sys/kern/kern_lock.c

   1 /*-
   2  * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice(s), this list of conditions and the following disclaimer as
  10  *    the first lines of this file unmodified other than the possible
  11  *    addition of one or more copyright notices.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice(s), this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
  17  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  18  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  19  * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
  20  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  21  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  22  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  23  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  26  * DAMAGE.
  27  */
  28
  29 #include "opt_adaptive_lockmgrs.h"
  30 #include "opt_ddb.h"
  31 #include "opt_kdtrace.h"
  32
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 #include <sys/param.h>
  37 #include <sys/ktr.h>
  38 #include <sys/lock.h>
  39 #include <sys/lock_profile.h>
  40 #include <sys/lockmgr.h>
  41 #include <sys/mutex.h>
  42 #include <sys/proc.h>
  43 #include <sys/sleepqueue.h>
  44 #ifdef DEBUG_LOCKS
  45 #include <sys/stack.h>
  46 #endif
  47 #include <sys/sysctl.h>
  48 #include <sys/systm.h>
  49
  50 #include <machine/cpu.h>
  51
  52 #ifdef DDB
  53 #include <ddb/ddb.h>
  54 #endif
  55
  56 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
  57     (LK_ADAPTIVE | LK_NOSHARE));
  58 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
  59     ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
  60
  61 #define SQ_EXCLUSIVE_QUEUE      0
  62 #define SQ_SHARED_QUEUE         1
  63
  64 #ifndef INVARIANTS
  65 #define _lockmgr_assert(lk, what, file, line)
  66 #define TD_LOCKS_INC(td)
  67 #define TD_LOCKS_DEC(td)
  68 #else
  69 #define TD_LOCKS_INC(td)        ((td)->td_locks++)
  70 #define TD_LOCKS_DEC(td)        ((td)->td_locks--)
  71 #endif
  72 #define TD_SLOCKS_INC(td)       ((td)->td_lk_slocks++)
  73 #define TD_SLOCKS_DEC(td)       ((td)->td_lk_slocks--)
  74
  75 #ifndef DEBUG_LOCKS
  76 #define STACK_PRINT(lk)
  77 #define STACK_SAVE(lk)
  78 #define STACK_ZERO(lk)
  79 #else
  80 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
  81 #define STACK_SAVE(lk)  stack_save(&(lk)->lk_stack)
  82 #define STACK_ZERO(lk)  stack_zero(&(lk)->lk_stack)
  83 #endif
  84
  85 #define LOCK_LOG2(lk, string, arg1, arg2)                               \
  86         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  87                 CTR2(KTR_LOCK, (string), (arg1), (arg2))
  88 #define LOCK_LOG3(lk, string, arg1, arg2, arg3)                         \
  89         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  90                 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
  91
  92 #define GIANT_DECLARE                                                   \
  93         int _i = 0;                                                     \
  94         WITNESS_SAVE_DECL(Giant)
  95 #define GIANT_RESTORE() do {                                            \
  96         if (_i > 0) {                                                   \
  97                 while (_i--)                                            \
  98                         mtx_lock(&Giant);                               \
  99                 WITNESS_RESTORE(&Giant.lock_object, Giant);             \
 100         }                                                               \
 101 } while (0)
 102 #define GIANT_SAVE() do {                                               \
 103         if (mtx_owned(&Giant)) {                                        \
 104                 WITNESS_SAVE(&Giant.lock_object, Giant);                \
 105                 while (mtx_owned(&Giant)) {                             \
 106                         _i++;                                           \
 107                         mtx_unlock(&Giant);                             \
 108                 }                                                       \
 109         }                                                               \
 110 } while (0)
 111
 112 #define LK_CAN_SHARE(x)                                                 \
 113         (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 ||      \
 114         ((x) & LK_EXCLUSIVE_SPINNERS) == 0 ||                           \
 115         curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT)))
 116 #define LK_TRYOP(x)                                                     \
 117         ((x) & LK_NOWAIT)
 118
 119 #define LK_CAN_WITNESS(x)                                               \
 120         (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
 121 #define LK_TRYWIT(x)                                                    \
 122         (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
 123
 124 #define LK_CAN_ADAPT(lk, f)                                             \
 125         (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 &&             \
 126         ((f) & LK_SLEEPFAIL) == 0)
 127
 128 #define lockmgr_disowned(lk)                                            \
 129         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
 130
 131 #define lockmgr_xlocked(lk)                                             \
 132         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
 133
 134 static void      assert_lockmgr(struct lock_object *lock, int how);
 135 #ifdef DDB
 136 static void      db_show_lockmgr(struct lock_object *lock);
 137 #endif
 138 static void      lock_lockmgr(struct lock_object *lock, int how);
 139 #ifdef KDTRACE_HOOKS
 140 static int       owner_lockmgr(struct lock_object *lock, struct thread **owner);
 141 #endif
 142 static int       unlock_lockmgr(struct lock_object *lock);
 143
 144 struct lock_class lock_class_lockmgr = {
 145         .lc_name = "lockmgr",
 146         .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
 147         .lc_assert = assert_lockmgr,
 148 #ifdef DDB
 149         .lc_ddb_show = db_show_lockmgr,
 150 #endif
 151         .lc_lock = lock_lockmgr,
 152         .lc_unlock = unlock_lockmgr,
 153 #ifdef KDTRACE_HOOKS
 154         .lc_owner = owner_lockmgr,
 155 #endif
 156 };
 157
 158 #ifdef ADAPTIVE_LOCKMGRS
 159 static u_int alk_retries = 10;
 160 static u_int alk_loops = 10000;
 161 SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, "lockmgr debugging");
 162 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, "");
 163 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, "");
 164 #endif
 165
 166 static __inline struct thread *
 167 lockmgr_xholder(struct lock *lk)
 168 {
 169         uintptr_t x;
 170
 171         x = lk->lk_lock;
 172         return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
 173 }
 174
 175 /*
 176  * It assumes sleepq_lock held and returns with this one unheld.
 177  * It also assumes the generic interlock is sane and previously checked.
 178  * If LK_INTERLOCK is specified the interlock is not reacquired after the
 179  * sleep.
