sys/kern/kern_lock.c

   1 /*-
   2  * Copyright (c) 2008 Attilio Rao <attilio@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(s), this list of conditions and the following disclaimer as
  10  *    the first lines of this file unmodified other than the possible
  11  *    addition of one or more copyright notices.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice(s), this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
  17  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  18  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  19  * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
  20  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  21  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  22  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  23  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  26  * DAMAGE.
  27  */
  28
  29 #include "opt_adaptive_lockmgrs.h"
  30 #include "opt_ddb.h"
  31 #include "opt_kdtrace.h"
  32
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 #include <sys/param.h>
  37 #include <sys/ktr.h>
  38 #include <sys/linker_set.h>
  39 #include <sys/lock.h>
  40 #include <sys/lock_profile.h>
  41 #include <sys/lockmgr.h>
  42 #include <sys/mutex.h>
  43 #include <sys/proc.h>
  44 #include <sys/sleepqueue.h>
  45 #ifdef DEBUG_LOCKS
  46 #include <sys/stack.h>
  47 #endif
  48 #include <sys/sysctl.h>
  49 #include <sys/systm.h>
  50
  51 #include <machine/cpu.h>
  52
  53 #ifdef DDB
  54 #include <ddb/ddb.h>
  55 #endif
  56
  57 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
  58     (LK_ADAPTIVE | LK_NOSHARE));
  59 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
  60     ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
  61
  62 #define SQ_EXCLUSIVE_QUEUE      0
  63 #define SQ_SHARED_QUEUE         1
  64
  65 #ifdef ADAPTIVE_LOCKMGRS
  66 #define ALK_RETRIES             10
  67 #define ALK_LOOPS               10000
  68 #endif
  69
  70 #ifndef INVARIANTS
  71 #define _lockmgr_assert(lk, what, file, line)
  72 #define TD_LOCKS_INC(td)
  73 #define TD_LOCKS_DEC(td)
  74 #else
  75 #define TD_LOCKS_INC(td)        ((td)->td_locks++)
  76 #define TD_LOCKS_DEC(td)        ((td)->td_locks--)
  77 #endif
  78 #define TD_SLOCKS_INC(td)       ((td)->td_lk_slocks++)
  79 #define TD_SLOCKS_DEC(td)       ((td)->td_lk_slocks--)
  80
  81 #ifndef DEBUG_LOCKS
  82 #define STACK_PRINT(lk)
  83 #define STACK_SAVE(lk)
  84 #define STACK_ZERO(lk)
  85 #else
  86 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
  87 #define STACK_SAVE(lk)  stack_save(&(lk)->lk_stack)
  88 #define STACK_ZERO(lk)  stack_zero(&(lk)->lk_stack)
  89 #endif
  90
  91 #define LOCK_LOG2(lk, string, arg1, arg2)                               \
  92         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  93                 CTR2(KTR_LOCK, (string), (arg1), (arg2))
  94 #define LOCK_LOG3(lk, string, arg1, arg2, arg3)                         \
  95         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  96                 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
  97
  98 #define GIANT_DECLARE                                                   \
  99         int _i = 0;                                                     \
 100         WITNESS_SAVE_DECL(Giant)
 101 #define GIANT_RESTORE() do {                                            \
 102         if (_i > 0) {                                                   \
 103                 while (_i--)                                            \
 104                         mtx_lock(&Giant);                               \
 105                 WITNESS_RESTORE(&Giant.lock_object, Giant);             \
 106         }                                                               \
 107 } while (0)
 108 #define GIANT_SAVE() do {                                               \
 109         if (mtx_owned(&Giant)) {                                        \
 110                 WITNESS_SAVE(&Giant.lock_object, Giant);                \
 111                 while (mtx_owned(&Giant)) {                             \
 112                         _i++;                                           \
 113                         mtx_unlock(&Giant);                             \
 114                 }                                                       \
 115         }                                                               \
 116 } while (0)
 117
 118 #define LK_CAN_SHARE(x)                                                 \
 119         (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 ||      \
 120         ((x) & LK_EXCLUSIVE_SPINNERS) == 0 ||                           \
 121         curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT)))
 122 #define LK_TRYOP(x)                                                     \
 123         ((x) & LK_NOWAIT)
 124
 125 #define LK_CAN_WITNESS(x)                                               \
 126         (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
 127 #define LK_TRYWIT(x)                                                    \
 128         (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
 129
 130 #define LK_CAN_ADAPT(lk, f)                                             \
 131         (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 &&             \
 132         ((f) & LK_SLEEPFAIL) == 0)
 133
 134 #define lockmgr_disowned(lk)                                            \
 135         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
 136
 137 #define lockmgr_xlocked(lk)                                             \
 138         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
 139
 140 static void      assert_lockmgr(struct lock_object *lock, int how);
 141 #ifdef DDB
 142 static void      db_show_lockmgr(struct lock_object *lock);
 143 #endif
 144 static void      lock_lockmgr(struct lock_object *lock, int how);
 145 #ifdef KDTRACE_HOOKS
 146 static int       owner_lockmgr(struct lock_object *lock, struct thread **owner);
 147 #endif
 148 static int       unlock_lockmgr(struct lock_object *lock);
 149
 150 struct lock_class lock_class_lockmgr = {
 151         .lc_name = "lockmgr",
 152         .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
 153         .lc_assert = assert_lockmgr,
 154 #ifdef DDB
 155         .lc_ddb_show = db_show_lockmgr,
 156 #endif
 157         .lc_lock = lock_lockmgr,
 158         .lc_unlock = unlock_lockmgr,
 159 #ifdef KDTRACE_HOOKS
 160         .lc_owner = owner_lockmgr,
 161 #endif
 162 };
 163
 164 static __inline struct thread *
 165 lockmgr_xholder(struct lock *lk)
 166 {
 167         uintptr_t x;
 168
 169         x = lk->lk_lock;
 170         return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
 171 }
 172
 173 /*
 174  * It assumes sleepq_lock held and returns with this one unheld.
