xref: /src/lib/libpthread/pthread_once.c

/*	$NetBSD: pthread_once.c,v 1.4.4.1 2025/08/02 05:54:55 perseant Exp $	*/

/*-
 * Copyright (c) 2001, 2003 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Nathan J. Williams, and by Jason R. Thorpe.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *        This product includes software developed by the NetBSD
 *        Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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>
__RCSID("$NetBSD: pthread_once.c,v 1.4.4.1 2025/08/02 05:54:55 perseant Exp $");

/* Need to use libc-private names for atomic operations. */
#include "../../common/lib/libc/atomic/atomic_op_namespace.h"

#include "pthread.h"
#include "pthread_int.h"
#include "reentrant.h"

static void
once_cleanup(void *closure)
{

       pthread_mutex_unlock((pthread_mutex_t *)closure);
}

int
pthread_once(pthread_once_t *once_control, void (*routine)(void))
{
	if (__predict_false(__uselibcstub))
		return __libc_thr_once_stub(once_control, routine);

	if (once_control->pto_done == 0) {
		pthread_mutex_lock(&once_control->pto_mutex);
		pthread_cleanup_push(&once_cleanup, &once_control->pto_mutex);
		if (once_control->pto_done == 0) {
			routine();
			membar_release();
			once_control->pto_done = 1;
		}
		pthread_cleanup_pop(1);
	} else {
		membar_acquire();
	}

	return 0;
}

__strong_alias(__libc_thr_once,pthread_once)