sys/kern/kern_lock.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org>
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice(s), this list of conditions and the following disclaimer as
  12  *    the first lines of this file unmodified other than the possible
  13  *    addition of one or more copyright notices.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice(s), this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
  19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  21  * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
  22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  25  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  28  * DAMAGE.
  29  */
  30
  31 #include "opt_ddb.h"
  32 #include "opt_hwpmc_hooks.h"
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include <sys/param.h>
  38 #include <sys/kdb.h>
  39 #include <sys/ktr.h>
  40 #include <sys/lock.h>
  41 #include <sys/lock_profile.h>
  42 #include <sys/lockmgr.h>
  43 #include <sys/lockstat.h>
  44 #include <sys/mutex.h>
  45 #include <sys/proc.h>
  46 #include <sys/sleepqueue.h>
  47 #ifdef DEBUG_LOCKS
  48 #include <sys/stack.h>
  49 #endif
  50 #include <sys/sysctl.h>
  51 #include <sys/systm.h>
  52
  53 #include <machine/cpu.h>
  54
  55 #ifdef DDB
  56 #include <ddb/ddb.h>
  57 #endif
  58
  59 #ifdef HWPMC_HOOKS
  60 #include <sys/pmckern.h>
  61 PMC_SOFT_DECLARE( , , lock, failed);
  62 #endif
  63
  64 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
  65     ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
  66
  67 #define SQ_EXCLUSIVE_QUEUE      0
  68 #define SQ_SHARED_QUEUE         1
  69
  70 #ifndef INVARIANTS
  71 #define _lockmgr_assert(lk, what, file, line)
  72 #endif
  73
  74 #define TD_SLOCKS_INC(td)       ((td)->td_lk_slocks++)
  75 #define TD_SLOCKS_DEC(td)       ((td)->td_lk_slocks--)
  76
  77 #ifndef DEBUG_LOCKS
  78 #define STACK_PRINT(lk)
  79 #define STACK_SAVE(lk)
  80 #define STACK_ZERO(lk)
  81 #else
  82 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
  83 #define STACK_SAVE(lk)  stack_save(&(lk)->lk_stack)
  84 #define STACK_ZERO(lk)  stack_zero(&(lk)->lk_stack)
  85 #endif
  86
  87 #define LOCK_LOG2(lk, string, arg1, arg2)                               \
  88         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  89                 CTR2(KTR_LOCK, (string), (arg1), (arg2))
  90 #define LOCK_LOG3(lk, string, arg1, arg2, arg3)                         \
  91         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  92                 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
  93
  94 #define GIANT_DECLARE                                                   \
  95         int _i = 0;                                                     \
  96         WITNESS_SAVE_DECL(Giant)
  97 #define GIANT_RESTORE() do {                                            \
  98         if (__predict_false(_i > 0)) {                                  \
  99                 while (_i--)                                            \
 100                         mtx_lock(&Giant);                               \
 101                 WITNESS_RESTORE(&Giant.lock_object, Giant);             \
 102         }                                                               \
 103 } while (0)
 104 #define GIANT_SAVE() do {                                               \
 105         if (__predict_false(mtx_owned(&Giant))) {                       \
 106                 WITNESS_SAVE(&Giant.lock_object, Giant);                \
 107                 while (mtx_owned(&Giant)) {                             \
 108                         _i++;                                           \
 109                         mtx_unlock(&Giant);                             \
 110                 }                                                       \
 111         }                                                               \
 112 } while (0)
 113
 114 static bool __always_inline
 115 LK_CAN_SHARE(uintptr_t x, int flags, bool fp)
 116 {
 117
 118         if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) ==
 119             LK_SHARE)
 120                 return (true);
 121         if (fp || (!(x & LK_SHARE)))
 122                 return (false);
 123         if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||
 124             (curthread->td_pflags & TDP_DEADLKTREAT))
 125                 return (true);
 126         return (false);
 127 }
 128
 129 #define LK_TRYOP(x)                                                     \
 130         ((x) & LK_NOWAIT)
 131
 132 #define LK_CAN_WITNESS(x)                                               \
 133         (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
 134 #define LK_TRYWIT(x)                                                    \
 135         (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
 136
 137 #define lockmgr_disowned(lk)                                            \
 138         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
 139
 140 #define lockmgr_xlocked_v(v)                                            \
 141         (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
 142
 143 #define lockmgr_xlocked(lk) lockmgr_xlocked_v(lockmgr_read_value(lk))
 144
 145 static void     assert_lockmgr(const struct lock_object *lock, int how);
 146 #ifdef DDB
 147 static void     db_show_lockmgr(const struct lock_object *lock);
 148 #endif
 149 static void     lock_lockmgr(struct lock_object *lock, uintptr_t how);
 150 #ifdef KDTRACE_HOOKS
 151 static int      owner_lockmgr(const struct lock_object *lock,
 152                     struct thread **owner);
 153 #endif
 154 static uintptr_t unlock_lockmgr(struct lock_object *lock);
 155
 156 struct lock_class lock_class_lockmgr = {
 157         .lc_name = "lockmgr",
 158         .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
 159         .lc_assert = assert_lockmgr,
 160 #ifdef DDB
 161         .lc_ddb_show = db_show_lockmgr,
 162 #endif
 163         .lc_lock = lock_lockmgr,
 164         .lc_unlock = unlock_lockmgr,
 165 #ifdef KDTRACE_HOOKS
 166         .lc_owner = owner_lockmgr,
 167 #endif
 168 };
 169
 170 static __read_mostly bool lk_adaptive = true;
 171 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, "lockmgr debugging");
 172 SYSCTL_BOOL(_debug_lockmgr, OID_AUTO, adaptive_spinning, CTLFLAG_RW, &lk_adaptive,
 173     0, "");
 174 #define lockmgr_delay  locks_delay
 175
 176 struct lockmgr_wait {
 177         const char *iwmesg;
 178         int ipri;
 179         int itimo;
 180 };
 181
 182 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
 183     int flags, bool fp);
 184 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp);
 185
 186 static void
 187 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper)
 188 {
 189         struct lock_class *class;
 190
 191         if (flags & LK_INTERLOCK) {
 192                 class = LOCK_CLASS(ilk);
 193                 class->lc_unlock(ilk);
 194         }
 195
 196         if (__predict_false(wakeup_swapper))
 197                 kick_proc0();
 198 }
 199
 200 static void
 201 lockmgr_note_shared_acquire(struct lock *lk, int contested,
 202     uint64_t waittime, const char *file, int line, int flags)
 203 {
 204
 205         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
 206             waittime, file, line, LOCKSTAT_READER);
 207         LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
 208         WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
 209         TD_LOCKS_INC(curthread);
 210         TD_SLOCKS_INC(curthread);
 211         STACK_SAVE(lk);
 212 }
 213
 214 static void
 215 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
 216 {
 217
 218         WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
 219         LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
 220         TD_LOCKS_DEC(curthread);
 221         TD_SLOCKS_DEC(curthread);
 222 }
 223
 224 static void
 225 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
 226     uint64_t waittime, const char *file, int line, int flags)
 227 {
 228
 229         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
 230             waittime, file, line, LOCKSTAT_WRITER);
 231         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
 232         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
 233             line);
 234         TD_LOCKS_INC(curthread);
 235         STACK_SAVE(lk);
 236 }
 237
 238 static void
 239 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
 240 {
 241
 242         if (LK_HOLDER(lockmgr_read_value(lk)) != LK_KERNPROC) {
 243                 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
 244                 TD_LOCKS_DEC(curthread);
 245         }
 246         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
 247             line);
 248 }
 249
 250 static __inline struct thread *
 251 lockmgr_xholder(const struct lock *lk)
 252 {
 253         uintptr_t x;
 254
 255         x = lockmgr_read_value(lk);
 256         return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
 257 }
 258
 259 /*
 260  * It assumes sleepq_lock held and returns with this one unheld.