 175  * It also assumes the generic interlock is sane and previously checked.
 176  * If LK_INTERLOCK is specified the interlock is not reacquired after the
 177  * sleep.
 178  */
 179 static __inline int
 180 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
 181     const char *wmesg, int pri, int timo, int queue)
 182 {
 183         GIANT_DECLARE;
 184         struct lock_class *class;
 185         int catch, error;
 186
 187         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 188         catch = pri & PCATCH;
 189         pri &= PRIMASK;
 190         error = 0;
 191
 192         LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
 193             (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
 194
 195         if (flags & LK_INTERLOCK)
 196                 class->lc_unlock(ilk);
 197         GIANT_SAVE();
 198         sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
 199             SLEEPQ_INTERRUPTIBLE : 0), queue);
 200         if ((flags & LK_TIMELOCK) && timo)
 201                 sleepq_set_timeout(&lk->lock_object, timo);
 202
 203         /*
 204          * Decisional switch for real sleeping.
 205          */
 206         if ((flags & LK_TIMELOCK) && timo && catch)
 207                 error = sleepq_timedwait_sig(&lk->lock_object, pri);
 208         else if ((flags & LK_TIMELOCK) && timo)
 209                 error = sleepq_timedwait(&lk->lock_object, pri);
 210         else if (catch)
 211                 error = sleepq_wait_sig(&lk->lock_object, pri);
 212         else
 213                 sleepq_wait(&lk->lock_object, pri);
 214         GIANT_RESTORE();
 215         if ((flags & LK_SLEEPFAIL) && error == 0)
 216                 error = ENOLCK;
 217
 218         return (error);
 219 }
 220
 221 static __inline int
 222 wakeupshlk(struct lock *lk, const char *file, int line)
 223 {
 224         uintptr_t v, x;
 225         int queue, wakeup_swapper;
 226
 227         TD_LOCKS_DEC(curthread);
 228         TD_SLOCKS_DEC(curthread);
 229         WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
 230         LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
 231
 232         wakeup_swapper = 0;
 233         for (;;) {
 234                 x = lk->lk_lock;
 235
 236                 /*
 237                  * If there is more than one shared lock held, just drop one
 238                  * and return.
 239                  */
 240                 if (LK_SHARERS(x) > 1) {
 241                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, x,
 242                             x - LK_ONE_SHARER))
 243                                 break;
 244                         continue;
 245                 }
 246
 247                 /*
 248                  * If there are not waiters on the exclusive queue, drop the
 249                  * lock quickly.
 250                  */
 251                 if ((x & LK_ALL_WAITERS) == 0) {
 252                         MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
 253                             LK_SHARERS_LOCK(1));
 254                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED))
 255                                 break;
 256                         continue;
 257                 }
 258
 259                 /*
 260                  * We should have a sharer with waiters, so enter the hard
 261                  * path in order to handle wakeups correctly.
 262                  */
 263                 sleepq_lock(&lk->lock_object);
 264                 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 265                 v = LK_UNLOCKED;
 266
 267                 /*
 268                  * If the lock has exclusive waiters, give them preference in
 269                  * order to avoid deadlock with shared runners up.
 270                  */
 271                 if (x & LK_EXCLUSIVE_WAITERS) {
 272                         queue = SQ_EXCLUSIVE_QUEUE;
 273                         v |= (x & LK_SHARED_WAITERS);
 274                 } else {
 275                         MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
 276                             LK_SHARED_WAITERS);
 277                         queue = SQ_SHARED_QUEUE;
 278                 }
 279
 280                 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
 281                     v)) {
 282                         sleepq_release(&lk->lock_object);
 283                         continue;
 284                 }
 285                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 286                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 287                     "exclusive");
 288                 wakeup_swapper = sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
 289                     0, queue);
 290                 sleepq_release(&lk->lock_object);
 291                 break;
 292         }
 293
 294         lock_profile_release_lock(&lk->lock_object);
 295         return (wakeup_swapper);
 296 }
 297
 298 static void
 299 assert_lockmgr(struct lock_object *lock, int what)
 300 {
 301
 302         panic("lockmgr locks do not support assertions");
 303 }
 304
 305 static void
 306 lock_lockmgr(struct lock_object *lock, int how)
 307 {
 308
 309         panic("lockmgr locks do not support sleep interlocking");
 310 }
 311
 312 static int
 313 unlock_lockmgr(struct lock_object *lock)
 314 {
 315
 316         panic("lockmgr locks do not support sleep interlocking");
 317 }
 318
 319 #ifdef KDTRACE_HOOKS
 320 static int
 321 owner_lockmgr(struct lock_object *lock, struct thread **owner)
 322 {
 323
 324         panic("lockmgr locks do not support owner inquiring");
 325 }
 326 #endif
 327
 328 void
 329 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 330 {
 331         int iflags;
 332
 333         MPASS((flags & ~LK_INIT_MASK) == 0);
 334         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
 335             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
 336             &lk->lk_lock));
 337
 338         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
 339         if (flags & LK_CANRECURSE)
 340                 iflags |= LO_RECURSABLE;
 341         if ((flags & LK_NODUP) == 0)
 342                 iflags |= LO_DUPOK;
 343         if (flags & LK_NOPROFILE)
 344                 iflags |= LO_NOPROFILE;
 345         if ((flags & LK_NOWITNESS) == 0)
