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/10/sys/sys/rwlock.h 323870 2017-09-21 19:24:11Z marius $
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_FLAGMASK						\
62	(RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS |	\
63	RW_LOCK_WRITE_SPINNER)
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	4
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/* Very simple operations on rw_lock. */
80
81/* Try to obtain a write lock once. */
82#define	_rw_write_lock(rw, tid)						\
83	atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
84
85/* Release a write lock quickly if there are no waiters. */
86#define	_rw_write_unlock(rw, tid)					\
87	atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
88
89/*
90 * Full lock operations that are suitable to be inlined in non-debug
91 * kernels.  If the lock cannot be acquired or released trivially then
92 * the work is deferred to another function.
93 */
94
95/* Acquire a write lock. */
96#define	__rw_wlock(rw, tid, file, line) do {				\
97	uintptr_t _tid = (uintptr_t)(tid);				\
98						                        \
99	if ((rw)->rw_lock != RW_UNLOCKED || !_rw_write_lock((rw), _tid))\
100		_rw_wlock_hard((rw), _tid, (file), (line));		\
101	else 								\
102		LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_WLOCK_ACQUIRE, \
103		    rw, 0, 0, (file), (line));				\
104} while (0)
105
106/* Release a write lock. */
107#define	__rw_wunlock(rw, tid, file, line) do {				\
108	uintptr_t _tid = (uintptr_t)(tid);				\
109									\
110	if ((rw)->rw_recurse)						\
111		(rw)->rw_recurse--;					\
112	else if (!_rw_write_unlock((rw), _tid))				\
113		_rw_wunlock_hard((rw), _tid, (file), (line));		\
114} while (0)
115
116/*
117 * Function prototypes.  Routines that start with _ are not part of the
118 * external API and should not be called directly.  Wrapper macros should
119 * be used instead.
120 */
121void	_rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
122void	_rw_destroy(volatile uintptr_t *c);
123void	rw_sysinit(void *arg);
124void	rw_sysinit_flags(void *arg);
125int	_rw_wowned(const volatile uintptr_t *c);
126void	_rw_wlock_cookie(volatile uintptr_t *c, const char *file, int line);
127int	__rw_try_wlock(volatile uintptr_t *c, const char *file, int line);
128void	_rw_wunlock_cookie(volatile uintptr_t *c, const char *file, int line);
129void	__rw_rlock(volatile uintptr_t *c, const char *file, int line);
130int	__rw_try_rlock(volatile uintptr_t *c, const char *file, int line);
131void	_rw_runlock_cookie(volatile uintptr_t *c, const char *file, int line);
132void	__rw_wlock_hard(volatile uintptr_t *c, uintptr_t tid, const char *file,
133	    int line);
134void	__rw_wunlock_hard(volatile uintptr_t *c, uintptr_t tid,
135	    const char *file, int line);
136int	__rw_try_upgrade(volatile uintptr_t *c, const char *file, int line);
137void	__rw_downgrade(volatile uintptr_t *c, const char *file, int line);
138#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
139void	__rw_assert(const volatile uintptr_t *c, int what, const char *file,
140	    int line);
141#endif
142
143/*
144 * Top-level macros to provide lock cookie once the actual rwlock is passed.
145 * They will also prevent passing a malformed object to the rwlock KPI by
146 * failing compilation as the rw_lock reserved member will not be found.
147 */
148#define	rw_init(rw, n)							\
149	_rw_init_flags(&(rw)->rw_lock, n, 0)
150#define	rw_init_flags(rw, n, o)						\
151	_rw_init_flags(&(rw)->rw_lock, n, o)
152#define	rw_destroy(rw)							\
153	_rw_destroy(&(rw)->rw_lock)
154#define	rw_wowned(rw)							\
155	_rw_wowned(&(rw)->rw_lock)
156#define	_rw_wlock(rw, f, l)						\
157	_rw_wlock_cookie(&(rw)->rw_lock, f, l)
158#define	_rw_try_wlock(rw, f, l)						\
159	__rw_try_wlock(&(rw)->rw_lock, f, l)
160#define	_rw_wunlock(rw, f, l)						\
161	_rw_wunlock_cookie(&(rw)->rw_lock, f, l)
162#define	_rw_rlock(rw, f, l)						\
163	__rw_rlock(&(rw)->rw_lock, f, l)
164#define	_rw_try_rlock(rw, f, l)						\
165	__rw_try_rlock(&(rw)->rw_lock, f, l)
166#define	_rw_runlock(rw, f, l)						\
167	_rw_runlock_cookie(&(rw)->rw_lock, f, l)
168#define	_rw_wlock_hard(rw, t, f, l)					\
169	__rw_wlock_hard(&(rw)->rw_lock, t, f, l)
170#define	_rw_wunlock_hard(rw, t, f, l)					\
171	__rw_wunlock_hard(&(rw)->rw_lock, t, f, l)
172#define	_rw_try_upgrade(rw, f, l)					\
173	__rw_try_upgrade(&(rw)->rw_lock, f, l)
174#define	_rw_downgrade(rw, f, l)						\
175	__rw_downgrade(&(rw)->rw_lock, f, l)
176#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
177#define	_rw_assert(rw, w, f, l)						\
178	__rw_assert(&(rw)->rw_lock, w, f, l)
179#endif
180
181
182/*
183 * Public interface for lock operations.
