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, xflags;
 281
 282         liflags = 0;
 283         if (!(opts & RM_NOWITNESS))
 284                 liflags |= LO_WITNESS;
 285         if (opts & RM_RECURSE)
 286                 liflags |= LO_RECURSABLE;
 287         if (opts & RM_NEW)
 288                 liflags |= LO_NEW;
 289         rm->rm_writecpus = all_cpus;
 290         LIST_INIT(&rm->rm_activeReaders);
 291         if (opts & RM_SLEEPABLE) {
 292                 liflags |= LO_SLEEPABLE;
 293                 lc = &lock_class_rm_sleepable;
 294                 xflags = (opts & RM_NEW ? SX_NEW : 0);
 295                 sx_init_flags(&rm->rm_lock_sx, "rmlock_sx",
 296                     xflags | SX_NOWITNESS);
 297         } else {
 298                 lc = &lock_class_rm;
 299                 xflags = (opts & RM_NEW ? MTX_NEW : 0);
 300                 mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx",
 301                     xflags | MTX_NOWITNESS);
 302         }
 303         lock_init(&rm->lock_object, lc, name, NULL, liflags);
 304 }
 305
 306 void
 307 rm_init(struct rmlock *rm, const char *name)
 308 {
 309
 310         rm_init_flags(rm, name, 0);
 311 }
 312
 313 void
 314 rm_destroy(struct rmlock *rm)
 315 {
 316
 317         rm_assert(rm, RA_UNLOCKED);
 318         LIST_FIRST(&rm->rm_activeReaders) = RM_DESTROYED;
 319         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 320                 sx_destroy(&rm->rm_lock_sx);
 321         else
 322                 mtx_destroy(&rm->rm_lock_mtx);
 323         lock_destroy(&rm->lock_object);
 324 }
 325
 326 int
 327 rm_wowned(const struct rmlock *rm)
 328 {
 329
 330         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 331                 return (sx_xlocked(&rm->rm_lock_sx));
 332         else
 333                 return (mtx_owned(&rm->rm_lock_mtx));
 334 }
 335
 336 void
 337 rm_sysinit(void *arg)
 338 {
 339         struct rm_args *args;
 340
 341         args = arg;
 342         rm_init_flags(args->ra_rm, args->ra_desc, args->ra_flags);
 343 }
 344
 345 static int
 346 _rm_rlock_hard(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
 347 {
 348         struct pcpu *pc;
 349
 350         critical_enter();
 351         pc = pcpu_find(curcpu);
 352
 353         /* Check if we just need to do a proper critical_exit. */
 354         if (!CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)) {
 355                 critical_exit();
 356                 return (1);
 357         }
 358
 359         /* Remove our tracker from the per-cpu list. */
 360         rm_tracker_remove(pc, tracker);
 361
 362         /* Check to see if the IPI granted us the lock after all. */
 363         if (tracker->rmp_flags) {
 364                 /* Just add back tracker - we hold the lock. */
 365                 rm_tracker_add(pc, tracker);
 366                 critical_exit();
 367                 return (1);
 368         }
 369
 370         /*
 371          * We allow readers to acquire a lock even if a writer is blocked if
 372          * the lock is recursive and the reader already holds the lock.
 373          */
 374         if ((rm->lock_object.lo_flags & LO_RECURSABLE) != 0) {
 375                 /*
 376                  * Just grant the lock if this thread already has a tracker
 377                  * for this lock on the per-cpu queue.
