1 /* $NetBSD: kern_cfglock.c,v 1.1 2010/08/21 13:17:31 pgoyette Exp $ */
2
3 /*-
4 * Copyright (c) 2002, 2006, 2007, 2008, 2009 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
9 * NASA Ames Research Center, and by Andrew Doran.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
22 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
23 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
24 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
30 * POSSIBILITY OF SUCH DAMAGE.
31 */
32
33 #include <sys/cdefs.h>
34 __KERNEL_RCSID(0, "$NetBSD: kern_cfglock.c,v 1.1 2010/08/21 13:17:31 pgoyette Exp $");
35
36 #include <sys/param.h>
37 #include <sys/cpu.h>
38 #include <sys/mutex.h>
39 #include <sys/lwp.h>
40 #include <sys/systm.h>
41
42 static kmutex_t kernconfig_mutex;
43 static lwp_t *kernconfig_lwp;
44 static int kernconfig_recurse;
45
46 /*
47 * Functions for manipulating the kernel configuration lock. This
48 * recursive lock should be used to protect all additions and removals
49 * of kernel functionality, such as device configuration and loading
50 * of modular kernel components.
51 */
52
53 void
kernconfig_lock_init(void)54 kernconfig_lock_init(void)
55 {
56
57 mutex_init(&kernconfig_mutex, MUTEX_DEFAULT, IPL_NONE);
58 kernconfig_lwp = NULL;
59 kernconfig_recurse = 0;
60 }
61
62 void
kernconfig_lock(void)63 kernconfig_lock(void)
64 {
65 lwp_t *my_lwp;
66
67 /*
68 * It's OK to check this unlocked, since it could only be set to
69 * curlwp by the current thread itself, and not by an interrupt
70 * or any other LWP.
71 */
72 KASSERT(!cpu_intr_p());
73 my_lwp = curlwp;
74 if (kernconfig_lwp == my_lwp) {
75 kernconfig_recurse++;
76 KASSERT(kernconfig_recurse > 1);
77 } else {
78 mutex_enter(&kernconfig_mutex);
79 kernconfig_lwp = my_lwp;
80 kernconfig_recurse = 1;
81 }
82 }
83
84 void
kernconfig_unlock(void)85 kernconfig_unlock(void)
86 {
87
88 KASSERT(kernconfig_is_held());
89 KASSERT(kernconfig_recurse != 0);
90 if (--kernconfig_recurse == 0) {
91 kernconfig_lwp = NULL;
92 mutex_exit(&kernconfig_mutex);
93 }
94 }
95
96 bool
kernconfig_is_held(void)97 kernconfig_is_held(void)
98 {
99
100 return mutex_owned(&kernconfig_mutex);
101 }
102