 261  * It also assumes the generic interlock is sane and previously checked.
 262  * If LK_INTERLOCK is specified the interlock is not reacquired after the
 263  * sleep.
 264  */
 265 static __inline int
 266 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
 267     const char *wmesg, int pri, int timo, int queue)
 268 {
 269         GIANT_DECLARE;
 270         struct lock_class *class;
 271         int catch, error;
 272
 273         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 274         catch = pri & PCATCH;
 275         pri &= PRIMASK;
 276         error = 0;
 277
 278         LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
 279             (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
 280
 281         if (flags & LK_INTERLOCK)
 282                 class->lc_unlock(ilk);
 283         if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
 284                 lk->lk_exslpfail++;
 285         GIANT_SAVE();
 286         sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
 287             SLEEPQ_INTERRUPTIBLE : 0), queue);
 288         if ((flags & LK_TIMELOCK) && timo)
 289                 sleepq_set_timeout(&lk->lock_object, timo);
 290
 291         /*
 292          * Decisional switch for real sleeping.
 293          */
 294         if ((flags & LK_TIMELOCK) && timo && catch)
 295                 error = sleepq_timedwait_sig(&lk->lock_object, pri);
 296         else if ((flags & LK_TIMELOCK) && timo)
 297                 error = sleepq_timedwait(&lk->lock_object, pri);
 298         else if (catch)
 299                 error = sleepq_wait_sig(&lk->lock_object, pri);
 300         else
 301                 sleepq_wait(&lk->lock_object, pri);
 302         GIANT_RESTORE();
 303         if ((flags & LK_SLEEPFAIL) && error == 0)
 304                 error = ENOLCK;
 305
 306         return (error);
 307 }
 308
 309 static __inline int
 310 wakeupshlk(struct lock *lk, const char *file, int line)
 311 {
 312         uintptr_t v, x, orig_x;
 313         u_int realexslp;
 314         int queue, wakeup_swapper;
 315
 316         wakeup_swapper = 0;
 317         for (;;) {
 318                 x = lockmgr_read_value(lk);
 319                 if (lockmgr_sunlock_try(lk, &x))
 320                         break;
 321
 322                 /*
 323                  * We should have a sharer with waiters, so enter the hard
 324                  * path in order to handle wakeups correctly.
 325                  */
 326                 sleepq_lock(&lk->lock_object);
 327                 orig_x = lockmgr_read_value(lk);
 328 retry_sleepq:
 329                 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 330                 v = LK_UNLOCKED;
 331
 332                 /*
 333                  * If the lock has exclusive waiters, give them preference in
 334                  * order to avoid deadlock with shared runners up.
 335                  * If interruptible sleeps left the exclusive queue empty
 336                  * avoid a starvation for the threads sleeping on the shared
 337                  * queue by giving them precedence and cleaning up the
 338                  * exclusive waiters bit anyway.
 339                  * Please note that lk_exslpfail count may be lying about
 340                  * the real number of waiters with the LK_SLEEPFAIL flag on
 341                  * because they may be used in conjunction with interruptible
 342                  * sleeps so lk_exslpfail might be considered an 'upper limit'
 343                  * bound, including the edge cases.
 344                  */
 345                 realexslp = sleepq_sleepcnt(&lk->lock_object,
 346                     SQ_EXCLUSIVE_QUEUE);
 347                 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
 348                         if (lk->lk_exslpfail < realexslp) {
 349                                 lk->lk_exslpfail = 0;
 350                                 queue = SQ_EXCLUSIVE_QUEUE;
 351                                 v |= (x & LK_SHARED_WAITERS);
 352                         } else {
 353                                 lk->lk_exslpfail = 0;
 354                                 LOCK_LOG2(lk,
 355                                     "%s: %p has only LK_SLEEPFAIL sleepers",
 356                                     __func__, lk);
 357                                 LOCK_LOG2(lk,
 358                             "%s: %p waking up threads on the exclusive queue",
 359                                     __func__, lk);
 360                                 wakeup_swapper =
 361                                     sleepq_broadcast(&lk->lock_object,
 362                                     SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
 363                                 queue = SQ_SHARED_QUEUE;
 364                         }
 365
 366                 } else {
 367
 368                         /*
 369                          * Exclusive waiters sleeping with LK_SLEEPFAIL on
 370                          * and using interruptible sleeps/timeout may have
 371                          * left spourious lk_exslpfail counts on, so clean
 372                          * it up anyway.
 373                          */
 374                         lk->lk_exslpfail = 0;
 375                         queue = SQ_SHARED_QUEUE;
 376                 }
 377
 378                 if (lockmgr_sunlock_try(lk, &orig_x)) {
 379                         sleepq_release(&lk->lock_object);
 380                         break;
 381                 }
 382
 383                 x |= LK_SHARERS_LOCK(1);
 384                 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
 385                         orig_x = x;
 386                         goto retry_sleepq;
 387                 }
 388                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 389                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 390                     "exclusive");
 391                 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
 392                     0, queue);
 393                 sleepq_release(&lk->lock_object);
 394                 break;
 395         }
 396
 397         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
 398         return (wakeup_swapper);
 399 }
 400
 401 static void
 402 assert_lockmgr(const struct lock_object *lock, int what)
 403 {
 404
 405         panic("lockmgr locks do not support assertions");
 406 }
 407
 408 static void
 409 lock_lockmgr(struct lock_object *lock, uintptr_t how)
 410 {
 411
 412         panic("lockmgr locks do not support sleep interlocking");
 413 }
 414
 415 static uintptr_t
 416 unlock_lockmgr(struct lock_object *lock)
 417 {
 418
 419         panic("lockmgr locks do not support sleep interlocking");
 420 }
 421
 422 #ifdef KDTRACE_HOOKS
 423 static int
 424 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
 425 {
 426
 427         panic("lockmgr locks do not support owner inquiring");
 428 }
 429 #endif
 430
 431 void
 432 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 433 {
 434         int iflags;
 435
 436         MPASS((flags & ~LK_INIT_MASK) == 0);
 437         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
 438             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
 439             &lk->lk_lock));
 440
 441         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
 442         if (flags & LK_CANRECURSE)
 443                 iflags |= LO_RECURSABLE;
 444         if ((flags & LK_NODUP) == 0)
 445                 iflags |= LO_DUPOK;
 446         if (flags & LK_NOPROFILE)
 447                 iflags |= LO_NOPROFILE;
 448         if ((flags & LK_NOWITNESS) == 0)
 449                 iflags |= LO_WITNESS;
 450         if (flags & LK_QUIET)
 451                 iflags |= LO_QUIET;
 452         if (flags & LK_IS_VNODE)
 453                 iflags |= LO_IS_VNODE;
 454         if (flags & LK_NEW)
 455                 iflags |= LO_NEW;
 456         iflags |= flags & LK_NOSHARE;
 457
 458         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
 459         lk->lk_lock = LK_UNLOCKED;
 460         lk->lk_recurse = 0;
 461         lk->lk_exslpfail = 0;
 462         lk->lk_timo = timo;
 463         lk->lk_pri = pri;
 464         STACK_ZERO(lk);
 465 }
 466
 467 /*
 468  * XXX: Gross hacks to manipulate external lock flags after
 469  * initialization.  Used for certain vnode and buf locks.
