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 } 98