rwlock.h revision 167387
1/*- 2 * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the author nor the names of any co-contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * $FreeBSD: head/sys/sys/rwlock.h 167387 2007-03-09 22:41:01Z jhb $ 30 */ 31 32#ifndef _SYS_RWLOCK_H_ 33#define _SYS_RWLOCK_H_ 34 35#include <sys/_lock.h> 36#include <sys/_rwlock.h> 37 38#ifdef _KERNEL 39#include <sys/pcpu.h> 40#include <machine/atomic.h> 41#endif 42 43/* 44 * The rw_lock field consists of several fields. The low bit indicates 45 * if the lock is locked with a read (shared) or write (exclusive) lock. 46 * A value of 0 indicates a write lock, and a value of 1 indicates a read 47 * lock. Bit 1 is a boolean indicating if there are any threads waiting 48 * for a read lock. Bit 2 is a boolean indicating if there are any threads 49 * waiting for a write lock. The rest of the variable's definition is 50 * dependent on the value of the first bit. For a write lock, it is a 51 * pointer to the thread holding the lock, similar to the mtx_lock field of 52 * mutexes. For read locks, it is a count of read locks that are held. 53 * 54 * When the lock is not locked by any thread, it is encoded as a read lock 55 * with zero waiters. 56 * 57 * A note about memory barriers. Write locks need to use the same memory 58 * barriers as mutexes: _acq when acquiring a write lock and _rel when 59 * releasing a write lock. Read locks also need to use an _acq barrier when 60 * acquiring a read lock. However, since read locks do not update any 61 * locked data (modulo bugs of course), no memory barrier is needed to when 62 * releasing a read lock. 63 */ 64 65#define RW_LOCK_READ 0x01 66#define RW_LOCK_READ_WAITERS 0x02 67#define RW_LOCK_WRITE_WAITERS 0x04 68#define RW_LOCK_FLAGMASK \ 69 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS) 70 71#define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK) 72#define RW_READERS_SHIFT 3 73#define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT) 74#define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ) 75#define RW_ONE_READER (1 << RW_READERS_SHIFT) 76 77#define RW_UNLOCKED RW_READERS_LOCK(0) 78 79#ifdef _KERNEL 80 81/* Very simple operations on rw_lock. */ 82 83/* Try to obtain a write lock once. */ 84#define _rw_write_lock(rw, tid) \ 85 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid)) 86 87/* Release a write lock quickly if there are no waiters. */ 88#define _rw_write_unlock(rw, tid) \ 89 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED) 90 91/* 92 * Full lock operations that are suitable to be inlined in non-debug 93 * kernels. If the lock cannot be acquired or released trivially then 94 * the work is deferred to another function. 95 */ 96 97/* Acquire a write lock. */ 98#define __rw_wlock(rw, tid, file, line) do { \ 99 uintptr_t _tid = (uintptr_t)(tid); \ 100 int contested = 0; \ 101 uint64_t waitstart = 0; \ 102 \ 103 if (!_rw_write_lock((rw), _tid)) { \ 104 lock_profile_obtain_lock_failed(&(rw)->rw_object, \ 105 &contested, &waitstart); \ 106 _rw_wlock_hard((rw), _tid, (file), (line)); \ 107 } \ 108 lock_profile_obtain_lock_success(&(rw)->rw_object, contested, \ 109 waitstart, (file), (line)); \ 110} while (0) 111 112/* Release a write lock. */ 113#define __rw_wunlock(rw, tid, file, line) do { \ 114 uintptr_t _tid = (uintptr_t)(tid); \ 115 \ 116 if (!_rw_write_unlock((rw), _tid)) \ 117 _rw_wunlock_hard((rw), _tid, (file), (line)); \ 118} while (0) 119 120/* 121 * Function prototypes. Routines that start with _ are not part of the 122 * external API and should not be called directly. Wrapper macros should 123 * be used instead. 124 */ 125 126void rw_init(struct rwlock *rw, const char *name); 127void rw_destroy(struct rwlock *rw); 128void rw_sysinit(void *arg); 129int rw_wowned(struct rwlock *rw); 130void _rw_wlock(struct rwlock *rw, const char *file, int line); 131void _rw_wunlock(struct rwlock *rw, const char *file, int line); 132void _rw_rlock(struct rwlock *rw, const char *file, int line); 133void _rw_runlock(struct rwlock *rw, const char *file, int line); 134void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, 135 int line); 136void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, 137 int line); 138int _rw_try_upgrade(struct rwlock *rw, const char *file, int line); 139void _rw_downgrade(struct rwlock *rw, const char *file, int line); 140#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 141void _rw_assert(struct rwlock *rw, int what, const char *file, int line); 142#endif 143 144/* 145 * Public interface for lock operations. 146 * 147 * XXX: Missing try locks. 148 */ 149 150#ifndef LOCK_DEBUG 151#error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h> 152#endif 153#if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE) 154#define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE) 155#define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE) 156#else 157#define rw_wlock(rw) \ 158 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE) 159#define rw_wunlock(rw) \ 160 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE) 161#endif 162#define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE) 163#define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE) 164#define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE) 165#define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE) 166#define rw_sleep(chan, rw, pri, wmesg, timo) \ 167 _sleep((chan), &(rw)->rw_object, (pri), (wmesg), (timo)) 168 169#define rw_initialized(rw) lock_initalized(&(rw)->rw_object) 170 171struct rw_args { 172 struct rwlock *ra_rw; 173 const char *ra_desc; 174}; 175 176#define RW_SYSINIT(name, rw, desc) \ 177 static struct rw_args name##_args = { \ 178 (rw), \ 179 (desc), \ 180 }; \ 181 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 182 rw_sysinit, &name##_args); \ 183 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 184 rw_destroy, (rw)) 185 186/* 187 * The INVARIANTS-enabled rw_assert() functionality. 188 * 189 * The constants need to be defined for INVARIANT_SUPPORT infrastructure 190 * support as _rw_assert() itself uses them and the latter implies that 191 * _rw_assert() must build. 192 */ 193#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 194#define RA_LOCKED LA_LOCKED 195#define RA_RLOCKED LA_SLOCKED 196#define RA_WLOCKED LA_XLOCKED 197#define RA_UNLOCKED LA_UNLOCKED 198#endif 199 200#ifdef INVARIANTS 201#define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE) 202#else 203#define rw_assert(rw, what) 204#endif 205 206#endif /* _KERNEL */ 207#endif /* !_SYS_RWLOCK_H_ */ 208