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                         THREAD_SLEEPING_OK();
 380                         sx_xlock(&rm->rm_lock_sx);
 381                         THREAD_NO_SLEEPING();
 382                 } else
 383                         mtx_lock(&rm->rm_lock_mtx);
 384         }
 385
 386         critical_enter();
 387         pc = pcpu_find(curcpu);
 388         CPU_CLR(pc->pc_cpuid, &rm->rm_writecpus);
 389         rm_tracker_add(pc, tracker);
 390         sched_pin();
 391         critical_exit();
 392
 393         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 394                 sx_xunlock(&rm->rm_lock_sx);
 395         else
 396                 mtx_unlock(&rm->rm_lock_mtx);
 397
 398         return (1);
 399 }
 400
 401 int
 402 _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
 403 {
 404         struct thread *td = curthread;
 405         struct pcpu *pc;
 406
 407         if (SCHEDULER_STOPPED())
 408                 return (1);
 409
 410         tracker->rmp_flags  = 0;
 411         tracker->rmp_thread = td;
 412         tracker->rmp_rmlock = rm;
 413
 414         td->td_critnest++;      /* critical_enter(); */
 415
 416         __compiler_membar();
 417
 418         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 419
 420         rm_tracker_add(pc, tracker);
 421
 422         sched_pin();
 423
 424         __compiler_membar();
 425
 426         td->td_critnest--;
 427
 428         /*
 429          * Fast path to combine two common conditions into a single
 430          * conditional jump.
 431          */
 432         if (0 == (td->td_owepreempt |
 433             CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)))
 434                 return (1);
 435
 436         /* We do not have a read token and need to acquire one. */
 437         return _rm_rlock_hard(rm, tracker, trylock);
 438 }
 439
 440 static void
 441 _rm_unlock_hard(struct thread *td,struct rm_priotracker *tracker)
 442 {
 443
 444         if (td->td_owepreempt) {
 445                 td->td_critnest++;
 446                 critical_exit();
 447         }
 448
 449         if (!tracker->rmp_flags)
 450                 return;
 451
 452         mtx_lock_spin(&rm_spinlock);
 453         LIST_REMOVE(tracker, rmp_qentry);
 454
 455         if (tracker->rmp_flags & RMPF_SIGNAL) {
 456                 struct rmlock *rm;
 457                 struct turnstile *ts;
 458
 459                 rm = tracker->rmp_rmlock;
 460
 461                 turnstile_chain_lock(&rm->lock_object);
 462                 mtx_unlock_spin(&rm_spinlock);
 463
 464                 ts = turnstile_lookup(&rm->lock_object);
 465
 466                 turnstile_signal(ts, TS_EXCLUSIVE_QUEUE);
 467                 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
 468                 turnstile_chain_unlock(&rm->lock_object);
 469         } else
 470                 mtx_unlock_spin(&rm_spinlock);
 471 }
 472
 473 void
 474 _rm_runlock(struct rmlock *rm, struct rm_priotracker *tracker)
 475 {
 476         struct pcpu *pc;
 477         struct thread *td = tracker->rmp_thread;
 478
 479         if (SCHEDULER_STOPPED())
 480                 return;
 481
 482         td->td_critnest++;      /* critical_enter(); */
 483         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 484         rm_tracker_remove(pc, tracker);
 485         td->td_critnest--;
 486         sched_unpin();
 487
 488         if (0 == (td->td_owepreempt | tracker->rmp_flags))
 489                 return;
 490
 491         _rm_unlock_hard(td, tracker);
 492 }
 493
 494 void
 495 _rm_wlock(struct rmlock *rm)
 496 {
 497         struct rm_priotracker *prio;
 498         struct turnstile *ts;
 499         cpuset_t readcpus;
 500
 501         if (SCHEDULER_STOPPED())
 502                 return;
 503
 504         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 505                 sx_xlock(&rm->rm_lock_sx);
 506         else
 507                 mtx_lock(&rm->rm_lock_mtx);
 508
 509         if (CPU_CMP(&rm->rm_writecpus, &all_cpus)) {
 510                 /* Get all read tokens back */
 511                 readcpus = all_cpus;
 512                 CPU_NAND(&readcpus, &rm->rm_writecpus);
 513                 rm->rm_writecpus = all_cpus;
 514
 515                 /*
 516                  * Assumes rm->rm_writecpus update is visible on other CPUs
 517                  * before rm_cleanIPI is called.
