Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/kern/kern_rmlock.c
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1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 2007 Stephan Uphoff <ups@FreeBSD.org> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the author nor the names of any co-contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER 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 29 * SUCH DAMAGE. 30 */ 31 32 /* 33 * Machine independent bits of reader/writer lock implementation. 34 */ 35 36 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD$"); 38 39 #include "opt_ddb.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 44 #include <sys/kernel.h> 45 #include <sys/kdb.h> 46 #include <sys/ktr.h> 47 #include <sys/lock.h> 48 #include <sys/mutex.h> 49 #include <sys/proc.h> 50 #include <sys/rmlock.h> 51 #include <sys/sched.h> 52 #include <sys/smp.h> 53 #include <sys/turnstile.h> 54 #include <sys/lock_profile.h> 55 #include <machine/cpu.h> 56 57 #ifdef DDB 58 #include <ddb/ddb.h> 59 #endif 60 61 /* 62 * A cookie to mark destroyed rmlocks. This is stored in the head of 63 * rm_activeReaders. 64 */ 65 #define RM_DESTROYED ((void *)0xdead) 66 67 #define rm_destroyed(rm) \ 68 (LIST_FIRST(&(rm)->rm_activeReaders) == RM_DESTROYED) 69 70 #define RMPF_ONQUEUE 1 71 #define RMPF_SIGNAL 2 72 73 #ifndef INVARIANTS 74 #define _rm_assert(c, what, file, line) 75 #endif 76 77 static void assert_rm(const struct lock_object *lock, int what); 78 #ifdef DDB 79 static void db_show_rm(const struct lock_object *lock); 80 #endif 81 static void lock_rm(struct lock_object *lock, uintptr_t how); 82 #ifdef KDTRACE_HOOKS 83 static int owner_rm(const struct lock_object *lock, struct thread **owner); 84 #endif 85 static uintptr_t unlock_rm(struct lock_object *lock); 86 87 struct lock_class lock_class_rm = { 88 .lc_name = "rm", 89 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE, 90 .lc_assert = assert_rm, 91 #ifdef DDB 92 .lc_ddb_show = db_show_rm, 93 #endif 94 .lc_lock = lock_rm, 95 .lc_unlock = unlock_rm, 96 #ifdef KDTRACE_HOOKS 97 .lc_owner = owner_rm, 98 #endif 99 }; 100 101 struct lock_class lock_class_rm_sleepable = { 102 .lc_name = "sleepable rm", 103 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE, 104 .lc_assert = assert_rm, 105 #ifdef DDB 106 .lc_ddb_show = db_show_rm, 107 #endif 108 .lc_lock = lock_rm, 109 .lc_unlock = unlock_rm, 110 #ifdef KDTRACE_HOOKS 111 .lc_owner = owner_rm, 112 #endif 113 }; 114 115 static void 116 assert_rm(const struct lock_object *lock, int what) 117 { 118 119 rm_assert((const struct rmlock *)lock, what); 120 } 121 122 static void 123 lock_rm(struct lock_object *lock, uintptr_t how) 124 { 125 struct rmlock *rm; 126 struct rm_priotracker *tracker; 127 128 rm = (struct rmlock *)lock; 129 if (how == 0) 130 rm_wlock(rm); 131 else { 132 tracker = (struct rm_priotracker *)how; 133 rm_rlock(rm, tracker); 134 } 135 } 136 137 static uintptr_t 138 unlock_rm(struct lock_object *lock) 139 { 140 struct thread *td; 141 struct pcpu *pc; 142 struct rmlock *rm; 143 struct rm_queue *queue; 144 struct rm_priotracker *tracker; 145 uintptr_t how; 146 147 rm = (struct rmlock *)lock; 148 tracker = NULL; 149 how = 0; 150 rm_assert(rm, RA_LOCKED | RA_NOTRECURSED); 151 if (rm_wowned(rm)) 152 rm_wunlock(rm); 153 else { 154 /* 155 * Find the right rm_priotracker structure for curthread. 