1 /*- 2 * Copyright (c) 2007 Stephan Uphoff <ups@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the author nor the names of any co-contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER 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 27 * SUCH DAMAGE. 28 */ 29 30 /* 31 * Machine independent bits of reader/writer lock implementation. 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_ddb.h" 38 #include "opt_kdtrace.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 43 #include <sys/kernel.h> 44 #include <sys/ktr.h> 45 #include <sys/lock.h> 46 #include <sys/mutex.h> 47 #include <sys/proc.h> 48 #include <sys/rmlock.h> 49 #include <sys/sched.h> 50 #include <sys/smp.h> 51 #include <sys/systm.h> 52 #include <sys/turnstile.h> 53 #include <sys/lock_profile.h> 54 #include <machine/cpu.h> 55 56 #ifdef DDB 57 #include <ddb/ddb.h> 58 #endif 59 60 #define RMPF_ONQUEUE 1 61 #define RMPF_SIGNAL 2 62 63 /* 64 * To support usage of rmlock in CVs and msleep yet another list for the 65 * priority tracker would be needed. Using this lock for cv and msleep also 66 * does not seem very useful 67 */ 68 69 static __inline void compiler_memory_barrier(void) { 70 __asm __volatile("":::"memory"); 71 } 72 73 static void assert_rm(struct lock_object *lock, int what); 74 static void lock_rm(struct lock_object *lock, int how); 75 #ifdef KDTRACE_HOOKS 76 static int owner_rm(struct lock_object *lock, struct thread **owner); 77 #endif 78 static int unlock_rm(struct lock_object *lock); 79 80 struct lock_class lock_class_rm = { 81 .lc_name = "rm", 82 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE, 83 .lc_assert = assert_rm, 84 #if 0 85 #ifdef DDB 86 .lc_ddb_show = db_show_rwlock, 87 #endif 88 #endif 89 .lc_lock = lock_rm, 90 .lc_unlock = unlock_rm, 91 #ifdef KDTRACE_HOOKS 92 .lc_owner = owner_rm, 93 #endif 94 }; 95 96 static void 97 assert_rm(struct lock_object *lock, int what) 98 { 99 100 panic("assert_rm called"); 101 } 102 103 static void 104 lock_rm(struct lock_object *lock, int how) 105 { 106 107 panic("lock_rm called"); 108 } 109 110 static int 111 unlock_rm(struct lock_object *lock) 112 { 113 114 panic("unlock_rm called"); 115 } 116 117 #ifdef KDTRACE_HOOKS 118 static int 119 owner_rm(struct lock_object *lock, struct thread **owner) 120 { 121 122 panic("owner_rm called"); 123 } 124 #endif 125 126 static struct mtx rm_spinlock; 127 128 MTX_SYSINIT(rm_spinlock, &rm_spinlock, "rm_spinlock", MTX_SPIN); 129 130 /* 131 * Add or remove tracker from per cpu list. 132 * 133 * The per cpu list can be traversed at any time in forward direction from an 134 * interrupt on the *local* cpu. 135 */ 136 static void inline 137 rm_tracker_add(struct pcpu *pc, struct rm_priotracker *tracker) 138 { 139 struct rm_queue *next; 140 141 /* Initialize all tracker pointers */ 142 tracker->rmp_cpuQueue.rmq_prev = &pc->pc_rm_queue; 143 next = pc->pc_rm_queue.rmq_next; 144 tracker->rmp_cpuQueue.rmq_next = next; 145 146 /* rmq_prev is not used during froward traversal. */ 147 next->rmq_prev = &tracker->rmp_cpuQueue; 148 149 /* Update pointer to first element. */ 150 pc->pc_rm_queue.rmq_next = &tracker->rmp_cpuQueue; 151 } 152 153 static void inline 154 rm_tracker_remove(struct pcpu *pc, struct rm_priotracker *tracker) 155 { 156 struct rm_queue *next, *prev; 157 158 next = tracker->rmp_cpuQueue.rmq_next; 159 prev = tracker->rmp_cpuQueue.rmq_prev; 160 161 /* Not used during forward traversal. */ 162 next->rmq_prev = prev; 163 164 /* Remove from list. */ 165 prev->rmq_next = next; 166 } 167 168 static void 169 rm_cleanIPI(void *arg) 170 { 171 struct pcpu *pc; 172 struct rmlock *rm = arg; 173 struct rm_priotracker *tracker; 174 struct rm_queue *queue; 175 pc = pcpu_find(curcpu); 176 177 for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue; 178 queue = queue->rmq_next) { 179 tracker = (struct rm_priotracker *)queue; 180 if (tracker->rmp_rmlock == rm && tracker->rmp_flags == 0) { 181 tracker->rmp_flags = RMPF_ONQUEUE; 182 mtx_lock_spin(&rm_spinlock); 183 LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker, 184 rmp_qentry); 185 mtx_unlock_spin(&rm_spinlock); 186 } 187 } 188 } 189 190 void 191 rm_init(struct rmlock *rm, const char *name, int opts) 192 { 193 194 rm->rm_noreadtoken = 1; 195 LIST_INIT(&rm->rm_activeReaders); 196 mtx_init(&rm->rm_lock, name, "RM_MTX",MTX_NOWITNESS); 197 lock_init(&rm->lock_object, &lock_class_rm, name, NULL, 198 (opts & LO_RECURSABLE)| LO_WITNESS); 199 } 200 201 void 202 rm_destroy(struct rmlock *rm) 203 { 204 205 mtx_destroy(&rm->rm_lock); 206 lock_destroy(&rm->lock_object); 207 } 208 209 int 210 rm_wowned(struct rmlock *rm) 211 { 212 213 return (mtx_owned(&rm->rm_lock)); 214 } 215 216 void 217 rm_sysinit(void *arg) 218 { 219 220 struct rm_args *args = arg; 221 rm_init(args->ra_rm, args->ra_desc, args->ra_opts); 222 } 223 224 static void 225 _rm_rlock_hard(struct rmlock *rm, struct rm_priotracker *tracker) 226 { 227 struct pcpu *pc; 228 struct rm_queue *queue; 229 struct rm_priotracker *atracker; 230 231 critical_enter(); 232 pc = pcpu_find(curcpu); 233 234 /* Check if we just need to do a proper critical_exit. */ 235 if (0 == rm->rm_noreadtoken) { 236 critical_exit(); 237 return; 238 } 239 240 /* Remove our tracker from the per cpu list. */ 241 rm_tracker_remove(pc, tracker); 242 243 /* Check to see if the IPI granted us the lock after all. */ 244 if (tracker->rmp_flags) { 245 /* Just add back tracker - we hold the lock. */ 246 rm_tracker_add(pc, tracker); 247 critical_exit(); 248 return; 249 } 250 251 /* 252 * We allow readers to aquire a lock even if a writer is blocked if 253 * the lock is recursive and the reader already holds the lock. 254 */ 255 if ((rm->lock_object.lo_flags & LO_RECURSABLE) != 0) { 256 /* 257 * Just grand the lock if this thread already have a tracker 258 * for this lock on the per cpu queue. 259 */ 260 for (queue = pc->pc_rm_queue.rmq_next; 261 queue != &pc->pc_rm_queue; queue = queue->rmq_next) { 262 atracker = (struct rm_priotracker *)queue; 263 if ((atracker->rmp_rmlock == rm) && 264 (atracker->rmp_thread == tracker->rmp_thread)) { 265 mtx_lock_spin(&rm_spinlock); 266 LIST_INSERT_HEAD(&rm->rm_activeReaders, 267 tracker, rmp_qentry); 268 tracker->rmp_flags = RMPF_ONQUEUE; 269 mtx_unlock_spin(&rm_spinlock); 270 rm_tracker_add(pc, tracker); 271 critical_exit(); 272 return; 273 } 274 } 275 } 276 277 sched_unpin(); 278 critical_exit(); 279 280 mtx_lock(&rm->rm_lock); 281 rm->rm_noreadtoken = 0; 282 critical_enter(); 283 284 pc = pcpu_find(curcpu); 285 rm_tracker_add(pc, tracker); 286 sched_pin(); 287 critical_exit(); 288 289 mtx_unlock(&rm->rm_lock); 290 } 291 292 void 293 _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker) 294 { 295 struct thread *td = curthread; 296 struct pcpu *pc; 297 298 tracker->rmp_flags = 0; 299 tracker->rmp_thread = td; 300 tracker->rmp_rmlock = rm; 301 302 td->td_critnest++; /* critical_enter(); */ 303 304 compiler_memory_barrier(); 305 306 pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */ 307 308 rm_tracker_add(pc, tracker); 309 310 td->td_pinned++; /* sched_pin(); */ 311 312 compiler_memory_barrier(); 313 314 td->td_critnest--; 315 316 /* 317 * Fast path to combine two common conditions into a single 318 * conditional jump. 319 */ 320 if (0 == (td->td_owepreempt | rm->rm_noreadtoken)) 321 return; 322 323 /* We do not have a read token and need to acquire one. */ 324 _rm_rlock_hard(rm, tracker); 325 } 326 327 static void 328 _rm_unlock_hard(struct thread *td,struct rm_priotracker *tracker) 329 { 330 331 if (td->td_owepreempt) { 332 td->td_critnest++; 333 critical_exit(); 334 } 335 336 if (!tracker->rmp_flags) 337 return; 338 339 mtx_lock_spin(&rm_spinlock); 340 LIST_REMOVE(tracker, rmp_qentry); 341 342 if (tracker->rmp_flags & RMPF_SIGNAL) { 343 struct rmlock *rm; 344 struct turnstile *ts; 345 346 