FreeBSD/Linux Kernel Cross Reference
sys/sys/sx.h
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: releng/7.3/sys/sys/sx.h 197984 2009-10-12 15:56:27Z 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 <machine/atomic.h>
42 #endif
43
44 /*
45 * In general, the sx locks and rwlocks use very similar algorithms.
46 * The main difference in the implementations is how threads are
47 * blocked when a lock is unavailable. For this, sx locks use sleep
48 * queues which do not support priority propagation, and rwlocks use
49 * turnstiles which do.
50 *
51 * The sx_lock field consists of several fields. The low bit
52 * indicates if the lock is locked with a shared or exclusive lock. A
53 * value of 0 indicates an exclusive lock, and a value of 1 indicates
54 * a shared lock. Bit 1 is a boolean indicating if there are any
55 * threads waiting for a shared lock. Bit 2 is a boolean indicating
56 * if there are any threads waiting for an exclusive lock. Bit 3 is a
57 * boolean indicating if an exclusive lock is recursively held. The
58 * rest of the variable's definition is dependent on the value of the
59 * first bit. For an exclusive lock, it is a pointer to the thread
60 * holding the lock, similar to the mtx_lock field of mutexes. For
61 * shared locks, it is a count of read locks that are held.
62 *
63 * When the lock is not locked by any thread, it is encoded as a
64 * shared lock with zero waiters.
65 */
66
67 #define SX_LOCK_SHARED 0x01
68 #define SX_LOCK_SHARED_WAITERS 0x02
69 #define SX_LOCK_EXCLUSIVE_WAITERS 0x04
70 #define SX_LOCK_RECURSED 0x08
71 #define SX_LOCK_FLAGMASK \
72 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \
73 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED)
74
75 #define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK)
76 #define SX_SHARERS_SHIFT 4
77 #define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT)
78 #define SX_SHARERS_LOCK(x) \
79 ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED)
80 #define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT)
81
82 #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0)
83 #define SX_LOCK_DESTROYED \
84 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
85
86 #ifdef _KERNEL
87
88 /*
89 * Function prototipes. Routines that start with an underscore are not part
90 * of the public interface and are wrappered with a macro.
91 */
92 void sx_sysinit(void *arg);
93 #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0)
94 void sx_init_flags(struct sx *sx, const char *description, int opts);
95 void sx_destroy(struct sx *sx);
96 int _sx_slock(struct sx *sx, int opts, const char *file, int line);
97 int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
98 int _sx_try_slock(struct sx *sx, const char *file, int line);
99 int _sx_try_xlock(struct sx *sx, const char *file, int line);
100 void _sx_sunlock(struct sx *sx, const char *file, int line);
101 void _sx_xunlock(struct sx *sx, const char *file, int line);
102 int _sx_try_upgrade(struct sx *sx, const char *file, int line);
103 void _sx_downgrade(struct sx *sx, const char *file, int line);
104 int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts,
105 const char *file, int line);
106 int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line);
107 void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int
108 line);
109 void _sx_sunlock_hard(struct sx *sx, const char *file, int line);
110 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
111 void _sx_assert(struct sx *sx, int what, const char *file, int line);
112 #endif
113 #ifdef DDB
114 int sx_chain(struct thread *td, struct thread **ownerp);
115 #endif
116
117 struct sx_args {
118 struct sx *sa_sx;
119 const char *sa_desc;
120 };
121
122 #define SX_SYSINIT(name, sxa, desc) \
123 static struct sx_args name##_args = { \
124 (sxa), \
125 (desc) \
126 }; \
127 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
128 sx_sysinit, &name##_args); \
129 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
130 sx_destroy, (sxa))
131
132 /*
133 * Full lock operations that are suitable to be inlined in non-debug kernels.
134 * If the lock can't be acquired or released trivially then the work is
135 * deferred to 'tougher' functions.
136 */
137
138 /* Acquire an exclusive lock. */
139 static __inline int
140 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
141 int line)
142 {
143 uintptr_t tid = (uintptr_t)td;
144 int error = 0;
145
146 if (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid))
147 error = _sx_xlock_hard(sx, tid, opts, file, line);
148 else
149 lock_profile_obtain_lock_success(&sx->lock_object, 0, 0, file,
150 line);
151
152 return (error);
153 }
154
155 /* Release an exclusive lock. */
156 static __inline void
157 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
158 {
159 uintptr_t tid = (uintptr_t)td;
160
161 if (!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
162 _sx_xunlock_hard(sx, tid, file, line);
163 }
164
165 /* Acquire a shared lock. */
166 static __inline int
167 __sx_slock(struct sx *sx, int opts, const char *file, int line)
168 {
169 uintptr_t x = sx->sx_lock;
170 int error = 0;
171
172 if (!(x & SX_LOCK_SHARED) ||
173 !atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER))
174 error = _sx_slock_hard(sx, opts, file, line);
175 #ifdef LOCK_PROFILING_SHARED
176 else if (SX_SHARERS(x) == 0)
177 lock_profile_obtain_lock_success(&sx->lock_object, 0, 0, file,
178 line);
179 #endif
180
181 return (error);
182 }
183
184 /*
185 * Release a shared lock. We can just drop a single shared lock so
186 * long as we aren't trying to drop the last shared lock when other
187 * threads are waiting for an exclusive lock. This takes advantage of
188 * the fact that an unlocked lock is encoded as a shared lock with a
189 * count of 0.