156 * The guarantee about its uniqueness is given by the fact 157 * we already asserted the lock wasn't recursively acquired. 158 */ 159 critical_enter(); 160 td = curthread; 161 pc = get_pcpu(); 162 for (queue = pc->pc_rm_queue.rmq_next; 163 queue != &pc->pc_rm_queue; queue = queue->rmq_next) { 164 tracker = (struct rm_priotracker *)queue; 165 if ((tracker->rmp_rmlock == rm) && 166 (tracker->rmp_thread == td)) { 167 how = (uintptr_t)tracker; 168 break; 169 } 170 } 171 KASSERT(tracker != NULL, 172 ("rm_priotracker is non-NULL when lock held in read mode")); 173 critical_exit(); 174 rm_runlock(rm, tracker); 175 } 176 return (how); 177 } 178 179 #ifdef KDTRACE_HOOKS 180 static int 181 owner_rm(const struct lock_object *lock, struct thread **owner) 182 { 183 const struct rmlock *rm; 184 struct lock_class *lc; 185 186 rm = (const struct rmlock *)lock; 187 lc = LOCK_CLASS(&rm->rm_wlock_object); 188 return (lc->lc_owner(&rm->rm_wlock_object, owner)); 189 } 190 #endif 191 192 static struct mtx rm_spinlock; 193 194 MTX_SYSINIT(rm_spinlock, &rm_spinlock, "rm_spinlock", MTX_SPIN); 195 196 /* 197 * Add or remove tracker from per-cpu list. 198 * 199 * The per-cpu list can be traversed at any time in forward direction from an 200 * interrupt on the *local* cpu. 201 */ 202 static void inline 203 rm_tracker_add(struct pcpu *pc, struct rm_priotracker *tracker) 204 { 205 struct rm_queue *next; 206 207 /* Initialize all tracker pointers */ 208 tracker->rmp_cpuQueue.rmq_prev = &pc->pc_rm_queue; 209 next = pc->pc_rm_queue.rmq_next; 210 tracker->rmp_cpuQueue.rmq_next = next; 211 212 /* rmq_prev is not used during froward traversal. */ 213 next->rmq_prev = &tracker->rmp_cpuQueue; 214 215 /* Update pointer to first element. */ 216 pc->pc_rm_queue.rmq_next = &tracker->rmp_cpuQueue; 217 } 218 219 /* 220 * Return a count of the number of trackers the thread 'td' already 221 * has on this CPU for the lock 'rm'. 222 */ 223 static int 224 rm_trackers_present(const struct pcpu *pc, const struct rmlock *rm, 225 const struct thread *td) 226 { 227 struct rm_queue *queue; 228 struct rm_priotracker *tracker; 229 int count; 230 231 count = 0; 232 for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue; 233 queue = queue->rmq_next) { 234 tracker = (struct rm_priotracker *)queue; 235 if ((tracker->rmp_rmlock == rm) && (tracker->rmp_thread == td)) 236 count++; 237 } 238 return (count); 239 } 240 241 static void inline 242 rm_tracker_remove(struct pcpu *pc, struct rm_priotracker *tracker) 243 { 244 struct rm_queue *next, *prev; 245 246 next = tracker->rmp_cpuQueue.rmq_next; 247 prev = tracker->rmp_cpuQueue.rmq_prev; 248 249 /* Not used during forward traversal. */ 250 next->rmq_prev = prev; 251 252 /* Remove from list. */ 253 prev->rmq_next = next; 254 } 255 256 static void 257 rm_cleanIPI(void *arg) 258 { 259 struct pcpu *pc; 260 