 470  */
 471 void
 472 lockallowshare(struct lock *lk)
 473 {
 474
 475         lockmgr_assert(lk, KA_XLOCKED);
 476         lk->lock_object.lo_flags &= ~LK_NOSHARE;
 477 }
 478
 479 void
 480 lockdisableshare(struct lock *lk)
 481 {
 482
 483         lockmgr_assert(lk, KA_XLOCKED);
 484         lk->lock_object.lo_flags |= LK_NOSHARE;
 485 }
 486
 487 void
 488 lockallowrecurse(struct lock *lk)
 489 {
 490
 491         lockmgr_assert(lk, KA_XLOCKED);
 492         lk->lock_object.lo_flags |= LO_RECURSABLE;
 493 }
 494
 495 void
 496 lockdisablerecurse(struct lock *lk)
 497 {
 498
 499         lockmgr_assert(lk, KA_XLOCKED);
 500         lk->lock_object.lo_flags &= ~LO_RECURSABLE;
 501 }
 502
 503 void
 504 lockdestroy(struct lock *lk)
 505 {
 506
 507         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
 508         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
 509         KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
 510         lock_destroy(&lk->lock_object);
 511 }
 512
 513 static bool __always_inline
 514 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
 515 {
 516
 517         /*
 518          * If no other thread has an exclusive lock, or
 519          * no exclusive waiter is present, bump the count of
 520          * sharers.  Since we have to preserve the state of
 521          * waiters, if we fail to acquire the shared lock
 522          * loop back and retry.
 523          */
 524         while (LK_CAN_SHARE(*xp, flags, fp)) {
 525                 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
 526                     *xp + LK_ONE_SHARER)) {
 527                         return (true);
 528                 }
 529         }
 530         return (false);
 531 }
 532
 533 static bool __always_inline
 534 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
 535 {
 536
 537         for (;;) {
 538                 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
 539                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
 540                             *xp - LK_ONE_SHARER))
 541                                 return (true);
 542                         continue;
 543                 }
 544                 break;
 545         }
 546         return (false);
 547 }
 548
 549 static bool
 550 lockmgr_slock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp,
 551     int flags)
 552 {
 553         struct thread *owner;
 554         uintptr_t x;
 555
 556         x = *xp;
 557         MPASS(x != LK_UNLOCKED);
 558         owner = (struct thread *)LK_HOLDER(x);
 559         for (;;) {
 560                 MPASS(owner != curthread);
 561                 if (owner == (struct thread *)LK_KERNPROC)
 562                         return (false);
 563                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
 564                         return (false);
 565                 if (owner == NULL)
 566                         return (false);
 567                 if (!TD_IS_RUNNING(owner))
 568                         return (false);
 569                 if ((x & LK_ALL_WAITERS) != 0)
 570                         return (false);
 571                 lock_delay(lda);
 572                 x = lockmgr_read_value(lk);
 573                 if (LK_CAN_SHARE(x, flags, false)) {
 574                         *xp = x;
 575                         return (true);
 576                 }
 577                 owner = (struct thread *)LK_HOLDER(x);
 578         }
 579 }
 580
 581 static __noinline int
 582 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 583     const char *file, int line, struct lockmgr_wait *lwa)
 584 {
 585         uintptr_t tid, x;
 586         int error = 0;
 587         const char *iwmesg;
 588         int ipri, itimo;
 589
 590 #ifdef KDTRACE_HOOKS
 591         uint64_t sleep_time = 0;
 592 #endif
 593 #ifdef LOCK_PROFILING
 594         uint64_t waittime = 0;
 595         int contested = 0;
 596 #endif
 597         struct lock_delay_arg lda;
 598
 599         if (KERNEL_PANICKED())
 600                 goto out;
 601
 602         tid = (uintptr_t)curthread;
 603
 604         if (LK_CAN_WITNESS(flags))
 605                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 606                     file, line, flags & LK_INTERLOCK ? ilk : NULL);
 607         lock_delay_arg_init(&lda, &lockmgr_delay);
 608         if (!lk_adaptive)
 609                 flags &= ~LK_ADAPTIVE;
 610         x = lockmgr_read_value(lk);
 611         /*
 612          * The lock may already be locked exclusive by curthread,
 613          * avoid deadlock.
 614          */
 615         if (LK_HOLDER(x) == tid) {
 616                 LOCK_LOG2(lk,
 617                     "%s: %p already held in exclusive mode",
 618                     __func__, lk);
 619                 error = EDEADLK;
 620                 goto out;
 621         }
 622
 623         for (;;) {
 624                 if (lockmgr_slock_try(lk, &x, flags, false))
 625                         break;
 626
 627                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
 628                         if (lockmgr_slock_adaptive(&lda, lk, &x, flags))
 629                                 continue;
 630                 }
 631
 632 #ifdef HWPMC_HOOKS
 633                 PMC_SOFT_CALL( , , lock, failed);
 634 #endif
 635                 lock_profile_obtain_lock_failed(&lk->lock_object,
 636                     &contested, &waittime);
 637
 638                 /*
 639                  * If the lock is expected to not sleep just give up
 640                  * and return.
 641                  */
 642                 if (LK_TRYOP(flags)) {
 643                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 644                             __func__, lk);
 645                         error = EBUSY;
 646                         break;
 647                 }
 648
 649                 /*
 650                  * Acquire the sleepqueue chain lock because we
 651                  * probabilly will need to manipulate waiters flags.
 652                  */
 653                 sleepq_lock(&lk->lock_object);
 654                 x = lockmgr_read_value(lk);
 655 retry_sleepq:
 656
 657                 /*
 658                  * if the lock can be acquired in shared mode, try
 659                  * again.
 660                  */
 661                 if (LK_CAN_SHARE(x, flags, false)) {
 662                         sleepq_release(&lk->lock_object);
 663                         continue;
 664                 }
 665
 666                 /*
 667                  * Try to set the LK_SHARED_WAITERS flag.  If we fail,
 668                  * loop back and retry.
 669                  */
 670                 if ((x & LK_SHARED_WAITERS) == 0) {
 671                         if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 672                             x | LK_SHARED_WAITERS)) {
 673                                 goto retry_sleepq;
 674                         }
 675                         LOCK_LOG2(lk, "%s: %p set shared waiters flag",
 676                             __func__, lk);
 677                 }
 678
 679                 if (lwa == NULL) {
 680                         iwmesg = lk->lock_object.lo_name;
 681                         ipri = lk->lk_pri;
 682                         itimo = lk->lk_timo;
 683                 } else {
 684                         iwmesg = lwa->iwmesg;
 685                         ipri = lwa->ipri;
 686                         itimo = lwa->itimo;
 687                 }
 688
 689                 /*
 690                  * As far as we have been unable to acquire the
 691                  * shared lock and the shared waiters flag is set,
 692                  * we will sleep.
