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