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(const struct lock_object *lock, int what);
  77 #ifdef DDB
  78 static void     db_show_rm(const struct lock_object *lock);
  79 #endif
  80 static void     lock_rm(struct lock_object *lock, uintptr_t how);
  81 #ifdef KDTRACE_HOOKS
  82 static int      owner_rm(const struct lock_object *lock, struct thread **owner);
  83 #endif
  84 static uintptr_t 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(const struct lock_object *lock, int what)
 116 {
 117
 118         rm_assert((const struct rmlock *)lock, what);
 119 }
 120
 121 static void
 122 lock_rm(struct lock_object *lock, uintptr_t how)
 123 {
 124         struct rmlock *rm;
 125         struct rm_priotracker *tracker;
 126
 127         rm = (struct rmlock *)lock;
 128         if (how == 0)
 129                 rm_wlock(rm);
 130         else {
 131                 tracker = (struct rm_priotracker *)how;
 132                 rm_rlock(rm, tracker);
 133         }
 134 }
 135
 136 static uintptr_t
 137 unlock_rm(struct lock_object *lock)
 138 {
 139         struct thread *td;
 140         struct pcpu *pc;
 141         struct rmlock *rm;
 142         struct rm_queue *queue;
 143         struct rm_priotracker *tracker;
 144         uintptr_t how;
 145
 146         rm = (struct rmlock *)lock;
 147         tracker = NULL;
 148         how = 0;
 149         rm_assert(rm, RA_LOCKED | RA_NOTRECURSED);
 150         if (rm_wowned(rm))
 151                 rm_wunlock(rm);
 152         else {
 153                 /*
 154                  * Find the right rm_priotracker structure for curthread.
 155                  * The guarantee about its uniqueness is given by the fact
 156                  * we already asserted the lock wasn't recursively acquired.
 157                  */
 158                 critical_enter();
 159                 td = curthread;
 160                 pc = pcpu_find(curcpu);
 161                 for (queue = pc->pc_rm_queue.rmq_next;
 162                     queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
 163                         tracker = (struct rm_priotracker *)queue;
 164                                 if ((tracker->rmp_rmlock == rm) &&
 165                                     (tracker->rmp_thread == td)) {
 166                                         how = (uintptr_t)tracker;
 167                                         break;
 168                                 }
 169                 }
 170                 KASSERT(tracker != NULL,
 171                     ("rm_priotracker is non-NULL when lock held in read mode"));
 172                 critical_exit();
 173                 rm_runlock(rm, tracker);
 174         }
 175         return (how);
 176 }
 177
 178 #ifdef KDTRACE_HOOKS
 179 static int
 180 owner_rm(const struct lock_object *lock, struct thread **owner)
 181 {
 182         const struct rmlock *rm;
 183         struct lock_class *lc;
 184
 185         rm = (const struct rmlock *)lock;
 186         lc = LOCK_CLASS(&rm->rm_wlock_object);
 187         return (lc->lc_owner(&rm->rm_wlock_object, owner));
 188 }
 189 #endif
 190
 191 static struct mtx rm_spinlock;
 192
 193 MTX_SYSINIT(rm_spinlock, &rm_spinlock, "rm_spinlock", MTX_SPIN);
 194
 195 /*
 196  * Add or remove tracker from per-cpu list.
 197  *
 198  * The per-cpu list can be traversed at any time in forward direction from an
 199  * interrupt on the *local* cpu.
 200  */
 201 static void inline
 202 rm_tracker_add(struct pcpu *pc, struct rm_priotracker *tracker)
 203 {
 204         struct rm_queue *next;
 205
 206         /* Initialize all tracker pointers */
 207         tracker->rmp_cpuQueue.rmq_prev = &pc->pc_rm_queue;
 208         next = pc->pc_rm_queue.rmq_next;
 209         tracker->rmp_cpuQueue.rmq_next = next;
 210
 211         /* rmq_prev is not used during froward traversal. */
 212         next->rmq_prev = &tracker->rmp_cpuQueue;
 213
 214         /* Update pointer to first element. */
 215         pc->pc_rm_queue.rmq_next = &tracker->rmp_cpuQueue;
 216 }
 217
 218 /*
 219  * Return a count of the number of trackers the thread 'td' already
 220  * has on this CPU for the lock 'rm'.