 180  */
 181 static __inline int
 182 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
 183     const char *wmesg, int pri, int timo, int queue)
 184 {
 185         GIANT_DECLARE;
 186         struct lock_class *class;
 187         int catch, error;
 188
 189         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 190         catch = pri & PCATCH;
 191         pri &= PRIMASK;
 192         error = 0;
 193
 194         LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
 195             (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
 196
 197         if (flags & LK_INTERLOCK)
 198                 class->lc_unlock(ilk);
 199         if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
 200                 lk->lk_exslpfail++;
 201         GIANT_SAVE();
 202         sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
 203             SLEEPQ_INTERRUPTIBLE : 0), queue);
 204         if ((flags & LK_TIMELOCK) && timo)
 205                 sleepq_set_timeout(&lk->lock_object, timo);
 206
 207         /*
 208          * Decisional switch for real sleeping.
 209          */
 210         if ((flags & LK_TIMELOCK) && timo && catch)
 211                 error = sleepq_timedwait_sig(&lk->lock_object, pri);
 212         else if ((flags & LK_TIMELOCK) && timo)
 213                 error = sleepq_timedwait(&lk->lock_object, pri);
 214         else if (catch)
 215                 error = sleepq_wait_sig(&lk->lock_object, pri);
 216         else
 217                 sleepq_wait(&lk->lock_object, pri);
 218         GIANT_RESTORE();
 219         if ((flags & LK_SLEEPFAIL) && error == 0)
 220                 error = ENOLCK;
 221
 222         return (error);
 223 }
 224
 225 static __inline int
 226 wakeupshlk(struct lock *lk, const char *file, int line)
 227 {
 228         uintptr_t v, x;
 229         u_int realexslp;
 230         int queue, wakeup_swapper;
 231
 232         TD_LOCKS_DEC(curthread);
 233         TD_SLOCKS_DEC(curthread);
 234         WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
 235         LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
 236
 237         wakeup_swapper = 0;
 238         for (;;) {
 239                 x = lk->lk_lock;
 240
 241                 /*
 242                  * If there is more than one shared lock held, just drop one
 243                  * and return.
 244                  */
 245                 if (LK_SHARERS(x) > 1) {
 246                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, x,
 247                             x - LK_ONE_SHARER))
 248                                 break;
 249                         continue;
 250                 }
 251
 252                 /*
 253                  * If there are not waiters on the exclusive queue, drop the
 254                  * lock quickly.
 255                  */
 256                 if ((x & LK_ALL_WAITERS) == 0) {
 257                         MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
 258                             LK_SHARERS_LOCK(1));
 259                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED))
 260                                 break;
 261                         continue;
 262                 }
 263
 264                 /*
 265                  * We should have a sharer with waiters, so enter the hard
 266                  * path in order to handle wakeups correctly.
 267                  */
 268                 sleepq_lock(&lk->lock_object);
 269                 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 270                 v = LK_UNLOCKED;
 271
 272                 /*
 273                  * If the lock has exclusive waiters, give them preference in
 274                  * order to avoid deadlock with shared runners up.
 275                  * If interruptible sleeps left the exclusive queue empty
 276                  * avoid a starvation for the threads sleeping on the shared
 277                  * queue by giving them precedence and cleaning up the
 278                  * exclusive waiters bit anyway.
 279                  * Please note that lk_exslpfail count may be lying about
 280                  * the real number of waiters with the LK_SLEEPFAIL flag on
 281                  * because they may be used in conjuction with interruptible
 282                  * sleeps so lk_exslpfail might be considered an 'upper limit'
 283                  * bound, including the edge cases.
 284                  */
 285                 realexslp = sleepq_sleepcnt(&lk->lock_object,
 286                     SQ_EXCLUSIVE_QUEUE);
 287                 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
 288                         if (lk->lk_exslpfail < realexslp) {
 289                                 lk->lk_exslpfail = 0;
 290                                 queue = SQ_EXCLUSIVE_QUEUE;
 291                                 v |= (x & LK_SHARED_WAITERS);
 292                         } else {
 293                                 lk->lk_exslpfail = 0;
 294                                 LOCK_LOG2(lk,
 295                                     "%s: %p has only LK_SLEEPFAIL sleepers",
 296                                     __func__, lk);
 297                                 LOCK_LOG2(lk,
 298                             "%s: %p waking up threads on the exclusive queue",
 299                                     __func__, lk);
 300                                 wakeup_swapper =
 301                                     sleepq_broadcast(&lk->lock_object,
 302                                     SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
 303                                 queue = SQ_SHARED_QUEUE;
 304                         }
 305
 306                 } else {
 307
 308                         /*
 309                          * Exclusive waiters sleeping with LK_SLEEPFAIL on
 310                          * and using interruptible sleeps/timeout may have
 311                          * left spourious lk_exslpfail counts on, so clean
 312                          * it up anyway.
 313                          */
 314                         lk->lk_exslpfail = 0;
 315                         queue = SQ_SHARED_QUEUE;
 316                 }
 317
 318                 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
 319                     v)) {
 320                         sleepq_release(&lk->lock_object);
 321                         continue;
 322                 }
 323                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 324                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 325                     "exclusive");
 326                 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
 327                     0, queue);
 328                 sleepq_release(&lk->lock_object);
 329                 break;
 330         }
 331
 332         lock_profile_release_lock(&lk->lock_object);
 333         return (wakeup_swapper);
 334 }
 335
 336 static void
 337 assert_lockmgr(struct lock_object *lock, int what)
 338 {
 339
 340         panic("lockmgr locks do not support assertions");
 341 }
 342
 343 static void
 344 lock_lockmgr(struct lock_object *lock, int how)
 345 {
 346
 347         panic("lockmgr locks do not support sleep interlocking");
 348 }
 349
 350 static int
 351 unlock_lockmgr(struct lock_object *lock)
 352 {
 353
 354         panic("lockmgr locks do not support sleep interlocking");
 355 }
 356
 357 #ifdef KDTRACE_HOOKS
 358 static int
 359 owner_lockmgr(struct lock_object *lock, struct thread **owner)
 360 {
 361
 362         panic("lockmgr locks do not support owner inquiring");
 363 }
 364 #endif
 365
 366 void
 367 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 368 {
 369         int iflags;
 370
 371         MPASS((flags & ~LK_INIT_MASK) == 0);
 372         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
 373             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
 374             &lk->lk_lock));
 375
 376         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
 377         if (flags & LK_CANRECURSE)
 378                 iflags |= LO_RECURSABLE;
 379         if ((flags & LK_NODUP) == 0)
 380                 iflags |= LO_DUPOK;
 381         if (flags & LK_NOPROFILE)
 382                 iflags |= LO_NOPROFILE;
 383         if ((flags & LK_NOWITNESS) == 0)
 384                 iflags |= LO_WITNESS;
 385         if (flags & LK_QUIET)
 386                 iflags |= LO_QUIET;
 387         iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
 388
 389         lk->lk_lock = LK_UNLOCKED;
 390         lk->lk_recurse = 0;
 391         lk->lk_exslpfail = 0;
 392         lk->lk_timo = timo;
 393         lk->lk_pri = pri;
 394         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
 395         STACK_ZERO(lk);
 396 }
 397
 398 /*
 399  * XXX: Gross hacks to manipulate external lock flags after
 400  * initialization.  Used for certain vnode and buf locks.
