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 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 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) do {} while (0) 305 #define sx_try_xlock(s) (1) 306 #define sx_xunlock(s) do {} while (0) 307 #define SX_DUPOK 0 308 #define SX_NEW 0 309 #define SX_NOWITNESS 0 310 311 static __inline void 312 sx_init_flags(struct sx *sx, const char *description, int opts) 313 { 314 315 } 316 317 static __inline void 318 sx_destroy(struct sx *sx) 319 { 320 321 } 322 #endif /* _STANDALONE */ 323 324 #endif /* !_SYS_SX_H_ */ 325