 693                  */
 694 #ifdef KDTRACE_HOOKS
 695                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 696 #endif
 697                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 698                     SQ_SHARED_QUEUE);
 699 #ifdef KDTRACE_HOOKS
 700                 sleep_time += lockstat_nsecs(&lk->lock_object);
 701 #endif
 702                 flags &= ~LK_INTERLOCK;
 703                 if (error) {
 704                         LOCK_LOG3(lk,
 705                             "%s: interrupted sleep for %p with %d",
 706                             __func__, lk, error);
 707                         break;
 708                 }
 709                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 710                     __func__, lk);
 711                 x = lockmgr_read_value(lk);
 712         }
 713         if (error == 0) {
 714 #ifdef KDTRACE_HOOKS
 715                 if (sleep_time != 0)
 716                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 717                             LOCKSTAT_READER, (x & LK_SHARE) == 0,
 718                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 719 #endif
 720 #ifdef LOCK_PROFILING
 721                 lockmgr_note_shared_acquire(lk, contested, waittime,
 722                     file, line, flags);
 723 #else
 724                 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
 725                     flags);
 726 #endif
 727         }
 728
 729 out:
 730         lockmgr_exit(flags, ilk, 0);
 731         return (error);
 732 }
 733
 734 static bool
 735 lockmgr_xlock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp)
 736 {
 737         struct thread *owner;
 738         uintptr_t x;
 739
 740         x = *xp;
 741         MPASS(x != LK_UNLOCKED);
 742         owner = (struct thread *)LK_HOLDER(x);
 743         for (;;) {
 744                 MPASS(owner != curthread);
 745                 if (owner == NULL)
 746                         return (false);
 747                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
 748                         return (false);
 749                 if (owner == (struct thread *)LK_KERNPROC)
 750                         return (false);
 751                 if (!TD_IS_RUNNING(owner))
 752                         return (false);
 753                 if ((x & LK_ALL_WAITERS) != 0)
 754                         return (false);
 755                 lock_delay(lda);
 756                 x = lockmgr_read_value(lk);
 757                 if (x == LK_UNLOCKED) {
 758                         *xp = x;
 759                         return (true);
 760                 }
 761                 owner = (struct thread *)LK_HOLDER(x);
 762         }
 763 }
 764
 765 static __noinline int
 766 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 767     const char *file, int line, struct lockmgr_wait *lwa)
 768 {
 769         struct lock_class *class;
 770         uintptr_t tid, x, v;
 771         int error = 0;
 772         const char *iwmesg;
 773         int ipri, itimo;
 774
 775 #ifdef KDTRACE_HOOKS
 776         uint64_t sleep_time = 0;
 777 #endif
 778 #ifdef LOCK_PROFILING
 779         uint64_t waittime = 0;
 780         int contested = 0;
 781 #endif
 782         struct lock_delay_arg lda;
 783
 784         if (KERNEL_PANICKED())
 785                 goto out;
 786
 787         tid = (uintptr_t)curthread;
 788
 789         if (LK_CAN_WITNESS(flags))
 790                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 791                     LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 792                     ilk : NULL);
 793
 794         /*
 795          * If curthread already holds the lock and this one is
 796          * allowed to recurse, simply recurse on it.
 797          */
 798         if (lockmgr_xlocked(lk)) {
 799                 if ((flags & LK_CANRECURSE) == 0 &&
 800                     (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
 801                         /*
 802                          * If the lock is expected to not panic just
 803                          * give up and return.
 804                          */
 805                         if (LK_TRYOP(flags)) {
 806                                 LOCK_LOG2(lk,
 807                                     "%s: %p fails the try operation",
 808                                     __func__, lk);
 809                                 error = EBUSY;
 810                                 goto out;
 811                         }
 812                         if (flags & LK_INTERLOCK) {
 813                                 class = LOCK_CLASS(ilk);
 814                                 class->lc_unlock(ilk);
 815                         }
 816                         STACK_PRINT(lk);
 817                         panic("%s: recursing on non recursive lockmgr %p "
 818                             "@ %s:%d\n", __func__, lk, file, line);
 819                 }
 820                 atomic_set_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
 821                 lk->lk_recurse++;
 822                 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
 823                 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 824                     lk->lk_recurse, file, line);
 825                 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 826                     LK_TRYWIT(flags), file, line);
 827                 TD_LOCKS_INC(curthread);
 828                 goto out;
 829         }
 830
 831         x = LK_UNLOCKED;
 832         lock_delay_arg_init(&lda, &lockmgr_delay);
 833         if (!lk_adaptive)
 834                 flags &= ~LK_ADAPTIVE;
 835         for (;;) {
 836                 if (x == LK_UNLOCKED) {
 837                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, tid))
 838                                 break;
 839                         continue;
 840                 }
 841                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
 842                         if (lockmgr_xlock_adaptive(&lda, lk, &x))
 843                                 continue;
 844                 }
 845 #ifdef HWPMC_HOOKS
 846                 PMC_SOFT_CALL( , , lock, failed);
 847 #endif
 848                 lock_profile_obtain_lock_failed(&lk->lock_object,
 849                     &contested, &waittime);
 850
 851                 /*
 852                  * If the lock is expected to not sleep just give up
 853                  * and return.
 854                  */
 855                 if (LK_TRYOP(flags)) {
 856                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 857                             __func__, lk);
 858                         error = EBUSY;
 859                         break;
 860                 }
 861
 862                 /*
 863                  * Acquire the sleepqueue chain lock because we
 864                  * probabilly will need to manipulate waiters flags.
 865                  */
 866                 sleepq_lock(&lk->lock_object);
 867                 x = lockmgr_read_value(lk);
 868 retry_sleepq:
 869
 870                 /*
 871                  * if the lock has been released while we spun on
 872                  * the sleepqueue chain lock just try again.
 873                  */
 874                 if (x == LK_UNLOCKED) {
 875                         sleepq_release(&lk->lock_object);
 876                         continue;
 877                 }
 878
 879                 /*
 880                  * The lock can be in the state where there is a
 881                  * pending queue of waiters, but still no owner.
 882                  * This happens when the lock is contested and an
 883                  * owner is going to claim the lock.
 884                  * If curthread is the one successfully acquiring it
 885                  * claim lock ownership and return, preserving waiters
 886                  * flags.
 887                  */
 888                 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 889                 if ((x & ~v) == LK_UNLOCKED) {
 890                         v &= ~LK_EXCLUSIVE_SPINNERS;
 891                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 892                             tid | v)) {
 893                                 sleepq_release(&lk->lock_object);
 894                                 LOCK_LOG2(lk,
 895                                     "%s: %p claimed by a new writer",
 896                                     __func__, lk);
 897                                 break;
 898                         }
 899                         goto retry_sleepq;
 900                 }
 901
 902                 /*
 903                  * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
 904                  * fail, loop back and retry.
 905                  */
 906                 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
 907                         if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
 908                             x | LK_EXCLUSIVE_WAITERS)) {
 909                                 goto retry_sleepq;
 910                         }
 911                         LOCK_LOG2(lk, "%s: %p set excl waiters flag",
 912                             __func__, lk);
 913                 }
 914
 915                 if (lwa == NULL) {
 916                         iwmesg = lk->lock_object.lo_name;
 917                         ipri = lk->lk_pri;
 918                         itimo = lk->lk_timo;
 919                 } else {
 920                         iwmesg = lwa->iwmesg;
 921                         ipri = lwa->ipri;
 922                         itimo = lwa->itimo;
 923                 }
 924
 925                 /*
 926                  * As far as we have been unable to acquire the
 927                  * exclusive lock and the exclusive waiters flag
 928                  * is set, we will sleep.
