1/* $NetBSD: rwlock.h,v 1.10 2010/02/08 09:54:27 skrll Exp $ */
2
3/*-
4 * Copyright (c) 2002, 2006, 2007, 2008 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 *
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#ifndef _SYS_RWLOCK_H_
33#define _SYS_RWLOCK_H_
34
35/*
36 * The rwlock provides exclusive access when held as a "writer",
37 * and shared access when held as a "reader".
38 *
39 * Architectures may optionally provide stubs for the following functions to
40 * implement the easy (unlocked, no waiters) cases. If these stubs are
41 * provided, __HAVE_RW_STUBS should be defined.
42 *
43 * rw_enter()
44 * rw_exit()
45 * rw_tryenter()
46 */
47
48#if defined(_KERNEL_OPT)
49#include "opt_lockdebug.h"
50#endif
51
52#if !defined(_KERNEL)
53#include <sys/types.h>
54#include <sys/inttypes.h>
55#endif
56
57typedef enum krw_t {
58 RW_READER = 0,
59 RW_WRITER = 1
60} krw_t;
61
62typedef struct krwlock krwlock_t;
63
64#ifdef __RWLOCK_PRIVATE
65/*
66 * Bits in the owner field of the lock that indicate lock state. If the
67 * WRITE_LOCKED bit is clear, then the owner field is actually a count of
68 * the number of readers. The rw_owner field is laid out like so:
69 *
70 * N 4 3 2 1 0
71 * +---------------------------------------------------------+
72 * | owner or read count | nodbug | wrlock | wrwant | wait |
73 * +---------------------------------------------------------+
74 */
75#define RW_HAS_WAITERS 0x01UL /* lock has waiters */
76#define RW_WRITE_WANTED 0x02UL /* >= 1 waiter is a writer */
77#define RW_WRITE_LOCKED 0x04UL /* lock is currently write locked */
78#if defined(LOCKDEBUG)
79#define RW_NODEBUG 0x08UL /* LOCKDEBUG disabled */
80#else
81#define RW_NODEBUG 0x00UL /* do nothing */
82#endif /* LOCKDEBUG */
83
84#define RW_READ_COUNT_SHIFT 4
85#define RW_READ_INCR (1UL << RW_READ_COUNT_SHIFT)
86#define RW_THREAD ((uintptr_t)-RW_READ_INCR)
87#define RW_OWNER(rw) ((rw)->rw_owner & RW_THREAD)
88#define RW_COUNT(rw) ((rw)->rw_owner & RW_THREAD)
89#define RW_FLAGS(rw) ((rw)->rw_owner & ~RW_THREAD)
90
91void rw_vector_enter(krwlock_t *, const krw_t);
92void rw_vector_exit(krwlock_t *);
93int rw_vector_tryenter(krwlock_t *, const krw_t);
94#endif /* __RWLOCK_PRIVATE */
95
96#include <machine/rwlock.h>
97
98#ifdef _KERNEL
99
100void rw_init(krwlock_t *);
101void rw_destroy(krwlock_t *);
102
103int rw_tryenter(krwlock_t *, const krw_t);
104int rw_tryupgrade(krwlock_t *);
105void rw_downgrade(krwlock_t *);
106
107int rw_read_held(krwlock_t *);
108int rw_write_held(krwlock_t *);
109int rw_lock_held(krwlock_t *);
110
111void rw_enter(krwlock_t *, const krw_t);
112void rw_exit(krwlock_t *);
113
114void rw_obj_init(void);
115krwlock_t *rw_obj_alloc(void);
116void rw_obj_hold(krwlock_t *);
117bool rw_obj_free(krwlock_t *);
118
119#endif /* _KERNEL */
120
121#endif /* _SYS_RWLOCK_H_ */
122