Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/sys/sx.h
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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 /* 90 * Function prototipes. Routines that start with an underscore are not part 91 * of the public interface and are wrappered with a macro. 92 */ 93 void sx_sysinit(void *arg); 94 #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0) 95 void sx_init_flags(struct sx *sx, const char *description, int opts); 96 void sx_destroy(struct sx *sx); 97 int sx_try_slock_(struct sx *sx, const char *file, int line); 98 int sx_try_xlock_(struct sx *sx, const char *file, int line); 99 int sx_try_upgrade_(struct sx *sx, const char *file, int line); 100 void sx_downgrade_(struct sx *sx, const char *file, int line); 101 int _sx_slock(struct sx *sx, int opts, const char *file, int line); 102 int _sx_xlock(struct sx *sx, int opts, const char *file, int line); 103 void _sx_sunlock(struct sx *sx, const char *file, int line); 104 void _sx_xunlock(struct sx *sx, const char *file, int line); 105 int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, 106 const char *file, int line); 107 int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line); 108 void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 109 line); 110 void _sx_sunlock_hard(struct sx *sx, const char *file, int line); 111 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 112 void _sx_assert(const struct sx *sx, int what, const char *file, int line); 113 #endif 114 #ifdef DDB 115 int sx_chain(struct thread *td, struct thread **ownerp); 116 #endif 117 118 struct sx_args { 119 struct sx *sa_sx; 120 const char *sa_desc; 121 int sa_flags; 122 }; 123 124 #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \ 125 static struct sx_args name##_args = { \ 126 (sxa), \ 127 (desc), \ 128 (flags) \ 129 }; \ 130 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 131 sx_sysinit, &name##_args); \ 132 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 133 sx_destroy, (sxa)) 134 135 #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0) 136 137 /* 138 * Full lock operations that are suitable to be inlined in non-debug kernels. 139 * If the lock can't be acquired or released trivially then the work is 140 * deferred to 'tougher' functions. 141 */ 142 143 /* Acquire an exclusive lock. */ 144 static __inline int 145 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file, 146 int line) 147 { 148 uintptr_t tid = (uintptr_t)td; 149 int error = 0; 150 151 if (sx->sx_lock != SX_LOCK_UNLOCKED || 152 !atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid)) 153 error = _sx_xlock_hard(sx, tid, opts, file, line); 154 else 155 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_XLOCK_ACQUIRE, 156 sx, 0, 0, file, line); 157 158 return (error); 159 } 160 161 /* Release an exclusive lock. */ 162 static __inline void 163 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line) 164 { 165 uintptr_t tid = (uintptr_t)td; 166 167 if (sx->sx_lock != tid || 168 !atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) 169 _sx_xunlock_hard(sx, tid, file, line); 170 } 171 172 /* Acquire a shared lock. */ 173 static __inline int 174 __sx_slock(struct sx *sx, int opts, const char *file, int line) 175 { 176 uintptr_t x = sx->sx_lock; 177 int error = 0; 178 179 if (!(x & SX_LOCK_SHARED) || 180 !atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER)) 181 error = _sx_slock_hard(sx, opts, file, line); 182 else 183 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_SLOCK_ACQUIRE, sx, 0, 184 0, file, line); 185 186 return (error); 187 } 188 189 /* 190 * Release a shared lock. We can just drop a single shared lock so 191 * long as we aren't trying to drop the last shared lock when other 192 * threads are waiting for an exclusive lock. This takes advantage of 193 * the fact that an unlocked lock is encoded as a shared lock with a 194 * count of 0. 195 */ 196 static __inline void 197 __sx_sunlock(struct sx *sx, const char *file, int line) 198 { 199 uintptr_t x = sx->sx_lock; 200 201 if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) || 202 !atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER)) 203 _sx_sunlock_hard(sx, file, line); 204 } 205 206 /* 207 * Public interface for lock operations. 