 518                  */
 519 #ifdef SMP
 520                 smp_rendezvous_cpus(readcpus,
 521                     smp_no_rendevous_barrier,
 522                     rm_cleanIPI,
 523                     smp_no_rendevous_barrier,
 524                     rm);
 525
 526 #else
 527                 rm_cleanIPI(rm);
 528 #endif
 529
 530                 mtx_lock_spin(&rm_spinlock);
 531                 while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) {
 532                         ts = turnstile_trywait(&rm->lock_object);
 533                         prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL;
 534                         mtx_unlock_spin(&rm_spinlock);
 535                         turnstile_wait(ts, prio->rmp_thread,
 536                             TS_EXCLUSIVE_QUEUE);
 537                         mtx_lock_spin(&rm_spinlock);
 538                 }
 539                 mtx_unlock_spin(&rm_spinlock);
 540         }
 541 }
 542
 543 void
 544 _rm_wunlock(struct rmlock *rm)
 545 {
 546
 547         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 548                 sx_xunlock(&rm->rm_lock_sx);
 549         else
 550                 mtx_unlock(&rm->rm_lock_mtx);
 551 }
 552
 553 #ifdef LOCK_DEBUG
 554
 555 void
 556 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
 557 {
 558
 559         if (SCHEDULER_STOPPED())
 560                 return;
 561
 562         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 563             ("rm_wlock() by idle thread %p on rmlock %s @ %s:%d",
 564             curthread, rm->lock_object.lo_name, file, line));
 565         KASSERT(!rm_destroyed(rm),
 566             ("rm_wlock() of destroyed rmlock @ %s:%d", file, line));
 567         _rm_assert(rm, RA_UNLOCKED, file, line);
 568
 569         WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE,
 570             file, line, NULL);
 571
 572         _rm_wlock(rm);
 573
 574         LOCK_LOG_LOCK("RMWLOCK", &rm->lock_object, 0, 0, file, line);
 575
 576         WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 577
 578         curthread->td_locks++;
 579
 580 }
 581
 582 void
 583 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 584 {
 585
 586         if (SCHEDULER_STOPPED())
 587                 return;
 588
 589         KASSERT(!rm_destroyed(rm),
 590             ("rm_wunlock() of destroyed rmlock @ %s:%d", file, line));
 591         _rm_assert(rm, RA_WLOCKED, file, line);
 592         WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 593         LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line);
 594         _rm_wunlock(rm);
 595         curthread->td_locks--;
 596 }
 597
 598 int
 599 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 600     int trylock, const char *file, int line)
 601 {
 602
 603         if (SCHEDULER_STOPPED())
 604                 return (1);
 605
 606 #ifdef INVARIANTS
 607         if (!(rm->lock_object.lo_flags & LO_RECURSABLE) && !trylock) {
 608                 critical_enter();
 609                 KASSERT(rm_trackers_present(pcpu_find(curcpu), rm,
 610                     curthread) == 0,
 611                     ("rm_rlock: recursed on non-recursive rmlock %s @ %s:%d\n",
 612                     rm->lock_object.lo_name, file, line));
 613                 critical_exit();
 614         }
 615 #endif
 616         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 617             ("rm_rlock() by idle thread %p on rmlock %s @ %s:%d",
 618             curthread, rm->lock_object.lo_name, file, line));
 619         KASSERT(!rm_destroyed(rm),
 620             ("rm_rlock() of destroyed rmlock @ %s:%d", file, line));
 621         if (!trylock) {
 622                 KASSERT(!rm_wowned(rm),
 623                     ("rm_rlock: wlock already held for %s @ %s:%d",
 624                     rm->lock_object.lo_name, file, line));
 625                 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line,
 626                     NULL);
 627         }
 628
 629         if (_rm_rlock(rm, tracker, trylock)) {
 630                 if (trylock)
 631                         LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 1, file,
 632                             line);
 633                 else
 634                         LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file,
 635                             line);
 636                 WITNESS_LOCK(&rm->lock_object, 0, file, line);
 637
 638                 curthread->td_locks++;
 639
 640                 return (1);
 641         } else if (trylock)
 642                 LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 0, file, line);
 643
 644         return (0);
 645 }
 646
 647 void
 648 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 649     const char *file, int line)
 650 {
 651
 652         if (SCHEDULER_STOPPED())
 653                 return;
 654
 655         KASSERT(!rm_destroyed(rm),
 656             ("rm_runlock() of destroyed rmlock @ %s:%d", file, line));
 657         _rm_assert(rm, RA_RLOCKED, file, line);
 658         WITNESS_UNLOCK(&rm->lock_object, 0, file, line);
 659         LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line);
 660         _rm_runlock(rm, tracker);
 661         curthread->td_locks--;
 662 }
 663
 664 #else
 665
 666 /*
 667  * Just strip out file and line arguments if no lock debugging is enabled in
 668  * the kernel - we are called from a kernel module.
 669  */
 670 void
 671 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
 672 {
 673
 674         _rm_wlock(rm);
 675 }
 676
 677 void
 678 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 679 {
 680
 681         _rm_wunlock(rm);
 682 }
 683
 684 int
 685 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 686     int trylock, const char *file, int line)
 687 {
 688
 689         return _rm_rlock(rm, tracker, trylock);
 690 }
 691
 692 void
 693 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 694     const char *file, int line)
 695 {
 696
 697         _rm_runlock(rm, tracker);
 698 }
 699
 700 #endif
 701
 702 #ifdef INVARIANT_SUPPORT
 703 #ifndef INVARIANTS
 704 #undef _rm_assert
 705 #endif
 706
 707 /*
 708  * Note that this does not need to use witness_assert() for read lock
 709  * assertions since an exact count of read locks held by this thread
 710  * is computable.
