sys/kern/kern_lock.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   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 #include <sys/param.h>
  36 #include <sys/kdb.h>
  37 #include <sys/ktr.h>
  38 #include <sys/limits.h>
  39 #include <sys/lock.h>
  40 #include <sys/lock_profile.h>
  41 #include <sys/lockmgr.h>
  42 #include <sys/lockstat.h>
  43 #include <sys/mutex.h>
  44 #include <sys/proc.h>
  45 #include <sys/sleepqueue.h>
  46 #ifdef DEBUG_LOCKS
  47 #include <sys/stack.h>
  48 #endif
  49 #include <sys/sysctl.h>
  50 #include <sys/systm.h>
  51
  52 #include <machine/cpu.h>
  53
  54 #ifdef DDB
  55 #include <ddb/ddb.h>
  56 #endif
  57
  58 #ifdef HWPMC_HOOKS
  59 #include <sys/pmckern.h>
  60 PMC_SOFT_DECLARE( , , lock, failed);
  61 #endif
  62
  63 /*
  64  * Hack. There should be prio_t or similar so that this is not necessary.
  65  */
  66 _Static_assert((PRILASTFLAG * 2) - 1 <= USHRT_MAX,
  67     "prio flags wont fit in u_short pri in struct lock");
  68
  69 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
  70     ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
  71
  72 #define SQ_EXCLUSIVE_QUEUE      0
  73 #define SQ_SHARED_QUEUE         1
  74
  75 #ifndef INVARIANTS
  76 #define _lockmgr_assert(lk, what, file, line)
  77 #endif
  78
  79 #define TD_SLOCKS_INC(td)       ((td)->td_lk_slocks++)
  80 #define TD_SLOCKS_DEC(td)       ((td)->td_lk_slocks--)
  81
  82 #ifndef DEBUG_LOCKS
  83 #define STACK_PRINT(lk)
  84 #define STACK_SAVE(lk)
  85 #define STACK_ZERO(lk)
  86 #else
  87 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
  88 #define STACK_SAVE(lk)  stack_save(&(lk)->lk_stack)
  89 #define STACK_ZERO(lk)  stack_zero(&(lk)->lk_stack)
  90 #endif
  91
  92 #define LOCK_LOG2(lk, string, arg1, arg2)                               \
  93         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  94                 CTR2(KTR_LOCK, (string), (arg1), (arg2))
  95 #define LOCK_LOG3(lk, string, arg1, arg2, arg3)                         \
  96         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  97                 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
  98
  99 #define GIANT_DECLARE                                                   \
 100         int _i = 0;                                                     \
 101         WITNESS_SAVE_DECL(Giant)
 102 #define GIANT_RESTORE() do {                                            \
 103         if (__predict_false(_i > 0)) {                                  \
 104                 while (_i--)                                            \
 105                         mtx_lock(&Giant);                               \
 106                 WITNESS_RESTORE(&Giant.lock_object, Giant);             \
 107         }                                                               \
 108 } while (0)
 109 #define GIANT_SAVE() do {                                               \
 110         if (__predict_false(mtx_owned(&Giant))) {                       \
 111                 WITNESS_SAVE(&Giant.lock_object, Giant);                \
 112                 while (mtx_owned(&Giant)) {                             \
 113                         _i++;                                           \
 114                         mtx_unlock(&Giant);                             \
 115                 }                                                       \
 116         }                                                               \
 117 } while (0)
 118
 119 static bool __always_inline
 120 LK_CAN_SHARE(uintptr_t x, int flags, bool fp)
 121 {
 122
 123         if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) ==
 124             LK_SHARE)
 125                 return (true);
 126         if (fp || (!(x & LK_SHARE)))
 127                 return (false);
 128         if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||
 129             (curthread->td_pflags & TDP_DEADLKTREAT))
 130                 return (true);
 131         return (false);
 132 }
 133
 134 #define LK_TRYOP(x)                                                     \
 135         ((x) & LK_NOWAIT)
 136
 137 #define LK_CAN_WITNESS(x)                                               \
 138         (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
 139 #define LK_TRYWIT(x)                                                    \
 140         (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
 141
 142 #define lockmgr_disowned(lk)                                            \
 143         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
 144
 145 #define lockmgr_xlocked_v(v)                                            \
 146         (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
 147
 148 #define lockmgr_xlocked(lk) lockmgr_xlocked_v(lockmgr_read_value(lk))
 149
 150 static void     assert_lockmgr(const struct lock_object *lock, int how);
 151 #ifdef DDB
 152 static void     db_show_lockmgr(const struct lock_object *lock);
 153 #endif
 154 static void     lock_lockmgr(struct lock_object *lock, uintptr_t how);
 155 #ifdef KDTRACE_HOOKS
 156 static int      owner_lockmgr(const struct lock_object *lock,
 157                     struct thread **owner);
 158 #endif
 159 static uintptr_t unlock_lockmgr(struct lock_object *lock);
 160
 161 struct lock_class lock_class_lockmgr = {
 162         .lc_name = "lockmgr",
 163         .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
 164         .lc_assert = assert_lockmgr,
 165 #ifdef DDB
 166         .lc_ddb_show = db_show_lockmgr,
 167 #endif
 168         .lc_lock = lock_lockmgr,
 169         .lc_unlock = unlock_lockmgr,
 170 #ifdef KDTRACE_HOOKS
 171         .lc_owner = owner_lockmgr,
 172 #endif
 173 };
 174
 175 static __read_mostly bool lk_adaptive = true;
 176 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, "lockmgr debugging");
 177 SYSCTL_BOOL(_debug_lockmgr, OID_AUTO, adaptive_spinning, CTLFLAG_RW, &lk_adaptive,
 178     0, "");
 179 #define lockmgr_delay  locks_delay
 180
 181 struct lockmgr_wait {
 182         const char *iwmesg;
 183         int ipri;
 184         int itimo;
 185 };
 186
 187 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
 188     int flags, bool fp);
 189 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp);
 190
 191 static void
 192 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper)
 193 {
 194         struct lock_class *class;
 195
 196         if (flags & LK_INTERLOCK) {
 197                 class = LOCK_CLASS(ilk);
 198                 class->lc_unlock(ilk);
 199         }
 200
 201         if (__predict_false(wakeup_swapper))
 202                 kick_proc0();
 203 }
 204
 205 static void
 206 lockmgr_note_shared_acquire(struct lock *lk, int contested,
 207     uint64_t waittime, const char *file, int line, int flags)
 208 {
 209
 210         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
 211             waittime, file, line, LOCKSTAT_READER);
 212         LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
 213         WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
 214         TD_LOCKS_INC(curthread);
 215         TD_SLOCKS_INC(curthread);
 216         STACK_SAVE(lk);
 217 }
 218
 219 static void
 220 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
 221 {
 222
 223         WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
 224         LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
 225         TD_LOCKS_DEC(curthread);
 226         TD_SLOCKS_DEC(curthread);
 227 }
 228
 229 static void
 230 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
 231     uint64_t waittime, const char *file, int line, int flags)
 232 {
 233
 234         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
 235             waittime, file, line, LOCKSTAT_WRITER);
 236         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
 237         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
 238             line);
 239         TD_LOCKS_INC(curthread);
 240         STACK_SAVE(lk);
 241 }
 242
 243 static void
 244 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
 245 {
 246
 247         if (LK_HOLDER(lockmgr_read_value(lk)) != LK_KERNPROC) {
 248                 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
 249                 TD_LOCKS_DEC(curthread);
 250         }
 251         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
 252             line);
 253 }
 254
 255 static __inline struct thread *
 256 lockmgr_xholder(const struct lock *lk)
 257 {
 258         uintptr_t x;
 259
 260         x = lockmgr_read_value(lk);
 261         return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
 262 }
 263
 264 /*
 265  * It assumes sleepq_lock held and returns with this one unheld.