184 */
185
186#ifndef LOCK_DEBUG
187#error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
188#endif
189#if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
190#define	rw_wlock(rw)		_rw_wlock((rw), LOCK_FILE, LOCK_LINE)
191#define	rw_wunlock(rw)		_rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
192#else
193#define	rw_wlock(rw)							\
194	__rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
195#define	rw_wunlock(rw)							\
196	__rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
197#endif
198#define	rw_rlock(rw)		_rw_rlock((rw), LOCK_FILE, LOCK_LINE)
199#define	rw_runlock(rw)		_rw_runlock((rw), LOCK_FILE, LOCK_LINE)
200#define	rw_try_rlock(rw)	_rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
201#define	rw_try_upgrade(rw)	_rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
202#define	rw_try_wlock(rw)	_rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
203#define	rw_downgrade(rw)	_rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
204#define	rw_unlock(rw)	do {						\
205	if (rw_wowned(rw))						\
206		rw_wunlock(rw);						\
207	else								\
208		rw_runlock(rw);						\
209} while (0)
210#define	rw_sleep(chan, rw, pri, wmesg, timo)				\
211	_sleep((chan), &(rw)->lock_object, (pri), (wmesg),		\
212	    tick_sbt * (timo), 0, C_HARDCLOCK)
213
214#define	rw_initialized(rw)	lock_initalized(&(rw)->lock_object)
215
216struct rw_args {
217	void		*ra_rw;
218	const char 	*ra_desc;
219};
220
221struct rw_args_flags {
222	void		*ra_rw;
223	const char 	*ra_desc;
224	int		ra_flags;
225};
226
227#define	RW_SYSINIT(name, rw, desc)					\
228	static struct rw_args name##_args = {				\
229		(rw),							\
230		(desc),							\
231	};								\
232	SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,	\
233	    rw_sysinit, &name##_args);					\
234	SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,	\
235	    _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
236
237
238#define	RW_SYSINIT_FLAGS(name, rw, desc, flags)				\
239	static struct rw_args_flags name##_args = {			\
240		(rw),							\
241		(desc),							\
242		(flags),						\
243	};								\
244	SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,	\
245	    rw_sysinit_flags, &name##_args);				\
246	SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,	\
247	    _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
248
249/*
250 * Options passed to rw_init_flags().
251 */
252#define	RW_DUPOK	0x01
253#define	RW_NOPROFILE	0x02
254#define	RW_NOWITNESS	0x04
255#define	RW_QUIET	0x08
256#define	RW_RECURSE	0x10
257#define	RW_NEW		0x20
258
259/*
260 * The INVARIANTS-enabled rw_assert() functionality.
261 *
262 * The constants need to be defined for INVARIANT_SUPPORT infrastructure
263 * support as _rw_assert() itself uses them and the latter implies that
264 * _rw_assert() must build.
265 */
266#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
267#define	RA_LOCKED		LA_LOCKED
268#define	RA_RLOCKED		LA_SLOCKED
269#define	RA_WLOCKED		LA_XLOCKED
270#define	RA_UNLOCKED		LA_UNLOCKED
271#define	RA_RECURSED		LA_RECURSED
272#define	RA_NOTRECURSED		LA_NOTRECURSED
273#endif
274
275#ifdef INVARIANTS
276#define	rw_assert(rw, what)	_rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
277#else
278#define	rw_assert(rw, what)
279#endif
280
281#endif /* _KERNEL */
282#endif /* !_SYS_RWLOCK_H_ */
283