 401  */
 402 void
 403 lockallowshare(struct lock *lk)
 404 {
 405
 406         lockmgr_assert(lk, KA_XLOCKED);
 407         lk->lock_object.lo_flags &= ~LK_NOSHARE;
 408 }
 409
 410 void
 411 lockallowrecurse(struct lock *lk)
 412 {
 413
 414         lockmgr_assert(lk, KA_XLOCKED);
 415         lk->lock_object.lo_flags |= LO_RECURSABLE;
 416 }
 417
 418 void
 419 lockdisablerecurse(struct lock *lk)
 420 {
 421
 422         lockmgr_assert(lk, KA_XLOCKED);
 423         lk->lock_object.lo_flags &= ~LO_RECURSABLE;
 424 }
 425
 426 void
 427 lockdestroy(struct lock *lk)
 428 {
 429
 430         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
 431         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
 432         KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
 433         lock_destroy(&lk->lock_object);
 434 }
 435
 436 int
 437 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
 438     const char *wmesg, int pri, int timo, const char *file, int line)
 439 {
 440         GIANT_DECLARE;
 441         struct lock_class *class;
 442         const char *iwmesg;
 443         uintptr_t tid, v, x;
 444         u_int op, realexslp;
 445         int error, ipri, itimo, queue, wakeup_swapper;
 446 #ifdef LOCK_PROFILING
 447         uint64_t waittime = 0;
 448         int contested = 0;
 449 #endif
 450 #ifdef ADAPTIVE_LOCKMGRS
 451         volatile struct thread *owner;
 452         u_int i, spintries = 0;
 453 #endif
 454
 455         error = 0;
 456         tid = (uintptr_t)curthread;
 457         op = (flags & LK_TYPE_MASK);
 458         iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
 459         ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
 460         itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
 461
 462         MPASS((flags & ~LK_TOTAL_MASK) == 0);
 463         KASSERT((op & (op - 1)) == 0,
 464             ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
 465         KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
 466             (op != LK_DOWNGRADE && op != LK_RELEASE),
 467             ("%s: Invalid flags in regard of the operation desired @ %s:%d",
 468             __func__, file, line));
 469         KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
 470             ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
 471             __func__, file, line));
 472
 473         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 474         if (panicstr != NULL) {
 475                 if (flags & LK_INTERLOCK)
 476                         class->lc_unlock(ilk);
 477                 return (0);
 478         }
 479
 480         if (lk->lock_object.lo_flags & LK_NOSHARE) {
 481                 switch (op) {
 482                 case LK_SHARED:
 483                         op = LK_EXCLUSIVE;
 484                         break;
 485                 case LK_UPGRADE:
 486                 case LK_DOWNGRADE:
 487                         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
 488                             file, line);
 489                         return (0);
 490                 }
 491         }
 492
 493         wakeup_swapper = 0;
 494         switch (op) {
 495         case LK_SHARED:
 496                 if (LK_CAN_WITNESS(flags))
 497                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 498                             file, line, ilk);
 499                 for (;;) {
 500                         x = lk->lk_lock;
 501
 502                         /*
 503                          * If no other thread has an exclusive lock, or
 504                          * no exclusive waiter is present, bump the count of
 505                          * sharers.  Since we have to preserve the state of
 506                          * waiters, if we fail to acquire the shared lock
 507                          * loop back and retry.
 508                          */
 509                         if (LK_CAN_SHARE(x)) {
 510                                 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
 511                                     x + LK_ONE_SHARER))
 512                                         break;
 513                                 continue;
 514                         }
 515                         lock_profile_obtain_lock_failed(&lk->lock_object,
 516                             &contested, &waittime);
 517
 518                         /*
 519                          * If the lock is already held by curthread in
 520                          * exclusive way avoid a deadlock.
 521                          */
 522                         if (LK_HOLDER(x) == tid) {
 523                                 LOCK_LOG2(lk,
 524                                     "%s: %p already held in exclusive mode",
 525                                     __func__, lk);
 526                                 error = EDEADLK;
 527                                 break;
 528                         }
 529
 530                         /*
 531                          * If the lock is expected to not sleep just give up
 532                          * and return.
 533                          */
 534                         if (LK_TRYOP(flags)) {
 535                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 536                                     __func__, lk);
 537                                 error = EBUSY;
 538                                 break;
 539                         }
 540
 541 #ifdef ADAPTIVE_LOCKMGRS
 542                         /*
 543                          * If the owner is running on another CPU, spin until
 544                          * the owner stops running or the state of the lock
 545                          * changes.  We need a double-state handle here
 546                          * because for a failed acquisition the lock can be
 547                          * either held in exclusive mode or shared mode
 548                          * (for the writer starvation avoidance technique).
 549                          */
 550                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 551                             LK_HOLDER(x) != LK_KERNPROC) {
 552                                 owner = (struct thread *)LK_HOLDER(x);
 553                                 if (LOCK_LOG_TEST(&lk->lock_object, 0))
 554                                         CTR3(KTR_LOCK,
 555                                             "%s: spinning on %p held by %p",
 556                                             __func__, lk, owner);
 557
 558                                 /*
 559                                  * If we are holding also an interlock drop it
 560                                  * in order to avoid a deadlock if the lockmgr
 561                                  * owner is adaptively spinning on the
 562                                  * interlock itself.