 929                  */
 930 #ifdef KDTRACE_HOOKS
 931                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 932 #endif
 933                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 934                     SQ_EXCLUSIVE_QUEUE);
 935 #ifdef KDTRACE_HOOKS
 936                 sleep_time += lockstat_nsecs(&lk->lock_object);
 937 #endif
 938                 flags &= ~LK_INTERLOCK;
 939                 if (error) {
 940                         LOCK_LOG3(lk,
 941                             "%s: interrupted sleep for %p with %d",
 942                             __func__, lk, error);
 943                         break;
 944                 }
 945                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 946                     __func__, lk);
 947                 x = lockmgr_read_value(lk);
 948         }
 949         if (error == 0) {
 950 #ifdef KDTRACE_HOOKS
 951                 if (sleep_time != 0)
 952                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 953                             LOCKSTAT_WRITER, (x & LK_SHARE) == 0,
 954                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 955 #endif
 956 #ifdef LOCK_PROFILING
 957                 lockmgr_note_exclusive_acquire(lk, contested, waittime,
 958                     file, line, flags);
 959 #else
 960                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 961                     flags);
 962 #endif
 963         }
 964
 965 out:
 966         lockmgr_exit(flags, ilk, 0);
 967         return (error);
 968 }
 969
 970 static __noinline int
 971 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
 972     const char *file, int line, struct lockmgr_wait *lwa)
 973 {
 974         uintptr_t tid, v, setv;
 975         int error = 0;
 976         int op;
 977
 978         if (KERNEL_PANICKED())
 979                 goto out;
 980
 981         tid = (uintptr_t)curthread;
 982
 983         _lockmgr_assert(lk, KA_SLOCKED, file, line);
 984
 985         op = flags & LK_TYPE_MASK;
 986         v = lockmgr_read_value(lk);
 987         for (;;) {
 988                 if (LK_SHARERS_LOCK(v) > 1) {
 989                         if (op == LK_TRYUPGRADE) {
 990                                 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
 991                                     __func__, lk);
 992                                 error = EBUSY;
 993                                 goto out;
 994                         }
 995                         if (lockmgr_sunlock_try(lk, &v)) {
 996                                 lockmgr_note_shared_release(lk, file, line);
 997                                 goto out_xlock;
 998                         }
 999                 }
1000                 MPASS((v & ~LK_ALL_WAITERS) == LK_SHARERS_LOCK(1));
1001
1002                 setv = tid;
1003                 setv |= (v & LK_ALL_WAITERS);
1004
1005                 /*
1006                  * Try to switch from one shared lock to an exclusive one.
1007                  * We need to preserve waiters flags during the operation.
1008                  */
1009                 if (atomic_fcmpset_ptr(&lk->lk_lock, &v, setv)) {
1010                         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
1011                             line);
1012                         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
1013                             LK_TRYWIT(flags), file, line);
1014                         LOCKSTAT_RECORD0(lockmgr__upgrade, lk);
1015                         TD_SLOCKS_DEC(curthread);
1016                         goto out;
1017                 }
1018         }
1019
1020 out_xlock:
1021         error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
1022         flags &= ~LK_INTERLOCK;
1023 out:
1024         lockmgr_exit(flags, ilk, 0);
1025         return (error);
1026 }
1027
1028 int
1029 lockmgr_lock_flags(struct lock *lk, u_int flags, struct lock_object *ilk,
1030     const char *file, int line)
1031 {
1032         struct lock_class *class;
1033         uintptr_t x, tid;
1034         u_int op;
1035         bool locked;
1036
1037         if (KERNEL_PANICKED())
1038                 return (0);
1039
1040         op = flags & LK_TYPE_MASK;
1041         locked = false;
1042         switch (op) {
1043         case LK_SHARED:
1044                 if (LK_CAN_WITNESS(flags))
1045                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
1046                             file, line, flags & LK_INTERLOCK ? ilk : NULL);
1047                 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
1048                         break;
1049                 x = lockmgr_read_value(lk);
1050                 if (lockmgr_slock_try(lk, &x, flags, true)) {
1051                         lockmgr_note_shared_acquire(lk, 0, 0,
1052                             file, line, flags);
1053                         locked = true;
1054                 } else {
1055                         return (lockmgr_slock_hard(lk, flags, ilk, file, line,
1056                             NULL));
1057                 }
1058                 break;
1059         case LK_EXCLUSIVE:
1060                 if (LK_CAN_WITNESS(flags))
1061                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1062                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1063                             ilk : NULL);
1064                 tid = (uintptr_t)curthread;
1065                 if (lockmgr_read_value(lk) == LK_UNLOCKED &&
1066                     atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1067                         lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
1068                             flags);
1069                         locked = true;
1070                 } else {
1071                         return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
1072                             NULL));
1073                 }
1074                 break;
1075         case LK_UPGRADE:
1076         case LK_TRYUPGRADE:
1077                 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
1078         default:
1079                 break;
1080         }
1081         if (__predict_true(locked)) {
1082                 if (__predict_false(flags & LK_INTERLOCK)) {
1083                         class = LOCK_CLASS(ilk);
1084                         class->lc_unlock(ilk);
1085                 }
1086                 return (0);
1087         } else {
1088                 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
1089                     LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
1090         }
1091 }
1092
1093 static __noinline int
1094 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1095     const char *file, int line)
1096
1097 {
1098         int wakeup_swapper = 0;
1099
1100         if (KERNEL_PANICKED())
1101                 goto out;
1102
1103         wakeup_swapper = wakeupshlk(lk, file, line);
1104
1105 out:
1106         lockmgr_exit(flags, ilk, wakeup_swapper);
1107         return (0);
1108 }
1109
1110 static __noinline int
1111 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1112     const char *file, int line)
1113 {
1114         uintptr_t tid, v;
1115         int wakeup_swapper = 0;
1116         u_int realexslp;
1117         int queue;
1118
1119         if (KERNEL_PANICKED())
1120                 goto out;
1121
1122         tid = (uintptr_t)curthread;
1123
1124         /*
1125          * As first option, treact the lock as if it has not
1126          * any waiter.
1127          * Fix-up the tid var if the lock has been disowned.
1128          */
1129         if (LK_HOLDER(x) == LK_KERNPROC)
1130                 tid = LK_KERNPROC;
1131
1132         /*
1133          * The lock is held in exclusive mode.
1134          * If the lock is recursed also, then unrecurse it.
1135          */
1136         if (lockmgr_recursed_v(x)) {
1137                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
1138                 lk->lk_recurse--;
1139                 if (lk->lk_recurse == 0)
1140                         atomic_clear_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
1141                 goto out;
1142         }
1143         if (tid != LK_KERNPROC)
1144                 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,
1145                     LOCKSTAT_WRITER);
1146
1147         if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
1148                 goto out;
1149
1150         sleepq_lock(&lk->lock_object);
1151         x = lockmgr_read_value(lk);
1152         v = LK_UNLOCKED;
1153
1154         /*
1155          * If the lock has exclusive waiters, give them
1156          * preference in order to avoid deadlock with
1157          * shared runners up.
1158          * If interruptible sleeps left the exclusive queue
1159          * empty avoid a starvation for the threads sleeping
1160          * on the shared queue by giving them precedence
1161          * and cleaning up the exclusive waiters bit anyway.
1162          * Please note that lk_exslpfail count may be lying
1163          * about the real number of waiters with the
1164          * LK_SLEEPFAIL flag on because they may be used in
1165          * conjunction with interruptible sleeps so
1166          * lk_exslpfail might be considered an 'upper limit'
1167          * bound, including the edge cases.
1168          */
1169         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1170         realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
1171         if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1172                 if (lk->lk_exslpfail < realexslp) {
1173                         lk->lk_exslpfail = 0;
1174                         queue = SQ_EXCLUSIVE_QUEUE;
1175                         v |= (x & LK_SHARED_WAITERS);
1176                 } else {
1177                         lk->lk_exslpfail = 0;
1178                         LOCK_LOG2(lk,
1179                             "%s: %p has only LK_SLEEPFAIL sleepers",
1180                             __func__, lk);
1181                         LOCK_LOG2(lk,
1182                             "%s: %p waking up threads on the exclusive queue",
1183                             __func__, lk);
1184                         wakeup_swapper = sleepq_broadcast(&lk->lock_object,
1185                             SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1186                         queue = SQ_SHARED_QUEUE;
1187                 }
1188         } else {
1189
1190                 /*
1191                  * Exclusive waiters sleeping with LK_SLEEPFAIL
1192                  * on and using interruptible sleeps/timeout
1193                  * may have left spourious lk_exslpfail counts
1194                  * on, so clean it up anyway.
