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