rwlock.h revision 331722 
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: stable/11/sys/sys/rwlock.h 331722 2018-03-29 02:50:57Z eadler $
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#endif
41
42/*
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.
52 *
53 * When the lock is not locked by any thread, it is encoded as a read lock
54 * with zero waiters.
55 */
56
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)
66
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)
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#define	RW_READ_VALUE(x)	((x)->rw_lock)
81
82/* Very simple operations on rw_lock. */
83
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))
87
88#define	_rw_write_lock_fetch(rw, vp, tid)				\
89	atomic_fcmpset_acq_ptr(&(rw)->rw_lock, vp, (tid))
90
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)
94
95#define	_rw_write_unlock_fetch(rw, tid)					\
96	atomic_fcmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
97
98/*
99 * Full lock operations that are suitable to be inlined in non-debug
100 * kernels.  If the lock cannot be acquired or released trivially then
101 * the work is deferred to another function.
102 */
103
104/* Acquire a write lock. */
105#define	__rw_wlock(rw, tid, file, line) do {				\
106	uintptr_t _tid = (uintptr_t)(tid);				\
107	uintptr_t _v = RW_UNLOCKED;					\
108									\
109	if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__acquire) ||	\
110	    !_rw_write_lock_fetch((rw), &_v, _tid)))			\
111		_rw_wlock_hard((rw), _v, (file), (line));		\
112} while (0)
113
114/* Release a write lock. */
115#define	__rw_wunlock(rw, tid, file, line) do {				\
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} while (0)
122
123/*
124 * Function prototypes.  Routines that start with _ are not part of the
125 * external API and should not be called directly.  Wrapper macros should
126 * be used instead.
127 */
128void	_rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
129void	_rw_destroy(volatile uintptr_t *c);
130void	rw_sysinit(void *arg);
131void	rw_sysinit_flags(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/*
214 * Public interface for lock operations.
215 */
216
217#ifndef LOCK_DEBUG
218#error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
219#endif
220#if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
221#define	rw_wlock(rw)		_rw_wlock((rw), LOCK_FILE, LOCK_LINE)
222#define	rw_wunlock(rw)		_rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
223#else
224#define	rw_wlock(rw)							\
225	__rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
226#define	rw_wunlock(rw)							\
227	__rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
228#endif
229#define	rw_rlock(rw)		_rw_rlock((rw), LOCK_FILE, LOCK_LINE)
230#define	rw_runlock(rw)		_rw_runlock((rw), LOCK_FILE, LOCK_LINE)
231#define	rw_try_rlock(rw)	_rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
232#define	rw_try_upgrade(rw)	_rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
233#define	rw_try_wlock(rw)	_rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
234#define	rw_downgrade(rw)	_rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
235#define	rw_unlock(rw)	do {						\
236	if (rw_wowned(rw))						\
237		rw_wunlock(rw);						\
238	else								\
239		rw_runlock(rw);						\
240} while (0)
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_ */
300