FreeBSD/Linux Kernel Cross Reference
sys/sys/rwlock.h
1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 * $FreeBSD$
28 */
29
30 #ifndef _SYS_RWLOCK_H_
31 #define _SYS_RWLOCK_H_
32
33 #include <sys/_lock.h>
34 #include <sys/_rwlock.h>
35 #include <sys/lock_profile.h>
36 #include <sys/lockstat.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
58 #define RW_LOCK_READ 0x01
59 #define RW_LOCK_READ_WAITERS 0x02
60 #define RW_LOCK_WRITE_WAITERS 0x04
61 #define RW_LOCK_WRITE_SPINNER 0x08
62 #define RW_LOCK_WRITER_RECURSED 0x10
63 #define RW_LOCK_FLAGMASK \
64 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
65 RW_LOCK_WRITE_SPINNER | RW_LOCK_WRITER_RECURSED)
66 #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
67
68 #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
69 #define RW_READERS_SHIFT 5
70 #define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
71 #define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
72 #define RW_ONE_READER (1 << RW_READERS_SHIFT)
73
74 #define RW_UNLOCKED RW_READERS_LOCK(0)
75 #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
76
77 #ifdef _KERNEL
78
79 #define rw_recurse lock_object.lo_data
80
81 #define RW_READ_VALUE(x) ((x)->rw_lock)
82
83 /* Very simple operations on rw_lock. */
84
85 /* Try to obtain a write lock once. */
86 #define _rw_write_lock(rw, tid) \
87 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
88
89 #define _rw_write_lock_fetch(rw, vp, tid) \
90 atomic_fcmpset_acq_ptr(&(rw)->rw_lock, vp, (tid))
91
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)
95
96 #define _rw_write_unlock_fetch(rw, tid) \
97 atomic_fcmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
98
99 /*
100 * Full lock operations that are suitable to be inlined in non-debug
101 * kernels. If the lock cannot be acquired or released trivially then
102 * the work is deferred to another function.
103 */
104
105 /* Acquire a write lock. */
106 #define __rw_wlock(rw, tid, file, line) __extension__ ({ \
107 uintptr_t _tid = (uintptr_t)(tid); \
108 uintptr_t _v = RW_UNLOCKED; \
109 \
110 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__acquire) || \
111 !_rw_write_lock_fetch((rw), &_v, _tid))) \
112 _rw_wlock_hard((rw), _v, (file), (line)); \
113 (void)0; /* ensure void type for expression */ \
114 })
115
116 /* Release a write lock. */
117 #define __rw_wunlock(rw, tid, file, line) __extension__ ({ \
118 uintptr_t _v = (uintptr_t)(tid); \
119 \
120 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) || \
121 !_rw_write_unlock_fetch((rw), &_v))) \
122 _rw_wunlock_hard((rw), _v, (file), (line)); \
123 (void)0; /* ensure void type for expression */ \
124 })
125
126 /*
127 * Function prototypes. Routines that start with _ are not part of the
128 * external API and should not be called directly. Wrapper macros should
129 * be used instead.
130 */
131 void _rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
132 void _rw_destroy(volatile uintptr_t *c);
133 void rw_sysinit(void *arg);
134 int _rw_wowned(const volatile uintptr_t *c);
135 void _rw_wlock_cookie(volatile uintptr_t *c, const char *file, int line);
136 int __rw_try_wlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
137 int __rw_try_wlock(volatile uintptr_t *c, const char *file, int line);
138 void _rw_wunlock_cookie(volatile uintptr_t *c, const char *file, int line);
139 void __rw_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
140 void __rw_rlock(volatile uintptr_t *c, const char *file, int line);
141 int __rw_try_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
142 int __rw_try_rlock(volatile uintptr_t *c, const char *file, int line);
143 void _rw_runlock_cookie_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
144 void _rw_runlock_cookie(volatile uintptr_t *c, const char *file, int line);
145 void __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v
146 LOCK_FILE_LINE_ARG_DEF);
147 void __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t v
148 LOCK_FILE_LINE_ARG_DEF);
149 int __rw_try_upgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
150 int __rw_try_upgrade(volatile uintptr_t *c, const char *file, int line);
151 void __rw_downgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
152 void __rw_downgrade(volatile uintptr_t *c, const char *file, int line);
153 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
154 void __rw_assert(const volatile uintptr_t *c, int what, const char *file,
155 int line);
156 #endif
157
158 /*
159 * Top-level macros to provide lock cookie once the actual rwlock is passed.
160 * They will also prevent passing a malformed object to the rwlock KPI by
161 * failing compilation as the rw_lock reserved member will not be found.
