1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org>
5 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice(s), this list of conditions and the following disclaimer as
13 * the first lines of this file unmodified other than the possible
14 * addition of one or more copyright notices.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice(s), this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
20 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
23 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
24 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
25 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
26 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
29 * DAMAGE.
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_WRITE_SPINNER 0x08
72 #define SX_LOCK_RECURSED 0x10
73 #define SX_LOCK_FLAGMASK \
74 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \
75 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED | SX_LOCK_WRITE_SPINNER)
76 #define SX_LOCK_WAITERS (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
77
78 #define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK)
79 #define SX_SHARERS_SHIFT 5
80 #define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT)
81 #define SX_SHARERS_LOCK(x) \
82 ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED)
83 #define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT)
84
85 #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0)
86 #define SX_LOCK_DESTROYED \
87 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
88
89 #ifdef _KERNEL
90
91 #define sx_recurse lock_object.lo_data
92
93 #define SX_READ_VALUE(sx) ((sx)->sx_lock)
94
95 #define lv_sx_owner(v) \
96 ((v & SX_LOCK_SHARED) ? NULL : (struct thread *)SX_OWNER(v))
97
98 /*
99 * Function prototipes. Routines that start with an underscore are not part
100 * of the public interface and are wrappered with a macro.
101 */
102 void sx_sysinit(void *arg);
103 #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0)
104 void sx_init_flags(struct sx *sx, const char *description, int opts);
105 void sx_destroy(struct sx *sx);
106 int sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
107 int sx_try_slock_(struct sx *sx, const char *file, int line);
108 int sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
109 int sx_try_xlock_(struct sx *sx, const char *file, int line);
110 int sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
111 int sx_try_upgrade_(struct sx *sx, const char *file, int line);
112 void sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
113 void sx_downgrade_(struct sx *sx, const char *file, int line);
114 int _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF);
115 int _sx_slock(struct sx *sx, int opts, const char *file, int line);
116 int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
117 void _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
118 void _sx_sunlock(struct sx *sx, const char *file, int line);
119 void _sx_xunlock(struct sx *sx, const char *file, int line);
120 int _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF);
121 void _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF);
122 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
123 void _sx_assert(const struct sx *sx, int what, const char *file, int line);
124 #endif
125 #ifdef DDB
126 int sx_chain(struct thread *td, struct thread **ownerp);
127 #endif
128
129 struct sx_args {
130 struct sx *sa_sx;
131 const char *sa_desc;
132 int sa_flags;
133 };
134
135 #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \
136 static struct sx_args name##_args = { \
137 (sxa), \
138 (desc), \
139 (flags) \
140 }; \
141 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
142 sx_sysinit, &name##_args); \
143 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
144 sx_destroy, (sxa))
145
146 #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0)
147
148 /*
149 * Full lock operations that are suitable to be inlined in non-debug kernels.
150 * If the lock can't be acquired or released trivially then the work is
151 * deferred to 'tougher' functions.
152 */
153
154 #if (LOCK_DEBUG == 0)
155 /* Acquire an exclusive lock. */
156 static __inline int
__sx_xlock(struct sx * sx,struct thread * td,int opts,const char * file,int line)157 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
158 int line)
159 {
160 uintptr_t tid = (uintptr_t)td;
161 uintptr_t v = SX_LOCK_UNLOCKED;
162 int error = 0;
163
164 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) ||
165 !atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid)))
166 error = _sx_xlock_hard(sx, v, opts);
167
168 return (error);
169 }
170
171 /* Release an exclusive lock. */
172 static __inline void
__sx_xunlock(struct sx * sx,struct thread * td,const char * file,int line)173 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
174 {
175 uintptr_t x = (uintptr_t)td;
176
177 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) ||
178 !atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, SX_LOCK_UNLOCKED)))
179 _sx_xunlock_hard(sx, x);
180 }
181 #endif
182
183 /*
184 * Public interface for lock operations.
