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
once_init(void)43 once_init(void)
44 {
45
46 mutex_init(&oncemtx, MUTEX_DEFAULT, IPL_NONE);
47 cv_init(&oncecv, "runonce");
48 }
49
50 int
_init_once(once_t * o,int (* fn)(void))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
_fini_once(once_t * o,void (* fn)(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