208 */ 209 #ifndef LOCK_DEBUG 210 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>" 211 #endif 212 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE) 213 #define sx_xlock_(sx, file, line) \ 214 (void)_sx_xlock((sx), 0, (file), (line)) 215 #define sx_xlock_sig_(sx, file, line) \ 216 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line)) 217 #define sx_xunlock_(sx, file, line) \ 218 _sx_xunlock((sx), (file), (line)) 219 #define sx_slock_(sx, file, line) \ 220 (void)_sx_slock((sx), 0, (file), (line)) 221 #define sx_slock_sig_(sx, file, line) \ 222 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line)) 223 #define sx_sunlock_(sx, file, line) \ 224 _sx_sunlock((sx), (file), (line)) 225 #else 226 #define sx_xlock_(sx, file, line) \ 227 (void)__sx_xlock((sx), curthread, 0, (file), (line)) 228 #define sx_xlock_sig_(sx, file, line) \ 229 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line)) 230 #define sx_xunlock_(sx, file, line) \ 231 __sx_xunlock((sx), curthread, (file), (line)) 232 #define sx_slock_(sx, file, line) \ 233 (void)__sx_slock((sx), 0, (file), (line)) 234 #define sx_slock_sig_(sx, file, line) \ 235 __sx_slock((sx), SX_INTERRUPTIBLE, (file), (line)) 236 #define sx_sunlock_(sx, file, line) \ 237 __sx_sunlock((sx), (file), (line)) 238 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */ 239 #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE) 240 #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE) 241 #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE) 242 #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE) 243 #ifdef INVARIANTS 244 #define sx_assert_(sx, what, file, line) \ 245 _sx_assert((sx), (what), (file), (line)) 246 #else 247 #define sx_assert_(sx, what, file, line) (void)0 248 #endif 249 250 #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE) 251 #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE) 252 #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE) 253 #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE) 254 #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE) 255 #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE) 256 #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__) 257 258 /* 259 * Return a pointer to the owning thread if the lock is exclusively 260 * locked. 261 */ 262 #define sx_xholder(sx) \ 263 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \ 264 (struct thread *)SX_OWNER((sx)->sx_lock)) 265 266 #define sx_xlocked(sx) \ 267 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ 268 (uintptr_t)curthread) 269 270 #define sx_unlock_(sx, file, line) do { \ 271 if (sx_xlocked(sx)) \ 272 sx_xunlock_(sx, file, line); \ 273 else \ 274 sx_sunlock_(sx, file, line); \ 275 } while (0) 276 277 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE) 278 279 #define sx_sleep(chan, sx, pri, wmesg, timo) \ 280 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \ 281 tick_sbt * (timo), 0, C_HARDCLOCK) 282 283 /* 284 * Options passed to sx_init_flags(). 285 */ 286 #define SX_DUPOK 0x01 287 #define SX_NOPROFILE 0x02 288 #define SX_NOWITNESS 0x04 289 #define SX_QUIET 0x08 290 #define SX_NOADAPTIVE 0x10 291 #define SX_RECURSE 0x20 292 #define SX_NEW 0x40 293 294 /* 295 * Options passed to sx_*lock_hard(). 296 */ 297 #define SX_INTERRUPTIBLE 0x40 298 299 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 300 #define SA_LOCKED LA_LOCKED 301 #define SA_SLOCKED LA_SLOCKED 302 #define SA_XLOCKED LA_XLOCKED 303 #define SA_UNLOCKED LA_UNLOCKED 304 #define SA_RECURSED LA_RECURSED 305 #define SA_NOTRECURSED LA_NOTRECURSED 306 307 /* Backwards compatibility. */ 308 #define SX_LOCKED LA_LOCKED 309 #define SX_SLOCKED LA_SLOCKED 310 #define SX_XLOCKED LA_XLOCKED 311 #define SX_UNLOCKED LA_UNLOCKED 312 #define SX_RECURSED LA_RECURSED 313 #define SX_NOTRECURSED LA_NOTRECURSED 314 #endif 315 316 #endif /* _KERNEL */ 317 318 #endif /* !_SYS_SX_H_ */
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