2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 #ifndef _SYS_RWLOCK_H_
32 #define _SYS_RWLOCK_H_
34 #include <sys/_lock.h>
35 #include <sys/_rwlock.h>
36 #include <sys/lock_profile.h>
37 #include <sys/lockstat.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
59 #define RW_LOCK_READ 0x01
60 #define RW_LOCK_READ_WAITERS 0x02
61 #define RW_LOCK_WRITE_WAITERS 0x04
62 #define RW_LOCK_WRITE_SPINNER 0x08
63 #define RW_LOCK_WRITER_RECURSED 0x10
64 #define RW_LOCK_FLAGMASK \
65 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
66 RW_LOCK_WRITE_SPINNER | RW_LOCK_WRITER_RECURSED)
67 #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
69 #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
70 #define RW_READERS_SHIFT 5
71 #define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
72 #define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
73 #define RW_ONE_READER (1 << RW_READERS_SHIFT)
75 #define RW_UNLOCKED RW_READERS_LOCK(0)
76 #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
80 #define rw_recurse lock_object.lo_data
82 #define RW_READ_VALUE(x) ((x)->rw_lock)
84 /* Very simple operations on rw_lock. */
86 /* Try to obtain a write lock once. */
87 #define _rw_write_lock(rw, tid) \
88 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
90 #define _rw_write_lock_fetch(rw, vp, tid) \
91 atomic_fcmpset_acq_ptr(&(rw)->rw_lock, vp, (tid))
93 /* Release a write lock quickly if there are no waiters. */
94 #define _rw_write_unlock(rw, tid) \
95 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
97 #define _rw_write_unlock_fetch(rw, tid) \
98 atomic_fcmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
101 * Full lock operations that are suitable to be inlined in non-debug
102 * kernels. If the lock cannot be acquired or released trivially then
103 * the work is deferred to another function.
106 /* Acquire a write lock. */
107 #define __rw_wlock(rw, tid, file, line) do { \
108 uintptr_t _tid = (uintptr_t)(tid); \
109 uintptr_t _v = RW_UNLOCKED; \
111 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__acquire) || \
112 !_rw_write_lock_fetch((rw), &_v, _tid))) \
113 _rw_wlock_hard((rw), _v, (file), (line)); \
116 /* Release a write lock. */
117 #define __rw_wunlock(rw, tid, file, line) do { \
118 uintptr_t _v = (uintptr_t)(tid); \
120 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) || \
121 !_rw_write_unlock_fetch((rw), &_v))) \
122 _rw_wunlock_hard((rw), _v, (file), (line)); \
126 * Function prototypes. Routines that start with _ are not part of the
127 * external API and should not be called directly. Wrapper macros should
130 void _rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
131 void _rw_destroy(volatile uintptr_t *c);
132 void rw_sysinit(void *arg);
133 int _rw_wowned(const volatile uintptr_t *c);
134 void _rw_wlock_cookie(volatile uintptr_t *c, const char *file, int line);
135 int __rw_try_wlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
136 int __rw_try_wlock(volatile uintptr_t *c, const char *file, int line);
137 void _rw_wunlock_cookie(volatile uintptr_t *c, const char *file, int line);
138 void __rw_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
139 void __rw_rlock(volatile uintptr_t *c, const char *file, int line);
140 int __rw_try_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
141 int __rw_try_rlock(volatile uintptr_t *c, const char *file, int line);
142 void _rw_runlock_cookie_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
143 void _rw_runlock_cookie(volatile uintptr_t *c, const char *file, int line);
144 void __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v
145 LOCK_FILE_LINE_ARG_DEF);
146 void __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t v
147 LOCK_FILE_LINE_ARG_DEF);
148 int __rw_try_upgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
149 int __rw_try_upgrade(volatile uintptr_t *c, const char *file, int line);
150 void __rw_downgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
151 void __rw_downgrade(volatile uintptr_t *c, const char *file, int line);
152 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
153 void __rw_assert(const volatile uintptr_t *c, int what, const char *file,
158 * Top-level macros to provide lock cookie once the actual rwlock is passed.
159 * They will also prevent passing a malformed object to the rwlock KPI by
160 * failing compilation as the rw_lock reserved member will not be found.