 221  */
 222 static int
 223 rm_trackers_present(const struct pcpu *pc, const struct rmlock *rm,
 224     const struct thread *td)
 225 {
 226         struct rm_queue *queue;
 227         struct rm_priotracker *tracker;
 228         int count;
 229
 230         count = 0;
 231         for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue;
 232             queue = queue->rmq_next) {
 233                 tracker = (struct rm_priotracker *)queue;
 234                 if ((tracker->rmp_rmlock == rm) && (tracker->rmp_thread == td))
 235                         count++;
 236         }
 237         return (count);
 238 }
 239
 240 static void inline
 241 rm_tracker_remove(struct pcpu *pc, struct rm_priotracker *tracker)
 242 {
 243         struct rm_queue *next, *prev;
 244
 245         next = tracker->rmp_cpuQueue.rmq_next;
 246         prev = tracker->rmp_cpuQueue.rmq_prev;
 247
 248         /* Not used during forward traversal. */
 249         next->rmq_prev = prev;
 250
 251         /* Remove from list. */
 252         prev->rmq_next = next;
 253 }
 254
 255 static void
 256 rm_cleanIPI(void *arg)
 257 {
 258         struct pcpu *pc;
 259         struct rmlock *rm = arg;
 260         struct rm_priotracker *tracker;
 261         struct rm_queue *queue;
 262         pc = pcpu_find(curcpu);
 263
 264         for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue;
 265             queue = queue->rmq_next) {
 266                 tracker = (struct rm_priotracker *)queue;
 267                 if (tracker->rmp_rmlock == rm && tracker->rmp_flags == 0) {
 268                         tracker->rmp_flags = RMPF_ONQUEUE;
 269                         mtx_lock_spin(&rm_spinlock);
 270                         LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker,
 271                             rmp_qentry);
 272                         mtx_unlock_spin(&rm_spinlock);
 273                 }
 274         }
 275 }
 276
 277 void
 278 rm_init_flags(struct rmlock *rm, const char *name, int opts)
 279 {
 280         struct lock_class *lc;
 281         int liflags;
 282
 283         liflags = 0;
 284         if (!(opts & RM_NOWITNESS))
 285                 liflags |= LO_WITNESS;
 286         if (opts & RM_RECURSE)
 287                 liflags |= LO_RECURSABLE;
 288         rm->rm_writecpus = all_cpus;
 289         LIST_INIT(&rm->rm_activeReaders);
 290         if (opts & RM_SLEEPABLE) {
 291                 liflags |= LO_SLEEPABLE;
 292                 lc = &lock_class_rm_sleepable;
 293                 sx_init_flags(&rm->rm_lock_sx, "rmlock_sx", SX_NOWITNESS);
 294         } else {
 295                 lc = &lock_class_rm;
 296                 mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx", MTX_NOWITNESS);
 297         }
 298         lock_init(&rm->lock_object, lc, name, NULL, liflags);
 299 }
 300
 301 void
 302 rm_init(struct rmlock *rm, const char *name)
 303 {
 304
 305         rm_init_flags(rm, name, 0);
 306 }
 307
 308 void
 309 rm_destroy(struct rmlock *rm)
 310 {
 311
 312         rm_assert(rm, RA_UNLOCKED);
 313         LIST_FIRST(&rm->rm_activeReaders) = RM_DESTROYED;
 314         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 315                 sx_destroy(&rm->rm_lock_sx);
 316         else
 317                 mtx_destroy(&rm->rm_lock_mtx);
 318         lock_destroy(&rm->lock_object);
 319 }
 320
 321 int
 322 rm_wowned(const struct rmlock *rm)
 323 {
 324
 325         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 326                 return (sx_xlocked(&rm->rm_lock_sx));
 327         else
 328                 return (mtx_owned(&rm->rm_lock_mtx));
 329 }
 330
 331 void
 332 rm_sysinit(void *arg)
 333 {
 334         struct rm_args *args = arg;
 335
 336         rm_init(args->ra_rm, args->ra_desc);
 337 }
 338
 339 void
 340 rm_sysinit_flags(void *arg)
 341 {
 342         struct rm_args_flags *args = arg;
 343
 344         rm_init_flags(args->ra_rm, args->ra_desc, args->ra_opts);
 345 }
 346
 347 static int
 348 _rm_rlock_hard(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
 349 {
 350         struct pcpu *pc;
 351
 352         critical_enter();
 353         pc = pcpu_find(curcpu);
 354
 355         /* Check if we just need to do a proper critical_exit. */
 356         if (!CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)) {
 357                 critical_exit();
 358                 return (1);
 359         }
 360
 361         /* Remove our tracker from the per-cpu list. */
 362         rm_tracker_remove(pc, tracker);
 363
 364         /* Check to see if the IPI granted us the lock after all. */
 365         if (tracker->rmp_flags) {
 366                 /* Just add back tracker - we hold the lock. */
 367                 rm_tracker_add(pc, tracker);
 368                 critical_exit();
 369                 return (1);
 370         }
 371
 372         /*
 373          * We allow readers to aquire a lock even if a writer is blocked if
 374          * the lock is recursive and the reader already holds the lock.