 346                 iflags |= LO_WITNESS;
 347         if (flags & LK_QUIET)
 348                 iflags |= LO_QUIET;
 349         iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
 350
 351         lk->lk_lock = LK_UNLOCKED;
 352         lk->lk_recurse = 0;
 353         lk->lk_timo = timo;
 354         lk->lk_pri = pri;
 355         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
 356         STACK_ZERO(lk);
 357 }
 358
 359 void
 360 lockdestroy(struct lock *lk)
 361 {
 362
 363         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
 364         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
 365         lock_destroy(&lk->lock_object);
 366 }
 367
 368 int
 369 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
 370     const char *wmesg, int pri, int timo, const char *file, int line)
 371 {
 372         GIANT_DECLARE;
 373         struct lock_class *class;
 374         const char *iwmesg;
 375         uintptr_t tid, v, x;
 376         u_int op;
 377         int error, ipri, itimo, queue, wakeup_swapper;
 378 #ifdef LOCK_PROFILING
 379         uint64_t waittime = 0;
 380         int contested = 0;
 381 #endif
 382 #ifdef ADAPTIVE_LOCKMGRS
 383         volatile struct thread *owner;
 384         u_int i, spintries = 0;
 385 #endif
 386
 387         error = 0;
 388         tid = (uintptr_t)curthread;
 389         op = (flags & LK_TYPE_MASK);
 390         iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
 391         ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
 392         itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
 393
 394         MPASS((flags & ~LK_TOTAL_MASK) == 0);
 395         KASSERT((op & (op - 1)) == 0,
 396             ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
 397         KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
 398             (op != LK_DOWNGRADE && op != LK_RELEASE),
 399             ("%s: Invalid flags in regard of the operation desired @ %s:%d",
 400             __func__, file, line));
 401         KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
 402             ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
 403             __func__, file, line));
 404
 405         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 406         if (panicstr != NULL) {
 407                 if (flags & LK_INTERLOCK)
 408                         class->lc_unlock(ilk);
 409                 return (0);
 410         }
 411
 412         if (op == LK_SHARED && (lk->lock_object.lo_flags & LK_NOSHARE))
 413                 op = LK_EXCLUSIVE;
 414
 415         wakeup_swapper = 0;
 416         switch (op) {
 417         case LK_SHARED:
 418                 if (LK_CAN_WITNESS(flags))
 419                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 420                             file, line, ilk);
 421                 for (;;) {
 422                         x = lk->lk_lock;
 423
 424                         /*
 425                          * If no other thread has an exclusive lock, or
 426                          * no exclusive waiter is present, bump the count of
 427                          * sharers.  Since we have to preserve the state of
 428                          * waiters, if we fail to acquire the shared lock
 429                          * loop back and retry.
 430                          */
 431                         if (LK_CAN_SHARE(x)) {
 432                                 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
 433                                     x + LK_ONE_SHARER))
 434                                         break;
 435                                 continue;
 436                         }
 437                         lock_profile_obtain_lock_failed(&lk->lock_object,
 438                             &contested, &waittime);
 439
 440                         /*
 441                          * If the lock is already held by curthread in
 442                          * exclusive way avoid a deadlock.
 443                          */
 444                         if (LK_HOLDER(x) == tid) {
 445                                 LOCK_LOG2(lk,
 446                                     "%s: %p already held in exclusive mode",
 447                                     __func__, lk);
 448                                 error = EDEADLK;
 449                                 break;
 450                         }
 451
 452                         /*
 453                          * If the lock is expected to not sleep just give up
 454                          * and return.
 455                          */
 456                         if (LK_TRYOP(flags)) {
 457                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 458                                     __func__, lk);
 459                                 error = EBUSY;
 460                                 break;
 461                         }
 462
 463 #ifdef ADAPTIVE_LOCKMGRS
 464                         /*
 465                          * If the owner is running on another CPU, spin until
 466                          * the owner stops running or the state of the lock
 467                          * changes.  We need a double-state handle here
 468                          * because for a failed acquisition the lock can be
 469                          * either held in exclusive mode or shared mode
 470                          * (for the writer starvation avoidance technique).
 471                          */
 472                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 473                             LK_HOLDER(x) != LK_KERNPROC) {
 474                                 owner = (struct thread *)LK_HOLDER(x);
 475                                 if (LOCK_LOG_TEST(&lk->lock_object, 0))
 476                                         CTR3(KTR_LOCK,
 477                                             "%s: spinning on %p held by %p",
 478                                             __func__, lk, owner);
 479
 480                                 /*
 481                                  * If we are holding also an interlock drop it
 482                                  * in order to avoid a deadlock if the lockmgr
 483                                  * owner is adaptively spinning on the
 484                                  * interlock itself.
