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/* $NetBSD: rwsem.h,v 1.5 2021/12/19 11:22:00 riastradh Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Taylor R. Campbell.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* These are not really semaphores; they are just reader/writer sleep
* locks, whereas what Linux calls an rwlock is a reader/writer spin
* lock.
*
* Notes on porting:
*
* - Linux does not have destroy_rwsem. You must add it yourself in
* the appropriate place.
*/
#ifndef _LINUX_RWSEM_H_
#define _LINUX_RWSEM_H_
#include <sys/mutex.h>
#define destroy_rwsem linux_destroy_rwsem
#define down_read linux_down_read
#define down_read_trylock linux_down_read_trylock
#define down_write linux_down_write
#define downgrade_write linux_downgrade_write
#define init_rwsem linux_init_rwsem
#define up_read linux_up_read
#define up_write linux_up_write
struct rw_semaphore {
/*
* Note: rws_lock and rws_cv must not be first; doing so
* confuses lockdebug.
*/
struct lwp *rws_writer;
unsigned rws_readers;
bool rws_writewanted;
bool rws_debug;
kmutex_t rws_lock;
kcondvar_t rws_cv;
};
void init_rwsem(struct rw_semaphore *);
void destroy_rwsem(struct rw_semaphore *);
void down_read(struct rw_semaphore *);
bool down_read_trylock(struct rw_semaphore *);
void down_write(struct rw_semaphore *);
void up_read(struct rw_semaphore *);
void up_write(struct rw_semaphore *);
void downgrade_write(struct rw_semaphore *);
#endif /* _LINUX_RWSEM_H_ */
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