2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org>
5 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org>
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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.
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
37 #include <sys/_lock.h>
42 #include <sys/lock_profile.h>
43 #include <sys/lockstat.h>
44 #include <machine/atomic.h>
48 * In general, the sx locks and rwlocks use very similar algorithms.
49 * The main difference in the implementations is how threads are
50 * blocked when a lock is unavailable. For this, sx locks use sleep
51 * queues which do not support priority propagation, and rwlocks use
52 * turnstiles which do.
54 * The sx_lock field consists of several fields. The low bit
55 * indicates if the lock is locked with a shared or exclusive lock. A
56 * value of 0 indicates an exclusive lock, and a value of 1 indicates
57 * a shared lock. Bit 1 is a boolean indicating if there are any
58 * threads waiting for a shared lock. Bit 2 is a boolean indicating
59 * if there are any threads waiting for an exclusive lock. Bit 3 is a
60 * boolean indicating if an exclusive lock is recursively held. The
61 * rest of the variable's definition is dependent on the value of the
62 * first bit. For an exclusive lock, it is a pointer to the thread
63 * holding the lock, similar to the mtx_lock field of mutexes. For
64 * shared locks, it is a count of read locks that are held.
66 * When the lock is not locked by any thread, it is encoded as a
67 * shared lock with zero waiters.
70 #define SX_LOCK_SHARED 0x01
71 #define SX_LOCK_SHARED_WAITERS 0x02
72 #define SX_LOCK_EXCLUSIVE_WAITERS 0x04
73 #define SX_LOCK_WRITE_SPINNER 0x08
74 #define SX_LOCK_RECURSED 0x10
75 #define SX_LOCK_FLAGMASK \
76 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \
77 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED | SX_LOCK_WRITE_SPINNER)
78 #define SX_LOCK_WAITERS (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
80 #define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK)
81 #define SX_SHARERS_SHIFT 5
82 #define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT)
83 #define SX_SHARERS_LOCK(x) \
84 ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED)
85 #define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT)
87 #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0)
88 #define SX_LOCK_DESTROYED \
89 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
93 #define sx_recurse lock_object.lo_data
95 #define SX_READ_VALUE(sx) ((sx)->sx_lock)
97 #define lv_sx_owner(v) \
98 ((v & SX_LOCK_SHARED) ? NULL : (struct thread *)SX_OWNER(v))
101 * Function prototipes. Routines that start with an underscore are not part
102 * of the public interface and are wrappered with a macro.
104 void sx_sysinit(void *arg);
105 #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0)
106 void sx_init_flags(struct sx *sx, const char *description, int opts);
107 void sx_destroy(struct sx *sx);
108 int sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
109 int sx_try_slock_(struct sx *sx, const char *file, int line);
110 int sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
111 int sx_try_xlock_(struct sx *sx, const char *file, int line);
112 int sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
113 int sx_try_upgrade_(struct sx *sx, const char *file, int line);
114 void sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
115 void sx_downgrade_(struct sx *sx, const char *file, int line);
116 int _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF);
117 int _sx_slock(struct sx *sx, int opts, const char *file, int line);
118 int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
119 void _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
120 void _sx_sunlock(struct sx *sx, const char *file, int line);
121 void _sx_xunlock(struct sx *sx, const char *file, int line);
122 int _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF);
123 void _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF);
124 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
125 void _sx_assert(const struct sx *sx, int what, const char *file, int line);
128 int sx_chain(struct thread *td, struct thread **ownerp);
137 #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \
138 static struct sx_args name##_args = { \
143 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
144 sx_sysinit, &name##_args); \
145 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
148 #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0)
151 * Full lock operations that are suitable to be inlined in non-debug kernels.
152 * If the lock can't be acquired or released trivially then the work is
153 * deferred to 'tougher' functions.
