2 * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
32 #ifndef _SYS_RWLOCK_H_
33 #define _SYS_RWLOCK_H_
35 #include <sys/_lock.h>
36 #include <sys/_rwlock.h>
37 #include <sys/lock_profile.h>
41 #include <machine/atomic.h>
45 * The rw_lock field consists of several fields. The low bit indicates
46 * if the lock is locked with a read (shared) or write (exclusive) lock.
47 * A value of 0 indicates a write lock, and a value of 1 indicates a read
48 * lock. Bit 1 is a boolean indicating if there are any threads waiting
49 * for a read lock. Bit 2 is a boolean indicating if there are any threads
50 * waiting for a write lock. The rest of the variable's definition is
51 * dependent on the value of the first bit. For a write lock, it is a
52 * pointer to the thread holding the lock, similar to the mtx_lock field of
53 * mutexes. For read locks, it is a count of read locks that are held.
55 * When the lock is not locked by any thread, it is encoded as a read lock
58 * A note about memory barriers. Write locks need to use the same memory
59 * barriers as mutexes: _acq when acquiring a write lock and _rel when
60 * releasing a write lock. Read locks also need to use an _acq barrier when
61 * acquiring a read lock. However, since read locks do not update any
62 * locked data (modulo bugs of course), no memory barrier is needed when
63 * releasing a read lock.
66 #define RW_LOCK_READ 0x01
67 #define RW_LOCK_READ_WAITERS 0x02
68 #define RW_LOCK_WRITE_WAITERS 0x04
69 #define RW_LOCK_WRITE_SPINNER 0x08
70 #define RW_LOCK_FLAGMASK \
71 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
72 RW_LOCK_WRITE_SPINNER)
73 #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
75 #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
76 #define RW_READERS_SHIFT 4
77 #define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
78 #define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
79 #define RW_ONE_READER (1 << RW_READERS_SHIFT)
81 #define RW_UNLOCKED RW_READERS_LOCK(0)
82 #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
86 /* Very simple operations on rw_lock. */
88 /* Try to obtain a write lock once. */
89 #define _rw_write_lock(rw, tid) \
90 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
92 /* Release a write lock quickly if there are no waiters. */
93 #define _rw_write_unlock(rw, tid) \
94 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
97 * Full lock operations that are suitable to be inlined in non-debug
98 * kernels. If the lock cannot be acquired or released trivially then
99 * the work is deferred to another function.
102 /* Acquire a write lock. */
103 #define __rw_wlock(rw, tid, file, line) do { \
104 uintptr_t _tid = (uintptr_t)(tid); \
106 if (!_rw_write_lock((rw), _tid)) \
107 _rw_wlock_hard((rw), _tid, (file), (line)); \
109 lock_profile_obtain_lock_success(&(rw)->lock_object, 0, \
110 0, (file), (line)); \
113 /* Release a write lock. */
114 #define __rw_wunlock(rw, tid, file, line) do { \
115 uintptr_t _tid = (uintptr_t)(tid); \
117 if ((rw)->rw_recurse) \
118 (rw)->rw_recurse--; \
119 else if (!_rw_write_unlock((rw), _tid)) \
120 _rw_wunlock_hard((rw), _tid, (file), (line)); \
124 * Function prototypes. Routines that start with _ are not part of the
125 * external API and should not be called directly. Wrapper macros should
129 #define rw_init(rw, name) rw_init_flags((rw), (name), 0)
130 void rw_init_flags(struct rwlock *rw, const char *name, int opts);
131 void rw_destroy(struct rwlock *rw);
132 void rw_sysinit(void *arg);
133 int rw_wowned(struct rwlock *rw);
134 void _rw_wlock(struct rwlock *rw, const char *file, int line);
135 int _rw_try_wlock(struct rwlock *rw, const char *file, int line);
136 void _rw_wunlock(struct rwlock *rw, const char *file, int line);
137 void _rw_rlock(struct rwlock *rw, const char *file, int line);
138 int _rw_try_rlock(struct rwlock *rw, const char *file, int line);
139 void _rw_runlock(struct rwlock *rw, const char *file, int line);
140 void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
142 void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
144 int _rw_try_upgrade(struct rwlock *rw, const char *file, int line);
145 void _rw_downgrade(struct rwlock *rw, const char *file, int line);
146 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
147 void _rw_assert(struct rwlock *rw, int what, const char *file, int line);
151 * Public interface for lock operations.
155 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
157 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
158 #define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
159 #define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
161 #define rw_wlock(rw) \
162 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
163 #define rw_wunlock(rw) \
164 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
166 #define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
167 #define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
168 #define rw_try_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
169 #define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
170 #define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
171 #define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
172 #define rw_unlock(rw) do { \
178 #define rw_sleep(chan, rw, pri, wmesg, timo) \
179 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), (timo))
181 #define rw_initialized(rw) lock_initalized(&(rw)->lock_object)
184 struct rwlock *ra_rw;
188 #define RW_SYSINIT(name, rw, desc) \
189 static struct rw_args name##_args = { \
193 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
194 rw_sysinit, &name##_args); \
195 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
199 * Options passed to rw_init_flags().
201 #define RW_DUPOK 0x01
202 #define RW_NOPROFILE 0x02
203 #define RW_NOWITNESS 0x04
204 #define RW_QUIET 0x08
205 #define RW_RECURSE 0x10
208 * The INVARIANTS-enabled rw_assert() functionality.
210 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
211 * support as _rw_assert() itself uses them and the latter implies that
212 * _rw_assert() must build.
214 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
215 #define RA_LOCKED LA_LOCKED
216 #define RA_RLOCKED LA_SLOCKED
217 #define RA_WLOCKED LA_XLOCKED
218 #define RA_UNLOCKED LA_UNLOCKED
219 #define RA_RECURSED LA_RECURSED
220 #define RA_NOTRECURSED LA_NOTRECURSED
224 #define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
226 #define rw_assert(rw, what)
230 #endif /* !_SYS_RWLOCK_H_ */