 378                  */
 379                 if (rm_trackers_present(pc, rm, curthread) != 0) {
 380                         mtx_lock_spin(&rm_spinlock);
 381                         LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker,
 382                             rmp_qentry);
 383                         tracker->rmp_flags = RMPF_ONQUEUE;
 384                         mtx_unlock_spin(&rm_spinlock);
 385                         rm_tracker_add(pc, tracker);
 386                         critical_exit();
 387                         return (1);
 388                 }
 389         }
 390
 391         sched_unpin();
 392         critical_exit();
 393
 394         if (trylock) {
 395                 if (rm->lock_object.lo_flags & LO_SLEEPABLE) {
 396                         if (!sx_try_xlock(&rm->rm_lock_sx))
 397                                 return (0);
 398                 } else {
 399                         if (!mtx_trylock(&rm->rm_lock_mtx))
 400                                 return (0);
 401                 }
 402         } else {
 403                 if (rm->lock_object.lo_flags & LO_SLEEPABLE) {
 404                         THREAD_SLEEPING_OK();
 405                         sx_xlock(&rm->rm_lock_sx);
 406                         THREAD_NO_SLEEPING();
 407                 } else
 408                         mtx_lock(&rm->rm_lock_mtx);
 409         }
 410
 411         critical_enter();
 412         pc = pcpu_find(curcpu);
 413         CPU_CLR(pc->pc_cpuid, &rm->rm_writecpus);
 414         rm_tracker_add(pc, tracker);
 415         sched_pin();
 416         critical_exit();
 417
 418         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 419                 sx_xunlock(&rm->rm_lock_sx);
 420         else
 421                 mtx_unlock(&rm->rm_lock_mtx);
 422
 423         return (1);
 424 }
 425
 426 int
 427 _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
 428 {
 429         struct thread *td = curthread;
 430         struct pcpu *pc;
 431
 432         if (SCHEDULER_STOPPED())
 433                 return (1);
 434
 435         tracker->rmp_flags  = 0;
 436         tracker->rmp_thread = td;
 437         tracker->rmp_rmlock = rm;
 438
 439         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 440                 THREAD_NO_SLEEPING();
 441
 442         td->td_critnest++;      /* critical_enter(); */
 443
 444         __compiler_membar();
 445
 446         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 447
 448         rm_tracker_add(pc, tracker);
 449
 450         sched_pin();
 451
 452         __compiler_membar();
 453
 454         td->td_critnest--;
 455
 456         /*
 457          * Fast path to combine two common conditions into a single
 458          * conditional jump.
 459          */
 460         if (0 == (td->td_owepreempt |
 461             CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)))
 462                 return (1);
 463
 464         /* We do not have a read token and need to acquire one. */
 465         return _rm_rlock_hard(rm, tracker, trylock);
 466 }
 467
 468 static void
 469 _rm_unlock_hard(struct thread *td,struct rm_priotracker *tracker)
 470 {
 471
 472         if (td->td_owepreempt) {
 473                 td->td_critnest++;
 474                 critical_exit();
 475         }
 476
 477         if (!tracker->rmp_flags)
 478                 return;
 479
 480         mtx_lock_spin(&rm_spinlock);
 481         LIST_REMOVE(tracker, rmp_qentry);
 482
 483         if (tracker->rmp_flags & RMPF_SIGNAL) {
 484                 struct rmlock *rm;
 485                 struct turnstile *ts;
 486
 487                 rm = tracker->rmp_rmlock;
 488
 489                 turnstile_chain_lock(&rm->lock_object);
 490                 mtx_unlock_spin(&rm_spinlock);
 491
 492                 ts = turnstile_lookup(&rm->lock_object);
 493
 494                 turnstile_signal(ts, TS_EXCLUSIVE_QUEUE);
 495                 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
 496                 turnstile_chain_unlock(&rm->lock_object);
 497         } else
 498                 mtx_unlock_spin(&rm_spinlock);
 499 }
 500
 501 void
 502 _rm_runlock(struct rmlock *rm, struct rm_priotracker *tracker)
 503 {
