1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
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
28#ifndef _SYS_RWLOCK_H_
29#define _SYS_RWLOCK_H_
30
31#include <sys/_lock.h>
32#include <sys/_rwlock.h>
33#include <sys/lock_profile.h>
34#include <sys/lockstat.h>
35
36#ifdef _KERNEL
37#include <sys/pcpu.h>
38#include <machine/atomic.h>
39#endif
40
41/*
42 * The rw_lock field consists of several fields. The low bit indicates
43 * if the lock is locked with a read (shared) or write (exclusive) lock.
44 * A value of 0 indicates a write lock, and a value of 1 indicates a read
45 * lock. Bit 1 is a boolean indicating if there are any threads waiting
46 * for a read lock. Bit 2 is a boolean indicating if there are any threads
47 * waiting for a write lock. The rest of the variable's definition is
48 * dependent on the value of the first bit. For a write lock, it is a
49 * pointer to the thread holding the lock, similar to the mtx_lock field of
50 * mutexes. For read locks, it is a count of read locks that are held.
51 *
52 * When the lock is not locked by any thread, it is encoded as a read lock
53 * with zero waiters.
54 */
55
56#define RW_LOCK_READ 0x01
57#define RW_LOCK_READ_WAITERS 0x02
58#define RW_LOCK_WRITE_WAITERS 0x04
59#define RW_LOCK_WRITE_SPINNER 0x08
60#define RW_LOCK_WRITER_RECURSED 0x10
61#define RW_LOCK_FLAGMASK \
62 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
63 RW_LOCK_WRITE_SPINNER | RW_LOCK_WRITER_RECURSED)
64#define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
65
66#define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
67#define RW_READERS_SHIFT 5
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)
71
72#define RW_UNLOCKED RW_READERS_LOCK(0)
73#define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
74
75#ifdef _KERNEL
76
77#define rw_recurse lock_object.lo_data
78
79#define RW_READ_VALUE(x) ((x)->rw_lock)
80
81/* Very simple operations on rw_lock. */
82
83/* Try to obtain a write lock once. */
84#define _rw_write_lock(rw, tid) \
85 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
86
87#define _rw_write_lock_fetch(rw, vp, tid) \
88 atomic_fcmpset_acq_ptr(&(rw)->rw_lock, vp, (tid))
89
90/* Release a write lock quickly if there are no waiters. */
91#define _rw_write_unlock(rw, tid) \
92 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
93
94#define _rw_write_unlock_fetch(rw, tid) \
95 atomic_fcmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
96
97/*
98 * Full lock operations that are suitable to be inlined in non-debug
99 * kernels. If the lock cannot be acquired or released trivially then
100 * the work is deferred to another function.
101 */
102
103/* Acquire a write lock. */
104#define __rw_wlock(rw, tid, file, line) __extension__ ({ \
105 uintptr_t _tid = (uintptr_t)(tid); \
106 uintptr_t _v = RW_UNLOCKED; \
107 \
108 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__acquire) || \
109 !_rw_write_lock_fetch((rw), &_v, _tid))) \
110 _rw_wlock_hard((rw), _v, (file), (line)); \
111 (void)0; /* ensure void type for expression */ \
112})
113
114/* Release a write lock. */
115#define __rw_wunlock(rw, tid, file, line) __extension__ ({ \
116 uintptr_t _v = (uintptr_t)(tid); \
117 \
118 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) || \
119 !_rw_write_unlock_fetch((rw), &_v))) \
120 _rw_wunlock_hard((rw), _v, (file), (line)); \
121 (void)0; /* ensure void type for expression */ \
122})
123
124/*
125 * Function prototypes. Routines that start with _ are not part of the
126 * external API and should not be called directly. Wrapper macros should
127 * be used instead.
128 */
129void _rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
130void _rw_destroy(volatile uintptr_t *c);
131void rw_sysinit(const void *arg);
132int _rw_wowned(const volatile uintptr_t *c);
133void _rw_wlock_cookie(volatile uintptr_t *c, const char *file, int line);
134int __rw_try_wlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
135int __rw_try_wlock(volatile uintptr_t *c, const char *file, int line);
136void _rw_wunlock_cookie(volatile uintptr_t *c, const char *file, int line);
137void __rw_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
138void __rw_rlock(volatile uintptr_t *c, const char *file, int line);
139int __rw_try_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
140int __rw_try_rlock(volatile uintptr_t *c, const char *file, int line);
141void _rw_runlock_cookie_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
142void _rw_runlock_cookie(volatile uintptr_t *c, const char *file, int line);
143void __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v
144 LOCK_FILE_LINE_ARG_DEF);
145void __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t v
146 LOCK_FILE_LINE_ARG_DEF);
147int __rw_try_upgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
148int __rw_try_upgrade(volatile uintptr_t *c, const char *file, int line);
149void __rw_downgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
150void __rw_downgrade(volatile uintptr_t *c, const char *file, int line);
151#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
152void __rw_assert(const volatile uintptr_t *c, int what, const char *file,
153 int line);
154#endif
155
156/*
157 * Top-level macros to provide lock cookie once the actual rwlock is passed.
158 * They will also prevent passing a malformed object to the rwlock KPI by
159 * failing compilation as the rw_lock reserved member will not be found.
