1 /*-
2 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org>
3 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org>
4 * All rights reserved.
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(s), this list of conditions and the following disclaimer as
11 * the first lines of this file unmodified other than the possible
12 * addition of one or more copyright notices.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice(s), this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
23 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
24 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
27 * DAMAGE.
28 *
29 * $FreeBSD: stable/9/sys/sys/sx.h 230799 2012-01-31 01:45:20Z attilio $
30 */
31
32 #ifndef _SYS_SX_H_
33 #define _SYS_SX_H_
34
35 #include <sys/_lock.h>
36 #include <sys/_sx.h>
37
38 #ifdef _KERNEL
39 #include <sys/pcpu.h>
40 #include <sys/lock_profile.h>
41 #include <sys/lockstat.h>
42 #include <machine/atomic.h>
43 #endif
44
45 /*
46 * In general, the sx locks and rwlocks use very similar algorithms.
47 * The main difference in the implementations is how threads are
48 * blocked when a lock is unavailable. For this, sx locks use sleep
49 * queues which do not support priority propagation, and rwlocks use
50 * turnstiles which do.
51 *
52 * The sx_lock field consists of several fields. The low bit
53 * indicates if the lock is locked with a shared or exclusive lock. A
54 * value of 0 indicates an exclusive lock, and a value of 1 indicates
55 * a shared lock. Bit 1 is a boolean indicating if there are any
56 * threads waiting for a shared lock. Bit 2 is a boolean indicating
57 * if there are any threads waiting for an exclusive lock. Bit 3 is a
58 * boolean indicating if an exclusive lock is recursively held. The
59 * rest of the variable's definition is dependent on the value of the
60 * first bit. For an exclusive lock, it is a pointer to the thread
61 * holding the lock, similar to the mtx_lock field of mutexes. For
62 * shared locks, it is a count of read locks that are held.
63 *
64 * When the lock is not locked by any thread, it is encoded as a
65 * shared lock with zero waiters.
66 */
67
68 #define SX_LOCK_SHARED 0x01
69 #define SX_LOCK_SHARED_WAITERS 0x02
70 #define SX_LOCK_EXCLUSIVE_WAITERS 0x04
71 #define SX_LOCK_RECURSED 0x08
72 #define SX_LOCK_FLAGMASK \
73 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \
74 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED)
75
76 #define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK)
77 #define SX_SHARERS_SHIFT 4
78 #define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT)
79 #define SX_SHARERS_LOCK(x) \
80 ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED)
81 #define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT)
82
83 #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0)
84 #define SX_LOCK_DESTROYED \
85 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
86
87 #ifdef _KERNEL
88
89 /*
90 * Function prototipes. Routines that start with an underscore are not part
91 * of the public interface and are wrappered with a macro.
92 */
93 void sx_sysinit(void *arg);
94 #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0)
95 void sx_init_flags(struct sx *sx, const char *description, int opts);
96 void sx_destroy(struct sx *sx);
97 int _sx_slock(struct sx *sx, int opts, const char *file, int line);
98 int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
99 int _sx_try_slock(struct sx *sx, const char *file, int line);
100 int _sx_try_xlock(struct sx *sx, const char *file, int line);
101 void _sx_sunlock(struct sx *sx, const char *file, int line);
102 void _sx_xunlock(struct sx *sx, const char *file, int line);
103 int _sx_try_upgrade(struct sx *sx, const char *file, int line);
104 void _sx_downgrade(struct sx *sx, const char *file, int line);
105 int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts,
106 const char *file, int line);
107 int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line);
108 void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int
109 line);
110 void _sx_sunlock_hard(struct sx *sx, const char *file, int line);
111 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
112 void _sx_assert(struct sx *sx, int what, const char *file, int line);
113 #endif
114 #ifdef DDB
115 int sx_chain(struct thread *td, struct thread **ownerp);
116 #endif
117
118 #define sx_downgrade_(sx, file, line) \
119 _sx_downgrade((sx), (file), (line))
120 #define sx_try_slock_(sx, file, line) \
121 _sx_try_slock((sx), (file), (line))
122 #define sx_try_xlock_(sx, file, line) \
123 _sx_try_xlock((sx), (file), (line))
124 #define sx_try_upgrade_(sx, file, line) \
125 _sx_try_upgrade((sx), (file), (line))
126
127 struct sx_args {
128 struct sx *sa_sx;
129 const char *sa_desc;
130 int sa_flags;
131 };
132
133 #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \
134 static struct sx_args name##_args = { \
135 (sxa), \
136 (desc), \
137 (flags) \
138 }; \
139 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
140 sx_sysinit, &name##_args); \
141 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
142 sx_destroy, (sxa))
143
144 #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0)
145
146 /*
147 * Full lock operations that are suitable to be inlined in non-debug kernels.
148 * If the lock can't be acquired or released trivially then the work is
149 * deferred to 'tougher' functions.
