1.\" $NetBSD: RUN_ONCE.9,v 1.2 2005/11/24 19:36:43 wiz Exp $ 2.\" 3.\" Copyright (c)2005 YAMAMOTO Takashi, 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" ------------------------------------------------------------ 28.Dd November 24, 2005 29.Dt RUN_ONCE 9 30.Os 31.\" ------------------------------------------------------------ 32.Sh NAME 33.Nm RUN_ONCE 34.Nd Run a function exactly once 35.\" ------------------------------------------------------------ 36.Sh SYNOPSIS 37.In sys/once.h 38.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 39.Vt ONCE_DECL(control); 40.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 41.Ft void 42.Fn RUN_ONCE \ 43"once_t *control" "void (*init_func)(void)" 44.\" ------------------------------------------------------------ 45.Sh DESCRIPTION 46.Fn RUN_ONCE 47provides a functionality similar to 48.Fn pthread_once 3 . 49It ensures that 50.Fn init_func 51is called exactly once for given 52.Fa control . 53It can sleep if it's called concurrently. 54.\" ------------------------------------------------------------ 55.Sh EXAMPLES 56The following example shows how 57.Fn RUN_ONCE 58is used. 59Regardless of how many times 60.Fn some_func 61is executed, 62.Fn init_func 63will be executed exactly once. 64.Bd -literal 65static void 66init_func(void) 67{ 68 69 /* 70 * do some initialization. 71 */ 72} 73 74int 75some_func(void) 76{ 77 static DECL_ONCE(control); 78 79 RUN_ONCE(\*[Am]control, init_func); 80 81 /* 82 * we are sure that init_func has already been completed here. 83 */ 84} 85.Ed 86.\" ------------------------------------------------------------ 87.Sh SEE ALSO 88.Xr pthread_once 3 , 89.Xr intro 9 , 90.Xr ltsleep 9 91