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                          * Exclusive waiters sleeping with LK_SLEEPFAIL on
 369                          * and using interruptible sleeps/timeout may have
 370                          * left spourious lk_exslpfail counts on, so clean
 371                          * it up anyway.
 372                          */
 373                         lk->lk_exslpfail = 0;
 374                         queue = SQ_SHARED_QUEUE;
 375                 }
 376
 377                 if (lockmgr_sunlock_try(lk, &orig_x)) {
 378                         sleepq_release(&lk->lock_object);
 379                         break;
 380                 }
 381
 382                 x |= LK_SHARERS_LOCK(1);
 383                 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
 384                         orig_x = x;
 385                         goto retry_sleepq;
 386                 }
 387                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 388                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 389                     "exclusive");
 390                 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
 391                     0, queue);
 392                 sleepq_release(&lk->lock_object);
 393                 break;
 394         }
 395
 396         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
 397         return (wakeup_swapper);
 398 }
 399
 400 static void
 401 assert_lockmgr(const struct lock_object *lock, int what)
 402 {
 403
 404         panic("lockmgr locks do not support assertions");
 405 }
 406
 407 static void
 408 lock_lockmgr(struct lock_object *lock, uintptr_t how)
 409 {
 410
 411         panic("lockmgr locks do not support sleep interlocking");
 412 }
 413
 414 static uintptr_t
 415 unlock_lockmgr(struct lock_object *lock)
 416 {
 417
 418         panic("lockmgr locks do not support sleep interlocking");
 419 }
 420
 421 #ifdef KDTRACE_HOOKS
 422 static int
 423 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
 424 {
 425
 426         panic("lockmgr locks do not support owner inquiring");
 427 }
 428 #endif
 429
 430 void
 431 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 432 {
 433         int iflags;
 434
 435         MPASS((flags & ~LK_INIT_MASK) == 0);
 436         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
 437             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
 438             &lk->lk_lock));
 439
 440         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
 441         if (flags & LK_CANRECURSE)
 442                 iflags |= LO_RECURSABLE;
 443         if ((flags & LK_NODUP) == 0)
 444                 iflags |= LO_DUPOK;
 445         if (flags & LK_NOPROFILE)
 446                 iflags |= LO_NOPROFILE;
 447         if ((flags & LK_NOWITNESS) == 0)
 448                 iflags |= LO_WITNESS;
 449         if (flags & LK_QUIET)
 450                 iflags |= LO_QUIET;
 451         if (flags & LK_IS_VNODE)
 452                 iflags |= LO_IS_VNODE;
 453         if (flags & LK_NEW)
 454                 iflags |= LO_NEW;
 455         iflags |= flags & LK_NOSHARE;
 456
 457         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
 458         lk->lk_lock = LK_UNLOCKED;
 459         lk->lk_recurse = 0;
 460         lk->lk_exslpfail = 0;
 461         lk->lk_timo = timo;
 462         lk->lk_pri = pri;
 463         STACK_ZERO(lk);
 464 }
 465
 466 /*
 467  * XXX: Gross hacks to manipulate external lock flags after
 468  * initialization.  Used for certain vnode and buf locks.
 469  */
 470 void
 471 lockallowshare(struct lock *lk)
 472 {
 473
 474         lockmgr_assert(lk, KA_XLOCKED);
 475         lk->lock_object.lo_flags &= ~LK_NOSHARE;
 476 }
 477
 478 void
 479 lockdisableshare(struct lock *lk)
 480 {
 481
 482         lockmgr_assert(lk, KA_XLOCKED);
 483         lk->lock_object.lo_flags |= LK_NOSHARE;
 484 }
 485
 486 void
 487 lockallowrecurse(struct lock *lk)
 488 {
 489
 490         lockmgr_assert(lk, KA_XLOCKED);
 491         lk->lock_object.lo_flags |= LO_RECURSABLE;
 492 }
 493
 494 void
 495 lockdisablerecurse(struct lock *lk)
 496 {
 497
 498         lockmgr_assert(lk, KA_XLOCKED);
 499         lk->lock_object.lo_flags &= ~LO_RECURSABLE;
 500 }
 501
 502 void
 503 lockdestroy(struct lock *lk)
 504 {
 505
 506         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
 507         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
 508         KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
 509         lock_destroy(&lk->lock_object);
 510 }
 511
 512 static bool __always_inline
 513 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
 514 {
 515
 516         /*
 517          * If no other thread has an exclusive lock, or
 518          * no exclusive waiter is present, bump the count of
 519          * sharers.  Since we have to preserve the state of
 520          * waiters, if we fail to acquire the shared lock
 521          * loop back and retry.
