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subr_once.c revision 1.3.16.2 
      1 /*	$NetBSD: subr_once.c,v 1.3.16.2 2006/06/21 15:09:38 yamt Exp $	*/
      2 
      3 /*-
      4  * Copyright (c)2005 YAMAMOTO Takashi,
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: subr_once.c,v 1.3.16.2 2006/06/21 15:09:38 yamt Exp $");
     31 
     32 #include <sys/param.h>
     33 #include <sys/systm.h>
     34 #include <sys/proc.h>
     35 #include <sys/once.h>
     36 
     37 int
     38 _run_once(once_t *o, int (*fn)(void))
     39 {
     40 	int error = 0;
     41 
     42 	simple_lock(&o->o_lock);
     43 	while ((o->o_flags & ONCE_RUNNING) != 0) {
     44 		ltsleep(o, PUSER, "runonce", 0, &o->o_lock);
     45 	}
     46 	if (o->o_flags & ONCE_DONE) {
     47 		goto done;
     48 	}
     49 	o->o_flags |= ONCE_RUNNING;
     50 	simple_unlock(&o->o_lock);
     51 
     52 	error = (*fn)();
     53 
     54 	simple_lock(&o->o_lock);
     55 	if (error == 0) {
     56 		o->o_flags = ONCE_DONE;
     57 	}
     58 	wakeup(o);
     59 done:
     60 	simple_unlock(&o->o_lock);
     61 
     62 	return error;
     63 }
     64