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 |
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 |
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 |
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 |
97 | kernconfig_is_held(void) |
98 | { |
99 | |
100 | return mutex_owned(&kernconfig_mutex); |
101 | } |
102 | |