 266  * It also assumes the generic interlock is sane and previously checked.
 267  * If LK_INTERLOCK is specified the interlock is not reacquired after the
 268  * sleep.
 269  */
 270 static __inline int
 271 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
 272     const char *wmesg, int pri, int timo, int queue)
 273 {
 274         GIANT_DECLARE;
 275         struct lock_class *class;
 276         int catch, error;
 277
 278         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 279         catch = pri & PCATCH;
 280         pri &= PRIMASK;
 281         error = 0;
 282
 283         LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
 284             (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
 285
 286         if (flags & LK_INTERLOCK)
 287                 class->lc_unlock(ilk);
 288         if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) {
 289                 if (lk->lk_exslpfail < USHRT_MAX)
 290                         lk->lk_exslpfail++;
 291         }
 292         GIANT_SAVE();
 293         sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
 294             SLEEPQ_INTERRUPTIBLE : 0), queue);
 295         if ((flags & LK_TIMELOCK) && timo)
 296                 sleepq_set_timeout(&lk->lock_object, timo);
 297
 298         /*
 299          * Decisional switch for real sleeping.
 300          */
 301         if ((flags & LK_TIMELOCK) && timo && catch)
 302                 error = sleepq_timedwait_sig(&lk->lock_object, pri);
 303         else if ((flags & LK_TIMELOCK) && timo)
 304                 error = sleepq_timedwait(&lk->lock_object, pri);
 305         else if (catch)
 306                 error = sleepq_wait_sig(&lk->lock_object, pri);
 307         else
 308                 sleepq_wait(&lk->lock_object, pri);
 309         GIANT_RESTORE();
 310         if ((flags & LK_SLEEPFAIL) && error == 0)
 311                 error = ENOLCK;
 312
 313         return (error);
 314 }
 315
 316 static __inline int
 317 wakeupshlk(struct lock *lk, const char *file, int line)
 318 {
 319         uintptr_t v, x, orig_x;
 320         u_int realexslp;
 321         int queue, wakeup_swapper;
 322
 323         wakeup_swapper = 0;
 324         for (;;) {
 325                 x = lockmgr_read_value(lk);
 326                 if (lockmgr_sunlock_try(lk, &x))
 327                         break;
 328
 329                 /*
 330                  * We should have a sharer with waiters, so enter the hard
 331                  * path in order to handle wakeups correctly.
 332                  */
 333                 sleepq_lock(&lk->lock_object);
 334                 orig_x = lockmgr_read_value(lk);
 335 retry_sleepq:
 336                 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 337                 v = LK_UNLOCKED;
 338
 339                 /*
 340                  * If the lock has exclusive waiters, give them preference in
 341                  * order to avoid deadlock with shared runners up.
 342                  * If interruptible sleeps left the exclusive queue empty
 343                  * avoid a starvation for the threads sleeping on the shared
 344                  * queue by giving them precedence and cleaning up the
 345                  * exclusive waiters bit anyway.
 346                  * Please note that lk_exslpfail count may be lying about
 347                  * the real number of waiters with the LK_SLEEPFAIL flag on
 348                  * because they may be used in conjunction with interruptible
 349                  * sleeps so lk_exslpfail might be considered an 'upper limit'
 350                  * bound, including the edge cases.
 351                  */
 352                 realexslp = sleepq_sleepcnt(&lk->lock_object,
 353                     SQ_EXCLUSIVE_QUEUE);
 354                 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
 355                         if (lk->lk_exslpfail != USHRT_MAX && lk->lk_exslpfail < realexslp) {
 356                                 lk->lk_exslpfail = 0;
 357                                 queue = SQ_EXCLUSIVE_QUEUE;
 358                                 v |= (x & LK_SHARED_WAITERS);
 359                         } else {
 360                                 lk->lk_exslpfail = 0;
 361                                 LOCK_LOG2(lk,
 362                                     "%s: %p has only LK_SLEEPFAIL sleepers",
 363                                     __func__, lk);
 364                                 LOCK_LOG2(lk,
 365                             "%s: %p waking up threads on the exclusive queue",
 366                                     __func__, lk);
 367                                 wakeup_swapper =
 368                                     sleepq_broadcast(&lk->lock_object,
 369                                     SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
 370                                 queue = SQ_SHARED_QUEUE;
 371                         }
 372                 } else {
 373                         /*
 374                          * Exclusive waiters sleeping with LK_SLEEPFAIL on
 375                          * and using interruptible sleeps/timeout may have
 376                          * left spourious lk_exslpfail counts on, so clean
 377                          * it up anyway.
 378                          */
 379                         lk->lk_exslpfail = 0;
 380                         queue = SQ_SHARED_QUEUE;
 381                 }
 382
 383                 if (lockmgr_sunlock_try(lk, &orig_x)) {
 384                         sleepq_release(&lk->lock_object);
 385                         break;
 386                 }
 387
 388                 x |= LK_SHARERS_LOCK(1);
 389                 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
 390                         orig_x = x;
 391                         goto retry_sleepq;
 392                 }
 393                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 394                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 395                     "exclusive");
 396                 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
 397                     0, queue);
 398                 sleepq_release(&lk->lock_object);
 399                 break;
 400         }
 401
 402         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
 403         return (wakeup_swapper);
 404 }
 405
 406 static void
 407 assert_lockmgr(const struct lock_object *lock, int what)
 408 {
 409
 410         panic("lockmgr locks do not support assertions");
 411 }
 412
 413 static void
 414 lock_lockmgr(struct lock_object *lock, uintptr_t how)
 415 {
 416
 417         panic("lockmgr locks do not support sleep interlocking");
 418 }
 419
 420 static uintptr_t
 421 unlock_lockmgr(struct lock_object *lock)
 422 {
 423
 424         panic("lockmgr locks do not support sleep interlocking");
 425 }
 426
 427 #ifdef KDTRACE_HOOKS
 428 static int
 429 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
 430 {
 431
 432         panic("lockmgr locks do not support owner inquiring");
 433 }
 434 #endif
 435
 436 void
 437 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 438 {
 439         int iflags;
 440
 441         MPASS((flags & ~LK_INIT_MASK) == 0);
 442         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
 443             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
 444             &lk->lk_lock));
 445
 446         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
 447         if (flags & LK_CANRECURSE)
 448                 iflags |= LO_RECURSABLE;
 449         if ((flags & LK_NODUP) == 0)
 450                 iflags |= LO_DUPOK;
 451         if (flags & LK_NOPROFILE)
 452                 iflags |= LO_NOPROFILE;
 453         if ((flags & LK_NOWITNESS) == 0)
 454                 iflags |= LO_WITNESS;
 455         if (flags & LK_QUIET)
 456                 iflags |= LO_QUIET;
 457         if (flags & LK_IS_VNODE)
 458                 iflags |= LO_IS_VNODE;
 459         if (flags & LK_NEW)
 460                 iflags |= LO_NEW;
 461         iflags |= flags & LK_NOSHARE;
 462
 463         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
 464         lk->lk_lock = LK_UNLOCKED;
 465         lk->lk_recurse = 0;
 466         lk->lk_exslpfail = 0;
 467         lk->lk_timo = timo;
 468         lk->lk_pri = pri;
 469         STACK_ZERO(lk);
 470 }
 471
 472 /*
 473  * XXX: Gross hacks to manipulate external lock flags after
 474  * initialization.  Used for certain vnode and buf locks.
