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/* $NetBSD: rwlock.h,v 1.17.2.1 2023/08/09 17:42:01 martin Exp $ */
/*-
* Copyright (c) 2002, 2006, 2007, 2008, 2019, 2020 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe and Andrew Doran.
*
* 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.
*/
#ifndef _SYS_RWLOCK_H_
#define _SYS_RWLOCK_H_
/*
* The rwlock provides exclusive access when held as a "writer",
* and shared access when held as a "reader".
*
* Architectures may optionally provide stubs for the following functions to
* implement the easy (unlocked, no waiters) cases. If these stubs are
* provided, __HAVE_RW_STUBS should be defined.
*
* rw_enter()
* rw_exit()
* rw_tryenter()
*/
#if !defined(_KERNEL)
#include <sys/types.h>
#include <sys/inttypes.h>
#endif
typedef enum krw_t {
RW_READER = 0,
RW_WRITER = 1
} krw_t;
typedef struct krwlock krwlock_t;
#ifdef __RWLOCK_PRIVATE
#include <sys/stdbool.h>
/*
* Bits in the owner field of the lock that indicate lock state. If the
* WRITE_LOCKED bit is clear, then the owner field is actually a count of
* the number of readers. The rw_owner field is laid out like so:
*
* N 5 4 3 2 1 0
* +------------------------------------------------------------------+
* | owner or read count | nodbug | <free> | wrlock | wrwant | wait |
* +------------------------------------------------------------------+
*/
#define RW_HAS_WAITERS 0x01UL /* lock has waiters */
#define RW_WRITE_WANTED 0x02UL /* >= 1 waiter is a writer */
#define RW_WRITE_LOCKED 0x04UL /* lock is currently write locked */
#define RW_NODEBUG 0x10UL /* LOCKDEBUG disabled */
#define RW_READ_COUNT_SHIFT 5
#define RW_READ_INCR (1UL << RW_READ_COUNT_SHIFT)
#define RW_THREAD ((uintptr_t)-RW_READ_INCR)
#define RW_OWNER(rw) ((rw)->rw_owner & RW_THREAD)
#define RW_COUNT(rw) ((rw)->rw_owner & RW_THREAD)
#define RW_FLAGS(rw) ((rw)->rw_owner & ~RW_THREAD)
void rw_vector_enter(krwlock_t *, const krw_t);
void rw_vector_exit(krwlock_t *);
int rw_vector_tryenter(krwlock_t *, const krw_t);
bool rw_owner_running(const krwlock_t *);
#endif /* __RWLOCK_PRIVATE */
struct krwlock {
volatile uintptr_t rw_owner;
};
#ifdef _KERNEL
void _rw_init(krwlock_t *, uintptr_t);
void rw_init(krwlock_t *);
void rw_destroy(krwlock_t *);
int rw_tryenter(krwlock_t *, const krw_t);
int rw_tryupgrade(krwlock_t *);
void rw_downgrade(krwlock_t *);
int rw_read_held(krwlock_t *);
int rw_write_held(krwlock_t *);
int rw_lock_held(krwlock_t *);
krw_t rw_lock_op(krwlock_t *);
void rw_enter(krwlock_t *, const krw_t);
void rw_exit(krwlock_t *);
void rw_obj_init(void);
krwlock_t *rw_obj_alloc(void);
void rw_obj_hold(krwlock_t *);
bool rw_obj_free(krwlock_t *);
u_int rw_obj_refcnt(krwlock_t *);
krwlock_t *rw_obj_tryalloc(void);
#endif /* _KERNEL */
#endif /* _SYS_RWLOCK_H_ */
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