 563                                  */
 564                                 if (flags & LK_INTERLOCK) {
 565                                         class->lc_unlock(ilk);
 566                                         flags &= ~LK_INTERLOCK;
 567                                 }
 568                                 GIANT_SAVE();
 569                                 while (LK_HOLDER(lk->lk_lock) ==
 570                                     (uintptr_t)owner && TD_IS_RUNNING(owner))
 571                                         cpu_spinwait();
 572                                 GIANT_RESTORE();
 573                                 continue;
 574                         } else if (LK_CAN_ADAPT(lk, flags) &&
 575                             (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
 576                             spintries < alk_retries) {
 577                                 if (flags & LK_INTERLOCK) {
 578                                         class->lc_unlock(ilk);
 579                                         flags &= ~LK_INTERLOCK;
 580                                 }
 581                                 GIANT_SAVE();
 582                                 spintries++;
 583                                 for (i = 0; i < alk_loops; i++) {
 584                                         if (LOCK_LOG_TEST(&lk->lock_object, 0))
 585                                                 CTR4(KTR_LOCK,
 586                                     "%s: shared spinning on %p with %u and %u",
 587                                                     __func__, lk, spintries, i);
 588                                         x = lk->lk_lock;
 589                                         if ((x & LK_SHARE) == 0 ||
 590                                             LK_CAN_SHARE(x) != 0)
 591                                                 break;
 592                                         cpu_spinwait();
 593                                 }
 594                                 GIANT_RESTORE();
 595                                 if (i != alk_loops)
 596                                         continue;
 597                         }
 598 #endif
 599
 600                         /*
 601                          * Acquire the sleepqueue chain lock because we
 602                          * probabilly will need to manipulate waiters flags.
 603                          */
 604                         sleepq_lock(&lk->lock_object);
 605                         x = lk->lk_lock;
 606
 607                         /*
 608                          * if the lock can be acquired in shared mode, try
 609                          * again.
 610                          */
 611                         if (LK_CAN_SHARE(x)) {
 612                                 sleepq_release(&lk->lock_object);
 613                                 continue;
 614                         }
 615
 616 #ifdef ADAPTIVE_LOCKMGRS
 617                         /*
 618                          * The current lock owner might have started executing
 619                          * on another CPU (or the lock could have changed
 620                          * owner) while we were waiting on the turnstile
 621                          * chain lock.  If so, drop the turnstile lock and try
 622                          * again.
 623                          */
 624                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 625                             LK_HOLDER(x) != LK_KERNPROC) {
 626                                 owner = (struct thread *)LK_HOLDER(x);
 627                                 if (TD_IS_RUNNING(owner)) {
 628                                         sleepq_release(&lk->lock_object);
 629                                         continue;
 630                                 }
 631                         }
 632 #endif
 633
 634                         /*
 635                          * Try to set the LK_SHARED_WAITERS flag.  If we fail,
 636                          * loop back and retry.
 637                          */
 638                         if ((x & LK_SHARED_WAITERS) == 0) {
 639                                 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
 640                                     x | LK_SHARED_WAITERS)) {
 641                                         sleepq_release(&lk->lock_object);
 642                                         continue;
 643                                 }
 644                                 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
 645                                     __func__, lk);
 646                         }
 647
 648                         /*
 649                          * As far as we have been unable to acquire the
 650                          * shared lock and the shared waiters flag is set,
 651                          * we will sleep.
 652                          */
 653                         error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 654                             SQ_SHARED_QUEUE);
 655                         flags &= ~LK_INTERLOCK;
 656                         if (error) {
 657                                 LOCK_LOG3(lk,
 658                                     "%s: interrupted sleep for %p with %d",
 659                                     __func__, lk, error);
 660                                 break;
 661                         }
 662                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 663                             __func__, lk);
 664                 }
 665                 if (error == 0) {
 666                         lock_profile_obtain_lock_success(&lk->lock_object,
 667                             contested, waittime, file, line);
 668                         LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
 669                             line);
 670                         WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
 671                             line);
 672                         TD_LOCKS_INC(curthread);
 673                         TD_SLOCKS_INC(curthread);
 674                         STACK_SAVE(lk);
 675                 }
 676                 break;
 677         case LK_UPGRADE:
 678                 _lockmgr_assert(lk, KA_SLOCKED, file, line);
 679                 v = lk->lk_lock;
 680                 x = v & LK_ALL_WAITERS;
 681                 v &= LK_EXCLUSIVE_SPINNERS;
 682
 683                 /*
 684                  * Try to switch from one shared lock to an exclusive one.
 685                  * We need to preserve waiters flags during the operation.
 686                  */
 687                 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
 688                     tid | x)) {
 689                         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
 690                             line);
 691                         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
 692                             LK_TRYWIT(flags), file, line);
 693                         TD_SLOCKS_DEC(curthread);
 694                         break;
 695                 }
 696
 697                 /*
 698                  * We have been unable to succeed in upgrading, so just
 699                  * give up the shared lock.
 700                  */
 701                 wakeup_swapper |= wakeupshlk(lk, file, line);
 702
 703                 /* FALLTHROUGH */
 704         case LK_EXCLUSIVE:
 705                 if (LK_CAN_WITNESS(flags))
 706                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 707                             LOP_EXCLUSIVE, file, line, ilk);
 708
 709                 /*
 710                  * If curthread already holds the lock and this one is
 711                  * allowed to recurse, simply recurse on it.
 712                  */
 713                 if (lockmgr_xlocked(lk)) {
 714                         if ((flags & LK_CANRECURSE) == 0 &&
 715                             (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
 716
 717                                 /*
 718                                  * If the lock is expected to not panic just
 719                                  * give up and return.
 720                                  */
 721                                 if (LK_TRYOP(flags)) {
 722                                         LOCK_LOG2(lk,
 723                                             "%s: %p fails the try operation",
 724                                             __func__, lk);
 725                                         error = EBUSY;
 726                                         break;
 727                                 }
 728                                 if (flags & LK_INTERLOCK)
 729                                         class->lc_unlock(ilk);
 730                 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
 731                                     __func__, iwmesg, file, line);
 732                         }
 733                         lk->lk_recurse++;
 734                         LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
 735                         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 736                             lk->lk_recurse, file, line);
 737                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 738                             LK_TRYWIT(flags), file, line);
 739                         TD_LOCKS_INC(curthread);
 740                         break;
 741                 }
 742
 743                 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
 744                     tid)) {
 745                         lock_profile_obtain_lock_failed(&lk->lock_object,
 746                             &contested, &waittime);
 747
 748                         /*
 749                          * If the lock is expected to not sleep just give up
 750                          * and return.