 504         struct pcpu *pc;
 505         struct thread *td = tracker->rmp_thread;
 506
 507         if (SCHEDULER_STOPPED())
 508                 return;
 509
 510         td->td_critnest++;      /* critical_enter(); */
 511         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 512         rm_tracker_remove(pc, tracker);
 513         td->td_critnest--;
 514         sched_unpin();
 515
 516         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 517                 THREAD_SLEEPING_OK();
 518
 519         if (0 == (td->td_owepreempt | tracker->rmp_flags))
 520                 return;
 521
 522         _rm_unlock_hard(td, tracker);
 523 }
 524
 525 void
 526 _rm_wlock(struct rmlock *rm)
 527 {
 528         struct rm_priotracker *prio;
 529         struct turnstile *ts;
 530         cpuset_t readcpus;
 531
 532         if (SCHEDULER_STOPPED())
 533                 return;
 534
 535         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 536                 sx_xlock(&rm->rm_lock_sx);
 537         else
 538                 mtx_lock(&rm->rm_lock_mtx);
 539
 540         if (CPU_CMP(&rm->rm_writecpus, &all_cpus)) {
 541                 /* Get all read tokens back */
 542                 readcpus = all_cpus;
 543                 CPU_NAND(&readcpus, &rm->rm_writecpus);
 544                 rm->rm_writecpus = all_cpus;
 545
 546                 /*
 547                  * Assumes rm->rm_writecpus update is visible on other CPUs
 548                  * before rm_cleanIPI is called.
 549                  */
 550 #ifdef SMP
 551                 smp_rendezvous_cpus(readcpus,
 552                     smp_no_rendezvous_barrier,
 553                     rm_cleanIPI,
 554                     smp_no_rendezvous_barrier,
 555                     rm);
 556
 557 #else
 558                 rm_cleanIPI(rm);
 559 #endif
 560
 561                 mtx_lock_spin(&rm_spinlock);
 562                 while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) {
 563                         ts = turnstile_trywait(&rm->lock_object);
 564                         prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL;
 565                         mtx_unlock_spin(&rm_spinlock);
 566                         turnstile_wait(ts, prio->rmp_thread,
 567                             TS_EXCLUSIVE_QUEUE);
 568                         mtx_lock_spin(&rm_spinlock);
 569                 }
 570                 mtx_unlock_spin(&rm_spinlock);
 571         }
 572 }
 573
 574 void
 575 _rm_wunlock(struct rmlock *rm)
 576 {
 577
 578         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 579                 sx_xunlock(&rm->rm_lock_sx);
 580         else
 581                 mtx_unlock(&rm->rm_lock_mtx);
 582 }
 583
 584 #if LOCK_DEBUG > 0
 585
 586 void
 587 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
 588 {
 589
 590         if (SCHEDULER_STOPPED())
 591                 return;
 592
 593         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 594             ("rm_wlock() by idle thread %p on rmlock %s @ %s:%d",
 595             curthread, rm->lock_object.lo_name, file, line));
 596         KASSERT(!rm_destroyed(rm),
 597             ("rm_wlock() of destroyed rmlock @ %s:%d", file, line));
 598         _rm_assert(rm, RA_UNLOCKED, file, line);
 599
 600         WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE,
 601             file, line, NULL);
 602
 603         _rm_wlock(rm);
 604
 605         LOCK_LOG_LOCK("RMWLOCK", &rm->lock_object, 0, 0, file, line);
 606         WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 607         TD_LOCKS_INC(curthread);
 608 }
 609
 610 void
 611 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 612 {
 613
 614         if (SCHEDULER_STOPPED())
 615                 return;
 616
 617         KASSERT(!rm_destroyed(rm),
 618             ("rm_wunlock() of destroyed rmlock @ %s:%d", file, line));
 619         _rm_assert(rm, RA_WLOCKED, file, line);
 620         WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 621         LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line);
 622         _rm_wunlock(rm);
 623         TD_LOCKS_DEC(curthread);
 624 }
 625
 626 int
