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