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