.Sh SYNOPSIS
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.In threads.h
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.Ft int
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.Fn cnd_broadcast "cnd_t *cond"
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.Ft void
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.Fn cnd_destroy "cnd_t *cond"
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.Ft int
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.Fn cnd_init "cnd_t *cond"
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.Ft int
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.Fn cnd_signal "cnd_t *cond"
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.Ft int
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.Fo cnd_timedwait
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.Fa "cnd_t * __restrict cond"
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.Fa "mtx_t * __restrict mtx"
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.Fa "const struct timespec * __restrict ts"
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.Fc
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.Ft int
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.Fn cnd_wait "cnd_t *cond" "mtx_t *mtx"
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.Sh DESCRIPTION
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The
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.Fn cnd_broadcast
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function unblocks all threads that are blocked on a condition variable
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.Fa cond
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at the time of the call.
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If no thread is blocked on the
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.Fa cond
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condition variable at the time of the call,
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the function does nothing and returns success.
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.Pp
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The
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.Fn cnd_destroy
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function destroys the
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.Fa cond
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condition variable.
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.Pp
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The
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.Fn cnd_init
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function initializes a new
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.Fa cond
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variable.
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.Pp
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The
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.Fn cnd_signal
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function unblock one thread that currently waits on the
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.Fa cond
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variable.
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If there are no threads blocked,
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.Fn cnd_signal
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does nothing and returns success.
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.Pp
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The
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.Fn cnd_timedwait
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function atomically unlocks the mutex
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.Fa mtx
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and blocks on the condition variable
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.Fa cond
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until a thread is signalled by a call to
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.Fn cnd_signal
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or
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.Fn cnd_broadcast
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or timeout
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.Fa ts
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has been reached.
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The
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.Fa ts
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parameter is specified as
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.Dv TIME_UTC
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based calendar time.
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If the mutex is not locked by the calling thread then behavior is undefined.
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.Pp
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The
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.Fn cnd_wait
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function atomically unlocks the mutex
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.Fa mtx
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and tries to block on the conditional variable
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.Fa cond
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until a thread is signalled by a call to
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.Fn cnd_signal
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or
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.Fn cnd_broadcast .
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The
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.Fa mtx
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mutex is locked again before the function returns.
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If the mutex is not locked by the calling thread then behavior is undefined.
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.Sh RETURN VALUES
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The
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.Fn cnd_broadcast
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function returns
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.Dv thrd_success
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on success or
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.Dv thrd_error
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on failure.
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.Pp
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The
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.Fn cnd_destroy
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function returns no value.
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.Pp
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The
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.Fn cnd_init
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function returns
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.Dv thrd_success
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on success or
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.Dv thrd_error
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on failure.
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.Pp
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The
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.Fn cnd_signal
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function returns
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.Dv thrd_success
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on success or
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.Dv thrd_error
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on failure.
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.Pp
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The
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.Fn cnd_timedwait
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function returns
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.Dv thrd_success
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on success, otherwise
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.Dv thrd_timedout
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to indicate that system time has reached or exceeded the time specified in
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.Dv ts ,
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or
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.Dv thrd_error
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on failure.
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.Pp
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The
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.Fn cnd_wait
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function returns
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.Dv thrd_success
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on success or
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.Dv thrd_error
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on failure.
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.Sh SEE ALSO
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.Xr pthread_cond 3 ,
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.Xr threads 3
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.Sh STANDARDS
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The
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.Nm
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interface conforms to
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.St -isoC-2011 .
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.Sh HISTORY
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This interface first appeared in
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.Nx 9 .
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.Sh AUTHORS
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.An Kamil Rytarowski Aq Mt kamil@NetBSD.org
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