 475  */
 476 void
 477 lockallowshare(struct lock *lk)
 478 {
 479
 480         lockmgr_assert(lk, KA_XLOCKED);
 481         lk->lock_object.lo_flags &= ~LK_NOSHARE;
 482 }
 483
 484 void
 485 lockdisableshare(struct lock *lk)
 486 {
 487
 488         lockmgr_assert(lk, KA_XLOCKED);
 489         lk->lock_object.lo_flags |= LK_NOSHARE;
 490 }
 491
 492 void
 493 lockallowrecurse(struct lock *lk)
 494 {
 495
 496         lockmgr_assert(lk, KA_XLOCKED);
 497         lk->lock_object.lo_flags |= LO_RECURSABLE;
 498 }
 499
 500 void
 501 lockdisablerecurse(struct lock *lk)
 502 {
 503
 504         lockmgr_assert(lk, KA_XLOCKED);
 505         lk->lock_object.lo_flags &= ~LO_RECURSABLE;
 506 }
 507
 508 void
 509 lockdestroy(struct lock *lk)
 510 {
 511
 512         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
 513         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
 514         KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
 515         lock_destroy(&lk->lock_object);
 516 }
 517
 518 static bool __always_inline
 519 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
 520 {
 521
 522         /*
 523          * If no other thread has an exclusive lock, or
 524          * no exclusive waiter is present, bump the count of
 525          * sharers.  Since we have to preserve the state of
 526          * waiters, if we fail to acquire the shared lock
 527          * loop back and retry.
 528          */
 529         while (LK_CAN_SHARE(*xp, flags, fp)) {
 530                 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
 531                     *xp + LK_ONE_SHARER)) {
 532                         return (true);
 533                 }
 534         }
 535         return (false);
 536 }
 537
 538 static bool __always_inline
 539 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
 540 {
 541
 542         for (;;) {
 543                 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
 544                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
 545                             *xp - LK_ONE_SHARER))
 546                                 return (true);
 547                         continue;
 548                 }
 549                 break;
 550         }
 551         return (false);
 552 }
 553
 554 static bool
 555 lockmgr_slock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp,
 556     int flags)
 557 {
 558         struct thread *owner;
 559         uintptr_t x;
 560
 561         x = *xp;
 562         MPASS(x != LK_UNLOCKED);
 563         owner = (struct thread *)LK_HOLDER(x);
 564         for (;;) {
 565                 MPASS(owner != curthread);
 566                 if (owner == (struct thread *)LK_KERNPROC)
 567                         return (false);
 568                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
 569                         return (false);
 570                 if (owner == NULL)
 571                         return (false);
 572                 if (!TD_IS_RUNNING(owner))
 573                         return (false);
 574                 if ((x & LK_ALL_WAITERS) != 0)
 575                         return (false);
 576                 lock_delay(lda);
 577                 x = lockmgr_read_value(lk);
 578                 if (LK_CAN_SHARE(x, flags, false)) {
 579                         *xp = x;
 580                         return (true);
 581                 }
 582                 owner = (struct thread *)LK_HOLDER(x);
 583         }
 584 }
 585
 586 static __noinline int
 587 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 588     const char *file, int line, struct lockmgr_wait *lwa)
 589 {
 590         uintptr_t tid, x;
 591         int error = 0;
 592         const char *iwmesg;
 593         int ipri, itimo;
 594
 595 #ifdef KDTRACE_HOOKS
 596         uint64_t sleep_time = 0;
 597 #endif
 598 #ifdef LOCK_PROFILING
 599         uint64_t waittime = 0;
 600         int contested = 0;
 601 #endif
 602         struct lock_delay_arg lda;
 603
 604         if (SCHEDULER_STOPPED())
 605                 goto out;
 606
 607         tid = (uintptr_t)curthread;
 608
 609         if (LK_CAN_WITNESS(flags))
 610                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 611                     file, line, flags & LK_INTERLOCK ? ilk : NULL);
 612         x = lockmgr_read_value(lk);
 613         lock_delay_arg_init(&lda, &lockmgr_delay);
 614         if (!lk_adaptive)
 615                 flags &= ~LK_ADAPTIVE;
 616         /*
 617          * The lock may already be locked exclusive by curthread,
 618          * avoid deadlock.
 619          */
 620         if (LK_HOLDER(x) == tid) {
 621                 LOCK_LOG2(lk,
 622                     "%s: %p already held in exclusive mode",
 623                     __func__, lk);
 624                 error = EDEADLK;
 625                 goto out;
 626         }
 627
 628         for (;;) {
 629                 if (lockmgr_slock_try(lk, &x, flags, false))
 630                         break;
 631
 632                 lock_profile_obtain_lock_failed(&lk->lock_object, false,
 633                     &contested, &waittime);
 634
 635                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
 636                         if (lockmgr_slock_adaptive(&lda, lk, &x, flags))
 637                                 continue;
 638                 }
 639
 640 #ifdef HWPMC_HOOKS
 641                 PMC_SOFT_CALL( , , lock, failed);
 642 #endif
 643
 644                 /*
 645                  * If the lock is expected to not sleep just give up
 646                  * and return.
 647                  */
 648                 if (LK_TRYOP(flags)) {
 649                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 650                             __func__, lk);
 651                         error = EBUSY;
 652                         break;
 653                 }
 654
 655                 /*
 656                  * Acquire the sleepqueue chain lock because we
 657                  * probabilly will need to manipulate waiters flags.
 658                  */
 659                 sleepq_lock(&lk->lock_object);
 660                 x = lockmgr_read_value(lk);
 661 retry_sleepq:
 662
 663                 /*
 664                  * if the lock can be acquired in shared mode, try
 665                  * again.
 666                  */
 667                 if (LK_CAN_SHARE(x, flags, false)) {
 668                         sleepq_release(&lk->lock_object);
 669                         continue;
 670                 }
 671
 672                 /*
 673                  * Try to set the LK_SHARED_WAITERS flag.  If we fail,
 674                  * loop back and retry.
 675                  */
 676                 if ((x & LK_SHARED_WAITERS) == 0) {
 677                         if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 678                             x | LK_SHARED_WAITERS)) {
 679                                 goto retry_sleepq;
 680                         }
 681                         LOCK_LOG2(lk, "%s: %p set shared waiters flag",
 682                             __func__, lk);
 683                 }
 684
 685                 if (lwa == NULL) {
 686                         iwmesg = lk->lock_object.lo_name;
 687                         ipri = lk->lk_pri;
 688                         itimo = lk->lk_timo;
 689                 } else {
 690                         iwmesg = lwa->iwmesg;
 691                         ipri = lwa->ipri;
 692                         itimo = lwa->itimo;
 693                 }
 694
 695                 /*
 696                  * As far as we have been unable to acquire the
 697                  * shared lock and the shared waiters flag is set,
 698                  * we will sleep.
