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_hwpmc_hooks.h"
  32
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 #include <sys/param.h>
  37 #include <sys/kdb.h>
  38 #include <sys/ktr.h>
  39 #include <sys/lock.h>
  40 #include <sys/lock_profile.h>
  41 #include <sys/lockmgr.h>
  42 #include <sys/mutex.h>
  43 #include <sys/proc.h>
  44 #include <sys/sleepqueue.h>
  45 #ifdef DEBUG_LOCKS
  46 #include <sys/stack.h>
  47 #endif
  48 #include <sys/sysctl.h>
  49 #include <sys/systm.h>
  50
  51 #include <machine/cpu.h>
  52
  53 #ifdef DDB
  54 #include <ddb/ddb.h>
  55 #endif
  56
  57 #ifdef HWPMC_HOOKS
  58 #include <sys/pmckern.h>
  59 PMC_SOFT_DECLARE( , , lock, failed);
  60 #endif
  61
  62 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
  63     (LK_ADAPTIVE | LK_NOSHARE));
  64 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
  65     ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
  66
  67 #define SQ_EXCLUSIVE_QUEUE      0
  68 #define SQ_SHARED_QUEUE         1
  69
  70 #ifndef INVARIANTS
  71 #define _lockmgr_assert(lk, what, file, line)
  72 #endif
  73
  74 #define TD_SLOCKS_INC(td)       ((td)->td_lk_slocks++)
  75 #define TD_SLOCKS_DEC(td)       ((td)->td_lk_slocks--)
  76
  77 #ifndef DEBUG_LOCKS
  78 #define STACK_PRINT(lk)
  79 #define STACK_SAVE(lk)
  80 #define STACK_ZERO(lk)
  81 #else
  82 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
  83 #define STACK_SAVE(lk)  stack_save(&(lk)->lk_stack)
  84 #define STACK_ZERO(lk)  stack_zero(&(lk)->lk_stack)
  85 #endif
  86
  87 #define LOCK_LOG2(lk, string, arg1, arg2)                               \
  88         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  89                 CTR2(KTR_LOCK, (string), (arg1), (arg2))
  90 #define LOCK_LOG3(lk, string, arg1, arg2, arg3)                         \
  91         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  92                 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
  93
  94 #define GIANT_DECLARE                                                   \
  95         int _i = 0;                                                     \
  96         WITNESS_SAVE_DECL(Giant)
  97 #define GIANT_RESTORE() do {                                            \
  98         if (_i > 0) {                                                   \
  99                 while (_i--)                                            \
 100                         mtx_lock(&Giant);                               \
 101                 WITNESS_RESTORE(&Giant.lock_object, Giant);             \
 102         }                                                               \
 103 } while (0)
 104 #define GIANT_SAVE() do {                                               \
 105         if (mtx_owned(&Giant)) {                                        \
 106                 WITNESS_SAVE(&Giant.lock_object, Giant);                \
 107                 while (mtx_owned(&Giant)) {                             \
 108                         _i++;                                           \
 109                         mtx_unlock(&Giant);                             \
 110                 }                                                       \
 111         }                                                               \
 112 } while (0)
 113
 114 #define LK_CAN_SHARE(x, flags)                                          \
 115         (((x) & LK_SHARE) &&                                            \
 116         (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \
 117         (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||  \
 118         (curthread->td_pflags & TDP_DEADLKTREAT)))
 119 #define LK_TRYOP(x)                                                     \
 120         ((x) & LK_NOWAIT)
 121
 122 #define LK_CAN_WITNESS(x)                                               \
 123         (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
 124 #define LK_TRYWIT(x)                                                    \
 125         (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
 126
 127 #define LK_CAN_ADAPT(lk, f)                                             \
 128         (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 &&             \
 129         ((f) & LK_SLEEPFAIL) == 0)
 130
 131 #define lockmgr_disowned(lk)                                            \
 132         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
 133
 134 #define lockmgr_xlocked(lk)                                             \
 135         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
 136
 137 static void     assert_lockmgr(const struct lock_object *lock, int how);
 138 #ifdef DDB
 139 static void     db_show_lockmgr(const struct lock_object *lock);
 140 #endif
 141 static void     lock_lockmgr(struct lock_object *lock, uintptr_t how);
 142 #ifdef KDTRACE_HOOKS
 143 static int      owner_lockmgr(const struct lock_object *lock,
 144                     struct thread **owner);
 145 #endif
 146 static uintptr_t unlock_lockmgr(struct lock_object *lock);
 147
 148 struct lock_class lock_class_lockmgr = {
 149         .lc_name = "lockmgr",
 150         .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
 151         .lc_assert = assert_lockmgr,
 152 #ifdef DDB
 153         .lc_ddb_show = db_show_lockmgr,
 154 #endif
 155         .lc_lock = lock_lockmgr,
 156         .lc_unlock = unlock_lockmgr,
 157 #ifdef KDTRACE_HOOKS
 158         .lc_owner = owner_lockmgr,
 159 #endif
 160 };
 161
 162 #ifdef ADAPTIVE_LOCKMGRS
 163 static u_int alk_retries = 10;
 164 static u_int alk_loops = 10000;
 165 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL,
 166     "lockmgr debugging");
 167 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, "");
 168 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, "");
 169 #endif
 170
 171 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
 172     int flags);
 173 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t x);
 174
 175 static void
 176 lockmgr_note_shared_acquire(struct lock *lk, int contested,
 177     uint64_t waittime, const char *file, int line, int flags)
 178 {
 179
 180         lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
 181             file, line);