 627 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 628     int trylock, const char *file, int line)
 629 {
 630
 631         if (SCHEDULER_STOPPED())
 632                 return (1);
 633
 634 #ifdef INVARIANTS
 635         if (!(rm->lock_object.lo_flags & LO_RECURSABLE) && !trylock) {
 636                 critical_enter();
 637                 KASSERT(rm_trackers_present(pcpu_find(curcpu), rm,
 638                     curthread) == 0,
 639                     ("rm_rlock: recursed on non-recursive rmlock %s @ %s:%d\n",
 640                     rm->lock_object.lo_name, file, line));
 641                 critical_exit();
 642         }
 643 #endif
 644         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 645             ("rm_rlock() by idle thread %p on rmlock %s @ %s:%d",
 646             curthread, rm->lock_object.lo_name, file, line));
 647         KASSERT(!rm_destroyed(rm),
 648             ("rm_rlock() of destroyed rmlock @ %s:%d", file, line));
 649         if (!trylock) {
 650                 KASSERT(!rm_wowned(rm),
 651                     ("rm_rlock: wlock already held for %s @ %s:%d",
 652                     rm->lock_object.lo_name, file, line));
 653                 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line,
 654                     NULL);
 655         }
 656
 657         if (_rm_rlock(rm, tracker, trylock)) {
 658                 if (trylock)
 659                         LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 1, file,
 660                             line);
 661                 else
 662                         LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file,
 663                             line);
 664                 WITNESS_LOCK(&rm->lock_object, 0, file, line);
 665                 TD_LOCKS_INC(curthread);
 666                 return (1);
 667         } else if (trylock)
 668                 LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 0, file, line);
 669
 670         return (0);
 671 }
 672
 673 void
 674 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 675     const char *file, int line)
 676 {
 677
 678         if (SCHEDULER_STOPPED())
 679                 return;
 680
 681         KASSERT(!rm_destroyed(rm),
 682             ("rm_runlock() of destroyed rmlock @ %s:%d", file, line));
 683         _rm_assert(rm, RA_RLOCKED, file, line);
 684         WITNESS_UNLOCK(&rm->lock_object, 0, file, line);
 685         LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line);
 686         _rm_runlock(rm, tracker);
 687         TD_LOCKS_DEC(curthread);
 688 }
 689
 690 #else
 691
 692 /*
 693  * Just strip out file and line arguments if no lock debugging is enabled in
 694  * the kernel - we are called from a kernel module.
 695  */
 696 void
 697 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
 698 {
 699
 700         _rm_wlock(rm);
 701 }
 702
 703 void
 704 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 705 {
 706
 707         _rm_wunlock(rm);
 708 }
 709
 710 int
 711 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 712     int trylock, const char *file, int line)
 713 {
 714
 715         return _rm_rlock(rm, tracker, trylock);
 716 }
 717
 718 void
 719 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 720     const char *file, int line)
 721 {
 722
 723         _rm_runlock(rm, tracker);
 724 }
 725
 726 #endif
 727
 728 #ifdef INVARIANT_SUPPORT
 729 #ifndef INVARIANTS
 730 #undef _rm_assert
 731 #endif
 732
 733 /*
 734  * Note that this does not need to use witness_assert() for read lock
 735  * assertions since an exact count of read locks held by this thread
 736  * is computable.
 737  */
 738 void
 739 _rm_assert(const struct rmlock *rm, int what, const char *file, int line)
 740 {
 741         int count;
 742
 743         if (SCHEDULER_STOPPED())
 744                 return;
 745         switch (what) {
 746         case RA_LOCKED:
 747         case RA_LOCKED | RA_RECURSED:
 748         case RA_LOCKED | RA_NOTRECURSED:
 749         case RA_RLOCKED:
 750         case RA_RLOCKED | RA_RECURSED:
 751         case RA_RLOCKED | RA_NOTRECURSED:
 752                 /*
 753                  * Handle the write-locked case.  Unlike other
 754                  * primitives, writers can never recurse.