struct rmlock *rm = arg; 261 struct rm_priotracker *tracker; 262 struct rm_queue *queue; 263 pc = get_pcpu(); 264 265 for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue; 266 queue = queue->rmq_next) { 267 tracker = (struct rm_priotracker *)queue; 268 if (tracker->rmp_rmlock == rm && tracker->rmp_flags == 0) { 269 tracker->rmp_flags = RMPF_ONQUEUE; 270 mtx_lock_spin(&rm_spinlock); 271 LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker, 272 rmp_qentry); 273 mtx_unlock_spin(&rm_spinlock); 274 } 275 } 276 } 277 278 void 279 rm_init_flags(struct rmlock *rm, const char *name, int opts) 280 { 281 struct lock_class *lc; 282 int liflags, xflags; 283 284 liflags = 0; 285 if (!(opts & RM_NOWITNESS)) 286 liflags |= LO_WITNESS; 287 if (opts & RM_RECURSE) 288 liflags |= LO_RECURSABLE; 289 if (opts & RM_NEW) 290 liflags |= LO_NEW; 291 if (opts & RM_DUPOK) 292 liflags |= LO_DUPOK; 293 rm->rm_writecpus = all_cpus; 294 LIST_INIT(&rm->rm_activeReaders); 295 if (opts & RM_SLEEPABLE) { 296 liflags |= LO_SLEEPABLE; 297 lc = &lock_class_rm_sleepable; 298 xflags = (opts & RM_NEW ? SX_NEW : 0); 299 sx_init_flags(&rm->rm_lock_sx, "rmlock_sx", 300 xflags | SX_NOWITNESS); 301 } else { 302 lc = &lock_class_rm; 303 xflags = (opts & RM_NEW ? MTX_NEW : 0); 304 mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx", 305 xflags | MTX_NOWITNESS); 306 } 307 lock_init(&rm->lock_object, lc, name, NULL, liflags); 308 } 309 310 void 311 rm_init(struct rmlock *rm, const char *name) 312 { 313 314 rm_init_flags(rm, name, 0); 315 } 316 317 void 318 rm_destroy(struct rmlock *rm) 319 { 320 321 rm_assert(rm, RA_UNLOCKED); 322 LIST_FIRST(&rm->rm_activeReaders) = RM_DESTROYED; 323 if (rm->lock_object.lo_flags & LO_SLEEPABLE) 324 sx_destroy(&rm->rm_lock_sx); 325 else 326 mtx_destroy(&rm->rm_lock_mtx); 327 lock_destroy(&rm->lock_object); 328 } 329 330 int 331 rm_wowned(const struct rmlock *rm) 332 { 333 334 if (rm->lock_object.lo_flags & LO_SLEEPABLE) 335 return (sx_xlocked(&rm->rm_lock_sx)); 336 else 337 return (mtx_owned(&rm->rm_lock_mtx)); 338 } 339 340 void 341 rm_sysinit(void *arg) 342 { 343 struct rm_args *args; 344 345 args = arg; 346 rm_init_flags(args->ra_rm, args->ra_desc, args->ra_flags); 347 } 348 349 static __noinline int 350 _rm_rlock_hard(struct rmlock *rm, struct rm_priotracker *tracker, int trylock) 351 { 352 struct pcpu *pc; 353 354 critical_enter(); 355 pc = get_pcpu(); 356 357 /* Check if we just need to do a proper critical_exit. */ 358 if (!CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)) { 359 critical_exit(); 360 return (1); 361 } 362 363 /* Remove our tracker from the per-cpu list. */ 364 rm_tracker_remove(pc, tracker); 365 366 /* 367 * Check to see if the IPI granted us the lock after all. The load of 368 * rmp_flags must happen after the tracker is removed from the list. 369 */ 370 __compiler_membar(); 371 if (tracker->rmp_flags) { 372 /* Just add back tracker - we hold the lock. */ 373 rm_tracker_add(pc, tracker); 374 critical_exit(); 375 return (1); 376 } 377 378 /* 379 * We allow readers to acquire a lock even if a writer is blocked if 380 * the lock is recursive and the reader already holds the lock. 381 */ 382 if ((rm->lock_object.lo_flags & LO_RECURSABLE) != 0) { 383 /* 384 * Just grant the lock if this thread already has a tracker 385 * for this lock on the per-cpu queue. 