 375          */
 376         if ((rm->lock_object.lo_flags & LO_RECURSABLE) != 0) {
 377                 /*
 378                  * Just grant the lock if this thread already has a tracker
 379                  * for this lock on the per-cpu queue.
 380                  */
 381                 if (rm_trackers_present(pc, rm, curthread) != 0) {
 382                         mtx_lock_spin(&rm_spinlock);
 383                         LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker,
 384                             rmp_qentry);
 385                         tracker->rmp_flags = RMPF_ONQUEUE;
 386                         mtx_unlock_spin(&rm_spinlock);
 387                         rm_tracker_add(pc, tracker);
 388                         critical_exit();
 389                         return (1);
 390                 }
 391         }
 392
 393         sched_unpin();
 394         critical_exit();
 395
 396         if (trylock) {
 397                 if (rm->lock_object.lo_flags & LO_SLEEPABLE) {
 398                         if (!sx_try_xlock(&rm->rm_lock_sx))
 399                                 return (0);
 400                 } else {
 401                         if (!mtx_trylock(&rm->rm_lock_mtx))
 402                                 return (0);
 403                 }
 404         } else {
 405                 if (rm->lock_object.lo_flags & LO_SLEEPABLE) {
 406                         THREAD_SLEEPING_OK();
 407                         sx_xlock(&rm->rm_lock_sx);
 408                         THREAD_NO_SLEEPING();
 409                 } else
 410                         mtx_lock(&rm->rm_lock_mtx);
 411         }
 412
 413         critical_enter();
 414         pc = pcpu_find(curcpu);
 415         CPU_CLR(pc->pc_cpuid, &rm->rm_writecpus);
 416         rm_tracker_add(pc, tracker);
 417         sched_pin();
 418         critical_exit();
 419
 420         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 421                 sx_xunlock(&rm->rm_lock_sx);
 422         else
 423                 mtx_unlock(&rm->rm_lock_mtx);
 424
 425         return (1);
 426 }
 427
 428 int
 429 _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
 430 {
 431         struct thread *td = curthread;
 432         struct pcpu *pc;
 433
 434         if (SCHEDULER_STOPPED())
 435                 return (1);
 436
 437         tracker->rmp_flags  = 0;
 438         tracker->rmp_thread = td;
 439         tracker->rmp_rmlock = rm;
 440
 441         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 442                 THREAD_NO_SLEEPING();
 443
 444         td->td_critnest++;      /* critical_enter(); */
 445
 446         __compiler_membar();
 447
 448         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 449
 450         rm_tracker_add(pc, tracker);
 451
 452         sched_pin();
 453
 454         __compiler_membar();
 455
 456         td->td_critnest--;
 457
 458         /*
 459          * Fast path to combine two common conditions into a single
 460          * conditional jump.
