1 /* $NetBSD: mutex.h,v 1.7 2007/03/09 19:21:58 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 2002, 2007 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 and Andrew Doran. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #ifndef _ARM_MUTEX_H_ 40 #define _ARM_MUTEX_H_ 41 42 /* 43 * The ARM mutex implementation is troublesome, because pre-v6 ARM lacks a 44 * compare-and-swap operation. However, there aren't any MP pre-v6 ARM 45 * systems to speak of. We are mostly concerned with atomicity with respect 46 * to interrupts. 47 * 48 * ARMv6, however, does have ldrex/strex, and can thus implement an MP-safe 49 * compare-and-swap. 50 * 51 * So, what we have done is impement simple mutexes using a compare-and-swap. 52 * We support pre-ARMv6 by implementing _lock_cas() as a restartable atomic 53 * sequence that is checked by the IRQ vector. MP-safe ARMv6 support will 54 * be added later. 55 */ 56 57 #ifndef __MUTEX_PRIVATE 58 59 struct kmutex { 60 uintptr_t mtx_pad1; 61 uint32_t mtx_pad2; 62 }; 63 64 #else /* __MUTEX_PRIVATE */ 65 66 struct kmutex { 67 union { 68 /* Adaptive mutex */ 69 volatile uintptr_t mtxa_owner; /* 0-3 */ 70 71 /* Spin mutex */ 72 struct { 73 volatile uint8_t mtxs_dummy; 74 ipl_cookie_t mtxs_ipl; 75 __cpu_simple_lock_t mtxs_lock; 76 volatile uint8_t mtxs_unused; 77 } s; 78 } u; 79 volatile uint32_t mtx_id; /* 4-7 */ 80 }; 81 82 #define mtx_owner u.mtxa_owner 83 #define mtx_ipl u.s.mtxs_ipl 84 #define mtx_lock u.s.mtxs_lock 85 86 #if 0 87 #define __HAVE_MUTEX_STUBS 1 88 #define __HAVE_SPIN_MUTEX_STUBS 1 89 #endif 90 #define __HAVE_SIMPLE_MUTEXES 1 91 92 /* 93 * MUTEX_RECEIVE: no memory barrier required; we're synchronizing against 94 * interrupts, not multiple processors. 95 */ 96 #define MUTEX_RECEIVE(mtx) /* nothing */ 97 98 /* 99 * MUTEX_GIVE: no memory barrier required; same reason. 100 */ 101 #define MUTEX_GIVE(mtx) /* nothing */ 102 103 bool _lock_cas(volatile uintptr_t *, uintptr_t, uintptr_t); 104 105 #define MUTEX_CAS(p, o, n) _lock_cas((p), (o), (n)) 106 107 #endif /* __MUTEX_PRIVATE */ 108 109 #endif /* _ARM_MUTEX_H_ */ 110