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_RECURSED 0x08
70 #define RW_LOCK_FLAGMASK \
71 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
74 #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
75 #define RW_READERS_SHIFT 4
76 #define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
77 #define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
78 #define RW_ONE_READER (1 << RW_READERS_SHIFT)
80 #define RW_UNLOCKED RW_READERS_LOCK(0)
81 #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
85 /* Very simple operations on rw_lock. */
87 /* Try to obtain a write lock once. */
88 #define _rw_write_lock(rw, tid) \
89 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
91 /* Release a write lock quickly if there are no waiters. */
92 #define _rw_write_unlock(rw, tid) \
93 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
96 * Full lock operations that are suitable to be inlined in non-debug
97 * kernels. If the lock cannot be acquired or released trivially then
98 * the work is deferred to another function.
101 /* Acquire a write lock. */
102 #define __rw_wlock(rw, tid, file, line) do { \
103 uintptr_t _tid = (uintptr_t)(tid); \
105 if (!_rw_write_lock((rw), _tid)) \
106 _rw_wlock_hard((rw), _tid, (file), (line)); \
108 lock_profile_obtain_lock_success(&(rw)->lock_object, 0, \
109 0, (file), (line)); \
112 /* Release a write lock. */
113 #define __rw_wunlock(rw, tid, file, line) do { \
114 uintptr_t _tid = (uintptr_t)(tid); \
116 if (!_rw_write_unlock((rw), _tid)) \
117 _rw_wunlock_hard((rw), _tid, (file), (line)); \
121 * Function prototypes. Routines that start with _ are not part of the
122 * external API and should not be called directly. Wrapper macros should
126 #define rw_init(rw, name) rw_init_flags((rw), (name), 0)
127 void rw_init_flags(struct rwlock *rw, const char *name, int opts);
128 void rw_destroy(struct rwlock *rw);
129 void rw_sysinit(void *arg);
130 int rw_wowned(struct rwlock *rw);
131 void _rw_wlock(struct rwlock *rw, const char *file, int line);
132 int _rw_try_wlock(struct rwlock *rw, const char *file, int line);
133 void _rw_wunlock(struct rwlock *rw, const char *file, int line);
134 void _rw_rlock(struct rwlock *rw, const char *file, int line);
135 int _rw_try_rlock(struct rwlock *rw, const char *file, int line);
136 void _rw_runlock(struct rwlock *rw, const char *file, int line);
137 void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
139 void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
141 int _rw_try_upgrade(struct rwlock *rw, const char *file, int line);
142 void _rw_downgrade(struct rwlock *rw, const char *file, int line);
143 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
144 void _rw_assert(struct rwlock *rw, int what, const char *file, int line);
148 * Public interface for lock operations.
152 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
154 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
155 #define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
156 #define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
158 #define rw_wlock(rw) \
159 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
160 #define rw_wunlock(rw) \
161 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
163 #define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
164 #define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
165 #define rw_try_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
166 #define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
167 #define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
168 #define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
169 #define rw_sleep(chan, rw, pri, wmesg, timo) \
170 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), (timo))
172 #define rw_initialized(rw) lock_initalized(&(rw)->lock_object)
175 struct rwlock *ra_rw;
179 #define RW_SYSINIT(name, rw, desc) \
180 static struct rw_args name##_args = { \
184 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
185 rw_sysinit, &name##_args); \
186 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
190 * Options passed to rw_init_flags().
192 #define RW_DUPOK 0x01
193 #define RW_NOPROFILE 0x02
194 #define RW_NOWITNESS 0x04
195 #define RW_QUIET 0x08
196 #define RW_RECURSE 0x10
199 * The INVARIANTS-enabled rw_assert() functionality.
201 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
202 * support as _rw_assert() itself uses them and the latter implies that
203 * _rw_assert() must build.
205 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
206 #define RA_LOCKED LA_LOCKED
207 #define RA_RLOCKED LA_SLOCKED
208 #define RA_WLOCKED LA_XLOCKED
209 #define RA_UNLOCKED LA_UNLOCKED
210 #define RA_RECURSED LA_RECURSED
211 #define RA_NOTRECURSED LA_NOTRECURSED
215 #define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
217 #define rw_assert(rw, what)
221 #endif /* !_SYS_RWLOCK_H_ */