 461          */
 462         if (0 == (td->td_owepreempt |
 463             CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)))
 464                 return (1);
 465
 466         /* We do not have a read token and need to acquire one. */
 467         return _rm_rlock_hard(rm, tracker, trylock);
 468 }
 469
 470 static void
 471 _rm_unlock_hard(struct thread *td,struct rm_priotracker *tracker)
 472 {
 473
 474         if (td->td_owepreempt) {
 475                 td->td_critnest++;
 476                 critical_exit();
 477         }
 478
 479         if (!tracker->rmp_flags)
 480                 return;
 481
 482         mtx_lock_spin(&rm_spinlock);
 483         LIST_REMOVE(tracker, rmp_qentry);
 484
 485         if (tracker->rmp_flags & RMPF_SIGNAL) {
 486                 struct rmlock *rm;
 487                 struct turnstile *ts;
 488
 489                 rm = tracker->rmp_rmlock;
 490
 491                 turnstile_chain_lock(&rm->lock_object);
 492                 mtx_unlock_spin(&rm_spinlock);
 493
 494                 ts = turnstile_lookup(&rm->lock_object);
 495
 496                 turnstile_signal(ts, TS_EXCLUSIVE_QUEUE);
 497                 turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
 498                 turnstile_chain_unlock(&rm->lock_object);
 499         } else
 500                 mtx_unlock_spin(&rm_spinlock);
 501 }
 502
 503 void
 504 _rm_runlock(struct rmlock *rm, struct rm_priotracker *tracker)
 505 {
 506         struct pcpu *pc;
 507         struct thread *td = tracker->rmp_thread;
 508
 509         if (SCHEDULER_STOPPED())
 510                 return;
 511
 512         td->td_critnest++;      /* critical_enter(); */
 513         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 514         rm_tracker_remove(pc, tracker);
 515         td->td_critnest--;
 516         sched_unpin();
 517
 518         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 519                 THREAD_SLEEPING_OK();
 520
 521         if (0 == (td->td_owepreempt | tracker->rmp_flags))
 522                 return;
 523
 524         _rm_unlock_hard(td, tracker);
 525 }
 526
 527 void
 528 _rm_wlock(struct rmlock *rm)
 529 {
 530         struct rm_priotracker *prio;
 531         struct turnstile *ts;
 532         cpuset_t readcpus;
 533
 534         if (SCHEDULER_STOPPED())
 535                 return;
 536
 537         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 538                 sx_xlock(&rm->rm_lock_sx);
 539         else
 540                 mtx_lock(&rm->rm_lock_mtx);
 541
 542         if (CPU_CMP(&rm->rm_writecpus, &all_cpus)) {
 543                 /* Get all read tokens back */
 544                 readcpus = all_cpus;
 545                 CPU_NAND(&readcpus, &rm->rm_writecpus);
 546                 rm->rm_writecpus = all_cpus;
 547
 548                 /*
 549                  * Assumes rm->rm_writecpus update is visible on other CPUs
 550                  * before rm_cleanIPI is called.
 551                  */
 552 #ifdef SMP
 553                 smp_rendezvous_cpus(readcpus,
 554                     smp_no_rendevous_barrier,
 555                     rm_cleanIPI,
 556                     smp_no_rendevous_barrier,
 557                     rm);
 558
 559 #else
 560                 rm_cleanIPI(rm);
 561 #endif
 562
 563                 mtx_lock_spin(&rm_spinlock);
 564                 while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) {
 565                         ts = turnstile_trywait(&rm->lock_object);
 566                         prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL;
 567                         mtx_unlock_spin(&rm_spinlock);
 568                         turnstile_wait(ts, prio->rmp_thread,
 569                             TS_EXCLUSIVE_QUEUE);
 570                         mtx_lock_spin(&rm_spinlock);
 571                 }
 572                 mtx_unlock_spin(&rm_spinlock);
 573         }
 574 }
 575
 576 void
 577 _rm_wunlock(struct rmlock *rm)
 578 {
 579
 580         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
 581                 sx_xunlock(&rm->rm_lock_sx);
 582         else
 583                 mtx_unlock(&rm->rm_lock_mtx);
 584 }
 585
 586 #if LOCK_DEBUG > 0
 587
 588 void
 589 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
 590 {
 591
 592         if (SCHEDULER_STOPPED())
 593                 return;
 594
 595         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 596             ("rm_wlock() by idle thread %p on rmlock %s @ %s:%d",
 597             curthread, rm->lock_object.lo_name, file, line));
 598         KASSERT(!rm_destroyed(rm),
 599             ("rm_wlock() of destroyed rmlock @ %s:%d", file, line));
 600         _rm_assert(rm, RA_UNLOCKED, file, line);
 601
 602         WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE,
 603             file, line, NULL);
 604
 605         _rm_wlock(rm);
 606
 607         LOCK_LOG_LOCK("RMWLOCK", &rm->lock_object, 0, 0, file, line);