150 */
151
152 /* Acquire an exclusive lock. */
153 static __inline int
__sx_xlock(struct sx * sx,struct thread * td,int opts,const char * file,int line)154 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
155 int line)
156 {
157 uintptr_t tid = (uintptr_t)td;
158 int error = 0;
159
160 if (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid))
161 error = _sx_xlock_hard(sx, tid, opts, file, line);
162 else
163 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_XLOCK_ACQUIRE,
164 sx, 0, 0, file, line);
165
166 return (error);
167 }
168
169 /* Release an exclusive lock. */
170 static __inline void
__sx_xunlock(struct sx * sx,struct thread * td,const char * file,int line)171 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
172 {
173 uintptr_t tid = (uintptr_t)td;
174
175 if (!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
176 _sx_xunlock_hard(sx, tid, file, line);
177 }
178
179 /* Acquire a shared lock. */
180 static __inline int
__sx_slock(struct sx * sx,int opts,const char * file,int line)181 __sx_slock(struct sx *sx, int opts, const char *file, int line)
182 {
183 uintptr_t x = sx->sx_lock;
184 int error = 0;
185
186 if (!(x & SX_LOCK_SHARED) ||
187 !atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER))
188 error = _sx_slock_hard(sx, opts, file, line);
189 else
190 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_SLOCK_ACQUIRE, sx, 0,
191 0, file, line);
192
193 return (error);
194 }
195
196 /*
197 * Release a shared lock. We can just drop a single shared lock so
198 * long as we aren't trying to drop the last shared lock when other
199 * threads are waiting for an exclusive lock. This takes advantage of
200 * the fact that an unlocked lock is encoded as a shared lock with a
201 * count of 0.
202 */
203 static __inline void
__sx_sunlock(struct sx * sx,const char * file,int line)204 __sx_sunlock(struct sx *sx, const char *file, int line)
205 {
206 uintptr_t x = sx->sx_lock;
207
208 if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) ||
209 !atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER))
210 _sx_sunlock_hard(sx, file, line);
211 }
212
213 /*
214 * Public interface for lock operations.
215 */
216 #ifndef LOCK_DEBUG
217 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
218 #endif
219 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
220 #define sx_xlock_(sx, file, line) \
221 (void)_sx_xlock((sx), 0, (file), (line))
222 #define sx_xlock_sig_(sx, file, line) \
223 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line))
224 #define sx_xunlock_(sx, file, line) \
225 _sx_xunlock((sx), (file), (line))
226 #define sx_slock_(sx, file, line) \
227 (void)_sx_slock((sx), 0, (file), (line))
228 #define sx_slock_sig_(sx, file, line) \
229 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line))
230 #define sx_sunlock_(sx, file, line) \
231 _sx_sunlock((sx), (file), (line))
232 #else
233 #define sx_xlock_(sx, file, line) \
234 (void)__sx_xlock((sx), curthread, 0, (file), (line))
235 #define sx_xlock_sig_(sx, file, line) \
236 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line))
237 #define sx_xunlock_(sx, file, line) \
238 __sx_xunlock((sx), curthread, (file), (line))
239 #define sx_slock_(sx, file, line) \
240 (void)__sx_slock((sx), 0, (file), (line))
241 #define sx_slock_sig_(sx, file, line) \
242 __sx_slock((sx), SX_INTERRUPTIBLE, (file), (line))
243 #define sx_sunlock_(sx, file, line) \
244 __sx_sunlock((sx), (file), (line))
245 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
246 #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE)
247 #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE)
248 #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE)
249 #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE)
250 #ifdef INVARIANTS
251 #define sx_assert_(sx, what, file, line) \
252 _sx_assert((sx), (what), (file), (line))
253 #else
254 #define sx_assert_(sx, what, file, line) (void)0
255 #endif
256
257 #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE)
258 #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE)
259 #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE)
260 #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE)
261 #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE)
262 #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE)
263 #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__)
264
265 /*
266 * Return a pointer to the owning thread if the lock is exclusively
267 * locked.
268 */
269 #define sx_xholder(sx) \
270 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
271 (struct thread *)SX_OWNER((sx)->sx_lock))
272
273 #define sx_xlocked(sx) \
274 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
275 (uintptr_t)curthread)
276
277 #define sx_unlock_(sx, file, line) do { \
278 if (sx_xlocked(sx)) \
279 sx_xunlock_(sx, file, line); \
280 else \
281 sx_sunlock_(sx, file, line); \
282 } while (0)
283
284 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE)
285
286 #define sx_sleep(chan, sx, pri, wmesg, timo) \
287 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), (timo))
288
289 /*
290 * Options passed to sx_init_flags().
291 */
292 #define SX_DUPOK 0x01
293 #define SX_NOPROFILE 0x02
294 #define SX_NOWITNESS 0x04
295 #define SX_QUIET 0x08
296 #define SX_NOADAPTIVE 0x10
297 #define SX_RECURSE 0x20
298
299 /*
300 * Options passed to sx_*lock_hard().
301 */
302 #define SX_INTERRUPTIBLE 0x40
303
304 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
305 #define SA_LOCKED LA_LOCKED
306 #define SA_SLOCKED LA_SLOCKED
307 #define SA_XLOCKED LA_XLOCKED
308 #define SA_UNLOCKED LA_UNLOCKED
309 #define SA_RECURSED LA_RECURSED
310 #define SA_NOTRECURSED LA_NOTRECURSED
311
312 /* Backwards compatability. */
313 #define SX_LOCKED LA_LOCKED
314 #define SX_SLOCKED LA_SLOCKED
315 #define SX_XLOCKED LA_XLOCKED
316 #define SX_UNLOCKED LA_UNLOCKED
317 #define SX_RECURSED LA_RECURSED
318 #define SX_NOTRECURSED LA_NOTRECURSED
319 #endif
320
321 #endif /* _KERNEL */
322
323 #endif /* !_SYS_SX_H_ */
324