1 /*-
2 * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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 *
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
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD$
27 */
28
29 #ifndef _SYS_RWLOCK_H_
30 #define _SYS_RWLOCK_H_
31
32 #include <sys/_lock.h>
33 #include <sys/_rwlock.h>
34 #include <sys/lock_profile.h>
35 #include <sys/lockstat.h>
36
37 #ifdef _KERNEL
38 #include <sys/pcpu.h>
39 #include <machine/atomic.h>
40 #include <sys/proc.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_FLAGMASK \
63 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
64 RW_LOCK_WRITE_SPINNER)
65 #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
66
67 #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
68 #define RW_READERS_SHIFT 4
69 #define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
70 #define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
71 #define RW_ONE_READER (1 << RW_READERS_SHIFT)
72
73 #define RW_UNLOCKED RW_READERS_LOCK(0)
74 #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
75
76 #ifdef _KERNEL
77
78 #define rw_recurse lock_object.lo_data
79
80 /* Very simple operations on rw_lock. */
81
82 /* Try to obtain a write lock once. */
83 #define _rw_write_lock(rw, tid) \
84 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
85
86 /* Release a write lock quickly if there are no waiters. */
87 #define _rw_write_unlock(rw, tid) \
88 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
89
90 /*
91 * Full lock operations that are suitable to be inlined in non-debug
92 * kernels. If the lock cannot be acquired or released trivially then
93 * the work is deferred to another function.
94 */
95
96 /* Acquire a write lock. */
97 #define __rw_wlock(rw, tid, file, line) do { \
98 uintptr_t _tid = (uintptr_t)(tid); \
99 \
100 if (!_rw_write_lock((rw), _tid)) \
101 _rw_wlock_hard((rw), _tid, (file), (line)); \
102 else \
103 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(rw__acquire, rw, \
104 0, 0, file, line, LOCKSTAT_WRITER); \
105 } while (0)
106
107 /* Release a write lock. */
108 #define __rw_wunlock(rw, tid, file, line) do { \
109 uintptr_t _tid = (uintptr_t)(tid); \
110 \
111 if ((rw)->rw_recurse) \
112 (rw)->rw_recurse--; \
113 else { \
114 LOCKSTAT_PROFILE_RELEASE_RWLOCK(rw__release, rw, \
115 LOCKSTAT_WRITER); \
116 if (!_rw_write_unlock((rw), _tid)) \
117 _rw_wunlock_hard((rw), _tid, (file), (line)); \
118 } \
119 } while (0)
120
121 /*
122 * Return the rwlock address when the lock cookie address is provided.
123 * This functionality assumes that struct rwlock* have a member named rw_lock.
124 */
125 #define rwlock2rw(c) (__containerof(c, struct rwlock, rw_lock))
126
127 /*
128 * Determines whether a new reader can acquire a lock. Succeeds if the
129 * reader already owns a read lock and the lock is locked for read to
130 * prevent deadlock from reader recursion. Also succeeds if the lock
131 * is unlocked and has no writer waiters or spinners. Failing otherwise
132 * prioritizes writers before readers.
133 */
134 #define RW_CAN_READ_TD(td, _rw) \
135 ((td->td_rw_rlocks && (_rw) & RW_LOCK_READ) || ((_rw) & \
136 (RW_LOCK_READ | RW_LOCK_WRITE_WAITERS | RW_LOCK_WRITE_SPINNER)) == \
137 RW_LOCK_READ)
138
139 #define RW_CAN_READ(_rw) RW_CAN_READ_TD(curthread, _rw)
140
141
142 /*
143 * Function prototypes. Routines that start with _ are not part of the
144 * external API and should not be called directly. Wrapper macros should
145 * be used instead.
146 */
147 void _rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
148 void _rw_destroy(volatile uintptr_t *c);
149 void rw_sysinit(void *arg);
150 void rw_sysinit_flags(void *arg);
151 int _rw_wowned(const volatile uintptr_t *c);
152 void _rw_wlock_cookie(volatile uintptr_t *c, const char *file, int line);
153 int __rw_try_wlock(volatile uintptr_t *c, const char *file, int line);
154 void _rw_wunlock_cookie(volatile uintptr_t *c, const char *file, int line);
155 void __rw_rlock_hard(volatile uintptr_t *c, const char *file, int line);
156 int __rw_try_rlock(volatile uintptr_t *c, const char *file, int line);
157 void _rw_runlock_cookie(volatile uintptr_t *c, const char *file, int line);
158 void __rw_wlock_hard(volatile uintptr_t *c, uintptr_t tid, const char *file,
159 int line);
160 void __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t tid,
161 const char *file, int line);
162 int __rw_try_upgrade(volatile uintptr_t *c, const char *file, int line);
163 void __rw_downgrade(volatile uintptr_t *c, const char *file, int line);
164 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
165 void __rw_assert(const volatile uintptr_t *c, int what, const char *file,
166 int line);
167 #endif
168
169 #ifdef WITNESS
170 #define __rw_rlock(c, file, line) __rw_rlock_hard(c, file, line)
171 #define __rw_runlock(c, file, line) _rw_runlock_cookie(c, file, line)
172 #else
173 static inline void
__rw_rlock(volatile uintptr_t * c,const char * file,int line)174 __rw_rlock(volatile uintptr_t *c, const char *file, int line)
175 {
176 struct rwlock *rw;
177 uintptr_t v;
178 struct thread *td = curthread;
179
180 rw = rwlock2rw(c);
181 v = rw->rw_lock;
182
183 if (RW_CAN_READ_TD(td, v) && atomic_cmpset_acq_ptr(&rw->rw_lock, v, v + RW_ONE_READER)) {
184 td->td_rw_rlocks++;
185 TD_LOCKS_INC(td);
186 return;
187 }
188 __rw_rlock_hard(c, file, line);
189 }
190
191
192 static inline void
__rw_runlock(volatile uintptr_t * c,const char * file,int line)193 __rw_runlock(volatile uintptr_t *c, const char *file, int line)
194 {
195 struct rwlock *rw;
196 uintptr_t v;
197 struct thread *td;
198
199 rw = rwlock2rw(c);
200 v = rw->rw_lock;
201
202 if ((!(v & RW_LOCK_WAITERS) || (RW_READERS(v) > 1)) && atomic_cmpset_rel_ptr(&rw->rw_lock, v, v - RW_ONE_READER)) {
203 td = curthread;
204 TD_LOCKS_DEC(td);
205 td->td_rw_rlocks--;
206 return;
207 }
208 _rw_runlock_cookie(c, file, line);
209 }
210 #endif
211 /*
212 * Top-level macros to provide lock cookie once the actual rwlock is passed.
