2005-11-24 22:36:43 +03:00
|
|
|
.\" $NetBSD: RUN_ONCE.9,v 1.2 2005/11/24 19:36:43 wiz Exp $
|
2005-11-24 11:14:13 +03:00
|
|
|
.\"
|
|
|
|
|
.\" Copyright (c)2005 YAMAMOTO Takashi,
|
|
|
|
|
.\" All rights reserved.
|
|
|
|
|
.\"
|
|
|
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
|
|
|
.\" modification, are permitted provided that the following conditions
|
|
|
|
|
.\" are met:
|
|
|
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
|
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
|
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
|
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
|
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
|
|
|
.\"
|
|
|
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
|
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
|
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
|
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
|
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
|
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
|
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
|
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
|
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
|
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
|
|
|
.\" SUCH DAMAGE.
|
|
|
|
|
.\"
|
|
|
|
|
.\" ------------------------------------------------------------
|
|
|
|
|
.Dd November 24, 2005
|
|
|
|
|
.Dt RUN_ONCE 9
|
|
|
|
|
.Os
|
|
|
|
|
.\" ------------------------------------------------------------
|
|
|
|
|
.Sh NAME
|
|
|
|
|
.Nm RUN_ONCE
|
|
|
|
|
.Nd Run a function exactly once
|
|
|
|
|
.\" ------------------------------------------------------------
|
|
|
|
|
.Sh SYNOPSIS
|
|
|
|
|
.In sys/once.h
|
|
|
|
|
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
|
|
|
.Vt ONCE_DECL(control);
|
|
|
|
|
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
|
|
|
.Ft void
|
|
|
|
|
.Fn RUN_ONCE \
|
|
|
|
|
"once_t *control" "void (*init_func)(void)"
|
|
|
|
|
.\" ------------------------------------------------------------
|
|
|
|
|
.Sh DESCRIPTION
|
|
|
|
|
.Fn RUN_ONCE
|
|
|
|
|
provides a functionality similar to
|
|
|
|
|
.Fn pthread_once 3 .
|
|
|
|
|
It ensures that
|
|
|
|
|
.Fn init_func
|
|
|
|
|
is called exactly once for given
|
|
|
|
|
.Fa control .
|
|
|
|
|
It can sleep if it's called concurrently.
|
|
|
|
|
.\" ------------------------------------------------------------
|
|
|
|
|
.Sh EXAMPLES
|
|
|
|
|
The following example shows how
|
|
|
|
|
.Fn RUN_ONCE
|
|
|
|
|
is used.
|
2005-11-24 22:36:43 +03:00
|
|
|
Regardless of how many times
|
2005-11-24 11:14:13 +03:00
|
|
|
.Fn some_func
|
|
|
|
|
is executed,
|
|
|
|
|
.Fn init_func
|
|
|
|
|
will be executed exactly once.
|
|
|
|
|
.Bd -literal
|
|
|
|
|
static void
|
|
|
|
|
init_func(void)
|
|
|
|
|
{
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* do some initialization.
|
|
|
|
|
*/
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
int
|
|
|
|
|
some_func(void)
|
|
|
|
|
{
|
|
|
|
|
static DECL_ONCE(control);
|
|
|
|
|
|
2005-11-24 22:36:43 +03:00
|
|
|
RUN_ONCE(\*[Am]control, init_func);
|
2005-11-24 11:14:13 +03:00
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* we are sure that init_func has already been completed here.
|
|
|
|
|
*/
|
|
|
|
|
}
|
|
|
|
|
.Ed
|
|
|
|
|
.\" ------------------------------------------------------------
|
|
|
|
|
.Sh SEE ALSO
|
2005-11-24 22:36:43 +03:00
|
|
|
.Xr pthread_once 3 ,
|
2005-11-24 11:14:13 +03:00
|
|
|
.Xr intro 9 ,
|
2005-11-24 22:36:43 +03:00
|
|
|
.Xr ltsleep 9
|