 699                  */
 700 #ifdef KDTRACE_HOOKS
 701                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 702 #endif
 703                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 704                     SQ_SHARED_QUEUE);
 705 #ifdef KDTRACE_HOOKS
 706                 sleep_time += lockstat_nsecs(&lk->lock_object);
 707 #endif
 708                 flags &= ~LK_INTERLOCK;
 709                 if (error) {
 710                         LOCK_LOG3(lk,
 711                             "%s: interrupted sleep for %p with %d",
 712                             __func__, lk, error);
 713                         break;
 714                 }
 715                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 716                     __func__, lk);
 717                 x = lockmgr_read_value(lk);
 718         }
 719         if (error == 0) {
 720 #ifdef KDTRACE_HOOKS
 721                 if (sleep_time != 0)
 722                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 723                             LOCKSTAT_READER, (x & LK_SHARE) == 0,
 724                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 725 #endif
 726 #ifdef LOCK_PROFILING
 727                 lockmgr_note_shared_acquire(lk, contested, waittime,
 728                     file, line, flags);
 729 #else
 730                 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
 731                     flags);
 732 #endif
 733         }
 734
 735 out:
 736         lockmgr_exit(flags, ilk, 0);
 737         return (error);
 738 }
 739
 740 static bool
 741 lockmgr_xlock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp)
 742 {
 743         struct thread *owner;
 744         uintptr_t x;
 745
 746         x = *xp;
 747         MPASS(x != LK_UNLOCKED);
 748         owner = (struct thread *)LK_HOLDER(x);
 749         for (;;) {
 750                 MPASS(owner != curthread);
 751                 if (owner == NULL)
 752                         return (false);
 753                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
 754                         return (false);
 755                 if (owner == (struct thread *)LK_KERNPROC)
 756                         return (false);
 757                 if (!TD_IS_RUNNING(owner))
 758                         return (false);
 759                 if ((x & LK_ALL_WAITERS) != 0)
 760                         return (false);
 761                 lock_delay(lda);
 762                 x = lockmgr_read_value(lk);
 763                 if (x == LK_UNLOCKED) {
 764                         *xp = x;
 765                         return (true);
 766                 }
 767                 owner = (struct thread *)LK_HOLDER(x);
 768         }
 769 }
 770
 771 static __noinline int
 772 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 773     const char *file, int line, struct lockmgr_wait *lwa)
 774 {
 775         struct lock_class *class;
 776         uintptr_t tid, x, v;
 777         int error = 0;
 778         const char *iwmesg;
 779         int ipri, itimo;
 780
 781 #ifdef KDTRACE_HOOKS
 782         uint64_t sleep_time = 0;
 783 #endif
 784 #ifdef LOCK_PROFILING
 785         uint64_t waittime = 0;
 786         int contested = 0;
 787 #endif
 788         struct lock_delay_arg lda;
 789
 790         if (SCHEDULER_STOPPED())
 791                 goto out;
 792
 793         tid = (uintptr_t)curthread;
 794
 795         if (LK_CAN_WITNESS(flags))
 796                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 797                     LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 798                     ilk : NULL);
 799
 800         /*
 801          * If curthread already holds the lock and this one is
 802          * allowed to recurse, simply recurse on it.
 803          */
 804         if (lockmgr_xlocked(lk)) {
 805                 if ((flags & LK_CANRECURSE) == 0 &&
 806                     (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
 807                         /*
 808                          * If the lock is expected to not panic just
 809                          * give up and return.
 810                          */
 811                         if (LK_TRYOP(flags)) {
 812                                 LOCK_LOG2(lk,
 813                                     "%s: %p fails the try operation",
 814                                     __func__, lk);
 815                                 error = EBUSY;
 816                                 goto out;
 817                         }
 818                         if (flags & LK_INTERLOCK) {
 819                                 class = LOCK_CLASS(ilk);
 820                                 class->lc_unlock(ilk);
 821                         }
 822                         STACK_PRINT(lk);
 823                         panic("%s: recursing on non recursive lockmgr %p "
 824                             "@ %s:%d\n", __func__, lk, file, line);
 825                 }
 826                 atomic_set_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
 827                 lk->lk_recurse++;
 828                 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
 829                 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 830                     lk->lk_recurse, file, line);
 831                 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 832                     LK_TRYWIT(flags), file, line);
 833                 TD_LOCKS_INC(curthread);
 834                 goto out;
 835         }
 836
 837         x = LK_UNLOCKED;
 838         lock_delay_arg_init(&lda, &lockmgr_delay);
 839         if (!lk_adaptive)
 840                 flags &= ~LK_ADAPTIVE;
 841         for (;;) {
 842                 if (x == LK_UNLOCKED) {
 843                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, tid))
 844                                 break;
 845                         continue;
 846                 }
 847
 848                 lock_profile_obtain_lock_failed(&lk->lock_object, false,
 849                     &contested, &waittime);
 850
 851                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
 852                         if (lockmgr_xlock_adaptive(&lda, lk, &x))
 853                                 continue;
 854                 }
 855 #ifdef HWPMC_HOOKS
 856                 PMC_SOFT_CALL( , , lock, failed);
 857 #endif
 858
 859                 /*
 860                  * If the lock is expected to not sleep just give up
 861                  * and return.
 862                  */
 863                 if (LK_TRYOP(flags)) {
 864                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 865                             __func__, lk);
 866                         error = EBUSY;
 867                         break;
 868                 }
 869
 870                 /*
 871                  * Acquire the sleepqueue chain lock because we
 872                  * probabilly will need to manipulate waiters flags.
 873                  */
 874                 sleepq_lock(&lk->lock_object);
 875                 x = lockmgr_read_value(lk);
 876 retry_sleepq:
 877
 878                 /*
 879                  * if the lock has been released while we spun on
 880                  * the sleepqueue chain lock just try again.
 881                  */
 882                 if (x == LK_UNLOCKED) {
 883                         sleepq_release(&lk->lock_object);
 884                         continue;
 885                 }
 886
 887                 /*
 888                  * The lock can be in the state where there is a
 889                  * pending queue of waiters, but still no owner.
 890                  * This happens when the lock is contested and an
 891                  * owner is going to claim the lock.
 892                  * If curthread is the one successfully acquiring it
 893                  * claim lock ownership and return, preserving waiters
 894                  * flags.
 895                  */
 896                 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 897                 if ((x & ~v) == LK_UNLOCKED) {
 898                         v &= ~LK_EXCLUSIVE_SPINNERS;
 899                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 900                             tid | v)) {
 901                                 sleepq_release(&lk->lock_object);
 902                                 LOCK_LOG2(lk,
 903                                     "%s: %p claimed by a new writer",
 904                                     __func__, lk);
 905                                 break;
 906                         }
 907                         goto retry_sleepq;
 908                 }
 909
 910                 /*
 911                  * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
 912                  * fail, loop back and retry.
 913                  */
 914                 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
 915                         if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
 916                             x | LK_EXCLUSIVE_WAITERS)) {
 917                                 goto retry_sleepq;
 918                         }
 919                         LOCK_LOG2(lk, "%s: %p set excl waiters flag",
 920                             __func__, lk);
 921                 }
 922
 923                 if (lwa == NULL) {
 924                         iwmesg = lk->lock_object.lo_name;
 925                         ipri = lk->lk_pri;
 926                         itimo = lk->lk_timo;
 927                 } else {
 928                         iwmesg = lwa->iwmesg;
 929                         ipri = lwa->ipri;
 930                         itimo = lwa->itimo;
 931                 }
 932
 933                 /*
 934                  * As far as we have been unable to acquire the
 935                  * exclusive lock and the exclusive waiters flag
 936                  * is set, we will sleep.