 522          */
 523         while (LK_CAN_SHARE(*xp, flags, fp)) {
 524                 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
 525                     *xp + LK_ONE_SHARER)) {
 526                         return (true);
 527                 }
 528         }
 529         return (false);
 530 }
 531
 532 static bool __always_inline
 533 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
 534 {
 535
 536         for (;;) {
 537                 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
 538                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
 539                             *xp - LK_ONE_SHARER))
 540                                 return (true);
 541                         continue;
 542                 }
 543                 break;
 544         }
 545         return (false);
 546 }
 547
 548 static bool
 549 lockmgr_slock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp,
 550     int flags)
 551 {
 552         struct thread *owner;
 553         uintptr_t x;
 554
 555         x = *xp;
 556         MPASS(x != LK_UNLOCKED);
 557         owner = (struct thread *)LK_HOLDER(x);
 558         for (;;) {
 559                 MPASS(owner != curthread);
 560                 if (owner == (struct thread *)LK_KERNPROC)
 561                         return (false);
 562                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
 563                         return (false);
 564                 if (owner == NULL)
 565                         return (false);
 566                 if (!TD_IS_RUNNING(owner))
 567                         return (false);
 568                 if ((x & LK_ALL_WAITERS) != 0)
 569                         return (false);
 570                 lock_delay(lda);
 571                 x = lockmgr_read_value(lk);
 572                 if (LK_CAN_SHARE(x, flags, false)) {
 573                         *xp = x;
 574                         return (true);
 575                 }
 576                 owner = (struct thread *)LK_HOLDER(x);
 577         }
 578 }
 579
 580 static __noinline int
 581 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 582     const char *file, int line, struct lockmgr_wait *lwa)
 583 {
 584         uintptr_t tid, x;
 585         int error = 0;
 586         const char *iwmesg;
 587         int ipri, itimo;
 588
 589 #ifdef KDTRACE_HOOKS
 590         uint64_t sleep_time = 0;
 591 #endif
 592 #ifdef LOCK_PROFILING
 593         uint64_t waittime = 0;
 594         int contested = 0;
 595 #endif
 596         struct lock_delay_arg lda;
 597
 598         if (KERNEL_PANICKED())
 599                 goto out;
 600
 601         tid = (uintptr_t)curthread;
 602
 603         if (LK_CAN_WITNESS(flags))
 604                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 605                     file, line, flags & LK_INTERLOCK ? ilk : NULL);
 606         x = lockmgr_read_value(lk);
 607         lock_delay_arg_init(&lda, &lockmgr_delay);
 608         if (!lk_adaptive)
 609                 flags &= ~LK_ADAPTIVE;
 610         /*
 611          * The lock may already be locked exclusive by curthread,
 612          * avoid deadlock.
 613          */
 614         if (LK_HOLDER(x) == tid) {
 615                 LOCK_LOG2(lk,
 616                     "%s: %p already held in exclusive mode",
 617                     __func__, lk);
 618                 error = EDEADLK;
 619                 goto out;
 620         }
 621
 622         for (;;) {
 623                 if (lockmgr_slock_try(lk, &x, flags, false))
 624                         break;
 625
 626                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
 627                         if (lockmgr_slock_adaptive(&lda, lk, &x, flags))
 628                                 continue;
 629                 }
 630
 631 #ifdef HWPMC_HOOKS
 632                 PMC_SOFT_CALL( , , lock, failed);
 633 #endif
 634                 lock_profile_obtain_lock_failed(&lk->lock_object,
 635                     &contested, &waittime);
 636
 637                 /*
 638                  * If the lock is expected to not sleep just give up
 639                  * and return.
 640                  */
 641                 if (LK_TRYOP(flags)) {
 642                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 643                             __func__, lk);
 644                         error = EBUSY;
 645                         break;
 646                 }
 647
 648                 /*
 649                  * Acquire the sleepqueue chain lock because we
 650                  * probabilly will need to manipulate waiters flags.
 651                  */
 652                 sleepq_lock(&lk->lock_object);
 653                 x = lockmgr_read_value(lk);
 654 retry_sleepq:
 655
 656                 /*
 657                  * if the lock can be acquired in shared mode, try
 658                  * again.
 659                  */
 660                 if (LK_CAN_SHARE(x, flags, false)) {
 661                         sleepq_release(&lk->lock_object);
 662                         continue;
 663                 }
 664
 665                 /*
 666                  * Try to set the LK_SHARED_WAITERS flag.  If we fail,
 667                  * loop back and retry.
 668                  */
 669                 if ((x & LK_SHARED_WAITERS) == 0) {
 670                         if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 671                             x | LK_SHARED_WAITERS)) {
 672                                 goto retry_sleepq;
 673                         }
 674                         LOCK_LOG2(lk, "%s: %p set shared waiters flag",
 675                             __func__, lk);
 676                 }
 677
 678                 if (lwa == NULL) {
 679                         iwmesg = lk->lock_object.lo_name;
 680                         ipri = lk->lk_pri;
 681                         itimo = lk->lk_timo;
 682                 } else {
 683                         iwmesg = lwa->iwmesg;
 684                         ipri = lwa->ipri;
 685                         itimo = lwa->itimo;
 686                 }
 687
 688                 /*
 689                  * As far as we have been unable to acquire the
 690                  * shared lock and the shared waiters flag is set,
 691                  * we will sleep.
