1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org> 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 */ 27 28 #ifndef _SYS__RWLOCK_H_ 29 #define _SYS__RWLOCK_H_ 30 31 #include <machine/param.h> 32 33 /* 34 * Reader/writer lock. 35 * 36 * All reader/writer lock implementations must always have a member 37 * called rw_lock. Other locking primitive structures are not allowed to 38 * use this name for their members. 39 * If this rule needs to change, the bits in the reader/writer lock 40 * implementation must be modified appropriately. 41 */ 42 struct rwlock { 43 struct lock_object lock_object; 44 volatile uintptr_t rw_lock; 45 }; 46 47 /* 48 * Members of struct rwlock_padalign must mirror members of struct rwlock. 49 * rwlock_padalign rwlocks can use the rwlock(9) API transparently without 50 * modification. 51 * Pad-aligned rwlocks used within structures should generally be the 52 * first member of the struct. Otherwise, the compiler can generate 53 * additional padding for the struct to keep a correct alignment for 54 * the rwlock. 55 */ 56 struct rwlock_padalign { 57 struct lock_object lock_object; 58 volatile uintptr_t rw_lock; 59 } __aligned(CACHE_LINE_SIZE); 60 61 #endif /* !_SYS__RWLOCK_H_ */ 62