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_WRITER_RECURSED 0x10
62 #define RW_LOCK_FLAGMASK \
63 (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
64 RW_LOCK_WRITE_SPINNER | RW_LOCK_WRITER_RECURSED)
65 #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
67 #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
68 #define RW_READERS_SHIFT 5
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)
73 #define RW_UNLOCKED RW_READERS_LOCK(0)
74 #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
78 #define rw_recurse lock_object.lo_data
80 #define RW_READ_VALUE(x) ((x)->rw_lock)
82 /* Very simple operations on rw_lock. */
84 /* Try to obtain a write lock once. */
85 #define _rw_write_lock(rw, tid) \
86 atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
88 #define _rw_write_lock_fetch(rw, vp, tid) \
89 atomic_fcmpset_acq_ptr(&(rw)->rw_lock, vp, (tid))
91 /* Release a write lock quickly if there are no waiters. */
92 #define _rw_write_unlock(rw, tid) \
93 atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
96 * Full lock operations that are suitable to be inlined in non-debug
97 * kernels. If the lock cannot be acquired or released trivially then
98 * the work is deferred to another function.
101 /* Acquire a write lock. */
102 #define __rw_wlock(rw, tid, file, line) do { \
103 uintptr_t _tid = (uintptr_t)(tid); \
104 uintptr_t _v = RW_UNLOCKED; \
106 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__acquire) || \
107 !_rw_write_lock_fetch((rw), &_v, _tid))) \
108 _rw_wlock_hard((rw), _v, _tid, (file), (line)); \
111 /* Release a write lock. */
112 #define __rw_wunlock(rw, tid, file, line) do { \
113 uintptr_t _tid = (uintptr_t)(tid); \
115 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) || \
116 !_rw_write_unlock((rw), _tid))) \
117 _rw_wunlock_hard((rw), _tid, (file), (line)); \
121 * Function prototypes. Routines that start with _ are not part of the
122 * external API and should not be called directly. Wrapper macros should
125 void _rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
126 void _rw_destroy(volatile uintptr_t *c);
127 void rw_sysinit(void *arg);
128 void rw_sysinit_flags(void *arg);
129 int _rw_wowned(const volatile uintptr_t *c);
130 void _rw_wlock_cookie(volatile uintptr_t *c, const char *file, int line);
131 int __rw_try_wlock(volatile uintptr_t *c, const char *file, int line);
132 void _rw_wunlock_cookie(volatile uintptr_t *c, const char *file, int line);
133 void __rw_rlock(volatile uintptr_t *c, const char *file, int line);
134 int __rw_try_rlock(volatile uintptr_t *c, const char *file, int line);
135 void _rw_runlock_cookie(volatile uintptr_t *c, const char *file, int line);
136 void __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v, uintptr_t tid,
137 const char *file, int line);
138 void __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t tid,
139 const char *file, int line);
140 int __rw_try_upgrade(volatile uintptr_t *c, const char *file, int line);
141 void __rw_downgrade(volatile uintptr_t *c, const char *file, int line);
142 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
143 void __rw_assert(const volatile uintptr_t *c, int what, const char *file,
148 * Top-level macros to provide lock cookie once the actual rwlock is passed.
149 * They will also prevent passing a malformed object to the rwlock KPI by
150 * failing compilation as the rw_lock reserved member will not be found.
152 #define rw_init(rw, n) \
153 _rw_init_flags(&(rw)->rw_lock, n, 0)
154 #define rw_init_flags(rw, n, o) \
155 _rw_init_flags(&(rw)->rw_lock, n, o)
156 #define rw_destroy(rw) \
157 _rw_destroy(&(rw)->rw_lock)
158 #define rw_wowned(rw) \
159 _rw_wowned(&(rw)->rw_lock)
160 #define _rw_wlock(rw, f, l) \
161 _rw_wlock_cookie(&(rw)->rw_lock, f, l)
162 #define _rw_try_wlock(rw, f, l) \
163 __rw_try_wlock(&(rw)->rw_lock, f, l)
164 #define _rw_wunlock(rw, f, l) \
165 _rw_wunlock_cookie(&(rw)->rw_lock, f, l)
166 #define _rw_rlock(rw, f, l) \
167 __rw_rlock(&(rw)->rw_lock, f, l)
168 #define _rw_try_rlock(rw, f, l) \
169 __rw_try_rlock(&(rw)->rw_lock, f, l)
170 #define _rw_runlock(rw, f, l) \
171 _rw_runlock_cookie(&(rw)->rw_lock, f, l)
172 #define _rw_wlock_hard(rw, v, t, f, l) \
173 __rw_wlock_hard(&(rw)->rw_lock, v, t, f, l)
174 #define _rw_wunlock_hard(rw, t, f, l) \
175 __rw_wunlock_hard(&(rw)->rw_lock, t, f, l)
176 #define _rw_try_upgrade(rw, f, l) \
177 __rw_try_upgrade(&(rw)->rw_lock, f, l)
178 #define _rw_downgrade(rw, f, l) \
179 __rw_downgrade(&(rw)->rw_lock, f, l)
180 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
181 #define _rw_assert(rw, w, f, l) \
182 __rw_assert(&(rw)->rw_lock, w, f, l)
187 * Public interface for lock operations.
191 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
193 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
194 #define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
195 #define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
197 #define rw_wlock(rw) \
198 __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
199 #define rw_wunlock(rw) \
200 __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
202 #define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
203 #define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
204 #define rw_try_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
205 #define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
206 #define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
207 #define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
208 #define rw_unlock(rw) do { \
214 #define rw_sleep(chan, rw, pri, wmesg, timo) \
215 _sleep((chan), &(rw)->lock_object, (pri), (wmesg), \
216 tick_sbt * (timo), 0, C_HARDCLOCK)
218 #define rw_initialized(rw) lock_initialized(&(rw)->lock_object)
225 struct rw_args_flags {
231 #define RW_SYSINIT(name, rw, desc) \
232 static struct rw_args name##_args = { \
236 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
237 rw_sysinit, &name##_args); \
238 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
239 _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
242 #define RW_SYSINIT_FLAGS(name, rw, desc, flags) \
243 static struct rw_args_flags name##_args = { \
248 SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
249 rw_sysinit_flags, &name##_args); \
250 SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
251 _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
254 * Options passed to rw_init_flags().
256 #define RW_DUPOK 0x01
257 #define RW_NOPROFILE 0x02
258 #define RW_NOWITNESS 0x04
259 #define RW_QUIET 0x08
260 #define RW_RECURSE 0x10
264 * The INVARIANTS-enabled rw_assert() functionality.
266 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
267 * support as _rw_assert() itself uses them and the latter implies that
268 * _rw_assert() must build.
270 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
271 #define RA_LOCKED LA_LOCKED
272 #define RA_RLOCKED LA_SLOCKED
273 #define RA_WLOCKED LA_XLOCKED
274 #define RA_UNLOCKED LA_UNLOCKED
275 #define RA_RECURSED LA_RECURSED
276 #define RA_NOTRECURSED LA_NOTRECURSED
280 #define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
282 #define rw_assert(rw, what)
286 #endif /* !_SYS_RWLOCK_H_ */