rm = tracker->rmp_rmlock; 347 348 turnstile_chain_lock(&rm->lock_object); 349 mtx_unlock_spin(&rm_spinlock); 350 351 ts = turnstile_lookup(&rm->lock_object); 352 353 turnstile_signal(ts, TS_EXCLUSIVE_QUEUE); 354 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 355 turnstile_chain_unlock(&rm->lock_object); 356 } else 357 mtx_unlock_spin(&rm_spinlock); 358 } 359 360 void 361 _rm_runlock(struct rmlock *rm, struct rm_priotracker *tracker) 362 { 363 struct pcpu *pc; 364 struct thread *td = tracker->rmp_thread; 365 366 td->td_critnest++; /* critical_enter(); */ 367 pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */ 368 rm_tracker_remove(pc, tracker); 369 td->td_critnest--; 370 td->td_pinned--; /* sched_unpin(); */ 371 372 if (0 == (td->td_owepreempt | tracker->rmp_flags)) 373 return; 374 375 _rm_unlock_hard(td, tracker); 376 } 377 378 void 379 _rm_wlock(struct rmlock *rm) 380 { 381 struct rm_priotracker *prio; 382 struct turnstile *ts; 383 384 mtx_lock(&rm->rm_lock); 385 386 if (rm->rm_noreadtoken == 0) { 387 /* Get all read tokens back */ 388 389 rm->rm_noreadtoken = 1; 390 391 /* 392 * Assumes rm->rm_noreadtoken update is visible on other CPUs 393 * before rm_cleanIPI is called. 394 */ 395 #ifdef SMP 396 smp_rendezvous(smp_no_rendevous_barrier, 397 rm_cleanIPI, 398 smp_no_rendevous_barrier, 399 rm); 400 401 #else 402 rm_cleanIPI(rm); 403 #endif 404 405 mtx_lock_spin(&rm_spinlock); 406 while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) { 407 ts = turnstile_trywait(&rm->lock_object); 408 prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL; 409 mtx_unlock_spin(&rm_spinlock); 410 turnstile_wait(ts, prio->rmp_thread, 411 TS_EXCLUSIVE_QUEUE); 412 mtx_lock_spin(&rm_spinlock); 413 } 414 mtx_unlock_spin(&rm_spinlock); 415 } 416 } 417 418 void 419 _rm_wunlock(struct rmlock *rm) 420 { 421 422 mtx_unlock(&rm->rm_lock); 423 } 424 425 #ifdef LOCK_DEBUG 426 427 void _rm_wlock_debug(struct rmlock *rm, const char *file, int line) 428 { 429 430 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, 431 file, line, NULL); 432 433 _rm_wlock(rm); 434 435 LOCK_LOG_LOCK("RMWLOCK", &rm->lock_object, 0, 0, file, line); 436 437 WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line); 438 439 curthread->td_locks++; 440 441 } 442 443 void 444 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line) 445 { 446 447 curthread->td_locks--; 448 WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line); 449 LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line); 450 _rm_wunlock(rm); 451 } 452 453 void 454 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 455 const char *file, int line) 456 { 457 458 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line, NULL); 459 460 _rm_rlock(rm, tracker); 461 462 LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file, line); 463 464 WITNESS_LOCK(&rm->lock_object, 0, file, line); 465 466 curthread->td_locks++; 467 } 468 469 void 470 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 471 const char *file, int line) 472 { 473 474 curthread->td_locks--; 475 WITNESS_UNLOCK(&rm->lock_object, 0, file, line); 476 LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line); 477 _rm_runlock(rm, tracker); 478 } 479 480 #else 481 482 /* 483 * Just strip out file and line arguments if no lock debugging is enabled in 484 * the kernel - we are called from a kernel module. 485 */ 486 void 487 _rm_wlock_debug(struct rmlock *rm, const char *file, int line) 488 { 489 490 _rm_wlock(rm); 491 } 492 493 void 494 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line) 495 { 496 497 _rm_wunlock(rm); 498 } 499 500 void 501 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 502 const char *file, int line) 503 { 504 505 _rm_rlock(rm, tracker); 506 } 507 508 void 509 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 510 const char *file, int line) { 511 512 _rm_runlock(rm, tracker); 513 } 514 515 #endif 516