 485                                  */
 486                                 if (flags & LK_INTERLOCK) {
 487                                         class->lc_unlock(ilk);
 488                                         flags &= ~LK_INTERLOCK;
 489                                 }
 490                                 GIANT_SAVE();
 491                                 while (LK_HOLDER(lk->lk_lock) ==
 492                                     (uintptr_t)owner && TD_IS_RUNNING(owner))
 493                                         cpu_spinwait();
 494                                 GIANT_RESTORE();
 495                                 continue;
 496                         } else if (LK_CAN_ADAPT(lk, flags) &&
 497                             (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
 498                             spintries < ALK_RETRIES) {
 499                                 if (flags & LK_INTERLOCK) {
 500                                         class->lc_unlock(ilk);
 501                                         flags &= ~LK_INTERLOCK;
 502                                 }
 503                                 GIANT_SAVE();
 504                                 spintries++;
 505                                 for (i = 0; i < ALK_LOOPS; i++) {
 506                                         if (LOCK_LOG_TEST(&lk->lock_object, 0))
 507                                                 CTR4(KTR_LOCK,
 508                                     "%s: shared spinning on %p with %u and %u",
 509                                                     __func__, lk, spintries, i);
 510                                         x = lk->lk_lock;
 511                                         if ((x & LK_SHARE) == 0 ||
 512                                             LK_CAN_SHARE(x) != 0)
 513                                                 break;
 514                                         cpu_spinwait();
 515                                 }
 516                                 GIANT_RESTORE();
 517                                 if (i != ALK_LOOPS)
 518                                         continue;
 519                         }
 520 #endif
 521
 522                         /*
 523                          * Acquire the sleepqueue chain lock because we
 524                          * probabilly will need to manipulate waiters flags.
 525                          */
 526                         sleepq_lock(&lk->lock_object);
 527                         x = lk->lk_lock;
 528
 529                         /*
 530                          * if the lock can be acquired in shared mode, try
 531                          * again.
 532                          */
 533                         if (LK_CAN_SHARE(x)) {
 534                                 sleepq_release(&lk->lock_object);
 535                                 continue;
 536                         }
 537
 538 #ifdef ADAPTIVE_LOCKMGRS
 539                         /*
 540                          * The current lock owner might have started executing
 541                          * on another CPU (or the lock could have changed
 542                          * owner) while we were waiting on the turnstile
 543                          * chain lock.  If so, drop the turnstile lock and try
 544                          * again.
 545                          */
 546                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 547                             LK_HOLDER(x) != LK_KERNPROC) {
 548                                 owner = (struct thread *)LK_HOLDER(x);
 549                                 if (TD_IS_RUNNING(owner)) {
 550                                         sleepq_release(&lk->lock_object);
 551                                         continue;
 552                                 }
 553                         }
 554 #endif
 555
 556                         /*
 557                          * Try to set the LK_SHARED_WAITERS flag.  If we fail,
 558                          * loop back and retry.
 559                          */
 560                         if ((x & LK_SHARED_WAITERS) == 0) {
 561                                 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
 562                                     x | LK_SHARED_WAITERS)) {
 563                                         sleepq_release(&lk->lock_object);
 564                                         continue;
 565                                 }
 566                                 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
 567                                     __func__, lk);
 568                         }
 569
 570                         /*
 571                          * As far as we have been unable to acquire the
 572                          * shared lock and the shared waiters flag is set,
 573                          * we will sleep.
 574                          */
 575                         error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 576                             SQ_SHARED_QUEUE);
 577                         flags &= ~LK_INTERLOCK;
 578                         if (error) {
 579                                 LOCK_LOG3(lk,
 580                                     "%s: interrupted sleep for %p with %d",
 581                                     __func__, lk, error);
 582                                 break;
 583                         }
 584                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 585                             __func__, lk);
 586                 }
 587                 if (error == 0) {
 588                         lock_profile_obtain_lock_success(&lk->lock_object,
 589                             contested, waittime, file, line);
 590                         LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
 591                             line);
 592                         WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
 593                             line);
 594                         TD_LOCKS_INC(curthread);
 595                         TD_SLOCKS_INC(curthread);
 596                         STACK_SAVE(lk);
 597                 }
 598                 break;
 599         case LK_UPGRADE:
 600                 _lockmgr_assert(lk, KA_SLOCKED, file, line);
 601                 v = lk->lk_lock;
 602                 x = v & LK_ALL_WAITERS;
 603                 v &= LK_EXCLUSIVE_SPINNERS;
 604
 605                 /*
 606                  * Try to switch from one shared lock to an exclusive one.
 607                  * We need to preserve waiters flags during the operation.
 608                  */
 609                 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
 610                     tid | x)) {
 611                         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
 612                             line);
 613                         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
 614                             LK_TRYWIT(flags), file, line);
 615                         TD_SLOCKS_DEC(curthread);
 616                         break;
 617                 }
 618
 619                 /*
 620                  * We have been unable to succeed in upgrading, so just
 621                  * give up the shared lock.
 622                  */
 623                 wakeup_swapper |= wakeupshlk(lk, file, line);
 624
 625                 /* FALLTHROUGH */
 626         case LK_EXCLUSIVE:
 627                 if (LK_CAN_WITNESS(flags))
 628                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 629                             LOP_EXCLUSIVE, file, line, ilk);
 630
 631                 /*
 632                  * If curthread already holds the lock and this one is
 633                  * allowed to recurse, simply recurse on it.
 634                  */
 635                 if (lockmgr_xlocked(lk)) {
 636                         if ((flags & LK_CANRECURSE) == 0 &&
 637                             (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
 638
 639                                 /*
 640                                  * If the lock is expected to not panic just
 641                                  * give up and return.
