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subr_once.c revision 1.5 
      1 /*	$NetBSD: subr_once.c,v 1.5 2008/10/09 12:14:06 pooka Exp $	*/
      2 
      3 /*-
      4  * Copyright (c)2005 YAMAMOTO Takashi,
      5  * Copyright (c)2008 Antti Kantee,
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     27  * SUCH DAMAGE.
     28  */
     29 
     30 #include <sys/cdefs.h>
     31 __KERNEL_RCSID(0, "$NetBSD: subr_once.c,v 1.5 2008/10/09 12:14:06 pooka Exp $");
     32 
     33 #include <sys/param.h>
     34 #include <sys/systm.h>
     35 #include <sys/condvar.h>
     36 #include <sys/mutex.h>
     37 #include <sys/once.h>
     38 
     39 static kmutex_t oncemtx;
     40 static kcondvar_t oncecv;
     41 
     42 void
     43 once_init()
     44 {
     45 
     46 	mutex_init(&oncemtx, MUTEX_DEFAULT, IPL_NONE);
     47 	cv_init(&oncecv, "runonce");
     48 }
     49 
     50 int
     51 _run_once(once_t *o, int (*fn)(void))
     52 {
     53 
     54 	/* Fastpath handled by RUN_ONCE() */
     55 
     56 	mutex_enter(&oncemtx);
     57 	if (o->o_status == ONCE_VIRGIN) {
     58 		o->o_status = ONCE_RUNNING;
     59 		mutex_exit(&oncemtx);
     60 		o->o_error = fn();
     61 		mutex_enter(&oncemtx);
     62 		o->o_status = ONCE_DONE;
     63 		cv_broadcast(&oncecv);
     64 	}
     65 	while (o->o_status != ONCE_DONE)
     66 		cv_wait(&oncecv, &oncemtx);
     67 	mutex_exit(&oncemtx);
     68 
     69 	KASSERT(o->o_status == ONCE_DONE);
     70 	return o->o_error;
     71 }
     72