1 /* $NetBSD: rwsem.h,v 1.5 2021/12/19 11:22:00 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2014 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Taylor R. Campbell. 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 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * These are not really semaphores; they are just reader/writer sleep 34 * locks, whereas what Linux calls an rwlock is a reader/writer spin 35 * lock. 36 * 37 * Notes on porting: 38 * 39 * - Linux does not have destroy_rwsem. You must add it yourself in 40 * the appropriate place. 41 */ 42 43 #ifndef _LINUX_RWSEM_H_ 44 #define _LINUX_RWSEM_H_ 45 46 #include <sys/mutex.h> 47 48 #define destroy_rwsem linux_destroy_rwsem 49 #define down_read linux_down_read 50 #define down_read_trylock linux_down_read_trylock 51 #define down_write linux_down_write 52 #define downgrade_write linux_downgrade_write 53 #define init_rwsem linux_init_rwsem 54 #define up_read linux_up_read 55 #define up_write linux_up_write 56 57 struct rw_semaphore { 58 /* 59 * Note: rws_lock and rws_cv must not be first; doing so 60 * confuses lockdebug. 61 */ 62 struct lwp *rws_writer; 63 unsigned rws_readers; 64 bool rws_writewanted; 65 bool rws_debug; 66 kmutex_t rws_lock; 67 kcondvar_t rws_cv; 68 }; 69 70 void init_rwsem(struct rw_semaphore *); 71 void destroy_rwsem(struct rw_semaphore *); 72 void down_read(struct rw_semaphore *); 73 bool down_read_trylock(struct rw_semaphore *); 74 void down_write(struct rw_semaphore *); 75 void up_read(struct rw_semaphore *); 76 void up_write(struct rw_semaphore *); 77 void downgrade_write(struct rw_semaphore *); 78 79 #endif /* _LINUX_RWSEM_H_ */ 80