 642                                  */
 643                                 if (LK_TRYOP(flags)) {
 644                                         LOCK_LOG2(lk,
 645                                             "%s: %p fails the try operation",
 646                                             __func__, lk);
 647                                         error = EBUSY;
 648                                         break;
 649                                 }
 650                                 if (flags & LK_INTERLOCK)
 651                                         class->lc_unlock(ilk);
 652                 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
 653                                     __func__, iwmesg, file, line);
 654                         }
 655                         lk->lk_recurse++;
 656                         LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
 657                         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 658                             lk->lk_recurse, file, line);
 659                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 660                             LK_TRYWIT(flags), file, line);
 661                         TD_LOCKS_INC(curthread);
 662                         break;
 663                 }
 664
 665                 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
 666                     tid)) {
 667                         lock_profile_obtain_lock_failed(&lk->lock_object,
 668                             &contested, &waittime);
 669
 670                         /*
 671                          * If the lock is expected to not sleep just give up
 672                          * and return.
 673                          */
 674                         if (LK_TRYOP(flags)) {
 675                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 676                                     __func__, lk);
 677                                 error = EBUSY;
 678                                 break;
 679                         }
 680
 681 #ifdef ADAPTIVE_LOCKMGRS
 682                         /*
 683                          * If the owner is running on another CPU, spin until
 684                          * the owner stops running or the state of the lock
 685                          * changes.
 686                          */
 687                         x = lk->lk_lock;
 688                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 689                             LK_HOLDER(x) != LK_KERNPROC) {
 690                                 owner = (struct thread *)LK_HOLDER(x);
 691                                 if (LOCK_LOG_TEST(&lk->lock_object, 0))
 692                                         CTR3(KTR_LOCK,
 693                                             "%s: spinning on %p held by %p",
 694                                             __func__, lk, owner);
 695
 696                                 /*
 697                                  * If we are holding also an interlock drop it
 698                                  * in order to avoid a deadlock if the lockmgr
 699                                  * owner is adaptively spinning on the
 700                                  * interlock itself.
 701                                  */
 702                                 if (flags & LK_INTERLOCK) {
 703                                         class->lc_unlock(ilk);
 704                                         flags &= ~LK_INTERLOCK;
 705                                 }
 706                                 GIANT_SAVE();
 707                                 while (LK_HOLDER(lk->lk_lock) ==
 708                                     (uintptr_t)owner && TD_IS_RUNNING(owner))
 709                                         cpu_spinwait();
 710                                 GIANT_RESTORE();
 711                                 continue;
 712                         } else if (LK_CAN_ADAPT(lk, flags) &&
 713                             (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
 714                             spintries < ALK_RETRIES) {
 715                                 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
 716                                     !atomic_cmpset_ptr(&lk->lk_lock, x,
 717                                     x | LK_EXCLUSIVE_SPINNERS))
 718                                         continue;
 719                                 if (flags & LK_INTERLOCK) {
 720                                         class->lc_unlock(ilk);
 721                                         flags &= ~LK_INTERLOCK;
 722                                 }
 723                                 GIANT_SAVE();
 724                                 spintries++;
 725                                 for (i = 0; i < ALK_LOOPS; i++) {
 726                                         if (LOCK_LOG_TEST(&lk->lock_object, 0))
 727                                                 CTR4(KTR_LOCK,
 728                                     "%s: shared spinning on %p with %u and %u",
 729                                                     __func__, lk, spintries, i);
 730                                         if ((lk->lk_lock &
 731                                             LK_EXCLUSIVE_SPINNERS) == 0)
 732                                                 break;
 733                                         cpu_spinwait();
 734                                 }
 735                                 GIANT_RESTORE();
 736                                 if (i != ALK_LOOPS)
 737                                         continue;
 738                         }
 739 #endif
 740
 741                         /*
 742                          * Acquire the sleepqueue chain lock because we
 743                          * probabilly will need to manipulate waiters flags.
 744                          */
 745                         sleepq_lock(&lk->lock_object);
 746                         x = lk->lk_lock;
 747
 748                         /*
 749                          * if the lock has been released while we spun on
 750                          * the sleepqueue chain lock just try again.
 751                          */
 752                         if (x == LK_UNLOCKED) {
 753                                 sleepq_release(&lk->lock_object);
 754                                 continue;
 755                         }
 756
 757 #ifdef ADAPTIVE_LOCKMGRS
 758                         /*
 759                          * The current lock owner might have started executing
 760                          * on another CPU (or the lock could have changed
 761                          * owner) while we were waiting on the turnstile
 762                          * chain lock.  If so, drop the turnstile lock and try
 763                          * again.
 764                          */
 765                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 766                             LK_HOLDER(x) != LK_KERNPROC) {
 767                                 owner = (struct thread *)LK_HOLDER(x);
 768                                 if (TD_IS_RUNNING(owner)) {
 769                                         sleepq_release(&lk->lock_object);
 770                                         continue;
 771                                 }
 772                         }
 773 #endif
 774
 775                         /*
 776                          * The lock can be in the state where there is a
 777                          * pending queue of waiters, but still no owner.
 778                          * This happens when the lock is contested and an
 779                          * owner is going to claim the lock.
 780                          * If curthread is the one successfully acquiring it
 781                          * claim lock ownership and return, preserving waiters
 782                          * flags.
 783                          */
 784                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 785                         if ((x & ~v) == LK_UNLOCKED) {
 786                                 v &= ~LK_EXCLUSIVE_SPINNERS;
 787                                 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
 788                                     tid | v)) {
 789                                         sleepq_release(&lk->lock_object);
 790                                         LOCK_LOG2(lk,
 791                                             "%s: %p claimed by a new writer",
 792                                             __func__, lk);
 793                                         break;
 794                                 }
 795                                 sleepq_release(&lk->lock_object);
 796                                 continue;
 797                         }
 798
 799                         /*
 800                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
 801                          * fail, loop back and retry.
