| 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 | |
| 57 | typedef enum krw_t { |
| 58 | RW_READER = 0, |
| 59 | RW_WRITER = 1 |
| 60 | } krw_t; |
| 61 | |
| 62 | typedef 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 | |
| 91 | void rw_vector_enter(krwlock_t *, const krw_t); |
| 92 | void rw_vector_exit(krwlock_t *); |
| 93 | int rw_vector_tryenter(krwlock_t *, const krw_t); |
| 94 | #endif /* __RWLOCK_PRIVATE */ |
| 95 | |
| 96 | #include <machine/rwlock.h> |
| 97 | |
| 98 | #ifdef _KERNEL |
| 99 | |
| 100 | void rw_init(krwlock_t *); |
| 101 | void rw_destroy(krwlock_t *); |
| 102 | |
| 103 | int rw_tryenter(krwlock_t *, const krw_t); |
| 104 | int rw_tryupgrade(krwlock_t *); |
| 105 | void rw_downgrade(krwlock_t *); |
| 106 | |
| 107 | int rw_read_held(krwlock_t *); |
| 108 | int rw_write_held(krwlock_t *); |
| 109 | int rw_lock_held(krwlock_t *); |
| 110 | |
| 111 | void rw_enter(krwlock_t *, const krw_t); |
| 112 | void rw_exit(krwlock_t *); |
| 113 | |
| 114 | void rw_obj_init(void); |
| 115 | krwlock_t *rw_obj_alloc(void); |
| 116 | void rw_obj_hold(krwlock_t *); |
| 117 | bool rw_obj_free(krwlock_t *); |
| 118 | |
| 119 | #endif /* _KERNEL */ |
| 120 | |
| 121 | #endif /* _SYS_RWLOCK_H_ */ |
| 122 | |