1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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 * $FreeBSD$ 32 */ 33 34 #ifndef _SYS_SX_H_ 35 #define _SYS_SX_H_ 36 37 #include <sys/_lock.h> 38 #include <sys/_sx.h> 39 40 #ifdef _KERNEL 41 #include <sys/pcpu.h> 42 #include <sys/lock_profile.h> 43 #include <sys/lockstat.h> 44 #include <machine/atomic.h> 45 #endif 46 47 /* 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. 53 * 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. 65 * 66 * When the lock is not locked by any thread, it is encoded as a 67 * shared lock with zero waiters. 68 */ 69 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) 79 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) 86 87 #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0) 88 #define SX_LOCK_DESTROYED \ 89 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS) 90 91 #ifdef _KERNEL 92 93 #define sx_recurse lock_object.lo_data 94 95 #define SX_READ_VALUE(sx) ((sx)->sx_lock) 96 97 #define lv_sx_owner(v) \ 98 ((v & SX_LOCK_SHARED) ? NULL : (struct thread *)SX_OWNER(v)) 99 100 /* 101 * Function prototipes. Routines that start with an underscore are not part 102 * of the public interface and are wrappered with a macro. 103 */ 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); 126 #endif 127 #ifdef DDB 128 int sx_chain(struct thread *td, struct thread **ownerp); 129 #endif 130 131 struct sx_args { 132 struct sx *sa_sx; 133 const char *sa_desc; 134 int sa_flags; 135 }; 136 137 #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \ 138 static struct sx_args name##_args = { \ 139 (sxa), \ 140 (desc), \ 141 (flags) \ 142 }; \ 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, \ 146 sx_destroy, (sxa)) 147 148 #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0) 149 150 /* 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. 154 */ 155 156 #if (LOCK_DEBUG == 0) 157 /* Acquire an exclusive lock. */ 158 static __inline int 159 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file, 160 int line) 161 { 162 uintptr_t tid = (uintptr_t)td; 163 uintptr_t v = SX_LOCK_UNLOCKED; 164 int error = 0; 165 166 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); 169 170 return (error); 171 } 172 173 /* Release an exclusive lock. */ 174 static __inline void 175 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line) 176 { 177 uintptr_t x = (uintptr_t)td; 178 179 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); 182 } 183 #endif 184 185 /* 186 * Public interface for lock operations. 187 */ 188 #ifndef LOCK_DEBUG 189 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>" 190 #endif 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)) 198 #else 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 */ 206 #if (LOCK_DEBUG > 0) 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) 217 #else 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)) 228 #endif 229 #ifdef INVARIANTS 230 #define sx_assert_(sx, what, file, line) \ 231 _sx_assert((sx), (what), (file), (line)) 232 #else 233 #define sx_assert_(sx, what, file, line) (void)0 234 #endif 235 236 #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__) 243 244 /* 245 * Return a pointer to the owning thread if the lock is exclusively 246 * locked. 247 */ 248 #define sx_xholder(sx) \ 249 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \ 250 (struct thread *)SX_OWNER((sx)->sx_lock)) 251 252 #define sx_xlocked(sx) \ 253 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ 254 (uintptr_t)curthread) 255 256 #define sx_unlock_(sx, file, line) __extension__ ({ \ 257 if (sx_xlocked(sx)) \ 258 sx_xunlock_(sx, file, line); \ 259 else \ 260 sx_sunlock_(sx, file, line); \ 261 (void)0; /* ensure void type for expression */ \ 262 }) 263 264 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE) 265 266 #define sx_sleep(chan, sx, pri, wmesg, timo) \ 267 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \ 268 tick_sbt * (timo), 0, C_HARDCLOCK) 269 270 /* 271 * Options passed to sx_init_flags(). 272 */ 273 #define SX_DUPOK 0x01 274 #define SX_NOPROFILE 0x02 275 #define SX_NOWITNESS 0x04 276 #define SX_QUIET 0x08 277 #define SX_RECURSE 0x20 278 #define SX_NEW 0x40 279 280 /* 281 * Options passed to sx_*lock_hard(). 282 */ 283 #define SX_INTERRUPTIBLE 0x40 284 285 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 286 #define SA_LOCKED LA_LOCKED 287 #define SA_SLOCKED LA_SLOCKED 288 #define SA_XLOCKED LA_XLOCKED 289 #define SA_UNLOCKED LA_UNLOCKED 290 #define SA_RECURSED LA_RECURSED 291 #define SA_NOTRECURSED LA_NOTRECURSED 292 293 /* Backwards compatibility. */ 294 #define SX_LOCKED LA_LOCKED 295 #define SX_SLOCKED LA_SLOCKED 296 #define SX_XLOCKED LA_XLOCKED 297 #define SX_UNLOCKED LA_UNLOCKED 298 #define SX_RECURSED LA_RECURSED 299 #define SX_NOTRECURSED LA_NOTRECURSED 300 #endif 301 302 #endif /* _KERNEL */ 303 304 #ifdef _STANDALONE 305 /* since we have no threads in the boot loader, trivially implement no-op version */ 306 #define sx_xlock(s) (1) 307 #define sx_try_xlock(s) (1) 308 #define sx_xunlock(s) (1) 309 #define SX_DUPOK 0 310 #define SX_NEW 0 311 #define SX_NOWITNESS 0 312 313 static __inline void 314 sx_init_flags(struct sx *sx, const char *description, int opts) 315 { 316 317 } 318 319 static __inline void 320 sx_destroy(struct sx *sx) 321 { 322 323 } 324 #endif /* _STANDALONE */ 325 326 #endif /* !_SYS_SX_H_ */ 327