 802                          */
 803                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
 804                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
 805                                     x | LK_EXCLUSIVE_WAITERS)) {
 806                                         sleepq_release(&lk->lock_object);
 807                                         continue;
 808                                 }
 809                                 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
 810                                     __func__, lk);
 811                         }
 812
 813                         /*
 814                          * As far as we have been unable to acquire the
 815                          * exclusive lock and the exclusive waiters flag
 816                          * is set, we will sleep.
 817                          */
 818                         error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 819                             SQ_EXCLUSIVE_QUEUE);
 820                         flags &= ~LK_INTERLOCK;
 821                         if (error) {
 822                                 LOCK_LOG3(lk,
 823                                     "%s: interrupted sleep for %p with %d",
 824                                     __func__, lk, error);
 825                                 break;
 826                         }
 827                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 828                             __func__, lk);
 829                 }
 830                 if (error == 0) {
 831                         lock_profile_obtain_lock_success(&lk->lock_object,
 832                             contested, waittime, file, line);
 833                         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 834                             lk->lk_recurse, file, line);
 835                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 836                             LK_TRYWIT(flags), file, line);
 837                         TD_LOCKS_INC(curthread);
 838                         STACK_SAVE(lk);
 839                 }
 840                 break;
 841         case LK_DOWNGRADE:
 842                 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
 843                 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
 844                 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
 845                 TD_SLOCKS_INC(curthread);
 846
 847                 /*
 848                  * In order to preserve waiters flags, just spin.
 849                  */
 850                 for (;;) {
 851                         x = lk->lk_lock;
 852                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
 853                         x &= LK_ALL_WAITERS;
 854                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
 855                             LK_SHARERS_LOCK(1) | x))
 856                                 break;
 857                         cpu_spinwait();
 858                 }
 859                 break;
 860         case LK_RELEASE:
 861                 _lockmgr_assert(lk, KA_LOCKED, file, line);
 862                 x = lk->lk_lock;
 863
 864                 if ((x & LK_SHARE) == 0) {
 865
 866                         /*
 867                          * As first option, treact the lock as if it has not
 868                          * any waiter.
 869                          * Fix-up the tid var if the lock has been disowned.
 870                          */
 871                         if (LK_HOLDER(x) == LK_KERNPROC)
 872                                 tid = LK_KERNPROC;
 873                         else {
 874                                 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
 875                                     file, line);
 876                                 TD_LOCKS_DEC(curthread);
 877                         }
 878                         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
 879                             lk->lk_recurse, file, line);
 880
 881                         /*
 882                          * The lock is held in exclusive mode.
 883                          * If the lock is recursed also, then unrecurse it.
 884                          */
 885                         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
 886                                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
 887                                     lk);
 888                                 lk->lk_recurse--;
 889                                 break;
 890                         }
 891                         if (tid != LK_KERNPROC)
 892                                 lock_profile_release_lock(&lk->lock_object);
 893
 894                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
 895                             LK_UNLOCKED))
 896                                 break;
 897
 898                         sleepq_lock(&lk->lock_object);
 899                         x = lk->lk_lock;
 900                         v = LK_UNLOCKED;
 901
 902                         /*
 903                          * If the lock has exclusive waiters, give them
 904                          * preference in order to avoid deadlock with
 905                          * shared runners up.
 906                          */
 907                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
 908                         if (x & LK_EXCLUSIVE_WAITERS) {
 909                                 queue = SQ_EXCLUSIVE_QUEUE;
 910                                 v |= (x & LK_SHARED_WAITERS);
 911                         } else {
 912                                 MPASS((x & LK_ALL_WAITERS) ==
 913                                     LK_SHARED_WAITERS);
 914                                 queue = SQ_SHARED_QUEUE;
 915                         }
 916
 917                         LOCK_LOG3(lk,
 918                             "%s: %p waking up threads on the %s queue",
 919                             __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 920                             "exclusive");
 921                         atomic_store_rel_ptr(&lk->lk_lock, v);
 922                         wakeup_swapper = sleepq_broadcast(&lk->lock_object,
 923                             SLEEPQ_LK, 0, queue);
 924                         sleepq_release(&lk->lock_object);
 925                         break;
 926                 } else
 927                         wakeup_swapper = wakeupshlk(lk, file, line);
 928                 break;
 929         case LK_DRAIN:
 930                 if (LK_CAN_WITNESS(flags))
 931                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 932                             LOP_EXCLUSIVE, file, line, ilk);
 933
 934                 /*
 935                  * Trying to drain a lock we already own will result in a
 936                  * deadlock.
 937                  */
 938                 if (lockmgr_xlocked(lk)) {
 939                         if (flags & LK_INTERLOCK)
 940                                 class->lc_unlock(ilk);
 941                         panic("%s: draining %s with the lock held @ %s:%d\n",
 942                             __func__, iwmesg, file, line);
 943                 }
 944
 945                 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
 946                         lock_profile_obtain_lock_failed(&lk->lock_object,
 947                             &contested, &waittime);
 948
 949                         /*
 950                          * If the lock is expected to not sleep just give up
 951                          * and return.
 952                          */
 953                         if (LK_TRYOP(flags)) {
 954                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 955                                     __func__, lk);
 956                                 error = EBUSY;
 957                                 break;
 958                         }
 959
 960                         /*
 961                          * Acquire the sleepqueue chain lock because we
 962                          * probabilly will need to manipulate waiters flags.
 963                          */
 964                         sleepq_lock(&lk->lock_object);
 965                         x = lk->lk_lock;
 966
 967                         /*
 968                          * if the lock has been released while we spun on
 969                          * the sleepqueue chain lock just try again.