156 #if (LOCK_DEBUG == 0)
157 /* Acquire an exclusive lock. */
159 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
162 uintptr_t tid = (uintptr_t)td;
163 uintptr_t v = SX_LOCK_UNLOCKED;
166 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) ||
167 !atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid)))
168 error = _sx_xlock_hard(sx, v, opts);
173 /* Release an exclusive lock. */
175 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
177 uintptr_t x = (uintptr_t)td;
179 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) ||
180 !atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, SX_LOCK_UNLOCKED)))
181 _sx_xunlock_hard(sx, x);
186 * Public interface for lock operations.
189 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
191 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
192 #define sx_xlock_(sx, file, line) \
193 (void)_sx_xlock((sx), 0, (file), (line))
194 #define sx_xlock_sig_(sx, file, line) \
195 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line))
196 #define sx_xunlock_(sx, file, line) \
197 _sx_xunlock((sx), (file), (line))
199 #define sx_xlock_(sx, file, line) \
200 (void)__sx_xlock((sx), curthread, 0, (file), (line))
201 #define sx_xlock_sig_(sx, file, line) \
202 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line))
203 #define sx_xunlock_(sx, file, line) \
204 __sx_xunlock((sx), curthread, (file), (line))
205 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
207 #define sx_slock_(sx, file, line) \
208 (void)_sx_slock((sx), 0, (file), (line))
209 #define sx_slock_sig_(sx, file, line) \
210 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line))
211 #define sx_sunlock_(sx, file, line) \
212 _sx_sunlock((sx), (file), (line))
213 #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE)
214 #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE)
215 #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE)
216 #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE)
218 #define sx_slock_(sx, file, line) \
219 (void)_sx_slock_int((sx), 0)
220 #define sx_slock_sig_(sx, file, line) \
221 _sx_slock_int((sx), SX_INTERRUPTIBLE)
222 #define sx_sunlock_(sx, file, line) \
223 _sx_sunlock_int((sx))
224 #define sx_try_slock(sx) sx_try_slock_int((sx))
225 #define sx_try_xlock(sx) sx_try_xlock_int((sx))
226 #define sx_try_upgrade(sx) sx_try_upgrade_int((sx))
227 #define sx_downgrade(sx) sx_downgrade_int((sx))
230 #define sx_assert_(sx, what, file, line) \
231 _sx_assert((sx), (what), (file), (line))
233 #define sx_assert_(sx, what, file, line) (void)0
236 #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE)
237 #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE)
238 #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE)
239 #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE)
240 #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE)
241 #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE)
242 #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__)
245 * Return a pointer to the owning thread if the lock is exclusively
248 #define sx_xholder(sx) \
249 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
250 (struct thread *)SX_OWNER((sx)->sx_lock))
252 #define sx_xlocked(sx) \
253 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
254 (uintptr_t)curthread)
256 #define sx_unlock_(sx, file, line) do { \
257 if (sx_xlocked(sx)) \
258 sx_xunlock_(sx, file, line); \
260 sx_sunlock_(sx, file, line); \
263 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE)
265 #define sx_sleep(chan, sx, pri, wmesg, timo) \
266 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \
267 tick_sbt * (timo), 0, C_HARDCLOCK)
270 * Options passed to sx_init_flags().
272 #define SX_DUPOK 0x01
273 #define SX_NOPROFILE 0x02
274 #define SX_NOWITNESS 0x04
275 #define SX_QUIET 0x08
276 #define SX_RECURSE 0x20
280 * Options passed to sx_*lock_hard().
282 #define SX_INTERRUPTIBLE 0x40
284 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
285 #define SA_LOCKED LA_LOCKED
286 #define SA_SLOCKED LA_SLOCKED
287 #define SA_XLOCKED LA_XLOCKED
288 #define SA_UNLOCKED LA_UNLOCKED
289 #define SA_RECURSED LA_RECURSED
290 #define SA_NOTRECURSED LA_NOTRECURSED
292 /* Backwards compatibility. */
293 #define SX_LOCKED LA_LOCKED
294 #define SX_SLOCKED LA_SLOCKED
295 #define SX_XLOCKED LA_XLOCKED
296 #define SX_UNLOCKED LA_UNLOCKED
297 #define SX_RECURSED LA_RECURSED
298 #define SX_NOTRECURSED LA_NOTRECURSED
303 #endif /* !_SYS_SX_H_ */