 937                  */
 938 #ifdef KDTRACE_HOOKS
 939                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 940 #endif
 941                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 942                     SQ_EXCLUSIVE_QUEUE);
 943 #ifdef KDTRACE_HOOKS
 944                 sleep_time += lockstat_nsecs(&lk->lock_object);
 945 #endif
 946                 flags &= ~LK_INTERLOCK;
 947                 if (error) {
 948                         LOCK_LOG3(lk,
 949                             "%s: interrupted sleep for %p with %d",
 950                             __func__, lk, error);
 951                         break;
 952                 }
 953                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 954                     __func__, lk);
 955                 x = lockmgr_read_value(lk);
 956         }
 957         if (error == 0) {
 958 #ifdef KDTRACE_HOOKS
 959                 if (sleep_time != 0)
 960                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 961                             LOCKSTAT_WRITER, (x & LK_SHARE) == 0,
 962                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 963 #endif
 964 #ifdef LOCK_PROFILING
 965                 lockmgr_note_exclusive_acquire(lk, contested, waittime,
 966                     file, line, flags);
 967 #else
 968                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 969                     flags);
 970 #endif
 971         }
 972
 973 out:
 974         lockmgr_exit(flags, ilk, 0);
 975         return (error);
 976 }
 977
 978 static __noinline int
 979 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
 980     const char *file, int line, struct lockmgr_wait *lwa)
 981 {
 982         uintptr_t tid, v, setv;
 983         int error = 0;
 984         int op;
 985
 986         if (SCHEDULER_STOPPED())
 987                 goto out;
 988
 989         tid = (uintptr_t)curthread;
 990
 991         _lockmgr_assert(lk, KA_SLOCKED, file, line);
 992
 993         op = flags & LK_TYPE_MASK;
 994         v = lockmgr_read_value(lk);
 995         for (;;) {
 996                 if (LK_SHARERS(v) > 1) {
 997                         if (op == LK_TRYUPGRADE) {
 998                                 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
 999                                     __func__, lk);
1000                                 error = EBUSY;
1001                                 goto out;
1002                         }
1003                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &v,
1004                             v - LK_ONE_SHARER)) {
1005                                 lockmgr_note_shared_release(lk, file, line);
1006                                 goto out_xlock;
1007                         }
1008                         continue;
1009                 }
1010                 MPASS((v & ~LK_ALL_WAITERS) == LK_SHARERS_LOCK(1));
1011
1012                 setv = tid;
1013                 setv |= (v & LK_ALL_WAITERS);
1014
1015                 /*
1016                  * Try to switch from one shared lock to an exclusive one.
1017                  * We need to preserve waiters flags during the operation.
1018                  */
1019                 if (atomic_fcmpset_ptr(&lk->lk_lock, &v, setv)) {
1020                         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
1021                             line);
1022                         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
1023                             LK_TRYWIT(flags), file, line);
1024                         LOCKSTAT_RECORD0(lockmgr__upgrade, lk);
1025                         TD_SLOCKS_DEC(curthread);
1026                         goto out;
1027                 }
1028         }
1029
1030 out_xlock:
1031         error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
1032         flags &= ~LK_INTERLOCK;
1033 out:
1034         lockmgr_exit(flags, ilk, 0);
1035         return (error);
1036 }
1037
1038 int
1039 lockmgr_lock_flags(struct lock *lk, u_int flags, struct lock_object *ilk,
1040     const char *file, int line)
1041 {
1042         struct lock_class *class;
1043         uintptr_t x, tid;
1044         u_int op;
1045         bool locked;
1046
1047         if (SCHEDULER_STOPPED())
1048                 return (0);
1049
1050         op = flags & LK_TYPE_MASK;
1051         locked = false;
1052         switch (op) {
1053         case LK_SHARED:
1054                 if (LK_CAN_WITNESS(flags))
1055                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
1056                             file, line, flags & LK_INTERLOCK ? ilk : NULL);
1057                 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
1058                         break;
1059                 x = lockmgr_read_value(lk);
1060                 if (lockmgr_slock_try(lk, &x, flags, true)) {
1061                         lockmgr_note_shared_acquire(lk, 0, 0,
1062                             file, line, flags);
1063                         locked = true;
1064                 } else {
1065                         return (lockmgr_slock_hard(lk, flags, ilk, file, line,
1066                             NULL));
1067                 }
1068                 break;
1069         case LK_EXCLUSIVE:
1070                 if (LK_CAN_WITNESS(flags))
1071                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1072                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1073                             ilk : NULL);
1074                 tid = (uintptr_t)curthread;
1075                 if (lockmgr_read_value(lk) == LK_UNLOCKED &&
1076                     atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1077                         lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
1078                             flags);
1079                         locked = true;
1080                 } else {
1081                         return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
1082                             NULL));
1083                 }
1084                 break;
1085         case LK_UPGRADE:
1086         case LK_TRYUPGRADE:
1087                 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
1088         default:
1089                 break;
1090         }
1091         if (__predict_true(locked)) {
1092                 if (__predict_false(flags & LK_INTERLOCK)) {
1093                         class = LOCK_CLASS(ilk);
1094                         class->lc_unlock(ilk);
1095                 }
1096                 return (0);
1097         } else {
1098                 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
1099                     LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
1100         }
1101 }
1102
1103 static __noinline int
1104 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1105     const char *file, int line)
1106
1107 {
1108         int wakeup_swapper = 0;
1109
1110         if (SCHEDULER_STOPPED())
1111                 goto out;
1112
1113         wakeup_swapper = wakeupshlk(lk, file, line);
1114
1115 out:
1116         lockmgr_exit(flags, ilk, wakeup_swapper);
1117         return (0);
1118 }
1119
1120 static __noinline int
1121 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1122     const char *file, int line)
1123 {
1124         uintptr_t tid, v;
1125         int wakeup_swapper = 0;
1126         u_int realexslp;
1127         int queue;
1128
1129         if (SCHEDULER_STOPPED())
1130                 goto out;
1131
1132         tid = (uintptr_t)curthread;
1133
1134         /*
1135          * As first option, treact the lock as if it has not
1136          * any waiter.
1137          * Fix-up the tid var if the lock has been disowned.
1138          */
1139         if (LK_HOLDER(x) == LK_KERNPROC)
1140                 tid = LK_KERNPROC;
1141
1142         /*
1143          * The lock is held in exclusive mode.
1144          * If the lock is recursed also, then unrecurse it.
1145          */
1146         if (lockmgr_recursed_v(x)) {
1147                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
1148                 lk->lk_recurse--;
1149                 if (lk->lk_recurse == 0)
1150                         atomic_clear_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
1151                 goto out;
1152         }
1153         if (tid != LK_KERNPROC)
1154                 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,
1155                     LOCKSTAT_WRITER);
1156
1157         if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
1158                 goto out;
1159
1160         sleepq_lock(&lk->lock_object);
1161         x = lockmgr_read_value(lk);
1162         v = LK_UNLOCKED;
1163
1164         /*
1165          * If the lock has exclusive waiters, give them
1166          * preference in order to avoid deadlock with
1167          * shared runners up.
1168          * If interruptible sleeps left the exclusive queue
1169          * empty avoid a starvation for the threads sleeping
1170          * on the shared queue by giving them precedence
1171          * and cleaning up the exclusive waiters bit anyway.
1172          * Please note that lk_exslpfail count may be lying
1173          * about the real number of waiters with the
1174          * LK_SLEEPFAIL flag on because they may be used in
1175          * conjunction with interruptible sleeps so
1176          * lk_exslpfail might be considered an 'upper limit'
1177          * bound, including the edge cases.
1178          */
1179         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1180         realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
1181         if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1182                 if (lk->lk_exslpfail != USHRT_MAX && lk->lk_exslpfail < realexslp) {
1183                         lk->lk_exslpfail = 0;
1184                         queue = SQ_EXCLUSIVE_QUEUE;
1185                         v |= (x & LK_SHARED_WAITERS);
1186                 } else {
1187                         lk->lk_exslpfail = 0;
1188                         LOCK_LOG2(lk,
1189                             "%s: %p has only LK_SLEEPFAIL sleepers",
1190                             __func__, lk);
1191                         LOCK_LOG2(lk,
1192                             "%s: %p waking up threads on the exclusive queue",
1193                             __func__, lk);
1194                         wakeup_swapper = sleepq_broadcast(&lk->lock_object,
1195                             SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1196                         queue = SQ_SHARED_QUEUE;
1197                 }
1198         } else {
1199                 /*
1200                  * Exclusive waiters sleeping with LK_SLEEPFAIL
1201                  * on and using interruptible sleeps/timeout
1202                  * may have left spourious lk_exslpfail counts
1203                  * on, so clean it up anyway.