 970                          */
 971                         if (x == LK_UNLOCKED) {
 972                                 sleepq_release(&lk->lock_object);
 973                                 continue;
 974                         }
 975
 976                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 977                         if ((x & ~v) == LK_UNLOCKED) {
 978                                 v = (x & ~LK_EXCLUSIVE_SPINNERS);
 979                                 if (v & LK_EXCLUSIVE_WAITERS) {
 980                                         queue = SQ_EXCLUSIVE_QUEUE;
 981                                         v &= ~LK_EXCLUSIVE_WAITERS;
 982                                 } else {
 983                                         MPASS(v & LK_SHARED_WAITERS);
 984                                         queue = SQ_SHARED_QUEUE;
 985                                         v &= ~LK_SHARED_WAITERS;
 986                                 }
 987                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
 988                                         sleepq_release(&lk->lock_object);
 989                                         continue;
 990                                 }
 991                                 LOCK_LOG3(lk,
 992                                 "%s: %p waking up all threads on the %s queue",
 993                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
 994                                     "shared" : "exclusive");
 995                                 wakeup_swapper |= sleepq_broadcast(
 996                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
 997
 998                                 /*
 999                                  * If shared waiters have been woken up we need
1000                                  * to wait for one of them to acquire the lock
1001                                  * before to set the exclusive waiters in
1002                                  * order to avoid a deadlock.
1003                                  */
1004                                 if (queue == SQ_SHARED_QUEUE) {
1005                                         for (v = lk->lk_lock;
1006                                             (v & LK_SHARE) && !LK_SHARERS(v);
1007                                             v = lk->lk_lock)
1008                                                 cpu_spinwait();
1009                                 }
1010                         }
1011
1012                         /*
1013                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1014                          * fail, loop back and retry.
1015                          */
1016                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1017                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1018                                     x | LK_EXCLUSIVE_WAITERS)) {
1019                                         sleepq_release(&lk->lock_object);
1020                                         continue;
1021                                 }
1022                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1023                                     __func__, lk);
1024                         }
1025
1026                         /*
1027                          * As far as we have been unable to acquire the
1028                          * exclusive lock and the exclusive waiters flag
1029                          * is set, we will sleep.
1030                          */
1031                         if (flags & LK_INTERLOCK) {
1032                                 class->lc_unlock(ilk);
1033                                 flags &= ~LK_INTERLOCK;
1034                         }
1035                         GIANT_SAVE();
1036                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1037                             SQ_EXCLUSIVE_QUEUE);
1038                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1039                         GIANT_RESTORE();
1040                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1041                             __func__, lk);
1042                 }
1043
1044                 if (error == 0) {
1045                         lock_profile_obtain_lock_success(&lk->lock_object,
1046                             contested, waittime, file, line);
1047                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1048                             lk->lk_recurse, file, line);
1049                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1050                             LK_TRYWIT(flags), file, line);
1051                         TD_LOCKS_INC(curthread);
1052                         STACK_SAVE(lk);
1053                 }
1054                 break;
1055         default:
1056                 if (flags & LK_INTERLOCK)
1057                         class->lc_unlock(ilk);
1058                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1059         }
1060
1061         if (flags & LK_INTERLOCK)
1062                 class->lc_unlock(ilk);
1063         if (wakeup_swapper)
1064                 kick_proc0();
1065
1066         return (error);
1067 }
1068
1069 void
1070 _lockmgr_disown(struct lock *lk, const char *file, int line)
1071 {
1072         uintptr_t tid, x;
1073
1074         tid = (uintptr_t)curthread;
1075         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
1076
1077         /*
1078          * If the owner is already LK_KERNPROC just skip the whole operation.
1079          */
1080         if (LK_HOLDER(lk->lk_lock) != tid)
1081                 return;
1082         lock_profile_release_lock(&lk->lock_object);
1083         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1084         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1085         TD_LOCKS_DEC(curthread);
1086
1087         /*
1088          * In order to preserve waiters flags, just spin.
1089          */
1090         for (;;) {
1091                 x = lk->lk_lock;
1092                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1093                 x &= LK_ALL_WAITERS;
1094                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1095                     LK_KERNPROC | x))
1096                         return;
1097                 cpu_spinwait();
1098         }
1099 }
1100
1101 void
1102 lockmgr_printinfo(struct lock *lk)
1103 {
1104         struct thread *td;
1105         uintptr_t x;
1106
1107         if (lk->lk_lock == LK_UNLOCKED)
1108                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1109         else if (lk->lk_lock & LK_SHARE)
1110                 printf("lock type %s: SHARED (count %ju)\n",
1111                     lk->lock_object.lo_name,
1112                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1113         else {
1114                 td = lockmgr_xholder(lk);
1115                 printf("lock type %s: EXCL by thread %p (pid %d)\n",
1116                     lk->lock_object.lo_name, td, td->td_proc->p_pid);
1117         }
1118
1119         x = lk->lk_lock;
1120         if (x & LK_EXCLUSIVE_WAITERS)
1121                 printf(" with exclusive waiters pending\n");
1122         if (x & LK_SHARED_WAITERS)
1123                 printf(" with shared waiters pending\n");
1124         if (x & LK_EXCLUSIVE_SPINNERS)
1125                 printf(" with exclusive spinners pending\n");
1126
1127         STACK_PRINT(lk);
1128 }
1129
1130 int
1131 lockstatus(struct lock *lk)
1132 {
1133         uintptr_t v, x;
1134         int ret;
1135
1136         ret = LK_SHARED;
1137         x = lk->lk_lock;
1138         v = LK_HOLDER(x);
1139
1140         if ((x & LK_SHARE) == 0) {
1141                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1142                         ret = LK_EXCLUSIVE;
1143                 else
1144                         ret = LK_EXCLOTHER;
1145         } else if (x == LK_UNLOCKED)
1146                 ret = 0;
1147
1148         return (ret);
1149 }
1150
1151 #ifdef INVARIANT_SUPPORT
1152 #ifndef INVARIANTS
1153 #undef  _lockmgr_assert
1154 #endif
1155
1156 void
1157 _lockmgr_assert(struct lock *lk, int what, const char *file, int line)
1158 {
1159         int slocked = 0;
1160
1161         if (panicstr != NULL)
1162                 return;
1163         switch (what) {
1164         case KA_SLOCKED:
1165         case KA_SLOCKED | KA_NOTRECURSED:
1166         case KA_SLOCKED | KA_RECURSED:
1167                 slocked = 1;
1168         case KA_LOCKED:
1169         case KA_LOCKED | KA_NOTRECURSED:
1170         case KA_LOCKED | KA_RECURSED:
1171 #ifdef WITNESS
1172
1173                 /*
1174                  * We cannot trust WITNESS if the lock is held in exclusive
1175                  * mode and a call to lockmgr_disown() happened.
