xref: /src/sys/kern/subr_once.c

/*	$NetBSD: subr_once.c,v 1.3.16.2 2006/06/21 15:09:38 yamt Exp $	*/

/*-
 * 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_once.c,v 1.3.16.2 2006/06/21 15:09:38 yamt Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/once.h>

int
_run_once(once_t *o, int (*fn)(void))
{
	int error = 0;

	simple_lock(&o->o_lock);
	while ((o->o_flags & ONCE_RUNNING) != 0) {
		ltsleep(o, PUSER, "runonce", 0, &o->o_lock);
	}
	if (o->o_flags & ONCE_DONE) {
		goto done;
	}
	o->o_flags |= ONCE_RUNNING;
	simple_unlock(&o->o_lock);

	error = (*fn)();

	simple_lock(&o->o_lock);
	if (error == 0) {
		o->o_flags = ONCE_DONE;
	}
	wakeup(o);
done:
	simple_unlock(&o->o_lock);

	return error;
}