 711  */
 712 void
 713 _rm_assert(struct rmlock *rm, int what, const char *file, int line)
 714 {
 715         int count;
 716
 717         if (panicstr != NULL)
 718                 return;
 719         switch (what) {
 720         case RA_LOCKED:
 721         case RA_LOCKED | RA_RECURSED:
 722         case RA_LOCKED | RA_NOTRECURSED:
 723         case RA_RLOCKED:
 724         case RA_RLOCKED | RA_RECURSED:
 725         case RA_RLOCKED | RA_NOTRECURSED:
 726                 /*
 727                  * Handle the write-locked case.  Unlike other
 728                  * primitives, writers can never recurse.
 729                  */
 730                 if (rm_wowned(rm)) {
 731                         if (what & RA_RLOCKED)
 732                                 panic("Lock %s exclusively locked @ %s:%d\n",
 733                                     rm->lock_object.lo_name, file, line);
 734                         if (what & RA_RECURSED)
 735                                 panic("Lock %s not recursed @ %s:%d\n",
 736                                     rm->lock_object.lo_name, file, line);
 737                         break;
 738                 }
 739
 740                 critical_enter();
 741                 count = rm_trackers_present(pcpu_find(curcpu), rm, curthread);
 742                 critical_exit();
 743
 744                 if (count == 0)
 745                         panic("Lock %s not %slocked @ %s:%d\n",
 746                             rm->lock_object.lo_name, (what & RA_RLOCKED) ?
 747                             "read " : "", file, line);
 748                 if (count > 1) {
 749                         if (what & RA_NOTRECURSED)
 750                                 panic("Lock %s recursed @ %s:%d\n",
 751                                     rm->lock_object.lo_name, file, line);
 752                 } else if (what & RA_RECURSED)
 753                         panic("Lock %s not recursed @ %s:%d\n",
 754                             rm->lock_object.lo_name, file, line);
 755                 break;
 756         case RA_WLOCKED:
 757                 if (!rm_wowned(rm))
 758                         panic("Lock %s not exclusively locked @ %s:%d\n",
 759                             rm->lock_object.lo_name, file, line);
 760                 break;
 761         case RA_UNLOCKED:
 762                 if (rm_wowned(rm))
 763                         panic("Lock %s exclusively locked @ %s:%d\n",
 764                             rm->lock_object.lo_name, file, line);
 765
 766                 critical_enter();
 767                 count = rm_trackers_present(pcpu_find(curcpu), rm, curthread);
 768                 critical_exit();
 769
 770                 if (count != 0)
 771                         panic("Lock %s read locked @ %s:%d\n",
 772                             rm->lock_object.lo_name, file, line);
 773                 break;
 774         default:
 775                 panic("Unknown rm lock assertion: %d @ %s:%d", what, file,
 776                     line);
 777         }
 778 }
 779 #endif /* INVARIANT_SUPPORT */
 780
 781 #ifdef DDB
 782 static void
 783 print_tracker(struct rm_priotracker *tr)
 784 {
 785         struct thread *td;
 786
 787         td = tr->rmp_thread;
 788         db_printf("   thread %p (tid %d, pid %d, \"%s\") {", td, td->td_tid,
 789             td->td_proc->p_pid, td->td_name);
 790         if (tr->rmp_flags & RMPF_ONQUEUE) {
 791                 db_printf("ONQUEUE");
 792                 if (tr->rmp_flags & RMPF_SIGNAL)
 793                         db_printf(",SIGNAL");
 794         } else
 795                 db_printf("0");
 796         db_printf("}\n");
 797 }
 798
 799 static void
 800 db_show_rm(struct lock_object *lock)
 801 {
 802         struct rm_priotracker *tr;
 803         struct rm_queue *queue;
 804         struct rmlock *rm;
 805         struct lock_class *lc;
 806         struct pcpu *pc;
 807
 808         rm = (struct rmlock *)lock;
 809         db_printf(" writecpus: ");
 810         ddb_display_cpuset(__DEQUALIFY(const cpuset_t *, &rm->rm_writecpus));
 811         db_printf("\n");
 812         db_printf(" per-CPU readers:\n");
 813         STAILQ_FOREACH(pc, &cpuhead, pc_allcpu)
 814                 for (queue = pc->pc_rm_queue.rmq_next;
 815                     queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
 816                         tr = (struct rm_priotracker *)queue;
 817                         if (tr->rmp_rmlock == rm)
 818                                 print_tracker(tr);
 819                 }
 820         db_printf(" active readers:\n");
 821         LIST_FOREACH(tr, &rm->rm_activeReaders, rmp_qentry)
 822                 print_tracker(tr);
 823         lc = LOCK_CLASS(&rm->rm_wlock_object);
 824         db_printf("Backing write-lock (%s):\n", lc->lc_name);
 825         lc->lc_ddb_show(&rm->rm_wlock_object);
 826 }
 827 #endif