1176                  * Workaround this skipping the check if the lock is held in
1177                  * exclusive mode even for the KA_LOCKED case.
1178                  */
1179                 if (slocked || (lk->lk_lock & LK_SHARE)) {
1180                         witness_assert(&lk->lock_object, what, file, line);
1181                         break;
1182                 }
1183 #endif
1184                 if (lk->lk_lock == LK_UNLOCKED ||
1185                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1186                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1187                         panic("Lock %s not %slocked @ %s:%d\n",
1188                             lk->lock_object.lo_name, slocked ? "share" : "",
1189                             file, line);
1190
1191                 if ((lk->lk_lock & LK_SHARE) == 0) {
1192                         if (lockmgr_recursed(lk)) {
1193                                 if (what & KA_NOTRECURSED)
1194                                         panic("Lock %s recursed @ %s:%d\n",
1195                                             lk->lock_object.lo_name, file,
1196                                             line);
1197                         } else if (what & KA_RECURSED)
1198                                 panic("Lock %s not recursed @ %s:%d\n",
1199                                     lk->lock_object.lo_name, file, line);
1200                 }
1201                 break;
1202         case KA_XLOCKED:
1203         case KA_XLOCKED | KA_NOTRECURSED:
1204         case KA_XLOCKED | KA_RECURSED:
1205                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1206                         panic("Lock %s not exclusively locked @ %s:%d\n",
1207                             lk->lock_object.lo_name, file, line);
1208                 if (lockmgr_recursed(lk)) {
1209                         if (what & KA_NOTRECURSED)
1210                                 panic("Lock %s recursed @ %s:%d\n",
1211                                     lk->lock_object.lo_name, file, line);
1212                 } else if (what & KA_RECURSED)
1213                         panic("Lock %s not recursed @ %s:%d\n",
1214                             lk->lock_object.lo_name, file, line);
1215                 break;
1216         case KA_UNLOCKED:
1217                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1218                         panic("Lock %s exclusively locked @ %s:%d\n",
1219                             lk->lock_object.lo_name, file, line);
1220                 break;
1221         default:
1222                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1223                     line);
1224         }
1225 }
1226 #endif
1227
1228 #ifdef DDB
1229 int
1230 lockmgr_chain(struct thread *td, struct thread **ownerp)
1231 {
1232         struct lock *lk;
1233
1234         lk = td->td_wchan;
1235
1236         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1237                 return (0);
1238         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1239         if (lk->lk_lock & LK_SHARE)
1240                 db_printf("SHARED (count %ju)\n",
1241                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1242         else
1243                 db_printf("EXCL\n");
1244         *ownerp = lockmgr_xholder(lk);
1245
1246         return (1);
1247 }
1248
1249 static void
1250 db_show_lockmgr(struct lock_object *lock)
1251 {
1252         struct thread *td;
1253         struct lock *lk;
1254
1255         lk = (struct lock *)lock;
1256
1257         db_printf(" state: ");
1258         if (lk->lk_lock == LK_UNLOCKED)
1259                 db_printf("UNLOCKED\n");
1260         else if (lk->lk_lock & LK_SHARE)
1261                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1262         else {
1263                 td = lockmgr_xholder(lk);
1264                 if (td == (struct thread *)LK_KERNPROC)
1265                         db_printf("XLOCK: LK_KERNPROC\n");
1266                 else
1267                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1268                             td->td_tid, td->td_proc->p_pid,
1269                             td->td_proc->p_comm);
1270                 if (lockmgr_recursed(lk))
1271                         db_printf(" recursed: %d\n", lk->lk_recurse);
1272         }
1273         db_printf(" waiters: ");
1274         switch (lk->lk_lock & LK_ALL_WAITERS) {
1275         case LK_SHARED_WAITERS:
1276                 db_printf("shared\n");
1277                 break;
1278         case LK_EXCLUSIVE_WAITERS:
1279                 db_printf("exclusive\n");
1280                 break;
1281         case LK_ALL_WAITERS:
1282                 db_printf("shared and exclusive\n");
1283                 break;
1284         default:
1285                 db_printf("none\n");
1286         }
1287         db_printf(" spinners: ");
1288         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1289                 db_printf("exclusive\n");
1290         else
1291                 db_printf("none\n");
1292 }
1293 #endif