386 */ 387 if (rm_trackers_present(pc, rm, curthread) != 0) { 388 mtx_lock_spin(&rm_spinlock); 389 LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker, 390 rmp_qentry); 391 tracker->rmp_flags = RMPF_ONQUEUE; 392 mtx_unlock_spin(&rm_spinlock); 393 rm_tracker_add(pc, tracker); 394 critical_exit(); 395 return (1); 396 } 397 } 398 399 sched_unpin(); 400 critical_exit(); 401 402 if (trylock) { 403 if (rm->lock_object.lo_flags & LO_SLEEPABLE) { 404 if (!sx_try_xlock(&rm->rm_lock_sx)) 405 return (0); 406 } else { 407 if (!mtx_trylock(&rm->rm_lock_mtx)) 408 return (0); 409 } 410 } else { 411 if (rm->lock_object.lo_flags & LO_SLEEPABLE) { 412 THREAD_SLEEPING_OK(); 413 sx_xlock(&rm->rm_lock_sx); 414 THREAD_NO_SLEEPING(); 415 } else 416 mtx_lock(&rm->rm_lock_mtx); 417 } 418 419 critical_enter(); 420 pc = get_pcpu(); 421 CPU_CLR(pc->pc_cpuid, &rm->rm_writecpus); 422 rm_tracker_add(pc, tracker); 423 sched_pin(); 424 critical_exit(); 425 426 if (rm->lock_object.lo_flags & LO_SLEEPABLE) 427 sx_xunlock(&rm->rm_lock_sx); 428 else 429 mtx_unlock(&rm->rm_lock_mtx); 430 431 return (1); 432 } 433 434 int 435 _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock) 436 { 437 struct thread *td = curthread; 438 struct pcpu *pc; 439 440 if (SCHEDULER_STOPPED()) 441 return (1); 442 443 tracker->rmp_flags = 0; 444 tracker->rmp_thread = td; 445 tracker->rmp_rmlock = rm; 446 447 if (rm->lock_object.lo_flags & LO_SLEEPABLE) 448 THREAD_NO_SLEEPING(); 449 450 td->td_critnest++; /* critical_enter(); */ 451 452 __compiler_membar(); 453 454 pc = cpuid_to_pcpu[td->td_oncpu]; 455 456 rm_tracker_add(pc, tracker); 457 458 sched_pin(); 459 460 __compiler_membar(); 461 462 td->td_critnest--; 463 464 /* 465 * Fast path to combine two common conditions into a single 466 * conditional jump. 467 */ 468 if (__predict_true(0 == (td->td_owepreempt | 469 CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)))) 470 return (1); 471 472 /* We do not have a read token and need to acquire one. */ 473 return _rm_rlock_hard(rm, tracker, trylock); 474 } 475 476 static __noinline void 477 _rm_unlock_hard(struct thread *td,struct rm_priotracker *tracker) 478 { 479 480 if (td->td_owepreempt) { 481 td->td_critnest++; 482 critical_exit(); 483 } 484 485 if (!tracker->rmp_flags) 486 return; 487 488 mtx_lock_spin(&rm_spinlock); 489 LIST_REMOVE(tracker, rmp_qentry); 490 491 if (tracker->rmp_flags & RMPF_SIGNAL) { 492 struct rmlock *rm; 493 struct turnstile *ts; 494 495 rm = tracker->rmp_rmlock; 496 497 turnstile_chain_lock(&rm->lock_object); 498 mtx_unlock_spin(&rm_spinlock); 499 500 ts = turnstile_lookup(&rm->lock_object); 501 502 turnstile_signal(ts, TS_EXCLUSIVE_QUEUE); 503 turnstile_unpend(ts); 504 turnstile_chain_unlock(&rm->lock_object); 505 } else 506 mtx_unlock_spin(&rm_spinlock); 507 } 508 509 void 510 _rm_runlock(struct rmlock *rm, struct rm_priotracker *tracker) 511 { 512 struct