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 * $FreeBSD$
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 #define sx_recurse lock_object.lo_data
90
91 #define SX_READ_VALUE(sx) ((sx)->sx_lock)
92
93 #define lv_sx_owner(v) \
94 ((v & SX_LOCK_SHARED) ? NULL : (struct thread *)SX_OWNER(v))
95
96 /*
97 * Function prototipes. Routines that start with an underscore are not part
98 * of the public interface and are wrappered with a macro.
99 */
100 void sx_sysinit(void *arg);
101 #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0)
102 void sx_init_flags(struct sx *sx, const char *description, int opts);
103 void sx_destroy(struct sx *sx);
104 int sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
105 int sx_try_slock_(struct sx *sx, const char *file, int line);
106 int sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
107 int sx_try_xlock_(struct sx *sx, const char *file, int line);
108 int sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
109 int sx_try_upgrade_(struct sx *sx, const char *file, int line);
110 void sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
111 void sx_downgrade_(struct sx *sx, const char *file, int line);
112 int _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF);
113 int _sx_slock(struct sx *sx, int opts, const char *file, int line);
114 int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
115 void _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
116 void _sx_sunlock(struct sx *sx, const char *file, int line);
117 void _sx_xunlock(struct sx *sx, const char *file, int line);
118 int _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF);
119 void _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF);
120 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
121 void _sx_assert(const struct sx *sx, int what, const char *file, int line);
122 #endif
123 #ifdef DDB
124 int sx_chain(struct thread *td, struct thread **ownerp);
125 #endif
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 #if (LOCK_DEBUG == 0)
153 /* Acquire an exclusive lock. */
154 static __inline int
__sx_xlock(struct sx * sx,struct thread * td,int opts,const char * file,int line)155 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
156 int line)
157 {
158 uintptr_t tid = (uintptr_t)td;
159 uintptr_t v = SX_LOCK_UNLOCKED;
160 int error = 0;
161
162 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) ||
163 !atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid)))
164 error = _sx_xlock_hard(sx, v, opts);
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 x = (uintptr_t)td;
174
175 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) ||
176 !atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, SX_LOCK_UNLOCKED)))
177 _sx_xunlock_hard(sx, x);
178 }
179 #endif
180
181 /*
182 * Public interface for lock operations.
183 */
184 #ifndef LOCK_DEBUG
185 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
186 #endif
187 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
188 #define sx_xlock_(sx, file, line) \
189 (void)_sx_xlock((sx), 0, (file), (line))
190 #define sx_xlock_sig_(sx, file, line) \
191 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line))
192 #define sx_xunlock_(sx, file, line) \
193 _sx_xunlock((sx), (file), (line))
194 #else
195 #define sx_xlock_(sx, file, line) \
196 (void)__sx_xlock((sx), curthread, 0, (file), (line))
197 #define sx_xlock_sig_(sx, file, line) \
198 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line))
199 #define sx_xunlock_(sx, file, line) \
200 __sx_xunlock((sx), curthread, (file), (line))
201 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
202 #if (LOCK_DEBUG > 0)
203 #define sx_slock_(sx, file, line) \
204 (void)_sx_slock((sx), 0, (file), (line))
205 #define sx_slock_sig_(sx, file, line) \
206 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line))
207 #define sx_sunlock_(sx, file, line) \
208 _sx_sunlock((sx), (file), (line))
209 #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE)
210 #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE)
211 #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE)
212 #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE)
213 #else
214 #define sx_slock_(sx, file, line) \
215 (void)_sx_slock_int((sx), 0)
216 #define sx_slock_sig_(sx, file, line) \
217 _sx_slock_int((sx), SX_INTERRUPTIBLE)
218 #define sx_sunlock_(sx, file, line) \
219 _sx_sunlock_int((sx))
220 #define sx_try_slock(sx) sx_try_slock_int((sx))
221 #define sx_try_xlock(sx) sx_try_xlock_int((sx))
222 #define sx_try_upgrade(sx) sx_try_upgrade_int((sx))
223 #define sx_downgrade(sx) sx_downgrade_int((sx))
224 #endif
225 #ifdef INVARIANTS
226 #define sx_assert_(sx, what, file, line) \
227 _sx_assert((sx), (what), (file), (line))
228 #else
229 #define sx_assert_(sx, what, file, line) (void)0
230 #endif
231
232 #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE)
233 #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE)
234 #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE)
235 #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE)
236 #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE)
237 #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE)
238 #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__)
239
240 /*
241 * Return a pointer to the owning thread if the lock is exclusively
242 * locked.
243 */
244 #define sx_xholder(sx) \
245 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
246 (struct thread *)SX_OWNER((sx)->sx_lock))
247
248 #define sx_xlocked(sx) \
249 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
250 (uintptr_t)curthread)
251
252 #define sx_unlock_(sx, file, line) do { \
253 if (sx_xlocked(sx)) \
254 sx_xunlock_(sx, file, line); \
255 else \
256 sx_sunlock_(sx, file, line); \
257 } while (0)
258
259 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE)
260
261 #define sx_sleep(chan, sx, pri, wmesg, timo) \
262 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \
263 tick_sbt * (timo), 0, C_HARDCLOCK)
264
265 /*
266 * Options passed to sx_init_flags().
267 */
268 #define SX_DUPOK 0x01
269 #define SX_NOPROFILE 0x02
270 #define SX_NOWITNESS 0x04
271 #define SX_QUIET 0x08
272 #define SX_NOADAPTIVE 0x10
273 #define SX_RECURSE 0x20
274 #define SX_NEW 0x40
275
276 /*
277 * Options passed to sx_*lock_hard().
278 */
279 #define SX_INTERRUPTIBLE 0x40
280
281 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
282 #define SA_LOCKED LA_LOCKED
283 #define SA_SLOCKED LA_SLOCKED
284 #define SA_XLOCKED LA_XLOCKED
285 #define SA_UNLOCKED LA_UNLOCKED
286 #define SA_RECURSED LA_RECURSED
287 #define SA_NOTRECURSED LA_NOTRECURSED
288
289 /* Backwards compatibility. */
290 #define SX_LOCKED LA_LOCKED
291 #define SX_SLOCKED LA_SLOCKED
292 #define SX_XLOCKED LA_XLOCKED
293 #define SX_UNLOCKED LA_UNLOCKED
294 #define SX_RECURSED LA_RECURSED
295 #define SX_NOTRECURSED LA_NOTRECURSED
296 #endif
297
298 #endif /* _KERNEL */
299
300 #endif /* !_SYS_SX_H_ */
301