160 */
161#define rw_init(rw, n) \
162 _rw_init_flags(&(rw)->rw_lock, n, 0)
163#define rw_init_flags(rw, n, o) \
164 _rw_init_flags(&(rw)->rw_lock, n, o)
165#define rw_destroy(rw) \
166 _rw_destroy(&(rw)->rw_lock)
167#define rw_wowned(rw) \
168 _rw_wowned(&(rw)->rw_lock)
169#define _rw_wlock(rw, f, l) \
170 _rw_wlock_cookie(&(rw)->rw_lock, f, l)
171#define _rw_try_wlock(rw, f, l) \
172 __rw_try_wlock(&(rw)->rw_lock, f, l)
173#define _rw_wunlock(rw, f, l) \
174 _rw_wunlock_cookie(&(rw)->rw_lock, f, l)
175#define _rw_try_rlock(rw, f, l) \
176 __rw_try_rlock(&(rw)->rw_lock, f, l)
177#if LOCK_DEBUG > 0
178#define _rw_rlock(rw, f, l) \
179 __rw_rlock(&(rw)->rw_lock, f, l)
180#define _rw_runlock(rw, f, l) \
181 _rw_runlock_cookie(&(rw)->rw_lock, f, l)
182#else
183#define _rw_rlock(rw, f, l) \
184 __rw_rlock_int((struct rwlock *)rw)
185#define _rw_runlock(rw, f, l) \
186 _rw_runlock_cookie_int((struct rwlock *)rw)
187#endif
188#if LOCK_DEBUG > 0
189#define _rw_wlock_hard(rw, v, f, l) \
190 __rw_wlock_hard(&(rw)->rw_lock, v, f, l)
191#define _rw_wunlock_hard(rw, v, f, l) \
192 __rw_wunlock_hard(&(rw)->rw_lock, v, f, l)
193#define _rw_try_upgrade(rw, f, l) \
194 __rw_try_upgrade(&(rw)->rw_lock, f, l)
195#define _rw_downgrade(rw, f, l) \
196 __rw_downgrade(&(rw)->rw_lock, f, l)
197#else
198#define _rw_wlock_hard(rw, v, f, l) \
199 __rw_wlock_hard(&(rw)->rw_lock, v)
200#define _rw_wunlock_hard(rw, v, f, l) \
201 __rw_wunlock_hard(&(rw)->rw_lock, v)
202#define _rw_try_upgrade(rw, f, l) \
203 __rw_try_upgrade_int(rw)
204#define _rw_downgrade(rw, f, l) \
205 __rw_downgrade_int(rw)
206#endif
207#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
208#define _rw_assert(rw, w, f, l) \
209 __rw_assert(&(rw)->rw_lock, w, f, l)
210#endif
211
212/*
213 * Public interface for lock operations.
214 */
215
216#ifndef LOCK_DEBUG
217#error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
218#endif
219#if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
220#define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
221#define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
222#else
223#define rw_wlock(rw) \
224 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
225#define rw_wunlock(rw) \
226 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
227#endif
228#define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
229#define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
230#define rw_try_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
231#define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
232#define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
233#define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
234#define rw_unlock(rw) __extension__ ({ \
235 if (rw_wowned(rw)) \
236 rw_wunlock(rw); \
237 else \
238 rw_runlock(rw); \
239 (void)0; /* ensure void type for expression */ \
240})
241#define rw_sleep(chan, rw, pri, wmesg, timo) \
242 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), \
243 tick_sbt * (timo), 0, C_HARDCLOCK)
244
245#define rw_initialized(rw) lock_initialized(&(rw)->lock_object)
246
247struct rw_args {
248 void *ra_rw;
249 const char *ra_desc;
250 int ra_flags;
251};
252
253#define RW_SYSINIT_FLAGS(name, rw, desc, flags) \
254 static struct rw_args name##_args = { \
255 (rw), \
256 (desc), \
257 (flags), \
258 }; \
259 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
260 rw_sysinit, &name##_args); \
261 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
262 _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
263
264#define RW_SYSINIT(name, rw, desc) RW_SYSINIT_FLAGS(name, rw, desc, 0)
265
266/*
267 * Options passed to rw_init_flags().
268 */
269#define RW_DUPOK 0x01
270#define RW_NOPROFILE 0x02
271#define RW_NOWITNESS 0x04
272#define RW_QUIET 0x08
273#define RW_RECURSE 0x10
274#define RW_NEW 0x20
275
276/*
277 * The INVARIANTS-enabled rw_assert() functionality.
278 *
279 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
280 * support as _rw_assert() itself uses them and the latter implies that
281 * _rw_assert() must build.
282 */
283#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
284#define RA_LOCKED LA_LOCKED
285#define RA_RLOCKED LA_SLOCKED
286#define RA_WLOCKED LA_XLOCKED
287#define RA_UNLOCKED LA_UNLOCKED
288#define RA_RECURSED LA_RECURSED
289#define RA_NOTRECURSED LA_NOTRECURSED
290#endif
291
292#ifdef INVARIANTS
293#define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
294#else
295#define rw_assert(rw, what)
296#endif
297
298#endif /* _KERNEL */
299#endif /* !_SYS_RWLOCK_H_ */