 751                          */
 752                         if (LK_TRYOP(flags)) {
 753                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 754                                     __func__, lk);
 755                                 error = EBUSY;
 756                                 break;
 757                         }
 758
 759 #ifdef ADAPTIVE_LOCKMGRS
 760                         /*
 761                          * If the owner is running on another CPU, spin until
 762                          * the owner stops running or the state of the lock
 763                          * changes.
 764                          */
 765                         x = lk->lk_lock;
 766                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 767                             LK_HOLDER(x) != LK_KERNPROC) {
 768                                 owner = (struct thread *)LK_HOLDER(x);
 769                                 if (LOCK_LOG_TEST(&lk->lock_object, 0))
 770                                         CTR3(KTR_LOCK,
 771                                             "%s: spinning on %p held by %p",
 772                                             __func__, lk, owner);
 773
 774                                 /*
 775                                  * If we are holding also an interlock drop it
 776                                  * in order to avoid a deadlock if the lockmgr
 777                                  * owner is adaptively spinning on the
 778                                  * interlock itself.
 779                                  */
 780                                 if (flags & LK_INTERLOCK) {
 781                                         class->lc_unlock(ilk);
 782                                         flags &= ~LK_INTERLOCK;
 783                                 }
 784                                 GIANT_SAVE();
 785                                 while (LK_HOLDER(lk->lk_lock) ==
 786                                     (uintptr_t)owner && TD_IS_RUNNING(owner))
 787                                         cpu_spinwait();
 788                                 GIANT_RESTORE();
 789                                 continue;
 790                         } else if (LK_CAN_ADAPT(lk, flags) &&
 791                             (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
 792                             spintries < alk_retries) {
 793                                 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
 794                                     !atomic_cmpset_ptr(&lk->lk_lock, x,
 795                                     x | LK_EXCLUSIVE_SPINNERS))
 796                                         continue;
 797                                 if (flags & LK_INTERLOCK) {
 798                                         class->lc_unlock(ilk);
 799                                         flags &= ~LK_INTERLOCK;
 800                                 }
 801                                 GIANT_SAVE();
 802                                 spintries++;
 803                                 for (i = 0; i < alk_loops; i++) {
 804                                         if (LOCK_LOG_TEST(&lk->lock_object, 0))
 805                                                 CTR4(KTR_LOCK,
 806                                     "%s: shared spinning on %p with %u and %u",
 807                                                     __func__, lk, spintries, i);
 808                                         if ((lk->lk_lock &
 809                                             LK_EXCLUSIVE_SPINNERS) == 0)
 810                                                 break;
 811                                         cpu_spinwait();
 812                                 }
 813                                 GIANT_RESTORE();
 814                                 if (i != alk_loops)
 815                                         continue;
 816                         }
 817 #endif
 818
 819                         /*
 820                          * Acquire the sleepqueue chain lock because we
 821                          * probabilly will need to manipulate waiters flags.
 822                          */
 823                         sleepq_lock(&lk->lock_object);
 824                         x = lk->lk_lock;
 825
 826                         /*
 827                          * if the lock has been released while we spun on
 828                          * the sleepqueue chain lock just try again.
 829                          */
 830                         if (x == LK_UNLOCKED) {
 831                                 sleepq_release(&lk->lock_object);
 832                                 continue;
 833                         }
 834
 835 #ifdef ADAPTIVE_LOCKMGRS
 836                         /*
 837                          * The current lock owner might have started executing
 838                          * on another CPU (or the lock could have changed
 839                          * owner) while we were waiting on the turnstile
 840                          * chain lock.  If so, drop the turnstile lock and try
 841                          * again.
 842                          */
 843                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 844                             LK_HOLDER(x) != LK_KERNPROC) {
 845                                 owner = (struct thread *)LK_HOLDER(x);
 846                                 if (TD_IS_RUNNING(owner)) {
 847                                         sleepq_release(&lk->lock_object);
 848                                         continue;
 849                                 }
 850                         }
 851 #endif
 852
 853                         /*
 854                          * The lock can be in the state where there is a
 855                          * pending queue of waiters, but still no owner.
 856                          * This happens when the lock is contested and an
 857                          * owner is going to claim the lock.
 858                          * If curthread is the one successfully acquiring it
 859                          * claim lock ownership and return, preserving waiters
 860                          * flags.
 861                          */
 862                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 863                         if ((x & ~v) == LK_UNLOCKED) {
 864                                 v &= ~LK_EXCLUSIVE_SPINNERS;
 865                                 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
 866                                     tid | v)) {
 867                                         sleepq_release(&lk->lock_object);
 868                                         LOCK_LOG2(lk,
 869                                             "%s: %p claimed by a new writer",
 870                                             __func__, lk);
 871                                         break;
 872                                 }
 873                                 sleepq_release(&lk->lock_object);
 874                                 continue;
 875                         }
 876
 877                         /*
 878                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
 879                          * fail, loop back and retry.
 880                          */
 881                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
 882                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
 883                                     x | LK_EXCLUSIVE_WAITERS)) {
 884                                         sleepq_release(&lk->lock_object);
 885                                         continue;
 886                                 }
 887                                 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
 888                                     __func__, lk);
 889                         }
 890
 891                         /*
 892                          * As far as we have been unable to acquire the
 893                          * exclusive lock and the exclusive waiters flag
 894                          * is set, we will sleep.
 895                          */
 896                         error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 897                             SQ_EXCLUSIVE_QUEUE);
 898                         flags &= ~LK_INTERLOCK;
 899                         if (error) {
 900                                 LOCK_LOG3(lk,
 901                                     "%s: interrupted sleep for %p with %d",
 902                                     __func__, lk, error);
 903                                 break;
 904                         }
 905                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 906                             __func__, lk);
 907                 }
 908                 if (error == 0) {
 909                         lock_profile_obtain_lock_success(&lk->lock_object,
 910                             contested, waittime, file, line);
 911                         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 912                             lk->lk_recurse, file, line);
 913                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 914                             LK_TRYWIT(flags), file, line);
 915                         TD_LOCKS_INC(curthread);
 916                         STACK_SAVE(lk);
 917                 }
 918                 break;
 919         case LK_DOWNGRADE:
 920                 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
 921                 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
 922                 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
 923                 TD_SLOCKS_INC(curthread);
 924
 925                 /*
 926                  * In order to preserve waiters flags, just spin.