pcpu *pc; 513 struct thread *td = tracker->rmp_thread; 514 515 if (SCHEDULER_STOPPED()) 516 return; 517 518 td->td_critnest++; /* critical_enter(); */ 519 pc = cpuid_to_pcpu[td->td_oncpu]; 520 rm_tracker_remove(pc, tracker); 521 td->td_critnest--; 522 sched_unpin(); 523 524 if (rm->lock_object.lo_flags & LO_SLEEPABLE) 525 THREAD_SLEEPING_OK(); 526 527 if (__predict_true(0 == (td->td_owepreempt | tracker->rmp_flags))) 528 return; 529 530 _rm_unlock_hard(td, tracker); 531 } 532 533 void 534 _rm_wlock(struct rmlock *rm) 535 { 536 struct rm_priotracker *prio; 537 struct turnstile *ts; 538 cpuset_t readcpus; 539 540 if (SCHEDULER_STOPPED()) 541 return; 542 543 if (rm->lock_object.lo_flags & LO_SLEEPABLE) 544 sx_xlock(&rm->rm_lock_sx); 545 else 546 mtx_lock(&rm->rm_lock_mtx); 547 548 if (CPU_CMP(&rm->rm_writecpus, &all_cpus)) { 549 /* Get all read tokens back */ 550 readcpus = all_cpus; 551 CPU_NAND(&readcpus, &rm->rm_writecpus); 552 rm->rm_writecpus = all_cpus; 553 554 /* 555 * Assumes rm->rm_writecpus update is visible on other CPUs 556 * before rm_cleanIPI is called. 557 */ 558 #ifdef SMP 559 smp_rendezvous_cpus(readcpus, 560 smp_no_rendezvous_barrier, 561 rm_cleanIPI, 562 smp_no_rendezvous_barrier, 563 rm); 564 565 #else 566 rm_cleanIPI(rm); 567 #endif 568 569 mtx_lock_spin(&rm_spinlock); 570 while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) { 571 ts = turnstile_trywait(&rm->lock_object); 572 prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL; 573 mtx_unlock_spin(&rm_spinlock); 574 turnstile_wait(ts, prio->rmp_thread, 575 TS_EXCLUSIVE_QUEUE); 576 mtx_lock_spin(&rm_spinlock); 577 } 578 mtx_unlock_spin(&rm_spinlock); 579 } 580 } 581 582 void 583 _rm_wunlock(struct rmlock *rm) 584 { 585 586 if (rm->lock_object.lo_flags & LO_SLEEPABLE) 587 sx_xunlock(&rm->rm_lock_sx); 588 else 589 mtx_unlock(&rm->rm_lock_mtx); 590 } 591 592 #if LOCK_DEBUG > 0 593 594 void 595 _rm_wlock_debug(struct rmlock *rm, const char *file, int line) 596 { 597 598 if (SCHEDULER_STOPPED()) 599 return; 600 601 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 602 ("rm_wlock() by idle thread %p on rmlock %s @ %s:%d", 603 curthread, rm->lock_object.lo_name, file, line)); 604 KASSERT(!rm_destroyed(rm), 605 ("rm_wlock() of destroyed rmlock @ %s:%d", file, line)); 606 _rm_assert(rm, RA_UNLOCKED, file, line); 607 608 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, 609 file, line, NULL); 610 611 _rm_wlock(rm); 612 613 LOCK_LOG_LOCK("RMWLOCK", &rm->lock_object, 0, 0, file, line); 614 WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line); 615 TD_LOCKS_INC(curthread); 616 } 617 618 void 619 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line) 620 { 621 622 if (SCHEDULER_STOPPED()) 623 return; 624 625 KASSERT(!rm_destroyed(rm), 626 ("rm_wunlock() of destroyed rmlock @ %s:%d", file, line)); 627 _rm_assert(rm, RA_WLOCKED, file, line); 628 WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line); 629 LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line); 630 _rm_wunlock(rm); 631 TD_LOCKS_DEC(curthread); 632 } 633 634 int 635 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 636 int trylock, const char *file, int line) 637 { 638 639 if (SCHEDULER_STOPPED()) 640 return (1); 641 642 #ifdef INVARIANTS 643 if (!