 608
 609         WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 610
 611         curthread->td_locks++;
 612
 613 }
 614
 615 void
 616 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 617 {
 618
 619         if (SCHEDULER_STOPPED())
 620                 return;
 621
 622         KASSERT(!rm_destroyed(rm),
 623             ("rm_wunlock() of destroyed rmlock @ %s:%d", file, line));
 624         _rm_assert(rm, RA_WLOCKED, file, line);
 625         WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 626         LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line);
 627         _rm_wunlock(rm);
 628         curthread->td_locks--;
 629 }
 630
 631 int
 632 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 633     int trylock, const char *file, int line)
 634 {
 635
 636         if (SCHEDULER_STOPPED())
 637                 return (1);
 638
 639 #ifdef INVARIANTS
 640         if (!(rm->lock_object.lo_flags & LO_RECURSABLE) && !trylock) {
 641                 critical_enter();
 642                 KASSERT(rm_trackers_present(pcpu_find(curcpu), rm,
 643                     curthread) == 0,
 644                     ("rm_rlock: recursed on non-recursive rmlock %s @ %s:%d\n",
 645                     rm->lock_object.lo_name, file, line));
 646                 critical_exit();
 647         }
 648 #endif
 649         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 650             ("rm_rlock() by idle thread %p on rmlock %s @ %s:%d",
 651             curthread, rm->lock_object.lo_name, file, line));
 652         KASSERT(!rm_destroyed(rm),
 653             ("rm_rlock() of destroyed rmlock @ %s:%d", file, line));
 654         if (!trylock) {
 655                 KASSERT(!rm_wowned(rm),
 656                     ("rm_rlock: wlock already held for %s @ %s:%d",
 657                     rm->lock_object.lo_name, file, line));
 658                 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line,
 659                     NULL);
 660         }
 661
 662         if (_rm_rlock(rm, tracker, trylock)) {
 663                 if (trylock)
 664                         LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 1, file,
 665                             line);
 666                 else
 667                         LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file,
 668                             line);
 669                 WITNESS_LOCK(&rm->lock_object, 0, file, line);
 670
 671                 curthread->td_locks++;
 672
 673                 return (1);
 674         } else if (trylock)
 675                 LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 0, file, line);
 676
 677         return (0);
 678 }
 679
 680 void
 681 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 682     const char *file, int line)
 683 {
 684
 685         if (SCHEDULER_STOPPED())
 686                 return;
 687
 688         KASSERT(!rm_destroyed(rm),
 689             ("rm_runlock() of destroyed rmlock @ %s:%d", file, line));
 690         _rm_assert(rm, RA_RLOCKED, file, line);
 691         WITNESS_UNLOCK(&rm->lock_object, 0, file, line);
 692         LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line);
 693         _rm_runlock(rm, tracker);
 694         curthread->td_locks--;
 695 }
 696
 697 #else
 698
 699 /*
 700  * Just strip out file and line arguments if no lock debugging is enabled in
 701  * the kernel - we are called from a kernel module.
 702  */
 703 void
 704 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
 705 {
 706
 707         _rm_wlock(rm);
 708 }
 709
 710 void
 711 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 712 {
 713
 714         _rm_wunlock(rm);
 715 }
 716
 717 int
 718 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 719     int trylock, const char *file, int line)
 720 {
 721
 722         return _rm_rlock(rm, tracker, trylock);
 723 }
 724
 725 void
 726 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 727     const char *file, int line)
 728 {
 729
 730         _rm_runlock(rm, tracker);
 731 }
 732
 733 #endif
 734
 735 #ifdef INVARIANT_SUPPORT
 736 #ifndef INVARIANTS
 737 #undef _rm_assert
 738 #endif
 739
 740 /*
 741  * Note that this does not need to use witness_assert() for read lock
 742  * assertions since an exact count of read locks held by this thread
 743  * is computable.
 744  */
 745 void
 746 _rm_assert(const struct rmlock *rm, int what, const char *file, int line)
 747 {
 748         int count;
 749
 750         if (panicstr != NULL)
 751                 return;
 752         switch (what) {
 753         case RA_LOCKED:
 754         case RA_LOCKED | RA_RECURSED:
 755         case RA_LOCKED | RA_NOTRECURSED:
 756         case RA_RLOCKED:
 757         case RA_RLOCKED | RA_RECURSED:
 758         case RA_RLOCKED | RA_NOTRECURSED:
 759                 /*
 760                  * Handle the write-locked case.  Unlike other
 761                  * primitives, writers can never recurse.