 692                  */
 693 #ifdef KDTRACE_HOOKS
 694                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 695 #endif
 696                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 697                     SQ_SHARED_QUEUE);
 698 #ifdef KDTRACE_HOOKS
 699                 sleep_time += lockstat_nsecs(&lk->lock_object);
 700 #endif
 701                 flags &= ~LK_INTERLOCK;
 702                 if (error) {
 703                         LOCK_LOG3(lk,
 704                             "%s: interrupted sleep for %p with %d",
 705                             __func__, lk, error);
 706                         break;
 707                 }
 708                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 709                     __func__, lk);
 710                 x = lockmgr_read_value(lk);
 711         }
 712         if (error == 0) {
 713 #ifdef KDTRACE_HOOKS
 714                 if (sleep_time != 0)
 715                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 716                             LOCKSTAT_READER, (x & LK_SHARE) == 0,
 717                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 718 #endif
 719 #ifdef LOCK_PROFILING
 720                 lockmgr_note_shared_acquire(lk, contested, waittime,
 721                     file, line, flags);
 722 #else
 723                 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
 724                     flags);
 725 #endif
 726         }
 727
 728 out:
 729         lockmgr_exit(flags, ilk, 0);
 730         return (error);
 731 }
 732
 733 static bool
 734 lockmgr_xlock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp)
 735 {
 736         struct thread *owner;
 737         uintptr_t x;
 738
 739         x = *xp;
 740         MPASS(x != LK_UNLOCKED);
 741         owner = (struct thread *)LK_HOLDER(x);
 742         for (;;) {
 743                 MPASS(owner != curthread);
 744                 if (owner == NULL)
 745                         return (false);
 746                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
 747                         return (false);
 748                 if (owner == (struct thread *)LK_KERNPROC)
 749                         return (false);
 750                 if (!TD_IS_RUNNING(owner))
 751                         return (false);
 752                 if ((x & LK_ALL_WAITERS) != 0)
 753                         return (false);
 754                 lock_delay(lda);
 755                 x = lockmgr_read_value(lk);
 756                 if (x == LK_UNLOCKED) {
 757                         *xp = x;
 758                         return (true);
 759                 }
 760                 owner = (struct thread *)LK_HOLDER(x);
 761         }
 762 }
 763
 764 static __noinline int
 765 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 766     const char *file, int line, struct lockmgr_wait *lwa)
 767 {
 768         struct lock_class *class;
 769         uintptr_t tid, x, v;
 770         int error = 0;
 771         const char *iwmesg;
 772         int ipri, itimo;
 773
 774 #ifdef KDTRACE_HOOKS
 775         uint64_t sleep_time = 0;
 776 #endif
 777 #ifdef LOCK_PROFILING
 778         uint64_t waittime = 0;
 779         int contested = 0;
 780 #endif
 781         struct lock_delay_arg lda;
 782
 783         if (KERNEL_PANICKED())
 784                 goto out;
 785
 786         tid = (uintptr_t)curthread;
 787
 788         if (LK_CAN_WITNESS(flags))
 789                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 790                     LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 791                     ilk : NULL);
 792
 793         /*
 794          * If curthread already holds the lock and this one is
 795          * allowed to recurse, simply recurse on it.
 796          */
 797         if (lockmgr_xlocked(lk)) {
 798                 if ((flags & LK_CANRECURSE) == 0 &&
 799                     (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
 800                         /*
 801                          * If the lock is expected to not panic just
 802                          * give up and return.
 803                          */
 804                         if (LK_TRYOP(flags)) {
 805                                 LOCK_LOG2(lk,
 806                                     "%s: %p fails the try operation",
 807                                     __func__, lk);
 808                                 error = EBUSY;
 809                                 goto out;
 810                         }
 811                         if (flags & LK_INTERLOCK) {
 812                                 class = LOCK_CLASS(ilk);
 813                                 class->lc_unlock(ilk);
 814                         }
 815                         STACK_PRINT(lk);
 816                         panic("%s: recursing on non recursive lockmgr %p "
 817                             "@ %s:%d\n", __func__, lk, file, line);
 818                 }
 819                 atomic_set_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
 820                 lk->lk_recurse++;
 821                 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
 822                 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 823                     lk->lk_recurse, file, line);
 824                 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 825                     LK_TRYWIT(flags), file, line);
 826                 TD_LOCKS_INC(curthread);
 827                 goto out;
 828         }
 829
 830         x = LK_UNLOCKED;
 831         lock_delay_arg_init(&lda, &lockmgr_delay);
 832         if (!lk_adaptive)
 833                 flags &= ~LK_ADAPTIVE;
 834         for (;;) {
 835                 if (x == LK_UNLOCKED) {
 836                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, tid))
 837                                 break;
 838                         continue;
 839                 }
 840                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
 841                         if (lockmgr_xlock_adaptive(&lda, lk, &x))
 842                                 continue;
 843                 }
 844 #ifdef HWPMC_HOOKS
 845                 PMC_SOFT_CALL( , , lock, failed);
 846 #endif
 847                 lock_profile_obtain_lock_failed(&lk->lock_object,
 848                     &contested, &waittime);
 849
 850                 /*
 851                  * If the lock is expected to not sleep just give up
 852                  * and return.