(rm->lock_object.lo_flags & LO_RECURSABLE) && !trylock) { 644 critical_enter(); 645 KASSERT(rm_trackers_present(get_pcpu(), rm, 646 curthread) == 0, 647 ("rm_rlock: recursed on non-recursive rmlock %s @ %s:%d\n", 648 rm->lock_object.lo_name, file, line)); 649 critical_exit(); 650 } 651 #endif 652 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), 653 ("rm_rlock() by idle thread %p on rmlock %s @ %s:%d", 654 curthread, rm->lock_object.lo_name, file, line)); 655 KASSERT(!rm_destroyed(rm), 656 ("rm_rlock() of destroyed rmlock @ %s:%d", file, line)); 657 if (!trylock) { 658 KASSERT(!rm_wowned(rm), 659 ("rm_rlock: wlock already held for %s @ %s:%d", 660 rm->lock_object.lo_name, file, line)); 661 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line, 662 NULL); 663 } 664 665 if (_rm_rlock(rm, tracker, trylock)) { 666 if (trylock) 667 LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 1, file, 668 line); 669 else 670 LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file, 671 line); 672 WITNESS_LOCK(&rm->lock_object, 0, file, line); 673 TD_LOCKS_INC(curthread); 674 return (1); 675 } else if (trylock) 676 LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 0, file, line); 677 678 return (0); 679 } 680 681 void 682 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 683 const char *file, int line) 684 { 685 686 if (SCHEDULER_STOPPED()) 687 return; 688 689 KASSERT(!rm_destroyed(rm), 690 ("rm_runlock() of destroyed rmlock @ %s:%d", file, line)); 691 _rm_assert(rm, RA_RLOCKED, file, line); 692 WITNESS_UNLOCK(&rm->lock_object, 0, file, line); 693 LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line); 694 _rm_runlock(rm, tracker); 695 TD_LOCKS_DEC(curthread); 696 } 697 698 #else 699 700 /* 701 * Just strip out file and line arguments if no lock debugging is enabled in 702 * the kernel - we are called from a kernel module. 703 */ 704 void 705 _rm_wlock_debug(struct rmlock *rm, const char *file, int line) 706 { 707 708 _rm_wlock(rm); 709 } 710 711 void 712 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line) 713 { 714 715 _rm_wunlock(rm); 716 } 717 718 int 719 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 720 int trylock, const char *file, int line) 721 { 722 723 return _rm_rlock(rm, tracker, trylock); 724 } 725 726 void 727 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker, 728 const char *file, int line) 729 { 730 731 _rm_runlock(rm, tracker); 732 } 733 734 #endif 735 736 #ifdef INVARIANT_SUPPORT 737 #ifndef INVARIANTS 738 #undef _rm_assert 739 #endif 740 741 /* 742 * Note that this does not need to use witness_assert() for read lock 743 * assertions since an exact count of read locks held by this thread 744 * is computable. 745 */ 746 void 747 _rm_assert(const struct rmlock *rm, int what, const char *file, int line) 748 { 749 int count; 750 751 if (SCHEDULER_STOPPED()) 752 return; 753 switch (what) { 754 case RA_LOCKED: 755 case RA_LOCKED | RA_RECURSED: 756 case RA_LOCKED | RA_NOTRECURSED: 757 case RA_RLOCKED: 758 case RA_RLOCKED | RA_RECURSED: 759 case RA_RLOCKED | RA_NOTRECURSED: 760 /* 761 * Handle the write-locked case. Unlike other 762 * primitives, writers can never recurse. 