 927                  */
 928                 for (;;) {
 929                         x = lk->lk_lock;
 930                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
 931                         x &= LK_ALL_WAITERS;
 932                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
 933                             LK_SHARERS_LOCK(1) | x))
 934                                 break;
 935                         cpu_spinwait();
 936                 }
 937                 break;
 938         case LK_RELEASE:
 939                 _lockmgr_assert(lk, KA_LOCKED, file, line);
 940                 x = lk->lk_lock;
 941
 942                 if ((x & LK_SHARE) == 0) {
 943
 944                         /*
 945                          * As first option, treact the lock as if it has not
 946                          * any waiter.
 947                          * Fix-up the tid var if the lock has been disowned.
 948                          */
 949                         if (LK_HOLDER(x) == LK_KERNPROC)
 950                                 tid = LK_KERNPROC;
 951                         else {
 952                                 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
 953                                     file, line);
 954                                 TD_LOCKS_DEC(curthread);
 955                         }
 956                         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
 957                             lk->lk_recurse, file, line);
 958
 959                         /*
 960                          * The lock is held in exclusive mode.
 961                          * If the lock is recursed also, then unrecurse it.
 962                          */
 963                         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
 964                                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
 965                                     lk);
 966                                 lk->lk_recurse--;
 967                                 break;
 968                         }
 969                         if (tid != LK_KERNPROC)
 970                                 lock_profile_release_lock(&lk->lock_object);
 971
 972                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
 973                             LK_UNLOCKED))
 974                                 break;
 975
 976                         sleepq_lock(&lk->lock_object);
 977                         x = lk->lk_lock;
 978                         v = LK_UNLOCKED;
 979
 980                         /*
 981                          * If the lock has exclusive waiters, give them
 982                          * preference in order to avoid deadlock with
 983                          * shared runners up.
 984                          * If interruptible sleeps left the exclusive queue
 985                          * empty avoid a starvation for the threads sleeping
 986                          * on the shared queue by giving them precedence
 987                          * and cleaning up the exclusive waiters bit anyway.
 988                          * Please note that lk_exslpfail count may be lying
 989                          * about the real number of waiters with the
 990                          * LK_SLEEPFAIL flag on because they may be used in
 991                          * conjuction with interruptible sleeps so
 992                          * lk_exslpfail might be considered an 'upper limit'
 993                          * bound, including the edge cases.
 994                          */
 995                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
 996                         realexslp = sleepq_sleepcnt(&lk->lock_object,
 997                             SQ_EXCLUSIVE_QUEUE);
 998                         if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
 999                                 if (lk->lk_exslpfail < realexslp) {
1000                                         lk->lk_exslpfail = 0;
1001                                         queue = SQ_EXCLUSIVE_QUEUE;
1002                                         v |= (x & LK_SHARED_WAITERS);
1003                                 } else {
1004                                         lk->lk_exslpfail = 0;
1005                                         LOCK_LOG2(lk,
1006                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1007                                             __func__, lk);
1008                                         LOCK_LOG2(lk,
1009                         "%s: %p waking up threads on the exclusive queue",
1010                                             __func__, lk);
1011                                         wakeup_swapper =
1012                                             sleepq_broadcast(&lk->lock_object,
1013                                             SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1014                                         queue = SQ_SHARED_QUEUE;
1015                                 }
1016                         } else {
1017
1018                                 /*
1019                                  * Exclusive waiters sleeping with LK_SLEEPFAIL
1020                                  * on and using interruptible sleeps/timeout
1021                                  * may have left spourious lk_exslpfail counts
1022                                  * on, so clean it up anyway.
1023                                  */
1024                                 lk->lk_exslpfail = 0;
1025                                 queue = SQ_SHARED_QUEUE;
1026                         }
1027
1028                         LOCK_LOG3(lk,
1029                             "%s: %p waking up threads on the %s queue",
1030                             __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1031                             "exclusive");
1032                         atomic_store_rel_ptr(&lk->lk_lock, v);
1033                         wakeup_swapper |= sleepq_broadcast(&lk->lock_object,
1034                             SLEEPQ_LK, 0, queue);
1035                         sleepq_release(&lk->lock_object);
1036                         break;
1037                 } else
1038                         wakeup_swapper = wakeupshlk(lk, file, line);
1039                 break;
1040         case LK_DRAIN:
1041                 if (LK_CAN_WITNESS(flags))
1042                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1043                             LOP_EXCLUSIVE, file, line, ilk);
1044
1045                 /*
1046                  * Trying to drain a lock we already own will result in a
1047                  * deadlock.
1048                  */
1049                 if (lockmgr_xlocked(lk)) {
1050                         if (flags & LK_INTERLOCK)
1051                                 class->lc_unlock(ilk);
1052                         panic("%s: draining %s with the lock held @ %s:%d\n",
1053                             __func__, iwmesg, file, line);
1054                 }
1055
1056                 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1057                         lock_profile_obtain_lock_failed(&lk->lock_object,
1058                             &contested, &waittime);
1059
1060                         /*
1061                          * If the lock is expected to not sleep just give up
1062                          * and return.
1063                          */
1064                         if (LK_TRYOP(flags)) {
1065                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
1066                                     __func__, lk);
1067                                 error = EBUSY;
1068                                 break;
1069                         }
1070
1071                         /*
1072                          * Acquire the sleepqueue chain lock because we
1073                          * probabilly will need to manipulate waiters flags.
1074                          */
1075                         sleepq_lock(&lk->lock_object);
1076                         x = lk->lk_lock;
1077
1078                         /*
1079                          * if the lock has been released while we spun on
1080                          * the sleepqueue chain lock just try again.
1081                          */
1082                         if (x == LK_UNLOCKED) {
1083                                 sleepq_release(&lk->lock_object);
1084                                 continue;
1085                         }
1086
1087                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1088                         if ((x & ~v) == LK_UNLOCKED) {
1089                                 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1090
1091                                 /*
1092                                  * If interruptible sleeps left the exclusive
1093                                  * queue empty avoid a starvation for the
1094                                  * threads sleeping on the shared queue by
1095                                  * giving them precedence and cleaning up the
1096                                  * exclusive waiters bit anyway.