185 */
186 #ifndef LOCK_DEBUG
187 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
188 #endif
189 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
190 #define sx_xlock_(sx, file, line) \
191 (void)_sx_xlock((sx), 0, (file), (line))
192 #define sx_xlock_sig_(sx, file, line) \
193 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line))
194 #define sx_xunlock_(sx, file, line) \
195 _sx_xunlock((sx), (file), (line))
196 #else
197 #define sx_xlock_(sx, file, line) \
198 (void)__sx_xlock((sx), curthread, 0, (file), (line))
199 #define sx_xlock_sig_(sx, file, line) \
200 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line))
201 #define sx_xunlock_(sx, file, line) \
202 __sx_xunlock((sx), curthread, (file), (line))
203 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
204 #if (LOCK_DEBUG > 0)
205 #define sx_slock_(sx, file, line) \
206 (void)_sx_slock((sx), 0, (file), (line))
207 #define sx_slock_sig_(sx, file, line) \
208 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line))
209 #define sx_sunlock_(sx, file, line) \
210 _sx_sunlock((sx), (file), (line))
211 #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE)
212 #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE)
213 #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE)
214 #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE)
215 #else
216 #define sx_slock_(sx, file, line) \
217 (void)_sx_slock_int((sx), 0)
218 #define sx_slock_sig_(sx, file, line) \
219 _sx_slock_int((sx), SX_INTERRUPTIBLE)
220 #define sx_sunlock_(sx, file, line) \
221 _sx_sunlock_int((sx))
222 #define sx_try_slock(sx) sx_try_slock_int((sx))
223 #define sx_try_xlock(sx) sx_try_xlock_int((sx))
224 #define sx_try_upgrade(sx) sx_try_upgrade_int((sx))
225 #define sx_downgrade(sx) sx_downgrade_int((sx))
226 #endif
227 #ifdef INVARIANTS
228 #define sx_assert_(sx, what, file, line) \
229 _sx_assert((sx), (what), (file), (line))
230 #else
231 #define sx_assert_(sx, what, file, line) (void)0
232 #endif
233
234 #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE)
235 #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE)
236 #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE)
237 #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE)
238 #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE)
239 #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE)
240 #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__)
241
242 /*
243 * Return a pointer to the owning thread if the lock is exclusively
244 * locked.
245 */
246 #define sx_xholder(sx) \
247 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
248 (struct thread *)SX_OWNER((sx)->sx_lock))
249
250 #define sx_xlocked(sx) \
251 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
252 (uintptr_t)curthread)
253
254 #define sx_unlock_(sx, file, line) __extension__ ({ \
255 if (sx_xlocked(sx)) \
256 sx_xunlock_(sx, file, line); \
257 else \
258 sx_sunlock_(sx, file, line); \
259 (void)0; /* ensure void type for expression */ \
260 })
261
262 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE)
263
264 #define sx_sleep(chan, sx, pri, wmesg, timo) \
265 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \
266 tick_sbt * (timo), 0, C_HARDCLOCK)
267
268 /*
269 * Options passed to sx_init_flags().
270 */
271 #define SX_DUPOK 0x01
272 #define SX_NOPROFILE 0x02
273 #define SX_NOWITNESS 0x04
274 #define SX_QUIET 0x08
275 #define SX_RECURSE 0x20
276 #define SX_NEW 0x40
277
278 /*
279 * Options passed to sx_*lock_hard().
280 */
281 #define SX_INTERRUPTIBLE 0x40
282
283 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
284 #define SA_LOCKED LA_LOCKED
285 #define SA_SLOCKED LA_SLOCKED
286 #define SA_XLOCKED LA_XLOCKED
287 #define SA_UNLOCKED LA_UNLOCKED
288 #define SA_RECURSED LA_RECURSED
289 #define SA_NOTRECURSED LA_NOTRECURSED
290
291 /* Backwards compatibility. */
292 #define SX_LOCKED LA_LOCKED
293 #define SX_SLOCKED LA_SLOCKED
294 #define SX_XLOCKED LA_XLOCKED
295 #define SX_UNLOCKED LA_UNLOCKED
296 #define SX_RECURSED LA_RECURSED
297 #define SX_NOTRECURSED LA_NOTRECURSED
298 #endif
299
300 #endif /* _KERNEL */
301
302 #ifdef _STANDALONE
303 /* since we have no threads in the boot loader, trivially implement no-op version */
304 #define sx_xlock(s) (1)
305 #define sx_try_xlock(s) (1)
306 #define sx_xunlock(s) (1)
307 #define SX_DUPOK 0
308 #define SX_NEW 0
309 #define SX_NOWITNESS 0
310
311 static __inline void
sx_init_flags(struct sx * sx,const char * description,int opts)312 sx_init_flags(struct sx *sx, const char *description, int opts)
313 {
314
315 }
316
317 static __inline void
sx_destroy(struct sx * sx)318 sx_destroy(struct sx *sx)
319 {
320
321 }
322 #endif /* _STANDALONE */
323
324 #endif /* !_SYS_SX_H_ */
325