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      1 /*	$NetBSD: pthread_once.c,v 1.5 2025/03/04 00:41:00 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2001, 2003 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Nathan J. Williams, and by Jason R. Thorpe.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 __RCSID("$NetBSD: pthread_once.c,v 1.5 2025/03/04 00:41:00 riastradh Exp $");
     41 
     42 /* Need to use libc-private names for atomic operations. */
     43 #include "../../common/lib/libc/atomic/atomic_op_namespace.h"
     44 
     45 #include "pthread.h"
     46 #include "pthread_int.h"
     47 #include "reentrant.h"
     48 
     49 static void
     50 once_cleanup(void *closure)
     51 {
     52 
     53        pthread_mutex_unlock((pthread_mutex_t *)closure);
     54 }
     55 
     56 int
     57 pthread_once(pthread_once_t *once_control, void (*routine)(void))
     58 {
     59 	if (__predict_false(__uselibcstub))
     60 		return __libc_thr_once_stub(once_control, routine);
     61 
     62 	if (once_control->pto_done == 0) {
     63 		pthread_mutex_lock(&once_control->pto_mutex);
     64 		pthread_cleanup_push(&once_cleanup, &once_control->pto_mutex);
     65 		if (once_control->pto_done == 0) {
     66 			routine();
     67 			membar_release();
     68 			once_control->pto_done = 1;
     69 		}
     70 		pthread_cleanup_pop(1);
     71 	} else {
     72 		membar_acquire();
     73 	}
     74 
     75 	return 0;
     76 }
     77 
     78 __strong_alias(__libc_thr_once,pthread_once)
     79