162 #define rw_init(rw, n) \
163 _rw_init_flags(&(rw)->rw_lock, n, 0)
164 #define rw_init_flags(rw, n, o) \
165 _rw_init_flags(&(rw)->rw_lock, n, o)
166 #define rw_destroy(rw) \
167 _rw_destroy(&(rw)->rw_lock)
168 #define rw_wowned(rw) \
169 _rw_wowned(&(rw)->rw_lock)
170 #define _rw_wlock(rw, f, l) \
171 _rw_wlock_cookie(&(rw)->rw_lock, f, l)
172 #define _rw_try_wlock(rw, f, l) \
173 __rw_try_wlock(&(rw)->rw_lock, f, l)
174 #define _rw_wunlock(rw, f, l) \
175 _rw_wunlock_cookie(&(rw)->rw_lock, f, l)
176 #define _rw_try_rlock(rw, f, l) \
177 __rw_try_rlock(&(rw)->rw_lock, f, l)
179 #define _rw_rlock(rw, f, l) \
180 __rw_rlock(&(rw)->rw_lock, f, l)
181 #define _rw_runlock(rw, f, l) \
182 _rw_runlock_cookie(&(rw)->rw_lock, f, l)
184 #define _rw_rlock(rw, f, l) \
185 __rw_rlock_int((struct rwlock *)rw)
186 #define _rw_runlock(rw, f, l) \
187 _rw_runlock_cookie_int((struct rwlock *)rw)
190 #define _rw_wlock_hard(rw, v, f, l) \
191 __rw_wlock_hard(&(rw)->rw_lock, v, f, l)
192 #define _rw_wunlock_hard(rw, v, f, l) \
193 __rw_wunlock_hard(&(rw)->rw_lock, v, f, l)
194 #define _rw_try_upgrade(rw, f, l) \
195 __rw_try_upgrade(&(rw)->rw_lock, f, l)
196 #define _rw_downgrade(rw, f, l) \
197 __rw_downgrade(&(rw)->rw_lock, f, l)
199 #define _rw_wlock_hard(rw, v, f, l) \
200 __rw_wlock_hard(&(rw)->rw_lock, v)
201 #define _rw_wunlock_hard(rw, v, f, l) \
202 __rw_wunlock_hard(&(rw)->rw_lock, v)
203 #define _rw_try_upgrade(rw, f, l) \
204 __rw_try_upgrade_int(rw)
205 #define _rw_downgrade(rw, f, l) \
206 __rw_downgrade_int(rw)
208 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
209 #define _rw_assert(rw, w, f, l) \
210 __rw_assert(&(rw)->rw_lock, w, f, l)
215 * Public interface for lock operations.
219 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
221 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
222 #define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
223 #define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
225 #define rw_wlock(rw) \
226 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
227 #define rw_wunlock(rw) \
228 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
230 #define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
231 #define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
232 #define rw_try_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
233 #define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
234 #define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
235 #define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
236 #define rw_unlock(rw) do { \
242 #define rw_sleep(chan, rw, pri, wmesg, timo) \
243 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), \
244 tick_sbt * (timo), 0, C_HARDCLOCK)
246 #define rw_initialized(rw) lock_initialized(&(rw)->lock_object)
254 #define RW_SYSINIT_FLAGS(name, rw, desc, flags) \
255 static struct rw_args name##_args = { \
260 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
261 rw_sysinit, &name##_args); \
262 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
263 _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
265 #define RW_SYSINIT(name, rw, desc) RW_SYSINIT_FLAGS(name, rw, desc, 0)
268 * Options passed to rw_init_flags().
270 #define RW_DUPOK 0x01
271 #define RW_NOPROFILE 0x02
272 #define RW_NOWITNESS 0x04
273 #define RW_QUIET 0x08
274 #define RW_RECURSE 0x10
278 * The INVARIANTS-enabled rw_assert() functionality.
280 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
281 * support as _rw_assert() itself uses them and the latter implies that
282 * _rw_assert() must build.
284 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
285 #define RA_LOCKED LA_LOCKED
286 #define RA_RLOCKED LA_SLOCKED
287 #define RA_WLOCKED LA_XLOCKED
288 #define RA_UNLOCKED LA_UNLOCKED
289 #define RA_RECURSED LA_RECURSED
290 #define RA_NOTRECURSED LA_NOTRECURSED
294 #define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
296 #define rw_assert(rw, what)
300 #endif /* !_SYS_RWLOCK_H_ */