 853                  */
 854                 if (LK_TRYOP(flags)) {
 855                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 856                             __func__, lk);
 857                         error = EBUSY;
 858                         break;
 859                 }
 860
 861                 /*
 862                  * Acquire the sleepqueue chain lock because we
 863                  * probabilly will need to manipulate waiters flags.
 864                  */
 865                 sleepq_lock(&lk->lock_object);
 866                 x = lockmgr_read_value(lk);
 867 retry_sleepq:
 868
 869                 /*
 870                  * if the lock has been released while we spun on
 871                  * the sleepqueue chain lock just try again.
 872                  */
 873                 if (x == LK_UNLOCKED) {
 874                         sleepq_release(&lk->lock_object);
 875                         continue;
 876                 }
 877
 878                 /*
 879                  * The lock can be in the state where there is a
 880                  * pending queue of waiters, but still no owner.
 881                  * This happens when the lock is contested and an
 882                  * owner is going to claim the lock.
 883                  * If curthread is the one successfully acquiring it
 884                  * claim lock ownership and return, preserving waiters
 885                  * flags.
 886                  */
 887                 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 888                 if ((x & ~v) == LK_UNLOCKED) {
 889                         v &= ~LK_EXCLUSIVE_SPINNERS;
 890                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 891                             tid | v)) {
 892                                 sleepq_release(&lk->lock_object);
 893                                 LOCK_LOG2(lk,
 894                                     "%s: %p claimed by a new writer",
 895                                     __func__, lk);
 896                                 break;
 897                         }
 898                         goto retry_sleepq;
 899                 }
 900
 901                 /*
 902                  * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
 903                  * fail, loop back and retry.
 904                  */
 905                 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
 906                         if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
 907                             x | LK_EXCLUSIVE_WAITERS)) {
 908                                 goto retry_sleepq;
 909                         }
 910                         LOCK_LOG2(lk, "%s: %p set excl waiters flag",
 911                             __func__, lk);
 912                 }
 913
 914                 if (lwa == NULL) {
 915                         iwmesg = lk->lock_object.lo_name;
 916                         ipri = lk->lk_pri;
 917                         itimo = lk->lk_timo;
 918                 } else {
 919                         iwmesg = lwa->iwmesg;
 920                         ipri = lwa->ipri;
 921                         itimo = lwa->itimo;
 922                 }
 923
 924                 /*
 925                  * As far as we have been unable to acquire the
 926                  * exclusive lock and the exclusive waiters flag
 927                  * is set, we will sleep.
 928                  */
 929 #ifdef KDTRACE_HOOKS
 930                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 931 #endif
 932                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 933                     SQ_EXCLUSIVE_QUEUE);
 934 #ifdef KDTRACE_HOOKS
 935                 sleep_time += lockstat_nsecs(&lk->lock_object);
 936 #endif
 937                 flags &= ~LK_INTERLOCK;
 938                 if (error) {
 939                         LOCK_LOG3(lk,
 940                             "%s: interrupted sleep for %p with %d",
 941                             __func__, lk, error);
 942                         break;
 943                 }
 944                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 945                     __func__, lk);
 946                 x = lockmgr_read_value(lk);
 947         }
 948         if (error == 0) {
 949 #ifdef KDTRACE_HOOKS
 950                 if (sleep_time != 0)
 951                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 952                             LOCKSTAT_WRITER, (x & LK_SHARE) == 0,
 953                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 954 #endif
 955 #ifdef LOCK_PROFILING
 956                 lockmgr_note_exclusive_acquire(lk, contested, waittime,
 957                     file, line, flags);
 958 #else
 959                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 960                     flags);
 961 #endif
 962         }
 963
 964 out:
 965         lockmgr_exit(flags, ilk, 0);
 966         return (error);
 967 }
 968
 969 static __noinline int
 970 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
 971     const char *file, int line, struct lockmgr_wait *lwa)
 972 {
 973         uintptr_t tid, v, setv;
 974         int error = 0;
 975         int op;
 976
 977         if (KERNEL_PANICKED())
 978                 goto out;
 979
 980         tid = (uintptr_t)curthread;
 981
 982         _lockmgr_assert(lk, KA_SLOCKED, file, line);
 983
 984         op = flags & LK_TYPE_MASK;
 985         v = lockmgr_read_value(lk);
 986         for (;;) {
 987                 if (LK_SHARERS(v) > 1) {
 988                         if (op == LK_TRYUPGRADE) {
 989                                 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
 990                                     __func__, lk);
 991                                 error = EBUSY;
 992                                 goto out;
 993                         }
 994                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &v,
 995                             v - LK_ONE_SHARER)) {
 996                                 lockmgr_note_shared_release(lk, file, line);
 997                                 goto out_xlock;
 998                         }
 999                         continue;
1000                 }
1001                 MPASS((v & ~LK_ALL_WAITERS) == LK_SHARERS_LOCK(1));
1002
1003                 setv = tid;
1004                 setv |= (v & LK_ALL_WAITERS);
1005
1006                 /*
1007                  * Try to switch from one shared lock to an exclusive one.