1195                  */
1196                 lk->lk_exslpfail = 0;
1197                 queue = SQ_SHARED_QUEUE;
1198         }
1199
1200         LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
1201             __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1202             "exclusive");
1203         atomic_store_rel_ptr(&lk->lk_lock, v);
1204         wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue);
1205         sleepq_release(&lk->lock_object);
1206
1207 out:
1208         lockmgr_exit(flags, ilk, wakeup_swapper);
1209         return (0);
1210 }
1211
1212 /*
1213  * Lightweight entry points for common operations.
1214  *
1215  * Functionality is similar to sx locks, in that none of the additional lockmgr
1216  * features are supported. To be clear, these are NOT supported:
1217  * 1. shared locking disablement
1218  * 2. returning with an error after sleep
1219  * 3. unlocking the interlock
1220  *
1221  * If in doubt, use lockmgr_lock_flags.
1222  */
1223 int
1224 lockmgr_slock(struct lock *lk, u_int flags, const char *file, int line)
1225 {
1226         uintptr_t x;
1227
1228         MPASS((flags & LK_TYPE_MASK) == LK_SHARED);
1229         MPASS((flags & LK_INTERLOCK) == 0);
1230         MPASS((lk->lock_object.lo_flags & LK_NOSHARE) == 0);
1231
1232         if (LK_CAN_WITNESS(flags))
1233                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
1234                     file, line, NULL);
1235         x = lockmgr_read_value(lk);
1236         if (__predict_true(lockmgr_slock_try(lk, &x, flags, true))) {
1237                 lockmgr_note_shared_acquire(lk, 0, 0, file, line, flags);
1238                 return (0);
1239         }
1240
1241         return (lockmgr_slock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL));
1242 }
1243
1244 int
1245 lockmgr_xlock(struct lock *lk, u_int flags, const char *file, int line)
1246 {
1247         uintptr_t tid;
1248
1249         MPASS((flags & LK_TYPE_MASK) == LK_EXCLUSIVE);
1250         MPASS((flags & LK_INTERLOCK) == 0);
1251
1252         if (LK_CAN_WITNESS(flags))
1253                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1254                     LOP_EXCLUSIVE, file, line, NULL);
1255         tid = (uintptr_t)curthread;
1256         if (atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1257                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
1258                     flags);
1259                 return (0);
1260         }
1261
1262         return (lockmgr_xlock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL));
1263 }
1264
1265 int
1266 lockmgr_unlock(struct lock *lk)
1267 {
1268         uintptr_t x, tid;
1269         const char *file;
1270         int line;
1271
1272         file = __FILE__;
1273         line = __LINE__;
1274
1275         _lockmgr_assert(lk, KA_LOCKED, file, line);
1276         x = lockmgr_read_value(lk);
1277         if (__predict_true(x & LK_SHARE) != 0) {
1278                 lockmgr_note_shared_release(lk, file, line);
1279                 if (lockmgr_sunlock_try(lk, &x)) {
1280                         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
1281                 } else {
1282                         return (lockmgr_sunlock_hard(lk, x, LK_RELEASE, NULL, file, line));
1283                 }
1284         } else {
1285                 tid = (uintptr_t)curthread;
1286                 lockmgr_note_exclusive_release(lk, file, line);
1287                 if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
1288                         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,LOCKSTAT_WRITER);
1289                 } else {
1290                         return (lockmgr_xunlock_hard(lk, x, LK_RELEASE, NULL, file, line));
1291                 }
1292         }
1293         return (0);
1294 }
1295
1296 int
1297 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
1298     const char *wmesg, int pri, int timo, const char *file, int line)
1299 {
1300         GIANT_DECLARE;
1301         struct lockmgr_wait lwa;
1302         struct lock_class *class;
1303         const char *iwmesg;
1304         uintptr_t tid, v, x;
1305         u_int op, realexslp;
1306         int error, ipri, itimo, queue, wakeup_swapper;
1307 #ifdef LOCK_PROFILING
1308         uint64_t waittime = 0;
1309         int contested = 0;
1310 #endif
1311
1312         if (KERNEL_PANICKED())
1313                 return (0);
1314
1315         error = 0;
1316         tid = (uintptr_t)curthread;
1317         op = (flags & LK_TYPE_MASK);
1318         iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
1319         ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
1320         itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
1321
1322         lwa.iwmesg = iwmesg;
1323         lwa.ipri = ipri;
1324         lwa.itimo = itimo;
1325
1326         MPASS((flags & ~LK_TOTAL_MASK) == 0);
1327         KASSERT((op & (op - 1)) == 0,
1328             ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
1329         KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
1330             (op != LK_DOWNGRADE && op != LK_RELEASE),
1331             ("%s: Invalid flags in regard of the operation desired @ %s:%d",
1332             __func__, file, line));
1333         KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
1334             ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
1335             __func__, file, line));
1336         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
1337             ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
1338             lk->lock_object.lo_name, file, line));
1339
1340         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
1341
1342         if (lk->lock_object.lo_flags & LK_NOSHARE) {
1343                 switch (op) {
1344                 case LK_SHARED:
1345                         op = LK_EXCLUSIVE;
1346                         break;
1347                 case LK_UPGRADE:
1348                 case LK_TRYUPGRADE:
1349                 case LK_DOWNGRADE:
1350                         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
1351                             file, line);
1352                         if (flags & LK_INTERLOCK)
1353                                 class->lc_unlock(ilk);
1354                         return (0);
1355                 }
1356         }
1357
1358         wakeup_swapper = 0;
1359         switch (op) {
1360         case LK_SHARED:
1361                 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa));
1362                 break;
1363         case LK_UPGRADE:
1364         case LK_TRYUPGRADE:
1365                 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa));
1366                 break;
1367         case LK_EXCLUSIVE:
1368                 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa));
1369                 break;
1370         case LK_DOWNGRADE:
1371                 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1372                 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
1373
1374                 /*
1375                  * Panic if the lock is recursed.
1376                  */
1377                 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1378                         if (flags & LK_INTERLOCK)
1379                                 class->lc_unlock(ilk);
1380                         panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
1381                             __func__, iwmesg, file, line);
1382                 }
1383                 TD_SLOCKS_INC(curthread);
1384
1385                 /*
1386                  * In order to preserve waiters flags, just spin.
1387                  */
1388                 for (;;) {
1389                         x = lockmgr_read_value(lk);
1390                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1391                         x &= LK_ALL_WAITERS;
1392                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1393                             LK_SHARERS_LOCK(1) | x))
1394                                 break;
1395                         cpu_spinwait();
1396                 }
1397                 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
1398                 LOCKSTAT_RECORD0(lockmgr__downgrade, lk);
1399                 break;
1400         case LK_RELEASE:
1401                 _lockmgr_assert(lk, KA_LOCKED, file, line);
1402                 x = lockmgr_read_value(lk);
1403
1404                 if (__predict_true(x & LK_SHARE) != 0) {
1405                         lockmgr_note_shared_release(lk, file, line);
1406                         return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1407                 } else {
1408                         lockmgr_note_exclusive_release(lk, file, line);
1409                         return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1410                 }
1411                 break;
1412         case LK_DRAIN:
1413                 if (LK_CAN_WITNESS(flags))
1414                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1415                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1416                             ilk : NULL);
1417
1418                 /*
1419                  * Trying to drain a lock we already own will result in a
1420                  * deadlock.