763 */ 764 if (rm_wowned(rm)) { 765 if (what & RA_RLOCKED) 766 panic("Lock %s exclusively locked @ %s:%d\n", 767 rm->lock_object.lo_name, file, line); 768 if (what & RA_RECURSED) 769 panic("Lock %s not recursed @ %s:%d\n", 770 rm->lock_object.lo_name, file, line); 771 break; 772 } 773 774 critical_enter(); 775 count = rm_trackers_present(get_pcpu(), rm, curthread); 776 critical_exit(); 777 778 if (count == 0) 779 panic("Lock %s not %slocked @ %s:%d\n", 780 rm->lock_object.lo_name, (what & RA_RLOCKED) ? 781 "read " : "", file, line); 782 if (count > 1) { 783 if (what & RA_NOTRECURSED) 784 panic("Lock %s recursed @ %s:%d\n", 785 rm->lock_object.lo_name, file, line); 786 } else if (what & RA_RECURSED) 787 panic("Lock %s not recursed @ %s:%d\n", 788 rm->lock_object.lo_name, file, line); 789 break; 790 case RA_WLOCKED: 791 if (!rm_wowned(rm)) 792 panic("Lock %s not exclusively locked @ %s:%d\n", 793 rm->lock_object.lo_name, file, line); 794 break; 795 case RA_UNLOCKED: 796 if (rm_wowned(rm)) 797 panic("Lock %s exclusively locked @ %s:%d\n", 798 rm->lock_object.lo_name, file, line); 799 800 critical_enter(); 801 count = rm_trackers_present(get_pcpu(), rm, curthread); 802 critical_exit(); 803 804 if (count != 0) 805 panic("Lock %s read locked @ %s:%d\n", 806 rm->lock_object.lo_name, file, line); 807 break; 808 default: 809 panic("Unknown rm lock assertion: %d @ %s:%d", what, file, 810 line); 811 } 812 } 813 #endif /* INVARIANT_SUPPORT */ 814 815 #ifdef DDB 816 static void 817 print_tracker(struct rm_priotracker *tr) 818 { 819 struct thread *td; 820 821 td = tr->rmp_thread; 822 db_printf(" thread %p (tid %d, pid %d, \"%s\") {", td, td->td_tid, 823 td->td_proc->p_pid, td->td_name); 824 if (tr->rmp_flags & RMPF_ONQUEUE) { 825 db_printf("ONQUEUE"); 826 if (tr->rmp_flags & RMPF_SIGNAL) 827 db_printf(",SIGNAL"); 828 } else 829 db_printf(""); 830 db_printf("}\n"); 831 } 832 833 static void 834 db_show_rm(const struct lock_object *lock) 835 { 836 struct rm_priotracker *tr; 837 struct rm_queue *queue; 838 const struct rmlock *rm; 839 struct lock_class *lc; 840 struct pcpu *pc; 841 842 rm = (const struct rmlock *)lock; 843 db_printf(" writecpus: "); 844 ddb_display_cpuset(__DEQUALIFY(const cpuset_t *, &rm->rm_writecpus)); 845 db_printf("\n"); 846 db_printf(" per-CPU readers:\n"); 847 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) 848 for (queue = pc->pc_rm_queue.rmq_next; 849 queue != &pc->pc_rm_queue; queue = queue->rmq_next) { 850 tr = (struct rm_priotracker *)queue; 851 if (tr->rmp_rmlock == rm) 852 print_tracker(tr); 853 } 854 db_printf(" active readers:\n"); 855 LIST_FOREACH(tr, &rm->rm_activeReaders, rmp_qentry) 856 print_tracker(tr); 857 lc = LOCK_CLASS(&rm->rm_wlock_object); 858 db_printf("Backing write-lock (%s):\n", lc->lc_name); 859 lc->lc_ddb_show(&rm->rm_wlock_object); 860 } 861 #endif
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