1008                  * We need to preserve waiters flags during the operation.
1009                  */
1010                 if (atomic_fcmpset_ptr(&lk->lk_lock, &v, setv)) {
1011                         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
1012                             line);
1013                         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
1014                             LK_TRYWIT(flags), file, line);
1015                         LOCKSTAT_RECORD0(lockmgr__upgrade, lk);
1016                         TD_SLOCKS_DEC(curthread);
1017                         goto out;
1018                 }
1019         }
1020
1021 out_xlock:
1022         error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
1023         flags &= ~LK_INTERLOCK;
1024 out:
1025         lockmgr_exit(flags, ilk, 0);
1026         return (error);
1027 }
1028
1029 int
1030 lockmgr_lock_flags(struct lock *lk, u_int flags, struct lock_object *ilk,
1031     const char *file, int line)
1032 {
1033         struct lock_class *class;
1034         uintptr_t x, tid;
1035         u_int op;
1036         bool locked;
1037
1038         if (KERNEL_PANICKED())
1039                 return (0);
1040
1041         op = flags & LK_TYPE_MASK;
1042         locked = false;
1043         switch (op) {
1044         case LK_SHARED:
1045                 if (LK_CAN_WITNESS(flags))
1046                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
1047                             file, line, flags & LK_INTERLOCK ? ilk : NULL);
1048                 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
1049                         break;
1050                 x = lockmgr_read_value(lk);
1051                 if (lockmgr_slock_try(lk, &x, flags, true)) {
1052                         lockmgr_note_shared_acquire(lk, 0, 0,
1053                             file, line, flags);
1054                         locked = true;
1055                 } else {
1056                         return (lockmgr_slock_hard(lk, flags, ilk, file, line,
1057                             NULL));
1058                 }
1059                 break;
1060         case LK_EXCLUSIVE:
1061                 if (LK_CAN_WITNESS(flags))
1062                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1063                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1064                             ilk : NULL);
1065                 tid = (uintptr_t)curthread;
1066                 if (lockmgr_read_value(lk) == LK_UNLOCKED &&
1067                     atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1068                         lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
1069                             flags);
1070                         locked = true;
1071                 } else {
1072                         return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
1073                             NULL));
1074                 }
1075                 break;
1076         case LK_UPGRADE:
1077         case LK_TRYUPGRADE:
1078                 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
1079         default:
1080                 break;
1081         }
1082         if (__predict_true(locked)) {
1083                 if (__predict_false(flags & LK_INTERLOCK)) {
1084                         class = LOCK_CLASS(ilk);
1085                         class->lc_unlock(ilk);
1086                 }
1087                 return (0);
1088         } else {
1089                 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
1090                     LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
1091         }
1092 }
1093
1094 static __noinline int
1095 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1096     const char *file, int line)
1097
1098 {
1099         int wakeup_swapper = 0;
1100
1101         if (KERNEL_PANICKED())
1102                 goto out;
1103
1104         wakeup_swapper = wakeupshlk(lk, file, line);
1105
1106 out:
1107         lockmgr_exit(flags, ilk, wakeup_swapper);
1108         return (0);
1109 }
1110
1111 static __noinline int
1112 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1113     const char *file, int line)
1114 {
1115         uintptr_t tid, v;
1116         int wakeup_swapper = 0;
1117         u_int realexslp;
1118         int queue;
1119
1120         if (KERNEL_PANICKED())
1121                 goto out;
1122
1123         tid = (uintptr_t)curthread;
1124
1125         /*
1126          * As first option, treact the lock as if it has not
1127          * any waiter.
1128          * Fix-up the tid var if the lock has been disowned.
1129          */
1130         if (LK_HOLDER(x) == LK_KERNPROC)
1131                 tid = LK_KERNPROC;
1132
1133         /*
1134          * The lock is held in exclusive mode.
1135          * If the lock is recursed also, then unrecurse it.
