2 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org>
3 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org>
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
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.
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
35 #include <sys/_lock.h>
40 #include <sys/lock_profile.h>
41 #include <sys/lockstat.h>
42 #include <machine/atomic.h>
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.
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.
64 * When the lock is not locked by any thread, it is encoded as a
65 * shared lock with zero waiters.
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)
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)
83 #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0)
84 #define SX_LOCK_DESTROYED \
85 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
89 #define sx_recurse lock_object.lo_data
91 #define SX_READ_VALUE(sx) ((sx)->sx_lock)
93 #define lv_sx_owner(v) \
94 ((v & SX_LOCK_SHARED) ? NULL : (struct thread *)SX_OWNER(v))
97 * Function prototipes. Routines that start with an underscore are not part
98 * of the public interface and are wrappered with a macro.
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_(struct sx *sx, const char *file, int line);
105 int sx_try_xlock_(struct sx *sx, const char *file, int line);
106 int sx_try_upgrade_(struct sx *sx, const char *file, int line);
107 void sx_downgrade_(struct sx *sx, const char *file, int line);
108 int _sx_slock(struct sx *sx, int opts, const char *file, int line);
109 int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
110 void _sx_sunlock(struct sx *sx, const char *file, int line);
111 void _sx_xunlock(struct sx *sx, const char *file, int line);
112 int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts,
113 const char *file, int line);
114 int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line);
115 void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int
117 void _sx_sunlock_hard(struct sx *sx, const char *file, int line);
118 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
119 void _sx_assert(const struct sx *sx, int what, const char *file, int line);
122 int sx_chain(struct thread *td, struct thread **ownerp);
131 #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \
132 static struct sx_args name##_args = { \
137 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
138 sx_sysinit, &name##_args); \
139 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
142 #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0)
145 * Full lock operations that are suitable to be inlined in non-debug kernels.
146 * If the lock can't be acquired or released trivially then the work is
147 * deferred to 'tougher' functions.
150 /* Acquire an exclusive lock. */
152 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
155 uintptr_t tid = (uintptr_t)td;
158 if (sx->sx_lock != SX_LOCK_UNLOCKED ||
159 !atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid))
160 error = _sx_xlock_hard(sx, tid, opts, file, line);
162 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
163 0, 0, file, line, LOCKSTAT_WRITER);
168 /* Release an exclusive lock. */
170 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
172 uintptr_t tid = (uintptr_t)td;
174 if (sx->sx_recurse == 0)
175 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx,
177 if (sx->sx_lock != tid ||
178 !atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
179 _sx_xunlock_hard(sx, tid, file, line);
182 /* Acquire a shared lock. */
184 __sx_slock(struct sx *sx, int opts, const char *file, int line)
186 uintptr_t x = sx->sx_lock;
189 if (!(x & SX_LOCK_SHARED) ||
190 !atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER))
191 error = _sx_slock_hard(sx, opts, file, line);
193 LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
194 0, 0, file, line, LOCKSTAT_READER);
200 * Release a shared lock. We can just drop a single shared lock so
201 * long as we aren't trying to drop the last shared lock when other
202 * threads are waiting for an exclusive lock. This takes advantage of
203 * the fact that an unlocked lock is encoded as a shared lock with a
207 __sx_sunlock(struct sx *sx, const char *file, int line)
209 uintptr_t x = sx->sx_lock;
211 LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER);
212 if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) ||
213 !atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER))
214 _sx_sunlock_hard(sx, file, line);
218 * Public interface for lock operations.
221 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
223 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
224 #define sx_xlock_(sx, file, line) \
225 (void)_sx_xlock((sx), 0, (file), (line))
226 #define sx_xlock_sig_(sx, file, line) \
227 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line))
228 #define sx_xunlock_(sx, file, line) \
229 _sx_xunlock((sx), (file), (line))
230 #define sx_slock_(sx, file, line) \
231 (void)_sx_slock((sx), 0, (file), (line))
232 #define sx_slock_sig_(sx, file, line) \
233 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line))
234 #define sx_sunlock_(sx, file, line) \
235 _sx_sunlock((sx), (file), (line))
237 #define sx_xlock_(sx, file, line) \
238 (void)__sx_xlock((sx), curthread, 0, (file), (line))
239 #define sx_xlock_sig_(sx, file, line) \
240 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line))
241 #define sx_xunlock_(sx, file, line) \
242 __sx_xunlock((sx), curthread, (file), (line))
243 #define sx_slock_(sx, file, line) \
244 (void)__sx_slock((sx), 0, (file), (line))
245 #define sx_slock_sig_(sx, file, line) \
246 __sx_slock((sx), SX_INTERRUPTIBLE, (file), (line))
247 #define sx_sunlock_(sx, file, line) \
248 __sx_sunlock((sx), (file), (line))
249 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
250 #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE)
251 #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE)
252 #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE)
253 #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE)
255 #define sx_assert_(sx, what, file, line) \
256 _sx_assert((sx), (what), (file), (line))
258 #define sx_assert_(sx, what, file, line) (void)0
261 #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE)
262 #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE)
263 #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE)
264 #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE)
265 #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE)
266 #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE)
267 #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__)
270 * Return a pointer to the owning thread if the lock is exclusively
273 #define sx_xholder(sx) \
274 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
275 (struct thread *)SX_OWNER((sx)->sx_lock))
277 #define sx_xlocked(sx) \
278 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
279 (uintptr_t)curthread)
281 #define sx_unlock_(sx, file, line) do { \
282 if (sx_xlocked(sx)) \
283 sx_xunlock_(sx, file, line); \
285 sx_sunlock_(sx, file, line); \
288 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE)
290 #define sx_sleep(chan, sx, pri, wmesg, timo) \
291 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \
292 tick_sbt * (timo), 0, C_HARDCLOCK)
295 * Options passed to sx_init_flags().
297 #define SX_DUPOK 0x01
298 #define SX_NOPROFILE 0x02
299 #define SX_NOWITNESS 0x04
300 #define SX_QUIET 0x08
301 #define SX_NOADAPTIVE 0x10
302 #define SX_RECURSE 0x20
306 * Options passed to sx_*lock_hard().
308 #define SX_INTERRUPTIBLE 0x40
310 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
311 #define SA_LOCKED LA_LOCKED
312 #define SA_SLOCKED LA_SLOCKED
313 #define SA_XLOCKED LA_XLOCKED
314 #define SA_UNLOCKED LA_UNLOCKED
315 #define SA_RECURSED LA_RECURSED
316 #define SA_NOTRECURSED LA_NOTRECURSED
318 /* Backwards compatibility. */
319 #define SX_LOCKED LA_LOCKED
320 #define SX_SLOCKED LA_SLOCKED
321 #define SX_XLOCKED LA_XLOCKED
322 #define SX_UNLOCKED LA_UNLOCKED
323 #define SX_RECURSED LA_RECURSED
324 #define SX_NOTRECURSED LA_NOTRECURSED
329 #endif /* !_SYS_SX_H_ */