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                         sx_xlock(&rm->rm_lock_sx);
 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_rendevous_barrier,
 553                     rm_cleanIPI,
 554                     smp_no_rendevous_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 #ifdef LOCK_DEBUG
 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
 607         WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 608
 609         curthread->td_locks++;
 610
 611 }
 612
 613 void
 614 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 615 {
 616
 617         if (SCHEDULER_STOPPED())
 618                 return;
 619
 620         KASSERT(!rm_destroyed(rm),
 621             ("rm_wunlock() of destroyed rmlock @ %s:%d", file, line));
 622         _rm_assert(rm, RA_WLOCKED, file, line);
 623         WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
 624         LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line);
 625         _rm_wunlock(rm);
 626         curthread->td_locks--;
 627 }
 628
 629 int
 630 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 631     int trylock, const char *file, int line)
 632 {
 633
 634         if (SCHEDULER_STOPPED())
 635                 return (1);
 636
 637 #ifdef INVARIANTS
 638         if (!(rm->lock_object.lo_flags & LO_RECURSABLE) && !trylock) {
 639                 critical_enter();
 640                 KASSERT(rm_trackers_present(pcpu_find(curcpu), rm,
 641                     curthread) == 0,
 642                     ("rm_rlock: recursed on non-recursive rmlock %s @ %s:%d\n",
 643                     rm->lock_object.lo_name, file, line));
 644                 critical_exit();
 645         }
 646 #endif
 647         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 648             ("rm_rlock() by idle thread %p on rmlock %s @ %s:%d",
 649             curthread, rm->lock_object.lo_name, file, line));
 650         KASSERT(!rm_destroyed(rm),
 651             ("rm_rlock() of destroyed rmlock @ %s:%d", file, line));
 652         if (!trylock) {
 653                 KASSERT(!rm_wowned(rm),
 654                     ("rm_rlock: wlock already held for %s @ %s:%d",
 655                     rm->lock_object.lo_name, file, line));
 656                 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line,
 657                     NULL);
 658         }
 659
 660         if (_rm_rlock(rm, tracker, trylock)) {
 661                 if (trylock)
 662                         LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 1, file,
 663                             line);
 664                 else
 665                         LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file,
 666                             line);
 667                 WITNESS_LOCK(&rm->lock_object, 0, file, line);
 668
 669                 curthread->td_locks++;
 670
 671                 return (1);
 672         } else if (trylock)
 673                 LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 0, file, line);
 674
 675         return (0);
 676 }
 677
 678 void
 679 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 680     const char *file, int line)
 681 {
 682
 683         if (SCHEDULER_STOPPED())
 684                 return;
 685
 686         KASSERT(!rm_destroyed(rm),
 687             ("rm_runlock() of destroyed rmlock @ %s:%d", file, line));
 688         _rm_assert(rm, RA_RLOCKED, file, line);
 689         WITNESS_UNLOCK(&rm->lock_object, 0, file, line);
 690         LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line);
 691         _rm_runlock(rm, tracker);
 692         curthread->td_locks--;
 693 }
 694
 695 #else
 696
 697 /*
 698  * Just strip out file and line arguments if no lock debugging is enabled in
 699  * the kernel - we are called from a kernel module.
 700  */
 701 void
 702 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
 703 {
 704
 705         _rm_wlock(rm);
 706 }
 707
 708 void
 709 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
 710 {
 711
 712         _rm_wunlock(rm);
 713 }
 714
 715 int
 716 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 717     int trylock, const char *file, int line)
 718 {
 719
 720         return _rm_rlock(rm, tracker, trylock);
 721 }
 722
 723 void
 724 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
 725     const char *file, int line)
 726 {
 727
 728         _rm_runlock(rm, tracker);
 729 }
 730
 731 #endif
 732
 733 #ifdef INVARIANT_SUPPORT
 734 #ifndef INVARIANTS
 735 #undef _rm_assert
 736 #endif
 737
 738 /*
 739  * Note that this does not need to use witness_assert() for read lock
 740  * assertions since an exact count of read locks held by this thread
 741  * is computable.
 742  */
 743 void
 744 _rm_assert(const struct rmlock *rm, int what, const char *file, int line)
 745 {
 746         int count;
 747
 748         if (panicstr != NULL)
 749                 return;
 750         switch (what) {
 751         case RA_LOCKED:
 752         case RA_LOCKED | RA_RECURSED:
 753         case RA_LOCKED | RA_NOTRECURSED:
 754         case RA_RLOCKED:
 755         case RA_RLOCKED | RA_RECURSED:
 756         case RA_RLOCKED | RA_NOTRECURSED:
 757                 /*
 758                  * Handle the write-locked case.  Unlike other
 759                  * primitives, writers can never recurse.