1136          */
1137         if (lockmgr_recursed_v(x)) {
1138                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
1139                 lk->lk_recurse--;
1140                 if (lk->lk_recurse == 0)
1141                         atomic_clear_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
1142                 goto out;
1143         }
1144         if (tid != LK_KERNPROC)
1145                 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,
1146                     LOCKSTAT_WRITER);
1147
1148         if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
1149                 goto out;
1150
1151         sleepq_lock(&lk->lock_object);
1152         x = lockmgr_read_value(lk);
1153         v = LK_UNLOCKED;
1154
1155         /*
1156          * If the lock has exclusive waiters, give them
1157          * preference in order to avoid deadlock with
1158          * shared runners up.
1159          * If interruptible sleeps left the exclusive queue
1160          * empty avoid a starvation for the threads sleeping
1161          * on the shared queue by giving them precedence
1162          * and cleaning up the exclusive waiters bit anyway.
1163          * Please note that lk_exslpfail count may be lying
1164          * about the real number of waiters with the
1165          * LK_SLEEPFAIL flag on because they may be used in
1166          * conjunction with interruptible sleeps so
1167          * lk_exslpfail might be considered an 'upper limit'
1168          * bound, including the edge cases.
1169          */
1170         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1171         realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
1172         if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1173                 if (lk->lk_exslpfail < realexslp) {
1174                         lk->lk_exslpfail = 0;
1175                         queue = SQ_EXCLUSIVE_QUEUE;
1176                         v |= (x & LK_SHARED_WAITERS);
1177                 } else {
1178                         lk->lk_exslpfail = 0;
1179                         LOCK_LOG2(lk,
1180                             "%s: %p has only LK_SLEEPFAIL sleepers",
1181                             __func__, lk);
1182                         LOCK_LOG2(lk,
1183                             "%s: %p waking up threads on the exclusive queue",
1184                             __func__, lk);
1185                         wakeup_swapper = sleepq_broadcast(&lk->lock_object,
1186                             SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1187                         queue = SQ_SHARED_QUEUE;
1188                 }
1189         } else {
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                                          * Exclusive waiters sleeping with
1491                                          * LK_SLEEPFAIL on and using
1492                                          * interruptible sleeps/timeout may
1493                                          * have left spourious lk_exslpfail
1494                                          * counts on, so clean it up anyway.
1495                                          */
1496                                         MPASS(v & LK_SHARED_WAITERS);
1497                                         lk->lk_exslpfail = 0;
1498                                         queue = SQ_SHARED_QUEUE;
1499                                         v &= ~LK_SHARED_WAITERS;
1500                                 }
1501                                 if (queue == SQ_EXCLUSIVE_QUEUE) {
1502                                         realexslp =
1503                                             sleepq_sleepcnt(&lk->lock_object,
1504                                             SQ_EXCLUSIVE_QUEUE);
1505                                         if (lk->lk_exslpfail >= realexslp) {
1506                                                 lk->lk_exslpfail = 0;
1507                                                 queue = SQ_SHARED_QUEUE;
1508                                                 v &= ~LK_SHARED_WAITERS;
1509                                                 if (realexslp != 0) {
1510                                                         LOCK_LOG2(lk,
1511                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1512                                                             __func__, lk);
1513                                                         LOCK_LOG2(lk,
1514                         "%s: %p waking up threads on the exclusive queue",
1515                                                             __func__, lk);
1516                                                         wakeup_swapper =
1517                                                             sleepq_broadcast(
1518                                                             &lk->lock_object,
1519                                                             SLEEPQ_LK, 0,
1520                                                             SQ_EXCLUSIVE_QUEUE);
1521                                                 }
1522                                         } else
1523                                                 lk->lk_exslpfail = 0;
1524                                 }
1525                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1526                                         sleepq_release(&lk->lock_object);
1527                                         continue;
1528                                 }
1529                                 LOCK_LOG3(lk,
1530                                 "%s: %p waking up all threads on the %s queue",
1531                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
1532                                     "shared" : "exclusive");
1533                                 wakeup_swapper |= sleepq_broadcast(
1534                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
1535
1536                                 /*
1537                                  * If shared waiters have been woken up we need
1538                                  * to wait for one of them to acquire the lock
1539                                  * before to set the exclusive waiters in
1540                                  * order to avoid a deadlock.
1541                                  */
1542                                 if (queue == SQ_SHARED_QUEUE) {
1543                                         for (v = lk->lk_lock;
1544                                             (v & LK_SHARE) && !LK_SHARERS(v);
1545                                             v = lk->lk_lock)
1546                                                 cpu_spinwait();
1547                                 }
1548                         }
1549
1550                         /*
1551                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1552                          * fail, loop back and retry.
1553                          */
1554                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1555                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1556                                     x | LK_EXCLUSIVE_WAITERS)) {
1557                                         sleepq_release(&lk->lock_object);
1558                                         continue;
1559                                 }
1560                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1561                                     __func__, lk);
1562                         }
1563
1564                         /*
1565                          * As far as we have been unable to acquire the
1566                          * exclusive lock and the exclusive waiters flag
1567                          * is set, we will sleep.