162 */
163 #define rw_init(rw, n) \
164 _rw_init_flags(&(rw)->rw_lock, n, 0)
165 #define rw_init_flags(rw, n, o) \
166 _rw_init_flags(&(rw)->rw_lock, n, o)
167 #define rw_destroy(rw) \
168 _rw_destroy(&(rw)->rw_lock)
169 #define rw_wowned(rw) \
170 _rw_wowned(&(rw)->rw_lock)
171 #define _rw_wlock(rw, f, l) \
172 _rw_wlock_cookie(&(rw)->rw_lock, f, l)
173 #define _rw_try_wlock(rw, f, l) \
174 __rw_try_wlock(&(rw)->rw_lock, f, l)
175 #define _rw_wunlock(rw, f, l) \
176 _rw_wunlock_cookie(&(rw)->rw_lock, f, l)
177 #define _rw_try_rlock(rw, f, l) \
178 __rw_try_rlock(&(rw)->rw_lock, f, l)
179 #if LOCK_DEBUG > 0
180 #define _rw_rlock(rw, f, l) \
181 __rw_rlock(&(rw)->rw_lock, f, l)
182 #define _rw_runlock(rw, f, l) \
183 _rw_runlock_cookie(&(rw)->rw_lock, f, l)
184 #else
185 #define _rw_rlock(rw, f, l) \
186 __rw_rlock_int((struct rwlock *)rw)
187 #define _rw_runlock(rw, f, l) \
188 _rw_runlock_cookie_int((struct rwlock *)rw)
189 #endif
190 #if LOCK_DEBUG > 0
191 #define _rw_wlock_hard(rw, v, f, l) \
192 __rw_wlock_hard(&(rw)->rw_lock, v, f, l)
193 #define _rw_wunlock_hard(rw, v, f, l) \
194 __rw_wunlock_hard(&(rw)->rw_lock, v, f, l)
195 #define _rw_try_upgrade(rw, f, l) \
196 __rw_try_upgrade(&(rw)->rw_lock, f, l)
197 #define _rw_downgrade(rw, f, l) \
198 __rw_downgrade(&(rw)->rw_lock, f, l)
199 #else
200 #define _rw_wlock_hard(rw, v, f, l) \
201 __rw_wlock_hard(&(rw)->rw_lock, v)
202 #define _rw_wunlock_hard(rw, v, f, l) \
203 __rw_wunlock_hard(&(rw)->rw_lock, v)
204 #define _rw_try_upgrade(rw, f, l) \
205 __rw_try_upgrade_int(rw)
206 #define _rw_downgrade(rw, f, l) \
207 __rw_downgrade_int(rw)
208 #endif
209 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
210 #define _rw_assert(rw, w, f, l) \
211 __rw_assert(&(rw)->rw_lock, w, f, l)
212 #endif
213
214 /*
215 * Public interface for lock operations.
216 */
217
218 #ifndef LOCK_DEBUG
219 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
220 #endif
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)
224 #else
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)
229 #endif
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) __extension__ ({ \
237 if (rw_wowned(rw)) \
238 rw_wunlock(rw); \
239 else \
240 rw_runlock(rw); \
241 (void)0; /* ensure void type for expression */ \
242 })
243 #define rw_sleep(chan, rw, pri, wmesg, timo) \
244 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), \
245 tick_sbt * (timo), 0, C_HARDCLOCK)
246
247 #define rw_initialized(rw) lock_initialized(&(rw)->lock_object)
248
249 struct rw_args {
250 void *ra_rw;
251 const char *ra_desc;
252 int ra_flags;
253 };
254
255 #define RW_SYSINIT_FLAGS(name, rw, desc, flags) \
256 static struct rw_args name##_args = { \
257 (rw), \
258 (desc), \
259 (flags), \
260 }; \
261 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
262 rw_sysinit, &name##_args); \
263 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
264 _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
265
266 #define RW_SYSINIT(name, rw, desc) RW_SYSINIT_FLAGS(name, rw, desc, 0)
267
268 /*
269 * Options passed to rw_init_flags().
270 */
271 #define RW_DUPOK 0x01
272 #define RW_NOPROFILE 0x02
273 #define RW_NOWITNESS 0x04
274 #define RW_QUIET 0x08
275 #define RW_RECURSE 0x10
276 #define RW_NEW 0x20
277
278 /*
279 * The INVARIANTS-enabled rw_assert() functionality.
280 *
281 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
282 * support as _rw_assert() itself uses them and the latter implies that
283 * _rw_assert() must build.
284 */
285 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
286 #define RA_LOCKED LA_LOCKED
287 #define RA_RLOCKED LA_SLOCKED
288 #define RA_WLOCKED LA_XLOCKED
289 #define RA_UNLOCKED LA_UNLOCKED
290 #define RA_RECURSED LA_RECURSED
291 #define RA_NOTRECURSED LA_NOTRECURSED
292 #endif
293
294 #ifdef INVARIANTS
295 #define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
296 #else
297 #define rw_assert(rw, what)
298 #endif
299
300 #endif /* _KERNEL */
301 #endif /* !_SYS_RWLOCK_H_ */
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