 762                  */
 763                 if (rm_wowned(rm)) {
 764                         if (what & RA_RLOCKED)
 765                                 panic("Lock %s exclusively locked @ %s:%d\n",
 766                                     rm->lock_object.lo_name, file, line);
 767                         if (what & RA_RECURSED)
 768                                 panic("Lock %s not recursed @ %s:%d\n",
 769                                     rm->lock_object.lo_name, file, line);
 770                         break;
 771                 }
 772
 773                 critical_enter();
 774                 count = rm_trackers_present(pcpu_find(curcpu), rm, curthread);
 775                 critical_exit();
 776
 777                 if (count == 0)
 778                         panic("Lock %s not %slocked @ %s:%d\n",
 779                             rm->lock_object.lo_name, (what & RA_RLOCKED) ?
 780                             "read " : "", file, line);
 781                 if (count > 1) {
 782                         if (what & RA_NOTRECURSED)
 783                                 panic("Lock %s recursed @ %s:%d\n",
 784                                     rm->lock_object.lo_name, file, line);
 785                 } else if (what & RA_RECURSED)
 786                         panic("Lock %s not recursed @ %s:%d\n",
 787                             rm->lock_object.lo_name, file, line);
 788                 break;
 789         case RA_WLOCKED:
 790                 if (!rm_wowned(rm))
 791                         panic("Lock %s not exclusively locked @ %s:%d\n",
 792                             rm->lock_object.lo_name, file, line);
 793                 break;
 794         case RA_UNLOCKED:
 795                 if (rm_wowned(rm))
 796                         panic("Lock %s exclusively locked @ %s:%d\n",
 797                             rm->lock_object.lo_name, file, line);
 798
 799                 critical_enter();
 800                 count = rm_trackers_present(pcpu_find(curcpu), rm, curthread);
 801                 critical_exit();
 802
 803                 if (count != 0)
 804                         panic("Lock %s read locked @ %s:%d\n",
 805                             rm->lock_object.lo_name, file, line);
 806                 break;
 807         default:
 808                 panic("Unknown rm lock assertion: %d @ %s:%d", what, file,
 809                     line);
 810         }
 811 }
 812 #endif /* INVARIANT_SUPPORT */
 813
 814 #ifdef DDB
 815 static void
 816 print_tracker(struct rm_priotracker *tr)
 817 {
 818         struct thread *td;
 819
 820         td = tr->rmp_thread;
 821         db_printf("   thread %p (tid %d, pid %d, \"%s\") {", td, td->td_tid,
 822             td->td_proc->p_pid, td->td_name);
 823         if (tr->rmp_flags & RMPF_ONQUEUE) {
 824                 db_printf("ONQUEUE");
 825                 if (tr->rmp_flags & RMPF_SIGNAL)
 826                         db_printf(",SIGNAL");
 827         } else
 828                 db_printf("0");
 829         db_printf("}\n");
 830 }
 831
 832 static void
 833 db_show_rm(const struct lock_object *lock)
 834 {
 835         struct rm_priotracker *tr;
 836         struct rm_queue *queue;
 837         const struct rmlock *rm;
 838         struct lock_class *lc;
 839         struct pcpu *pc;
 840
 841         rm = (const struct rmlock *)lock;
 842         db_printf(" writecpus: ");
 843         ddb_display_cpuset(__DEQUALIFY(const cpuset_t *, &rm->rm_writecpus));
 844         db_printf("\n");
 845         db_printf(" per-CPU readers:\n");
 846         STAILQ_FOREACH(pc, &cpuhead, pc_allcpu)
 847                 for (queue = pc->pc_rm_queue.rmq_next;
 848                     queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
 849                         tr = (struct rm_priotracker *)queue;
 850                         if (tr->rmp_rmlock == rm)
 851                                 print_tracker(tr);
 852                 }
 853         db_printf(" active readers:\n");
 854         LIST_FOREACH(tr, &rm->rm_activeReaders, rmp_qentry)
 855                 print_tracker(tr);
 856         lc = LOCK_CLASS(&rm->rm_wlock_object);
 857         db_printf("Backing write-lock (%s):\n", lc->lc_name);
 858         lc->lc_ddb_show(&rm->rm_wlock_object);
 859 }
 860 #endif