sys/kern/subr_once.c

   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(void)
  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 }