1421                  */
1422                 if (lockmgr_xlocked(lk)) {
1423                         if (flags & LK_INTERLOCK)
1424                                 class->lc_unlock(ilk);
1425                         panic("%s: draining %s with the lock held @ %s:%d\n",
1426                             __func__, iwmesg, file, line);
1427                 }
1428
1429                 for (;;) {
1430                         if (lk->lk_lock == LK_UNLOCKED &&
1431                             atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
1432                                 break;
1433
1434 #ifdef HWPMC_HOOKS
1435                         PMC_SOFT_CALL( , , lock, failed);
1436 #endif
1437                         lock_profile_obtain_lock_failed(&lk->lock_object,
1438                             &contested, &waittime);
1439
1440                         /*
1441                          * If the lock is expected to not sleep just give up
1442                          * and return.
1443                          */
1444                         if (LK_TRYOP(flags)) {
1445                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
1446                                     __func__, lk);
1447                                 error = EBUSY;
1448                                 break;
1449                         }
1450
1451                         /*
1452                          * Acquire the sleepqueue chain lock because we
1453                          * probabilly will need to manipulate waiters flags.
1454                          */
1455                         sleepq_lock(&lk->lock_object);
1456                         x = lockmgr_read_value(lk);
1457
1458                         /*
1459                          * if the lock has been released while we spun on
1460                          * the sleepqueue chain lock just try again.
1461                          */
1462                         if (x == LK_UNLOCKED) {
1463                                 sleepq_release(&lk->lock_object);
1464                                 continue;
1465                         }
1466
1467                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1468                         if ((x & ~v) == LK_UNLOCKED) {
1469                                 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1470
1471                                 /*
1472                                  * If interruptible sleeps left the exclusive
1473                                  * queue empty avoid a starvation for the
1474                                  * threads sleeping on the shared queue by
1475                                  * giving them precedence and cleaning up the
1476                                  * exclusive waiters bit anyway.
1477                                  * Please note that lk_exslpfail count may be
1478                                  * lying about the real number of waiters with
1479                                  * the LK_SLEEPFAIL flag on because they may
1480                                  * be used in conjunction with interruptible
1481                                  * sleeps so lk_exslpfail might be considered
1482                                  * an 'upper limit' bound, including the edge
1483                                  * cases.
1484                                  */
1485                                 if (v & LK_EXCLUSIVE_WAITERS) {
1486                                         queue = SQ_EXCLUSIVE_QUEUE;
1487                                         v &= ~LK_EXCLUSIVE_WAITERS;
1488                                 } else {
1489
1490                                         /*
1491                                          * Exclusive waiters sleeping with
1492                                          * LK_SLEEPFAIL on and using
1493                                          * interruptible sleeps/timeout may
1494                                          * have left spourious lk_exslpfail
1495                                          * counts on, so clean it up anyway.
1496                                          */
1497                                         MPASS(v & LK_SHARED_WAITERS);
1498                                         lk->lk_exslpfail = 0;
1499                                         queue = SQ_SHARED_QUEUE;
1500                                         v &= ~LK_SHARED_WAITERS;
1501                                 }
1502                                 if (queue == SQ_EXCLUSIVE_QUEUE) {
1503                                         realexslp =
1504                                             sleepq_sleepcnt(&lk->lock_object,
1505                                             SQ_EXCLUSIVE_QUEUE);
1506                                         if (lk->lk_exslpfail >= realexslp) {
1507                                                 lk->lk_exslpfail = 0;
1508                                                 queue = SQ_SHARED_QUEUE;
1509                                                 v &= ~LK_SHARED_WAITERS;
1510                                                 if (realexslp != 0) {
1511                                                         LOCK_LOG2(lk,
1512                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1513                                                             __func__, lk);
1514                                                         LOCK_LOG2(lk,
1515                         "%s: %p waking up threads on the exclusive queue",
1516                                                             __func__, lk);
1517                                                         wakeup_swapper =
1518                                                             sleepq_broadcast(
1519                                                             &lk->lock_object,
1520                                                             SLEEPQ_LK, 0,
1521                                                             SQ_EXCLUSIVE_QUEUE);
1522                                                 }
1523                                         } else
1524                                                 lk->lk_exslpfail = 0;
1525                                 }
1526                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1527                                         sleepq_release(&lk->lock_object);
1528                                         continue;
1529                                 }
1530                                 LOCK_LOG3(lk,
1531                                 "%s: %p waking up all threads on the %s queue",
1532                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
1533                                     "shared" : "exclusive");
1534                                 wakeup_swapper |= sleepq_broadcast(
1535                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
1536
1537                                 /*
1538                                  * If shared waiters have been woken up we need
1539                                  * to wait for one of them to acquire the lock
1540                                  * before to set the exclusive waiters in
1541                                  * order to avoid a deadlock.
1542                                  */
1543                                 if (queue == SQ_SHARED_QUEUE) {
1544                                         for (v = lk->lk_lock;
1545                                             (v & LK_SHARE) && !LK_SHARERS(v);
1546                                             v = lk->lk_lock)
1547                                                 cpu_spinwait();
1548                                 }
1549                         }
1550
1551                         /*
1552                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1553                          * fail, loop back and retry.
1554                          */
1555                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1556                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1557                                     x | LK_EXCLUSIVE_WAITERS)) {
1558                                         sleepq_release(&lk->lock_object);
1559                                         continue;
1560                                 }
1561                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1562                                     __func__, lk);
1563                         }
1564
1565                         /*
1566                          * As far as we have been unable to acquire the
1567                          * exclusive lock and the exclusive waiters flag
1568                          * is set, we will sleep.
1569                          */
1570                         if (flags & LK_INTERLOCK) {
1571                                 class->lc_unlock(ilk);
1572                                 flags &= ~LK_INTERLOCK;
1573                         }
1574                         GIANT_SAVE();
1575                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1576                             SQ_EXCLUSIVE_QUEUE);
1577                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1578                         GIANT_RESTORE();
1579                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1580                             __func__, lk);
1581                 }
1582
1583                 if (error == 0) {
1584                         lock_profile_obtain_lock_success(&lk->lock_object,
1585                             contested, waittime, file, line);
1586                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1587                             lk->lk_recurse, file, line);
1588                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1589                             LK_TRYWIT(flags), file, line);
1590                         TD_LOCKS_INC(curthread);
1591                         STACK_SAVE(lk);
1592                 }
1593                 break;
1594         default:
1595                 if (flags & LK_INTERLOCK)
1596                         class->lc_unlock(ilk);
1597                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1598         }
1599
1600         if (flags & LK_INTERLOCK)
1601                 class->lc_unlock(ilk);
1602         if (wakeup_swapper)
1603                 kick_proc0();
1604
1605         return (error);
1606 }
1607
1608 void
1609 _lockmgr_disown(struct lock *lk, const char *file, int line)
1610 {
1611         uintptr_t tid, x;
1612
1613         if (SCHEDULER_STOPPED())
1614                 return;
1615
1616         tid = (uintptr_t)curthread;
1617         _lockmgr_assert(lk, KA_XLOCKED, file, line);
1618
1619         /*
1620          * Panic if the lock is recursed.
1621          */
1622         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1623                 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1624                     __func__,  file, line);
1625
1626         /*
1627          * If the owner is already LK_KERNPROC just skip the whole operation.
1628          */
1629         if (LK_HOLDER(lk->lk_lock) != tid)
1630                 return;
1631         lock_profile_release_lock(&lk->lock_object);
1632         LOCKSTAT_RECORD1(lockmgr__disown, lk, LOCKSTAT_WRITER);
1633         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1634         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1635         TD_LOCKS_DEC(curthread);
1636         STACK_SAVE(lk);
1637
1638         /*
1639          * In order to preserve waiters flags, just spin.
