sys/kern/kern_rmlock.c

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