1097                                  * Please note that lk_exslpfail count may be
1098                                  * lying about the real number of waiters with
1099                                  * the LK_SLEEPFAIL flag on because they may
1100                                  * be used in conjuction with interruptible
1101                                  * sleeps so lk_exslpfail might be considered
1102                                  * an 'upper limit' bound, including the edge
1103                                  * cases.
1104                                  */
1105                                 if (v & LK_EXCLUSIVE_WAITERS) {
1106                                         queue = SQ_EXCLUSIVE_QUEUE;
1107                                         v &= ~LK_EXCLUSIVE_WAITERS;
1108                                 } else {
1109
1110                                         /*
1111                                          * Exclusive waiters sleeping with
1112                                          * LK_SLEEPFAIL on and using
1113                                          * interruptible sleeps/timeout may
1114                                          * have left spourious lk_exslpfail
1115                                          * counts on, so clean it up anyway.
1116                                          */
1117                                         MPASS(v & LK_SHARED_WAITERS);
1118                                         lk->lk_exslpfail = 0;
1119                                         queue = SQ_SHARED_QUEUE;
1120                                         v &= ~LK_SHARED_WAITERS;
1121                                 }
1122                                 if (queue == SQ_EXCLUSIVE_QUEUE) {
1123                                         realexslp =
1124                                             sleepq_sleepcnt(&lk->lock_object,
1125                                             SQ_EXCLUSIVE_QUEUE);
1126                                         if (lk->lk_exslpfail >= realexslp) {
1127                                                 lk->lk_exslpfail = 0;
1128                                                 queue = SQ_SHARED_QUEUE;
1129                                                 v &= ~LK_SHARED_WAITERS;
1130                                                 if (realexslp != 0) {
1131                                                         LOCK_LOG2(lk,
1132                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1133                                                             __func__, lk);
1134                                                         LOCK_LOG2(lk,
1135                         "%s: %p waking up threads on the exclusive queue",
1136                                                             __func__, lk);
1137                                                         wakeup_swapper =
1138                                                             sleepq_broadcast(
1139                                                             &lk->lock_object,
1140                                                             SLEEPQ_LK, 0,
1141                                                             SQ_EXCLUSIVE_QUEUE);
1142                                                 }
1143                                         } else
1144                                                 lk->lk_exslpfail = 0;
1145                                 }
1146                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1147                                         sleepq_release(&lk->lock_object);
1148                                         continue;
1149                                 }
1150                                 LOCK_LOG3(lk,
1151                                 "%s: %p waking up all threads on the %s queue",
1152                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
1153                                     "shared" : "exclusive");
1154                                 wakeup_swapper |= sleepq_broadcast(
1155                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
1156
1157                                 /*
1158                                  * If shared waiters have been woken up we need
1159                                  * to wait for one of them to acquire the lock
1160                                  * before to set the exclusive waiters in
1161                                  * order to avoid a deadlock.
1162                                  */
1163                                 if (queue == SQ_SHARED_QUEUE) {
1164                                         for (v = lk->lk_lock;
1165                                             (v & LK_SHARE) && !LK_SHARERS(v);
1166                                             v = lk->lk_lock)
1167                                                 cpu_spinwait();
1168                                 }
1169                         }
1170
1171                         /*
1172                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1173                          * fail, loop back and retry.
1174                          */
1175                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1176                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1177                                     x | LK_EXCLUSIVE_WAITERS)) {
1178                                         sleepq_release(&lk->lock_object);
1179                                         continue;
1180                                 }
1181                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1182                                     __func__, lk);
1183                         }
1184
1185                         /*
1186                          * As far as we have been unable to acquire the
1187                          * exclusive lock and the exclusive waiters flag
1188                          * is set, we will sleep.
1189                          */
1190                         if (flags & LK_INTERLOCK) {
1191                                 class->lc_unlock(ilk);
1192                                 flags &= ~LK_INTERLOCK;
1193                         }
1194                         GIANT_SAVE();
1195                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1196                             SQ_EXCLUSIVE_QUEUE);
1197                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1198                         GIANT_RESTORE();
1199                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1200                             __func__, lk);
1201                 }
1202
1203                 if (error == 0) {
1204                         lock_profile_obtain_lock_success(&lk->lock_object,
1205                             contested, waittime, file, line);
1206                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1207                             lk->lk_recurse, file, line);
1208                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1209                             LK_TRYWIT(flags), file, line);
1210                         TD_LOCKS_INC(curthread);
1211                         STACK_SAVE(lk);
1212                 }
1213                 break;
1214         default:
1215                 if (flags & LK_INTERLOCK)
1216                         class->lc_unlock(ilk);
1217                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1218         }
1219
1220         if (flags & LK_INTERLOCK)
1221                 class->lc_unlock(ilk);
1222         if (wakeup_swapper)
1223                 kick_proc0();
1224
1225         return (error);
1226 }
1227
1228 void
1229 _lockmgr_disown(struct lock *lk, const char *file, int line)
1230 {
1231         uintptr_t tid, x;
1232
1233         tid = (uintptr_t)curthread;
1234         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
1235
1236         /*
1237          * If the owner is already LK_KERNPROC just skip the whole operation.
1238          */
1239         if (LK_HOLDER(lk->lk_lock) != tid)
1240                 return;
1241         lock_profile_release_lock(&lk->lock_object);
1242         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1243         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1244         TD_LOCKS_DEC(curthread);
1245         STACK_SAVE(lk);
1246
1247         /*
1248          * In order to preserve waiters flags, just spin.