1568                          */
1569                         if (flags & LK_INTERLOCK) {
1570                                 class->lc_unlock(ilk);
1571                                 flags &= ~LK_INTERLOCK;
1572                         }
1573                         GIANT_SAVE();
1574                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1575                             SQ_EXCLUSIVE_QUEUE);
1576                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1577                         GIANT_RESTORE();
1578                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1579                             __func__, lk);
1580                 }
1581
1582                 if (error == 0) {
1583                         lock_profile_obtain_lock_success(&lk->lock_object,
1584                             contested, waittime, file, line);
1585                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1586                             lk->lk_recurse, file, line);
1587                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1588                             LK_TRYWIT(flags), file, line);
1589                         TD_LOCKS_INC(curthread);
1590                         STACK_SAVE(lk);
1591                 }
1592                 break;
1593         default:
1594                 if (flags & LK_INTERLOCK)
1595                         class->lc_unlock(ilk);
1596                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1597         }
1598
1599         if (flags & LK_INTERLOCK)
1600                 class->lc_unlock(ilk);
1601         if (wakeup_swapper)
1602                 kick_proc0();
1603
1604         return (error);
1605 }
1606
1607 void
1608 _lockmgr_disown(struct lock *lk, const char *file, int line)
1609 {
1610         uintptr_t tid, x;
1611
1612         if (SCHEDULER_STOPPED())
1613                 return;
1614
1615         tid = (uintptr_t)curthread;
1616         _lockmgr_assert(lk, KA_XLOCKED, file, line);
1617
1618         /*
1619          * Panic if the lock is recursed.
1620          */
1621         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1622                 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1623                     __func__,  file, line);
1624
1625         /*
1626          * If the owner is already LK_KERNPROC just skip the whole operation.
1627          */
1628         if (LK_HOLDER(lk->lk_lock) != tid)
1629                 return;
1630         lock_profile_release_lock(&lk->lock_object);
1631         LOCKSTAT_RECORD1(lockmgr__disown, lk, LOCKSTAT_WRITER);
1632         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1633         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1634         TD_LOCKS_DEC(curthread);
1635         STACK_SAVE(lk);
1636
1637         /*
1638          * In order to preserve waiters flags, just spin.
1639          */
1640         for (;;) {
1641                 x = lockmgr_read_value(lk);
1642                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1643                 x &= LK_ALL_WAITERS;
1644                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1645                     LK_KERNPROC | x))
1646                         return;
1647                 cpu_spinwait();
1648         }
1649 }
1650
1651 void
1652 lockmgr_printinfo(const struct lock *lk)
1653 {
1654         struct thread *td;
1655         uintptr_t x;
1656
1657         if (lk->lk_lock == LK_UNLOCKED)
1658                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1659         else if (lk->lk_lock & LK_SHARE)
1660                 printf("lock type %s: SHARED (count %ju)\n",
1661                     lk->lock_object.lo_name,
1662                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1663         else {
1664                 td = lockmgr_xholder(lk);
1665                 if (td == (struct thread *)LK_KERNPROC)
1666                         printf("lock type %s: EXCL by KERNPROC\n",
1667                             lk->lock_object.lo_name);
1668                 else
1669                         printf("lock type %s: EXCL by thread %p "
1670                             "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1671                             td, td->td_proc->p_pid, td->td_proc->p_comm,
1672                             td->td_tid);
1673         }
1674
1675         x = lk->lk_lock;
1676         if (x & LK_EXCLUSIVE_WAITERS)
1677                 printf(" with exclusive waiters pending\n");
1678         if (x & LK_SHARED_WAITERS)
1679                 printf(" with shared waiters pending\n");
1680         if (x & LK_EXCLUSIVE_SPINNERS)
1681                 printf(" with exclusive spinners pending\n");
1682
1683         STACK_PRINT(lk);
1684 }
1685
1686 int
1687 lockstatus(const struct lock *lk)
1688 {
1689         uintptr_t v, x;
1690         int ret;
1691
1692         ret = LK_SHARED;
1693         x = lockmgr_read_value(lk);
1694         v = LK_HOLDER(x);
1695
1696         if ((x & LK_SHARE) == 0) {
1697                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1698                         ret = LK_EXCLUSIVE;
1699                 else
1700                         ret = LK_EXCLOTHER;
1701         } else if (x == LK_UNLOCKED)
1702                 ret = 0;
1703
1704         return (ret);
1705 }
1706
1707 #ifdef INVARIANT_SUPPORT
1708
1709 FEATURE(invariant_support,
1710     "Support for modules compiled with INVARIANTS option");
1711
1712 #ifndef INVARIANTS
1713 #undef  _lockmgr_assert
1714 #endif
1715
1716 void
1717 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1718 {
1719         int slocked = 0;
1720
1721         if (KERNEL_PANICKED())
1722                 return;
1723         switch (what) {
1724         case KA_SLOCKED:
1725         case KA_SLOCKED | KA_NOTRECURSED:
1726         case KA_SLOCKED | KA_RECURSED:
1727                 slocked = 1;
1728         case KA_LOCKED:
1729         case KA_LOCKED | KA_NOTRECURSED:
1730         case KA_LOCKED | KA_RECURSED:
1731 #ifdef WITNESS
1732
1733                 /*
1734                  * We cannot trust WITNESS if the lock is held in exclusive
1735                  * mode and a call to lockmgr_disown() happened.