213 * They will also prevent passing a malformed object to the rwlock KPI by
214 * failing compilation as the rw_lock reserved member will not be found.
215 */
216 #define rw_init(rw, n) \
217 _rw_init_flags(&(rw)->rw_lock, n, 0)
218 #define rw_init_flags(rw, n, o) \
219 _rw_init_flags(&(rw)->rw_lock, n, o)
220 #define rw_destroy(rw) \
221 _rw_destroy(&(rw)->rw_lock)
222 #define rw_wowned(rw) \
223 _rw_wowned(&(rw)->rw_lock)
224 #define _rw_wlock(rw, f, l) \
225 _rw_wlock_cookie(&(rw)->rw_lock, f, l)
226 #define _rw_try_wlock(rw, f, l) \
227 __rw_try_wlock(&(rw)->rw_lock, f, l)
228 #define _rw_wunlock(rw, f, l) \
229 _rw_wunlock_cookie(&(rw)->rw_lock, f, l)
230 #define _rw_rlock(rw, f, l) \
231 __rw_rlock(&(rw)->rw_lock, f, l)
232 #define _rw_try_rlock(rw, f, l) \
233 __rw_try_rlock(&(rw)->rw_lock, f, l)
234 #define _rw_runlock(rw, f, l) \
235 __rw_runlock(&(rw)->rw_lock, f, l)
236 #define _rw_wlock_hard(rw, t, f, l) \
237 __rw_wlock_hard(&(rw)->rw_lock, t, f, l)
238 #define _rw_wunlock_hard(rw, t, f, l) \
239 __rw_wunlock_hard(&(rw)->rw_lock, t, f, l)
240 #define _rw_try_upgrade(rw, f, l) \
241 __rw_try_upgrade(&(rw)->rw_lock, f, l)
242 #define _rw_downgrade(rw, f, l) \
243 __rw_downgrade(&(rw)->rw_lock, f, l)
244 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
245 #define _rw_assert(rw, w, f, l) \
246 __rw_assert(&(rw)->rw_lock, w, f, l)
247 #endif
248
249
250 /*
251 * Public interface for lock operations.
252 */
253
254 #ifndef LOCK_DEBUG
255 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
256 #endif
257 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
258 #define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
259 #define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
260 #else
261 #define rw_wlock(rw) \
262 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
263 #define rw_wunlock(rw) \
264 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
265 #endif
266 #define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
267 #define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
268 #define rw_try_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
269 #define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
270 #define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
271 #define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
272 #define rw_unlock(rw) do { \
273 if (rw_wowned(rw)) \
274 rw_wunlock(rw); \
275 else \
276 rw_runlock(rw); \
277 } while (0)
278 #define rw_sleep(chan, rw, pri, wmesg, timo) \
279 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), \
280 tick_sbt * (timo), 0, C_HARDCLOCK)
281
282 #define rw_initialized(rw) lock_initialized(&(rw)->lock_object)
283
284 struct rw_args {
285 void *ra_rw;
286 const char *ra_desc;
287 };
288
289 struct rw_args_flags {
290 void *ra_rw;
291 const char *ra_desc;
292 int ra_flags;
293 };
294
295 #define RW_SYSINIT(name, rw, desc) \
296 static struct rw_args name##_args = { \
297 (rw), \
298 (desc), \
299 }; \
300 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
301 rw_sysinit, &name##_args); \
302 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
303 _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
304
305
306 #define RW_SYSINIT_FLAGS(name, rw, desc, flags) \
307 static struct rw_args_flags name##_args = { \
308 (rw), \
309 (desc), \
310 (flags), \
311 }; \
312 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
313 rw_sysinit_flags, &name##_args); \
314 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
315 _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
316
317 /*
318 * Options passed to rw_init_flags().
319 */
320 #define RW_DUPOK 0x01
321 #define RW_NOPROFILE 0x02
322 #define RW_NOWITNESS 0x04
323 #define RW_QUIET 0x08
324 #define RW_RECURSE 0x10
325 #define RW_NEW 0x20
326
327 /*
328 * The INVARIANTS-enabled rw_assert() functionality.
329 *
330 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
331 * support as _rw_assert() itself uses them and the latter implies that
332 * _rw_assert() must build.
333 */
334 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
335 #define RA_LOCKED LA_LOCKED
336 #define RA_RLOCKED LA_SLOCKED
337 #define RA_WLOCKED LA_XLOCKED
338 #define RA_UNLOCKED LA_UNLOCKED
339 #define RA_RECURSED LA_RECURSED
340 #define RA_NOTRECURSED LA_NOTRECURSED
341 #endif
342
343 #ifdef INVARIANTS
344 #define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
345 #else
346 #define rw_assert(rw, what)
347 #endif
348
349 #endif /* _KERNEL */
350 #endif /* !_SYS_RWLOCK_H_ */
351