1204                  */
1205                 lk->lk_exslpfail = 0;
1206                 queue = SQ_SHARED_QUEUE;
1207         }
1208
1209         LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
1210             __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1211             "exclusive");
1212         atomic_store_rel_ptr(&lk->lk_lock, v);
1213         wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue);
1214         sleepq_release(&lk->lock_object);
1215
1216 out:
1217         lockmgr_exit(flags, ilk, wakeup_swapper);
1218         return (0);
1219 }
1220
1221 /*
1222  * Lightweight entry points for common operations.
1223  *
1224  * Functionality is similar to sx locks, in that none of the additional lockmgr
1225  * features are supported. To be clear, these are NOT supported:
1226  * 1. shared locking disablement
1227  * 2. returning with an error after sleep
1228  * 3. unlocking the interlock
1229  *
1230  * If in doubt, use lockmgr_lock_flags.
1231  */
1232 int
1233 lockmgr_slock(struct lock *lk, u_int flags, const char *file, int line)
1234 {
1235         uintptr_t x;
1236
1237         MPASS((flags & LK_TYPE_MASK) == LK_SHARED);
1238         MPASS((flags & LK_INTERLOCK) == 0);
1239         MPASS((lk->lock_object.lo_flags & LK_NOSHARE) == 0);
1240
1241         if (LK_CAN_WITNESS(flags))
1242                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
1243                     file, line, NULL);
1244         x = lockmgr_read_value(lk);
1245         if (__predict_true(lockmgr_slock_try(lk, &x, flags, true))) {
1246                 lockmgr_note_shared_acquire(lk, 0, 0, file, line, flags);
1247                 return (0);
1248         }
1249
1250         return (lockmgr_slock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL));
1251 }
1252
1253 int
1254 lockmgr_xlock(struct lock *lk, u_int flags, const char *file, int line)
1255 {
1256         uintptr_t tid;
1257
1258         MPASS((flags & LK_TYPE_MASK) == LK_EXCLUSIVE);
1259         MPASS((flags & LK_INTERLOCK) == 0);
1260
1261         if (LK_CAN_WITNESS(flags))
1262                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1263                     LOP_EXCLUSIVE, file, line, NULL);
1264         tid = (uintptr_t)curthread;
1265         if (atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1266                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
1267                     flags);
1268                 return (0);
1269         }
1270
1271         return (lockmgr_xlock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL));
1272 }
1273
1274 int
1275 lockmgr_unlock(struct lock *lk)
1276 {
1277         uintptr_t x, tid;
1278         const char *file;
1279         int line;
1280
1281         file = __FILE__;
1282         line = __LINE__;
1283
1284         _lockmgr_assert(lk, KA_LOCKED, file, line);
1285         x = lockmgr_read_value(lk);
1286         if (__predict_true(x & LK_SHARE) != 0) {
1287                 lockmgr_note_shared_release(lk, file, line);
1288                 if (lockmgr_sunlock_try(lk, &x)) {
1289                         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
1290                 } else {
1291                         return (lockmgr_sunlock_hard(lk, x, LK_RELEASE, NULL, file, line));
1292                 }
1293         } else {
1294                 tid = (uintptr_t)curthread;
1295                 lockmgr_note_exclusive_release(lk, file, line);
1296                 if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
1297                         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,LOCKSTAT_WRITER);
1298                 } else {
1299                         return (lockmgr_xunlock_hard(lk, x, LK_RELEASE, NULL, file, line));
1300                 }
1301         }
1302         return (0);
1303 }
1304
1305 int
1306 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
1307     const char *wmesg, int pri, int timo, const char *file, int line)
1308 {
1309         GIANT_DECLARE;
1310         struct lockmgr_wait lwa;
1311         struct lock_class *class;
1312         const char *iwmesg;
1313         uintptr_t tid, v, x;
1314         u_int op, realexslp;
1315         int error, ipri, itimo, queue, wakeup_swapper;
1316 #ifdef LOCK_PROFILING
1317         uint64_t waittime = 0;
1318         int contested = 0;
1319 #endif
1320
1321         if (SCHEDULER_STOPPED())
1322                 return (0);
1323
1324         error = 0;
1325         tid = (uintptr_t)curthread;
1326         op = (flags & LK_TYPE_MASK);
1327         iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
1328         ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
1329         itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
1330
1331         lwa.iwmesg = iwmesg;
1332         lwa.ipri = ipri;
1333         lwa.itimo = itimo;
1334
1335         MPASS((flags & ~LK_TOTAL_MASK) == 0);
1336         KASSERT((op & (op - 1)) == 0,
1337             ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
1338         KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
1339             (op != LK_DOWNGRADE && op != LK_RELEASE),
1340             ("%s: Invalid flags in regard of the operation desired @ %s:%d",
1341             __func__, file, line));
1342         KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
1343             ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
1344             __func__, file, line));
1345         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
1346             ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
1347             lk->lock_object.lo_name, file, line));
1348
1349         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
1350
1351         if (lk->lock_object.lo_flags & LK_NOSHARE) {
1352                 switch (op) {
1353                 case LK_SHARED:
1354                         op = LK_EXCLUSIVE;
1355                         break;
1356                 case LK_UPGRADE:
1357                 case LK_TRYUPGRADE:
1358                 case LK_DOWNGRADE:
1359                         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
1360                             file, line);
1361                         if (flags & LK_INTERLOCK)
1362                                 class->lc_unlock(ilk);
1363                         return (0);
1364                 }
1365         }
1366
1367         wakeup_swapper = 0;
1368         switch (op) {
1369         case LK_SHARED:
1370                 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa));
1371                 break;
1372         case LK_UPGRADE:
1373         case LK_TRYUPGRADE:
1374                 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa));
1375                 break;
1376         case LK_EXCLUSIVE:
1377                 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa));
1378                 break;
1379         case LK_DOWNGRADE:
1380                 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1381                 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
1382
1383                 /*
1384                  * Panic if the lock is recursed.
1385                  */
1386                 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1387                         if (flags & LK_INTERLOCK)
1388                                 class->lc_unlock(ilk);
1389                         panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
1390                             __func__, iwmesg, file, line);
1391                 }
1392                 TD_SLOCKS_INC(curthread);
1393
1394                 /*
1395                  * In order to preserve waiters flags, just spin.
1396                  */
1397                 for (;;) {
1398                         x = lockmgr_read_value(lk);
1399                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1400                         x &= LK_ALL_WAITERS;
1401                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1402                             LK_SHARERS_LOCK(1) | x))
1403                                 break;
1404                         cpu_spinwait();
1405                 }
1406                 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
1407                 LOCKSTAT_RECORD0(lockmgr__downgrade, lk);
1408                 break;
1409         case LK_RELEASE:
1410                 _lockmgr_assert(lk, KA_LOCKED, file, line);
1411                 x = lockmgr_read_value(lk);
1412
1413                 if (__predict_true(x & LK_SHARE) != 0) {
1414                         lockmgr_note_shared_release(lk, file, line);
1415                         return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1416                 } else {
1417                         lockmgr_note_exclusive_release(lk, file, line);
1418                         return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1419                 }
1420                 break;
1421         case LK_DRAIN:
1422                 if (LK_CAN_WITNESS(flags))
1423                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1424                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1425                             ilk : NULL);
1426
1427                 /*
1428                  * Trying to drain a lock we already own will result in a
1429                  * deadlock.
