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.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 #ifndef _SYS_RWLOCK_H_
30 #define _SYS_RWLOCK_H_
32 #include <sys/_lock.h>
33 #include <sys/_rwlock.h>
34 #include <sys/lock_profile.h>
35 #include <sys/lockstat.h>
39 #include <machine/atomic.h>
43 * The rw_lock field consists of several fields. The low bit indicates
44 * if the lock is locked with a read (shared) or write (exclusive) lock.
45 * A value of 0 indicates a write lock, and a value of 1 indicates a read
46 * lock. Bit 1 is a boolean indicating if there are any threads waiting
47 * for a read lock. Bit 2 is a boolean indicating if there are any threads
48 * waiting for a write lock. The rest of the variable's definition is
49 * dependent on the value of the first bit. For a write lock, it is a
50 * pointer to the thread holding the lock, similar to the mtx_lock field of
51 * mutexes. For read locks, it is a count of read locks that are held.
53 * When the lock is not locked by any thread, it is encoded as a read lock
57 #define RW_LOCK_READ 0x01
58 #define RW_LOCK_READ_WAITERS 0x02
59 #define RW_LOCK_WRITE_WAITERS 0x04
60 #define RW_LOCK_WRITE_SPINNER 0x08
61 #define RW_LOCK_FLAGMASK \
62 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
63 RW_LOCK_WRITE_SPINNER)
64 #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
66 #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
67 #define RW_READERS_SHIFT 4
68 #define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
69 #define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
70 #define RW_ONE_READER (1 << RW_READERS_SHIFT)
72 #define RW_UNLOCKED RW_READERS_LOCK(0)
73 #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
77 #define rw_recurse lock_object.lo_data
79 /* Very simple operations on rw_lock. */
81 /* Try to obtain a write lock once. */
82 #define _rw_write_lock(rw, tid) \
83 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
85 /* Release a write lock quickly if there are no waiters. */
86 #define _rw_write_unlock(rw, tid) \
87 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
90 * Full lock operations that are suitable to be inlined in non-debug
91 * kernels. If the lock cannot be acquired or released trivially then
92 * the work is deferred to another function.
95 /* Acquire a write lock. */
96 #define __rw_wlock(rw, tid, file, line) do { \
97 uintptr_t _tid = (uintptr_t)(tid); \
99 if (!_rw_write_lock((rw), _tid)) \
100 _rw_wlock_hard((rw), _tid, (file), (line)); \
102 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_WLOCK_ACQUIRE, \
103 rw, 0, 0, (file), (line)); \
106 /* Release a write lock. */
107 #define __rw_wunlock(rw, tid, file, line) do { \
108 uintptr_t _tid = (uintptr_t)(tid); \
110 if ((rw)->rw_recurse) \
111 (rw)->rw_recurse--; \
112 else if (!_rw_write_unlock((rw), _tid)) \
113 _rw_wunlock_hard((rw), _tid, (file), (line)); \
117 * Function prototypes. Routines that start with _ are not part of the
118 * external API and should not be called directly. Wrapper macros should
122 #define rw_init(rw, name) rw_init_flags((rw), (name), 0)
123 void rw_init_flags(struct rwlock *rw, const char *name, int opts);
124 void rw_destroy(struct rwlock *rw);
125 void rw_sysinit(void *arg);
126 void rw_sysinit_flags(void *arg);
127 int rw_wowned(struct rwlock *rw);
128 void _rw_wlock(struct rwlock *rw, const char *file, int line);
129 int _rw_try_wlock(struct rwlock *rw, const char *file, int line);
130 void _rw_wunlock(struct rwlock *rw, const char *file, int line);
131 void _rw_rlock(struct rwlock *rw, const char *file, int line);
132 int _rw_try_rlock(struct rwlock *rw, const char *file, int line);
133 void _rw_runlock(struct rwlock *rw, const char *file, int line);
134 void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
136 void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
138 int _rw_try_upgrade(struct rwlock *rw, const char *file, int line);
139 void _rw_downgrade(struct rwlock *rw, const char *file, int line);
140 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
141 void _rw_assert(struct rwlock *rw, int what, const char *file, int line);
145 * Public interface for lock operations.
149 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
151 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
152 #define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
153 #define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
155 #define rw_wlock(rw) \
156 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
157 #define rw_wunlock(rw) \
158 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
160 #define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
161 #define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
162 #define rw_try_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
163 #define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
164 #define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
165 #define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
166 #define rw_unlock(rw) do { \
172 #define rw_sleep(chan, rw, pri, wmesg, timo) \
173 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), (timo))
175 #define rw_initialized(rw) lock_initalized(&(rw)->lock_object)
178 struct rwlock *ra_rw;
182 struct rw_args_flags {
183 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 #define RW_SYSINIT_FLAGS(name, rw, desc, flags) \
200 static struct rw_args_flags name##_args = { \
205 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
206 rw_sysinit_flags, &name##_args); \
207 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
211 * Options passed to rw_init_flags().
213 #define RW_DUPOK 0x01
214 #define RW_NOPROFILE 0x02
215 #define RW_NOWITNESS 0x04
216 #define RW_QUIET 0x08
217 #define RW_RECURSE 0x10
220 * The INVARIANTS-enabled rw_assert() functionality.
222 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
223 * support as _rw_assert() itself uses them and the latter implies that
224 * _rw_assert() must build.
226 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
227 #define RA_LOCKED LA_LOCKED
228 #define RA_RLOCKED LA_SLOCKED
229 #define RA_WLOCKED LA_XLOCKED
230 #define RA_UNLOCKED LA_UNLOCKED
231 #define RA_RECURSED LA_RECURSED
232 #define RA_NOTRECURSED LA_NOTRECURSED
236 #define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
238 #define rw_assert(rw, what)
242 #endif /* !_SYS_RWLOCK_H_ */