 760                  */
 761                 if (rm_wowned(rm)) {
 762                         if (what & RA_RLOCKED)
 763                                 panic("Lock %s exclusively locked @ %s:%d\n",
 764                                     rm->lock_object.lo_name, file, line);
 765                         if (what & RA_RECURSED)
 766                                 panic("Lock %s not recursed @ %s:%d\n",
 767                                     rm->lock_object.lo_name, file, line);
 768                         break;
 769                 }
 770
 771                 critical_enter();
 772                 count = rm_trackers_present(pcpu_find(curcpu), rm, curthread);
 773                 critical_exit();
 774
 775                 if (count == 0)
 776                         panic("Lock %s not %slocked @ %s:%d\n",
 777                             rm->lock_object.lo_name, (what & RA_RLOCKED) ?
 778                             "read " : "", file, line);
 779                 if (count > 1) {
 780                         if (what & RA_NOTRECURSED)
 781                                 panic("Lock %s recursed @ %s:%d\n",
 782                                     rm->lock_object.lo_name, file, line);
 783                 } else if (what & RA_RECURSED)
 784                         panic("Lock %s not recursed @ %s:%d\n",
 785                             rm->lock_object.lo_name, file, line);
 786                 break;
 787         case RA_WLOCKED:
 788                 if (!rm_wowned(rm))
 789                         panic("Lock %s not exclusively locked @ %s:%d\n",
 790                             rm->lock_object.lo_name, file, line);
 791                 break;
 792         case RA_UNLOCKED:
 793                 if (rm_wowned(rm))
 794                         panic("Lock %s exclusively locked @ %s:%d\n",
 795                             rm->lock_object.lo_name, file, line);
 796
 797                 critical_enter();
 798                 count = rm_trackers_present(pcpu_find(curcpu), rm, curthread);
 799                 critical_exit();
 800
 801                 if (count != 0)
 802                         panic("Lock %s read locked @ %s:%d\n",
 803                             rm->lock_object.lo_name, file, line);
 804                 break;
 805         default:
 806                 panic("Unknown rm lock assertion: %d @ %s:%d", what, file,
 807                     line);
 808         }
 809 }
 810 #endif /* INVARIANT_SUPPORT */
 811
 812 #ifdef DDB
 813 static void
 814 print_tracker(struct rm_priotracker *tr)
 815 {
 816         struct thread *td;
 817
 818         td = tr->rmp_thread;
 819         db_printf("   thread %p (tid %d, pid %d, \"%s\") {", td, td->td_tid,
 820             td->td_proc->p_pid, td->td_name);
 821         if (tr->rmp_flags & RMPF_ONQUEUE) {
 822                 db_printf("ONQUEUE");
 823                 if (tr->rmp_flags & RMPF_SIGNAL)
 824                         db_printf(",SIGNAL");
 825         } else
 826                 db_printf("0");
 827         db_printf("}\n");
 828 }
 829
 830 static void
 831 db_show_rm(const struct lock_object *lock)
 832 {
 833         struct rm_priotracker *tr;
 834         struct rm_queue *queue;
 835         const struct rmlock *rm;
 836         struct lock_class *lc;
 837         struct pcpu *pc;
 838
 839         rm = (const struct rmlock *)lock;
 840         db_printf(" writecpus: ");
 841         ddb_display_cpuset(__DEQUALIFY(const cpuset_t *, &rm->rm_writecpus));
 842         db_printf("\n");
 843         db_printf(" per-CPU readers:\n");
 844         STAILQ_FOREACH(pc, &cpuhead, pc_allcpu)
 845                 for (queue = pc->pc_rm_queue.rmq_next;
 846                     queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
 847                         tr = (struct rm_priotracker *)queue;
 848                         if (tr->rmp_rmlock == rm)
 849                                 print_tracker(tr);
 850                 }
 851         db_printf(" active readers:\n");
 852         LIST_FOREACH(tr, &rm->rm_activeReaders, rmp_qentry)
 853                 print_tracker(tr);
 854         lc = LOCK_CLASS(&rm->rm_wlock_object);
 855         db_printf("Backing write-lock (%s):\n", lc->lc_name);
 856         lc->lc_ddb_show(&rm->rm_wlock_object);
 857 }
 858 #endif