190 */
191 static __inline void
192 __sx_sunlock(struct sx *sx, const char *file, int line)
193 {
194 uintptr_t x = sx->sx_lock;
195
196 if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) ||
197 !atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER))
198 _sx_sunlock_hard(sx, file, line);
199 }
200
201 /*
202 * Public interface for lock operations.
203 */
204 #ifndef LOCK_DEBUG
205 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
206 #endif
207 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
208 #define sx_xlock(sx) (void)_sx_xlock((sx), 0, LOCK_FILE, LOCK_LINE)
209 #define sx_xlock_sig(sx) \
210 _sx_xlock((sx), SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
211 #define sx_xunlock(sx) _sx_xunlock((sx), LOCK_FILE, LOCK_LINE)
212 #define sx_slock(sx) (void)_sx_slock((sx), 0, LOCK_FILE, LOCK_LINE)
213 #define sx_slock_sig(sx) \
214 _sx_slock((sx), SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
215 #define sx_sunlock(sx) _sx_sunlock((sx), LOCK_FILE, LOCK_LINE)
216 #else
217 #define sx_xlock(sx) \
218 (void)__sx_xlock((sx), curthread, 0, LOCK_FILE, LOCK_LINE)
219 #define sx_xlock_sig(sx) \
220 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
221 #define sx_xunlock(sx) \
222 __sx_xunlock((sx), curthread, LOCK_FILE, LOCK_LINE)
223 #define sx_slock(sx) (void)__sx_slock((sx), 0, LOCK_FILE, LOCK_LINE)
224 #define sx_slock_sig(sx) \
225 __sx_slock((sx), SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
226 #define sx_sunlock(sx) __sx_sunlock((sx), LOCK_FILE, LOCK_LINE)
227 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
228 #define sx_try_slock(sx) _sx_try_slock((sx), LOCK_FILE, LOCK_LINE)
229 #define sx_try_xlock(sx) _sx_try_xlock((sx), LOCK_FILE, LOCK_LINE)
230 #define sx_try_upgrade(sx) _sx_try_upgrade((sx), LOCK_FILE, LOCK_LINE)
231 #define sx_downgrade(sx) _sx_downgrade((sx), LOCK_FILE, LOCK_LINE)
232
233 /*
234 * Return a pointer to the owning thread if the lock is exclusively
235 * locked.
236 */
237 #define sx_xholder(sx) \
238 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
239 (struct thread *)SX_OWNER((sx)->sx_lock))
240
241 #define sx_xlocked(sx) \
242 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
243 (uintptr_t)curthread)
244
245 #define sx_unlock(sx) do { \
246 if (sx_xlocked(sx)) \
247 sx_xunlock(sx); \
248 else \
249 sx_sunlock(sx); \
250 } while (0)
251
252 #define sx_sleep(chan, sx, pri, wmesg, timo) \
253 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), (timo))
254
255 /*
256 * Options passed to sx_init_flags().
257 */
258 #define SX_DUPOK 0x01
259 #define SX_NOPROFILE 0x02
260 #define SX_NOWITNESS 0x04
261 #define SX_QUIET 0x08
262 #define SX_ADAPTIVESPIN 0x10
263 #define SX_RECURSE 0x20
264
265 /*
266 * Options passed to sx_*lock_hard().
267 */
268 #define SX_INTERRUPTIBLE 0x40
269
270 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
271 #define SA_LOCKED LA_LOCKED
272 #define SA_SLOCKED LA_SLOCKED
273 #define SA_XLOCKED LA_XLOCKED
274 #define SA_UNLOCKED LA_UNLOCKED
275 #define SA_RECURSED LA_RECURSED
276 #define SA_NOTRECURSED LA_NOTRECURSED
277
278 /* Backwards compatability. */
279 #define SX_LOCKED LA_LOCKED
280 #define SX_SLOCKED LA_SLOCKED
281 #define SX_XLOCKED LA_XLOCKED
282 #define SX_UNLOCKED LA_UNLOCKED
283 #define SX_RECURSED LA_RECURSED
284 #define SX_NOTRECURSED LA_NOTRECURSED
285 #endif
286
287 #ifdef INVARIANTS
288 #define sx_assert(sx, what) _sx_assert((sx), (what), LOCK_FILE, LOCK_LINE)
289 #else
290 #define sx_assert(sx, what)
291 #endif
292
293 #endif /* _KERNEL */
294
295 #endif /* !_SYS_SX_H_ */
Cache object: 0802ccff28736d8d971f55dd5fb5ef79
|