1430                  */
1431                 if (lockmgr_xlocked(lk)) {
1432                         if (flags & LK_INTERLOCK)
1433                                 class->lc_unlock(ilk);
1434                         panic("%s: draining %s with the lock held @ %s:%d\n",
1435                             __func__, iwmesg, file, line);
1436                 }
1437
1438                 for (;;) {
1439                         if (lk->lk_lock == LK_UNLOCKED &&
1440                             atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
1441                                 break;
1442
1443 #ifdef HWPMC_HOOKS
1444                         PMC_SOFT_CALL( , , lock, failed);
1445 #endif
1446                         lock_profile_obtain_lock_failed(&lk->lock_object, false,
1447                             &contested, &waittime);
1448
1449                         /*
1450                          * If the lock is expected to not sleep just give up
1451                          * and return.
1452                          */
1453                         if (LK_TRYOP(flags)) {
1454                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
1455                                     __func__, lk);
1456                                 error = EBUSY;
1457                                 break;
1458                         }
1459
1460                         /*
1461                          * Acquire the sleepqueue chain lock because we
1462                          * probabilly will need to manipulate waiters flags.
1463                          */
1464                         sleepq_lock(&lk->lock_object);
1465                         x = lockmgr_read_value(lk);
1466
1467                         /*
1468                          * if the lock has been released while we spun on
1469                          * the sleepqueue chain lock just try again.
1470                          */
1471                         if (x == LK_UNLOCKED) {
1472                                 sleepq_release(&lk->lock_object);
1473                                 continue;
1474                         }
1475
1476                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1477                         if ((x & ~v) == LK_UNLOCKED) {
1478                                 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1479
1480                                 /*
1481                                  * If interruptible sleeps left the exclusive
1482                                  * queue empty avoid a starvation for the
1483                                  * threads sleeping on the shared queue by
1484                                  * giving them precedence and cleaning up the
1485                                  * exclusive waiters bit anyway.
1486                                  * Please note that lk_exslpfail count may be
1487                                  * lying about the real number of waiters with
1488                                  * the LK_SLEEPFAIL flag on because they may
1489                                  * be used in conjunction with interruptible
1490                                  * sleeps so lk_exslpfail might be considered
1491                                  * an 'upper limit' bound, including the edge
1492                                  * cases.
1493                                  */
1494                                 if (v & LK_EXCLUSIVE_WAITERS) {
1495                                         queue = SQ_EXCLUSIVE_QUEUE;
1496                                         v &= ~LK_EXCLUSIVE_WAITERS;
1497                                 } else {
1498                                         /*
1499                                          * Exclusive waiters sleeping with
1500                                          * LK_SLEEPFAIL on and using
1501                                          * interruptible sleeps/timeout may
1502                                          * have left spourious lk_exslpfail
1503                                          * counts on, so clean it up anyway.
1504                                          */
1505                                         MPASS(v & LK_SHARED_WAITERS);
1506                                         lk->lk_exslpfail = 0;
1507                                         queue = SQ_SHARED_QUEUE;
1508                                         v &= ~LK_SHARED_WAITERS;
1509                                 }
1510                                 if (queue == SQ_EXCLUSIVE_QUEUE) {
1511                                         realexslp =
1512                                             sleepq_sleepcnt(&lk->lock_object,
1513                                             SQ_EXCLUSIVE_QUEUE);
1514                                         if (lk->lk_exslpfail >= realexslp) {
1515                                                 lk->lk_exslpfail = 0;
1516                                                 queue = SQ_SHARED_QUEUE;
1517                                                 v &= ~LK_SHARED_WAITERS;
1518                                                 if (realexslp != 0) {
1519                                                         LOCK_LOG2(lk,
1520                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1521                                                             __func__, lk);
1522                                                         LOCK_LOG2(lk,
1523                         "%s: %p waking up threads on the exclusive queue",
1524                                                             __func__, lk);
1525                                                         wakeup_swapper =
1526                                                             sleepq_broadcast(
1527                                                             &lk->lock_object,
1528                                                             SLEEPQ_LK, 0,
1529                                                             SQ_EXCLUSIVE_QUEUE);
1530                                                 }
1531                                         } else
1532                                                 lk->lk_exslpfail = 0;
1533                                 }
1534                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1535                                         sleepq_release(&lk->lock_object);
1536                                         continue;
1537                                 }
1538                                 LOCK_LOG3(lk,
1539                                 "%s: %p waking up all threads on the %s queue",
1540                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
1541                                     "shared" : "exclusive");
1542                                 wakeup_swapper |= sleepq_broadcast(
1543                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
1544
1545                                 /*
1546                                  * If shared waiters have been woken up we need
1547                                  * to wait for one of them to acquire the lock
1548                                  * before to set the exclusive waiters in
1549                                  * order to avoid a deadlock.
1550                                  */
1551                                 if (queue == SQ_SHARED_QUEUE) {
1552                                         for (v = lk->lk_lock;
1553                                             (v & LK_SHARE) && !LK_SHARERS(v);
1554                                             v = lk->lk_lock)
1555                                                 cpu_spinwait();
1556                                 }
1557                         }
1558
1559                         /*
1560                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1561                          * fail, loop back and retry.
1562                          */
1563                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1564                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1565                                     x | LK_EXCLUSIVE_WAITERS)) {
1566                                         sleepq_release(&lk->lock_object);
1567                                         continue;
1568                                 }
1569                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1570                                     __func__, lk);
1571                         }
1572
1573                         /*
1574                          * As far as we have been unable to acquire the
1575                          * exclusive lock and the exclusive waiters flag
1576                          * is set, we will sleep.
1577                          */
1578                         if (flags & LK_INTERLOCK) {
1579                                 class->lc_unlock(ilk);
1580                                 flags &= ~LK_INTERLOCK;
1581                         }
1582                         GIANT_SAVE();
1583                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1584                             SQ_EXCLUSIVE_QUEUE);
1585                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1586                         GIANT_RESTORE();
1587                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1588                             __func__, lk);
1589                 }
1590
1591                 if (error == 0) {
1592                         lock_profile_obtain_lock_success(&lk->lock_object,
1593                             false, contested, waittime, file, line);
1594                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1595                             lk->lk_recurse, file, line);
1596                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1597                             LK_TRYWIT(flags), file, line);
1598                         TD_LOCKS_INC(curthread);
1599                         STACK_SAVE(lk);
1600                 }
1601                 break;
1602         default:
1603                 if (flags & LK_INTERLOCK)
1604                         class->lc_unlock(ilk);
1605                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1606         }
1607
1608         if (flags & LK_INTERLOCK)
1609                 class->lc_unlock(ilk);
1610         if (wakeup_swapper)
1611                 kick_proc0();
1612
1613         return (error);
1614 }
1615
1616 void
1617 _lockmgr_disown(struct lock *lk, const char *file, int line)
1618 {
1619         uintptr_t tid, x;
1620
1621         if (SCHEDULER_STOPPED())
1622                 return;
1623
1624         tid = (uintptr_t)curthread;
1625         _lockmgr_assert(lk, KA_XLOCKED, file, line);
1626
1627         /*
1628          * Panic if the lock is recursed.
1629          */
1630         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1631                 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1632                     __func__,  file, line);
1633
1634         /*
1635          * If the owner is already LK_KERNPROC just skip the whole operation.