 755                  */
 756                 if (rm_wowned(rm)) {
 757                         if (what & RA_RLOCKED)
 758                                 panic("Lock %s exclusively locked @ %s:%d\n",
 759                                     rm->lock_object.lo_name, file, line);
 760                         if (what & RA_RECURSED)
 761                                 panic("Lock %s not recursed @ %s:%d\n",
 762                                     rm->lock_object.lo_name, file, line);
 763                         break;
 764                 }
 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 not %slocked @ %s:%d\n",
 772                             rm->lock_object.lo_name, (what & RA_RLOCKED) ?
 773                             "read " : "", file, line);
 774                 if (count > 1) {
 775                         if (what & RA_NOTRECURSED)
 776                                 panic("Lock %s recursed @ %s:%d\n",
 777                                     rm->lock_object.lo_name, file, line);
 778                 } else if (what & RA_RECURSED)
 779                         panic("Lock %s not recursed @ %s:%d\n",
 780                             rm->lock_object.lo_name, file, line);
 781                 break;
 782         case RA_WLOCKED:
 783                 if (!rm_wowned(rm))
 784                         panic("Lock %s not exclusively locked @ %s:%d\n",
 785                             rm->lock_object.lo_name, file, line);
 786                 break;
 787         case RA_UNLOCKED:
 788                 if (rm_wowned(rm))
 789                         panic("Lock %s exclusively locked @ %s:%d\n",
 790                             rm->lock_object.lo_name, file, line);
 791
 792                 critical_enter();
 793                 count = rm_trackers_present(pcpu_find(curcpu), rm, curthread);
 794                 critical_exit();
 795
 796                 if (count != 0)
 797                         panic("Lock %s read locked @ %s:%d\n",
 798                             rm->lock_object.lo_name, file, line);
 799                 break;
 800         default:
 801                 panic("Unknown rm lock assertion: %d @ %s:%d", what, file,
 802                     line);
 803         }
 804 }
 805 #endif /* INVARIANT_SUPPORT */
 806
 807 #ifdef DDB
 808 static void
 809 print_tracker(struct rm_priotracker *tr)
 810 {
 811         struct thread *td;
 812
 813         td = tr->rmp_thread;
 814         db_printf("   thread %p (tid %d, pid %d, \"%s\") {", td, td->td_tid,
 815             td->td_proc->p_pid, td->td_name);
 816         if (tr->rmp_flags & RMPF_ONQUEUE) {
 817                 db_printf("ONQUEUE");
 818                 if (tr->rmp_flags & RMPF_SIGNAL)
 819                         db_printf(",SIGNAL");
 820         } else
 821                 db_printf("0");
 822         db_printf("}\n");
 823 }
 824
 825 static void
 826 db_show_rm(const struct lock_object *lock)
 827 {
 828         struct rm_priotracker *tr;
 829         struct rm_queue *queue;
 830         const struct rmlock *rm;
 831         struct lock_class *lc;
 832         struct pcpu *pc;
 833
 834         rm = (const struct rmlock *)lock;
 835         db_printf(" writecpus: ");
 836         ddb_display_cpuset(__DEQUALIFY(const cpuset_t *, &rm->rm_writecpus));
 837         db_printf("\n");
 838         db_printf(" per-CPU readers:\n");
 839         STAILQ_FOREACH(pc, &cpuhead, pc_allcpu)
 840                 for (queue = pc->pc_rm_queue.rmq_next;
 841                     queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
 842                         tr = (struct rm_priotracker *)queue;
 843                         if (tr->rmp_rmlock == rm)
 844                                 print_tracker(tr);
 845                 }
 846         db_printf(" active readers:\n");
 847         LIST_FOREACH(tr, &rm->rm_activeReaders, rmp_qentry)
 848                 print_tracker(tr);
 849         lc = LOCK_CLASS(&rm->rm_wlock_object);
 850         db_printf("Backing write-lock (%s):\n", lc->lc_name);
 851         lc->lc_ddb_show(&rm->rm_wlock_object);
 852 }
 853 #endif