1249          */
1250         for (;;) {
1251                 x = lk->lk_lock;
1252                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1253                 x &= LK_ALL_WAITERS;
1254                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1255                     LK_KERNPROC | x))
1256                         return;
1257                 cpu_spinwait();
1258         }
1259 }
1260
1261 void
1262 lockmgr_printinfo(struct lock *lk)
1263 {
1264         struct thread *td;
1265         uintptr_t x;
1266
1267         if (lk->lk_lock == LK_UNLOCKED)
1268                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1269         else if (lk->lk_lock & LK_SHARE)
1270                 printf("lock type %s: SHARED (count %ju)\n",
1271                     lk->lock_object.lo_name,
1272                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1273         else {
1274                 td = lockmgr_xholder(lk);
1275                 printf("lock type %s: EXCL by thread %p (pid %d)\n",
1276                     lk->lock_object.lo_name, td, td->td_proc->p_pid);
1277         }
1278
1279         x = lk->lk_lock;
1280         if (x & LK_EXCLUSIVE_WAITERS)
1281                 printf(" with exclusive waiters pending\n");
1282         if (x & LK_SHARED_WAITERS)
1283                 printf(" with shared waiters pending\n");
1284         if (x & LK_EXCLUSIVE_SPINNERS)
1285                 printf(" with exclusive spinners pending\n");
1286
1287         STACK_PRINT(lk);
1288 }
1289
1290 int
1291 lockstatus(struct lock *lk)
1292 {
1293         uintptr_t v, x;
1294         int ret;
1295
1296         ret = LK_SHARED;
1297         x = lk->lk_lock;
1298         v = LK_HOLDER(x);
1299
1300         if ((x & LK_SHARE) == 0) {
1301                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1302                         ret = LK_EXCLUSIVE;
1303                 else
1304                         ret = LK_EXCLOTHER;
1305         } else if (x == LK_UNLOCKED)
1306                 ret = 0;
1307
1308         return (ret);
1309 }
1310
1311 #ifdef INVARIANT_SUPPORT
1312
1313 FEATURE(invariant_support,
1314     "Support for modules compiled with INVARIANTS option");
1315
1316 #ifndef INVARIANTS
1317 #undef  _lockmgr_assert
1318 #endif
1319
1320 void
1321 _lockmgr_assert(struct lock *lk, int what, const char *file, int line)
1322 {
1323         int slocked = 0;
1324
1325         if (panicstr != NULL)
1326                 return;
1327         switch (what) {
1328         case KA_SLOCKED:
1329         case KA_SLOCKED | KA_NOTRECURSED:
1330         case KA_SLOCKED | KA_RECURSED:
1331                 slocked = 1;
1332         case KA_LOCKED:
1333         case KA_LOCKED | KA_NOTRECURSED:
1334         case KA_LOCKED | KA_RECURSED:
1335 #ifdef WITNESS
1336
1337                 /*
1338                  * We cannot trust WITNESS if the lock is held in exclusive
1339                  * mode and a call to lockmgr_disown() happened.
1340                  * Workaround this skipping the check if the lock is held in
1341                  * exclusive mode even for the KA_LOCKED case.
1342                  */
1343                 if (slocked || (lk->lk_lock & LK_SHARE)) {
1344                         witness_assert(&lk->lock_object, what, file, line);
1345                         break;
1346                 }
1347 #endif
1348                 if (lk->lk_lock == LK_UNLOCKED ||
1349                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1350                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1351                         panic("Lock %s not %slocked @ %s:%d\n",
1352                             lk->lock_object.lo_name, slocked ? "share" : "",
1353                             file, line);
1354
1355                 if ((lk->lk_lock & LK_SHARE) == 0) {
1356                         if (lockmgr_recursed(lk)) {
1357                                 if (what & KA_NOTRECURSED)
1358                                         panic("Lock %s recursed @ %s:%d\n",
1359                                             lk->lock_object.lo_name, file,
1360                                             line);
1361                         } else if (what & KA_RECURSED)
1362                                 panic("Lock %s not recursed @ %s:%d\n",
1363                                     lk->lock_object.lo_name, file, line);
1364                 }
1365                 break;
1366         case KA_XLOCKED:
1367         case KA_XLOCKED | KA_NOTRECURSED:
1368         case KA_XLOCKED | KA_RECURSED:
1369                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1370                         panic("Lock %s not exclusively locked @ %s:%d\n",
1371                             lk->lock_object.lo_name, file, line);
1372                 if (lockmgr_recursed(lk)) {
1373                         if (what & KA_NOTRECURSED)
1374                                 panic("Lock %s recursed @ %s:%d\n",
1375                                     lk->lock_object.lo_name, file, line);
1376                 } else if (what & KA_RECURSED)
1377                         panic("Lock %s not recursed @ %s:%d\n",
1378                             lk->lock_object.lo_name, file, line);
1379                 break;
1380         case KA_UNLOCKED:
1381                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1382                         panic("Lock %s exclusively locked @ %s:%d\n",
1383                             lk->lock_object.lo_name, file, line);
1384                 break;
1385         default:
1386                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1387                     line);
1388         }
1389 }
1390 #endif
1391
1392 #ifdef DDB
1393 int
1394 lockmgr_chain(struct thread *td, struct thread **ownerp)
1395 {
1396         struct lock *lk;
1397
1398         lk = td->td_wchan;
1399
1400         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1401                 return (0);
1402         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1403         if (lk->lk_lock & LK_SHARE)
1404                 db_printf("SHARED (count %ju)\n",
1405                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1406         else
1407                 db_printf("EXCL\n");
1408         *ownerp = lockmgr_xholder(lk);
1409
1410         return (1);
1411 }
1412
1413 static void
1414 db_show_lockmgr(struct lock_object *lock)
1415 {
1416         struct thread *td;
1417         struct lock *lk;
1418
1419         lk = (struct lock *)lock;
1420
1421         db_printf(" state: ");
1422         if (lk->lk_lock == LK_UNLOCKED)
1423                 db_printf("UNLOCKED\n");
1424         else if (lk->lk_lock & LK_SHARE)
1425                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1426         else {
1427                 td = lockmgr_xholder(lk);
1428                 if (td == (struct thread *)LK_KERNPROC)
1429                         db_printf("XLOCK: LK_KERNPROC\n");
1430                 else
1431                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1432                             td->td_tid, td->td_proc->p_pid,
1433                             td->td_proc->p_comm);
1434                 if (lockmgr_recursed(lk))
1435                         db_printf(" recursed: %d\n", lk->lk_recurse);
1436         }
1437         db_printf(" waiters: ");
1438         switch (lk->lk_lock & LK_ALL_WAITERS) {
1439         case LK_SHARED_WAITERS:
1440                 db_printf("shared\n");
1441                 break;
1442         case LK_EXCLUSIVE_WAITERS:
1443                 db_printf("exclusive\n");
1444                 break;
1445         case LK_ALL_WAITERS:
1446                 db_printf("shared and exclusive\n");
1447                 break;
1448         default:
1449                 db_printf("none\n");
1450         }
1451         db_printf(" spinners: ");
1452         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1453                 db_printf("exclusive\n");
1454         else
1455                 db_printf("none\n");
1456 }
1457 #endif