1636          */
1637         if (LK_HOLDER(lk->lk_lock) != tid)
1638                 return;
1639         lock_profile_release_lock(&lk->lock_object, false);
1640         LOCKSTAT_RECORD1(lockmgr__disown, lk, LOCKSTAT_WRITER);
1641         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1642         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1643         TD_LOCKS_DEC(curthread);
1644         STACK_SAVE(lk);
1645
1646         /*
1647          * In order to preserve waiters flags, just spin.
1648          */
1649         for (;;) {
1650                 x = lockmgr_read_value(lk);
1651                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1652                 x &= LK_ALL_WAITERS;
1653                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1654                     LK_KERNPROC | x))
1655                         return;
1656                 cpu_spinwait();
1657         }
1658 }
1659
1660 void
1661 lockmgr_printinfo(const struct lock *lk)
1662 {
1663         struct thread *td;
1664         uintptr_t x;
1665
1666         if (lk->lk_lock == LK_UNLOCKED)
1667                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1668         else if (lk->lk_lock & LK_SHARE)
1669                 printf("lock type %s: SHARED (count %ju)\n",
1670                     lk->lock_object.lo_name,
1671                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1672         else {
1673                 td = lockmgr_xholder(lk);
1674                 if (td == (struct thread *)LK_KERNPROC)
1675                         printf("lock type %s: EXCL by KERNPROC\n",
1676                             lk->lock_object.lo_name);
1677                 else
1678                         printf("lock type %s: EXCL by thread %p "
1679                             "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1680                             td, td->td_proc->p_pid, td->td_proc->p_comm,
1681                             td->td_tid);
1682         }
1683
1684         x = lk->lk_lock;
1685         if (x & LK_EXCLUSIVE_WAITERS)
1686                 printf(" with exclusive waiters pending\n");
1687         if (x & LK_SHARED_WAITERS)
1688                 printf(" with shared waiters pending\n");
1689         if (x & LK_EXCLUSIVE_SPINNERS)
1690                 printf(" with exclusive spinners pending\n");
1691
1692         STACK_PRINT(lk);
1693 }
1694
1695 int
1696 lockstatus(const struct lock *lk)
1697 {
1698         uintptr_t v, x;
1699         int ret;
1700
1701         ret = LK_SHARED;
1702         x = lockmgr_read_value(lk);
1703         v = LK_HOLDER(x);
1704
1705         if ((x & LK_SHARE) == 0) {
1706                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1707                         ret = LK_EXCLUSIVE;
1708                 else
1709                         ret = LK_EXCLOTHER;
1710         } else if (x == LK_UNLOCKED)
1711                 ret = 0;
1712
1713         return (ret);
1714 }
1715
1716 #ifdef INVARIANT_SUPPORT
1717
1718 FEATURE(invariant_support,
1719     "Support for modules compiled with INVARIANTS option");
1720
1721 #ifndef INVARIANTS
1722 #undef  _lockmgr_assert
1723 #endif
1724
1725 void
1726 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1727 {
1728         int slocked = 0;
1729
1730         if (SCHEDULER_STOPPED())
1731                 return;
1732         switch (what) {
1733         case KA_SLOCKED:
1734         case KA_SLOCKED | KA_NOTRECURSED:
1735         case KA_SLOCKED | KA_RECURSED:
1736                 slocked = 1;
1737         case KA_LOCKED:
1738         case KA_LOCKED | KA_NOTRECURSED:
1739         case KA_LOCKED | KA_RECURSED:
1740 #ifdef WITNESS
1741
1742                 /*
1743                  * We cannot trust WITNESS if the lock is held in exclusive
1744                  * mode and a call to lockmgr_disown() happened.
1745                  * Workaround this skipping the check if the lock is held in
1746                  * exclusive mode even for the KA_LOCKED case.
1747                  */
1748                 if (slocked || (lk->lk_lock & LK_SHARE)) {
1749                         witness_assert(&lk->lock_object, what, file, line);
1750                         break;
1751                 }
1752 #endif
1753                 if (lk->lk_lock == LK_UNLOCKED ||
1754                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1755                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1756                         panic("Lock %s not %slocked @ %s:%d\n",
1757                             lk->lock_object.lo_name, slocked ? "share" : "",
1758                             file, line);
1759
1760                 if ((lk->lk_lock & LK_SHARE) == 0) {
1761                         if (lockmgr_recursed(lk)) {
1762                                 if (what & KA_NOTRECURSED)
1763                                         panic("Lock %s recursed @ %s:%d\n",
1764                                             lk->lock_object.lo_name, file,
1765                                             line);
1766                         } else if (what & KA_RECURSED)
1767                                 panic("Lock %s not recursed @ %s:%d\n",
1768                                     lk->lock_object.lo_name, file, line);
1769                 }
1770                 break;
1771         case KA_XLOCKED:
1772         case KA_XLOCKED | KA_NOTRECURSED:
1773         case KA_XLOCKED | KA_RECURSED:
1774                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1775                         panic("Lock %s not exclusively locked @ %s:%d\n",
1776                             lk->lock_object.lo_name, file, line);
1777                 if (lockmgr_recursed(lk)) {
1778                         if (what & KA_NOTRECURSED)
1779                                 panic("Lock %s recursed @ %s:%d\n",
1780                                     lk->lock_object.lo_name, file, line);
1781                 } else if (what & KA_RECURSED)
1782                         panic("Lock %s not recursed @ %s:%d\n",
1783                             lk->lock_object.lo_name, file, line);
1784                 break;
1785         case KA_UNLOCKED:
1786                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1787                         panic("Lock %s exclusively locked @ %s:%d\n",
1788                             lk->lock_object.lo_name, file, line);
1789                 break;
1790         default:
1791                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1792                     line);
1793         }
1794 }
1795 #endif
1796
1797 #ifdef DDB
1798 int
1799 lockmgr_chain(struct thread *td, struct thread **ownerp)
1800 {
1801         const struct lock *lk;
1802
1803         lk = td->td_wchan;
1804
1805         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1806                 return (0);
1807         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1808         if (lk->lk_lock & LK_SHARE)
1809                 db_printf("SHARED (count %ju)\n",
1810                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1811         else
1812                 db_printf("EXCL\n");
1813         *ownerp = lockmgr_xholder(lk);
1814
1815         return (1);
1816 }
1817
1818 static void
1819 db_show_lockmgr(const struct lock_object *lock)
1820 {
1821         struct thread *td;
1822         const struct lock *lk;
1823
1824         lk = (const struct lock *)lock;
1825
1826         db_printf(" state: ");
1827         if (lk->lk_lock == LK_UNLOCKED)
1828                 db_printf("UNLOCKED\n");
1829         else if (lk->lk_lock & LK_SHARE)
1830                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1831         else {
1832                 td = lockmgr_xholder(lk);
1833                 if (td == (struct thread *)LK_KERNPROC)
1834                         db_printf("XLOCK: LK_KERNPROC\n");
1835                 else
1836                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1837                             td->td_tid, td->td_proc->p_pid,
1838                             td->td_proc->p_comm);
1839                 if (lockmgr_recursed(lk))
1840                         db_printf(" recursed: %d\n", lk->lk_recurse);
1841         }
1842         db_printf(" waiters: ");
1843         switch (lk->lk_lock & LK_ALL_WAITERS) {
1844         case LK_SHARED_WAITERS:
1845                 db_printf("shared\n");
1846                 break;
1847         case LK_EXCLUSIVE_WAITERS:
1848                 db_printf("exclusive\n");
1849                 break;
1850         case LK_ALL_WAITERS:
1851                 db_printf("shared and exclusive\n");
1852                 break;
1853         default:
1854                 db_printf("none\n");
1855         }
1856         db_printf(" spinners: ");
1857         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1858                 db_printf("exclusive\n");
1859         else
1860                 db_printf("none\n");
1861 }
1862 #endif