1736                  * Workaround this skipping the check if the lock is held in
1737                  * exclusive mode even for the KA_LOCKED case.
1738                  */
1739                 if (slocked || (lk->lk_lock & LK_SHARE)) {
1740                         witness_assert(&lk->lock_object, what, file, line);
1741                         break;
1742                 }
1743 #endif
1744                 if (lk->lk_lock == LK_UNLOCKED ||
1745                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1746                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1747                         panic("Lock %s not %slocked @ %s:%d\n",
1748                             lk->lock_object.lo_name, slocked ? "share" : "",
1749                             file, line);
1750
1751                 if ((lk->lk_lock & LK_SHARE) == 0) {
1752                         if (lockmgr_recursed(lk)) {
1753                                 if (what & KA_NOTRECURSED)
1754                                         panic("Lock %s recursed @ %s:%d\n",
1755                                             lk->lock_object.lo_name, file,
1756                                             line);
1757                         } else if (what & KA_RECURSED)
1758                                 panic("Lock %s not recursed @ %s:%d\n",
1759                                     lk->lock_object.lo_name, file, line);
1760                 }
1761                 break;
1762         case KA_XLOCKED:
1763         case KA_XLOCKED | KA_NOTRECURSED:
1764         case KA_XLOCKED | KA_RECURSED:
1765                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1766                         panic("Lock %s not exclusively locked @ %s:%d\n",
1767                             lk->lock_object.lo_name, file, line);
1768                 if (lockmgr_recursed(lk)) {
1769                         if (what & KA_NOTRECURSED)
1770                                 panic("Lock %s recursed @ %s:%d\n",
1771                                     lk->lock_object.lo_name, file, line);
1772                 } else if (what & KA_RECURSED)
1773                         panic("Lock %s not recursed @ %s:%d\n",
1774                             lk->lock_object.lo_name, file, line);
1775                 break;
1776         case KA_UNLOCKED:
1777                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1778                         panic("Lock %s exclusively locked @ %s:%d\n",
1779                             lk->lock_object.lo_name, file, line);
1780                 break;
1781         default:
1782                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1783                     line);
1784         }
1785 }
1786 #endif
1787
1788 #ifdef DDB
1789 int
1790 lockmgr_chain(struct thread *td, struct thread **ownerp)
1791 {
1792         const struct lock *lk;
1793
1794         lk = td->td_wchan;
1795
1796         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1797                 return (0);
1798         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1799         if (lk->lk_lock & LK_SHARE)
1800                 db_printf("SHARED (count %ju)\n",
1801                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1802         else
1803                 db_printf("EXCL\n");
1804         *ownerp = lockmgr_xholder(lk);
1805
1806         return (1);
1807 }
1808
1809 static void
1810 db_show_lockmgr(const struct lock_object *lock)
1811 {
1812         struct thread *td;
1813         const struct lock *lk;
1814
1815         lk = (const struct lock *)lock;
1816
1817         db_printf(" state: ");
1818         if (lk->lk_lock == LK_UNLOCKED)
1819                 db_printf("UNLOCKED\n");
1820         else if (lk->lk_lock & LK_SHARE)
1821                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1822         else {
1823                 td = lockmgr_xholder(lk);
1824                 if (td == (struct thread *)LK_KERNPROC)
1825                         db_printf("XLOCK: LK_KERNPROC\n");
1826                 else
1827                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1828                             td->td_tid, td->td_proc->p_pid,
1829                             td->td_proc->p_comm);
1830                 if (lockmgr_recursed(lk))
1831                         db_printf(" recursed: %d\n", lk->lk_recurse);
1832         }
1833         db_printf(" waiters: ");
1834         switch (lk->lk_lock & LK_ALL_WAITERS) {
1835         case LK_SHARED_WAITERS:
1836                 db_printf("shared\n");
1837                 break;
1838         case LK_EXCLUSIVE_WAITERS:
1839                 db_printf("exclusive\n");
1840                 break;
1841         case LK_ALL_WAITERS:
1842                 db_printf("shared and exclusive\n");
1843                 break;
1844         default:
1845                 db_printf("none\n");
1846         }
1847         db_printf(" spinners: ");
1848         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1849                 db_printf("exclusive\n");
1850         else
1851                 db_printf("none\n");
1852 }
1853 #endif