subr_once.c

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    1 /*      $NetBSD: subr_once.c,v 1.7 2019/03/19 08:16:51 ryo 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 1.7 2019/03/19 08:16:51 ryo 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 _init_once(once_t *o, int (*fn)(void))
   52 {
   53         /* Fastpath handled by RUN_ONCE() */
   54 
   55         int error;
   56 
   57         mutex_enter(&oncemtx);
   58         while (o->o_status == ONCE_RUNNING)
   59                 cv_wait(&oncecv, &oncemtx);
   60 
   61         if (o->o_refcnt++ == 0) {
   62                 o->o_status = ONCE_RUNNING;
   63                 mutex_exit(&oncemtx);
   64                 o->o_error = fn();
   65                 mutex_enter(&oncemtx);
   66                 o->o_status = ONCE_DONE;
   67                 cv_broadcast(&oncecv);
   68         }
   69         KASSERT(o->o_refcnt != 0);      /* detect overflow */
   70 
   71         while (o->o_status == ONCE_RUNNING)
   72                 cv_wait(&oncecv, &oncemtx);
   73         error = o->o_error;
   74         mutex_exit(&oncemtx);
   75 
   76         return error;
   77 }
   78 
   79 void
   80 _fini_once(once_t *o, void (*fn)(void))
   81 {
   82         mutex_enter(&oncemtx);
   83         while (o->o_status == ONCE_RUNNING)
   84                 cv_wait(&oncecv, &oncemtx);
   85 
   86         KASSERT(o->o_refcnt != 0);      /* we need to call _init_once() once */
   87         if (--o->o_refcnt == 0) {
   88                 o->o_status = ONCE_RUNNING;
   89                 mutex_exit(&oncemtx);
   90                 fn();
   91                 mutex_enter(&oncemtx);
   92                 o->o_status = ONCE_VIRGIN;
   93                 cv_broadcast(&oncecv);
   94         }
   95 
   96         mutex_exit(&oncemtx);
   97 }

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FreeBSD/Linux Kernel Cross Reference sys/kern/subr_once.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_once.c