1640          */
1641         for (;;) {
1642                 x = lockmgr_read_value(lk);
1643                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1644                 x &= LK_ALL_WAITERS;
1645                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1646                     LK_KERNPROC | x))
1647                         return;
1648                 cpu_spinwait();
1649         }
1650 }
1651
1652 void
1653 lockmgr_printinfo(const struct lock *lk)
1654 {
1655         struct thread *td;
1656         uintptr_t x;
1657
1658         if (lk->lk_lock == LK_UNLOCKED)
1659                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1660         else if (lk->lk_lock & LK_SHARE)
1661                 printf("lock type %s: SHARED (count %ju)\n",
1662                     lk->lock_object.lo_name,
1663                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1664         else {
1665                 td = lockmgr_xholder(lk);
1666                 if (td == (struct thread *)LK_KERNPROC)
1667                         printf("lock type %s: EXCL by KERNPROC\n",
1668                             lk->lock_object.lo_name);
1669                 else
1670                         printf("lock type %s: EXCL by thread %p "
1671                             "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1672                             td, td->td_proc->p_pid, td->td_proc->p_comm,
1673                             td->td_tid);
1674         }
1675
1676         x = lk->lk_lock;
1677         if (x & LK_EXCLUSIVE_WAITERS)
1678                 printf(" with exclusive waiters pending\n");
1679         if (x & LK_SHARED_WAITERS)
1680                 printf(" with shared waiters pending\n");
1681         if (x & LK_EXCLUSIVE_SPINNERS)
1682                 printf(" with exclusive spinners pending\n");
1683
1684         STACK_PRINT(lk);
1685 }
1686
1687 int
1688 lockstatus(const struct lock *lk)
1689 {
1690         uintptr_t v, x;
1691         int ret;
1692
1693         ret = LK_SHARED;
1694         x = lockmgr_read_value(lk);
1695         v = LK_HOLDER(x);
1696
1697         if ((x & LK_SHARE) == 0) {
1698                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1699                         ret = LK_EXCLUSIVE;
1700                 else
1701                         ret = LK_EXCLOTHER;
1702         } else if (x == LK_UNLOCKED)
1703                 ret = 0;
1704
1705         return (ret);
1706 }
1707
1708 #ifdef INVARIANT_SUPPORT
1709
1710 FEATURE(invariant_support,
1711     "Support for modules compiled with INVARIANTS option");
1712
1713 #ifndef INVARIANTS
1714 #undef  _lockmgr_assert
1715 #endif
1716
1717 void
1718 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1719 {
1720         int slocked = 0;
1721
1722         if (KERNEL_PANICKED())
1723                 return;
1724         switch (what) {
1725         case KA_SLOCKED:
1726         case KA_SLOCKED | KA_NOTRECURSED:
1727         case KA_SLOCKED | KA_RECURSED:
1728                 slocked = 1;
1729         case KA_LOCKED:
1730         case KA_LOCKED | KA_NOTRECURSED:
1731         case KA_LOCKED | KA_RECURSED:
1732 #ifdef WITNESS
1733
1734                 /*
1735                  * We cannot trust WITNESS if the lock is held in exclusive
1736                  * mode and a call to lockmgr_disown() happened.
1737                  * Workaround this skipping the check if the lock is held in
1738                  * exclusive mode even for the KA_LOCKED case.
1739                  */
1740                 if (slocked || (lk->lk_lock & LK_SHARE)) {
1741                         witness_assert(&lk->lock_object, what, file, line);
1742                         break;
1743                 }
1744 #endif
1745                 if (lk->lk_lock == LK_UNLOCKED ||
1746                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1747                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1748                         panic("Lock %s not %slocked @ %s:%d\n",
1749                             lk->lock_object.lo_name, slocked ? "share" : "",
1750                             file, line);
1751
1752                 if ((lk->lk_lock & LK_SHARE) == 0) {
1753                         if (lockmgr_recursed(lk)) {
1754                                 if (what & KA_NOTRECURSED)
1755                                         panic("Lock %s recursed @ %s:%d\n",
1756                                             lk->lock_object.lo_name, file,
1757                                             line);
1758                         } else if (what & KA_RECURSED)
1759                                 panic("Lock %s not recursed @ %s:%d\n",
1760                                     lk->lock_object.lo_name, file, line);
1761                 }
1762                 break;
1763         case KA_XLOCKED:
1764         case KA_XLOCKED | KA_NOTRECURSED:
1765         case KA_XLOCKED | KA_RECURSED:
1766                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1767                         panic("Lock %s not exclusively locked @ %s:%d\n",
1768                             lk->lock_object.lo_name, file, line);
1769                 if (lockmgr_recursed(lk)) {
1770                         if (what & KA_NOTRECURSED)
1771                                 panic("Lock %s recursed @ %s:%d\n",
1772                                     lk->lock_object.lo_name, file, line);
1773                 } else if (what & KA_RECURSED)
1774                         panic("Lock %s not recursed @ %s:%d\n",
1775                             lk->lock_object.lo_name, file, line);
1776                 break;
1777         case KA_UNLOCKED:
1778                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1779                         panic("Lock %s exclusively locked @ %s:%d\n",
1780                             lk->lock_object.lo_name, file, line);
1781                 break;
1782         default:
1783                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1784                     line);
1785         }
1786 }
1787 #endif
1788
1789 #ifdef DDB
1790 int
1791 lockmgr_chain(struct thread *td, struct thread **ownerp)
1792 {
1793         const struct lock *lk;
1794
1795         lk = td->td_wchan;
1796
1797         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1798                 return (0);
1799         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1800         if (lk->lk_lock & LK_SHARE)
1801                 db_printf("SHARED (count %ju)\n",
1802                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1803         else
1804                 db_printf("EXCL\n");
1805         *ownerp = lockmgr_xholder(lk);
1806
1807         return (1);
1808 }
1809
1810 static void
1811 db_show_lockmgr(const struct lock_object *lock)
1812 {
1813         struct thread *td;
1814         const struct lock *lk;
1815
1816         lk = (const struct lock *)lock;
1817
1818         db_printf(" state: ");
1819         if (lk->lk_lock == LK_UNLOCKED)
1820                 db_printf("UNLOCKED\n");
1821         else if (lk->lk_lock & LK_SHARE)
1822                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1823         else {
1824                 td = lockmgr_xholder(lk);
1825                 if (td == (struct thread *)LK_KERNPROC)
1826                         db_printf("XLOCK: LK_KERNPROC\n");
1827                 else
1828                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1829                             td->td_tid, td->td_proc->p_pid,
1830                             td->td_proc->p_comm);
1831                 if (lockmgr_recursed(lk))
1832                         db_printf(" recursed: %d\n", lk->lk_recurse);
1833         }
1834         db_printf(" waiters: ");
1835         switch (lk->lk_lock & LK_ALL_WAITERS) {
1836         case LK_SHARED_WAITERS:
1837                 db_printf("shared\n");
1838                 break;
1839         case LK_EXCLUSIVE_WAITERS:
1840                 db_printf("exclusive\n");
1841                 break;
1842         case LK_ALL_WAITERS:
1843                 db_printf("shared and exclusive\n");
1844                 break;
1845         default:
1846                 db_printf("none\n");
1847         }
1848         db_printf(" spinners: ");
1849         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1850                 db_printf("exclusive\n");
1851         else
1852                 db_printf("none\n");
1853 }
1854 #endif