| 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 | |