 182         LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
 183         WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
 184         TD_LOCKS_INC(curthread);
 185         TD_SLOCKS_INC(curthread);
 186         STACK_SAVE(lk);
 187 }
 188
 189 static void
 190 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
 191 {
 192
 193         lock_profile_release_lock(&lk->lock_object);
 194         WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
 195         LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
 196         TD_LOCKS_DEC(curthread);
 197         TD_SLOCKS_DEC(curthread);
 198 }
 199
 200 static void
 201 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
 202     uint64_t waittime, const char *file, int line, int flags)
 203 {
 204
 205         lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
 206             file, line);
 207         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
 208         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
 209             line);
 210         TD_LOCKS_INC(curthread);
 211         STACK_SAVE(lk);
 212 }
 213
 214 static void
 215 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
 216 {
 217
 218         lock_profile_release_lock(&lk->lock_object);
 219         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
 220             line);
 221         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
 222         TD_LOCKS_DEC(curthread);
 223 }
 224
 225 static void
 226 lockmgr_note_exclusive_upgrade(struct lock *lk, const char *file, int line,
 227     int flags)
 228 {
 229
 230         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
 231             line);
 232         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
 233             LK_TRYWIT(flags), file, line);
 234         TD_SLOCKS_DEC(curthread);
 235 }
 236
 237 static __inline struct thread *
 238 lockmgr_xholder(const struct lock *lk)
 239 {
 240         uintptr_t x;
 241
 242         x = lk->lk_lock;
 243         return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
 244 }
 245
 246 /*
 247  * It assumes sleepq_lock held and returns with this one unheld.
 248  * It also assumes the generic interlock is sane and previously checked.
 249  * If LK_INTERLOCK is specified the interlock is not reacquired after the
 250  * sleep.
 251  */
 252 static __inline int
 253 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
 254     const char *wmesg, int pri, int timo, int queue)
 255 {
 256         GIANT_DECLARE;
 257         struct lock_class *class;
 258         int catch, error;
 259
 260         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 261         catch = pri & PCATCH;
 262         pri &= PRIMASK;
 263         error = 0;
 264
 265         LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
 266             (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
 267
 268         if (flags & LK_INTERLOCK)
 269                 class->lc_unlock(ilk);
 270         if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
 271                 lk->lk_exslpfail++;
 272         GIANT_SAVE();
 273         sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
 274             SLEEPQ_INTERRUPTIBLE : 0), queue);
 275         if ((flags & LK_TIMELOCK) && timo)
 276                 sleepq_set_timeout(&lk->lock_object, timo);
 277
 278         /*
 279          * Decisional switch for real sleeping.
 280          */
 281         if ((flags & LK_TIMELOCK) && timo && catch)
 282                 error = sleepq_timedwait_sig(&lk->lock_object, pri);
 283         else if ((flags & LK_TIMELOCK) && timo)
 284                 error = sleepq_timedwait(&lk->lock_object, pri);
 285         else if (catch)
 286                 error = sleepq_wait_sig(&lk->lock_object, pri);
 287         else
 288                 sleepq_wait(&lk->lock_object, pri);
 289         GIANT_RESTORE();
 290         if ((flags & LK_SLEEPFAIL) && error == 0)
 291                 error = ENOLCK;
 292
 293         return (error);
 294 }
 295
 296 static __inline int
 297 wakeupshlk(struct lock *lk, const char *file, int line)
 298 {
 299         uintptr_t v, x;
 300         u_int realexslp;
 301         int queue, wakeup_swapper;
 302
 303         wakeup_swapper = 0;
 304         for (;;) {
 305                 x = lk->lk_lock;
 306                 if (lockmgr_sunlock_try(lk, x))
 307                         break;
 308
 309                 /*
 310                  * We should have a sharer with waiters, so enter the hard
 311                  * path in order to handle wakeups correctly.
 312                  */
 313                 sleepq_lock(&lk->lock_object);
 314                 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 315                 v = LK_UNLOCKED;
 316
 317                 /*
 318                  * If the lock has exclusive waiters, give them preference in
 319                  * order to avoid deadlock with shared runners up.
 320                  * If interruptible sleeps left the exclusive queue empty
 321                  * avoid a starvation for the threads sleeping on the shared
 322                  * queue by giving them precedence and cleaning up the
 323                  * exclusive waiters bit anyway.
 324                  * Please note that lk_exslpfail count may be lying about
 325                  * the real number of waiters with the LK_SLEEPFAIL flag on
 326                  * because they may be used in conjunction with interruptible
 327                  * sleeps so lk_exslpfail might be considered an 'upper limit'
 328                  * bound, including the edge cases.
 329                  */
 330                 realexslp = sleepq_sleepcnt(&lk->lock_object,
 331                     SQ_EXCLUSIVE_QUEUE);
 332                 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
 333                         if (lk->lk_exslpfail < realexslp) {
 334                                 lk->lk_exslpfail = 0;
 335                                 queue = SQ_EXCLUSIVE_QUEUE;
 336                                 v |= (x & LK_SHARED_WAITERS);
 337                         } else {
 338                                 lk->lk_exslpfail = 0;
 339                                 LOCK_LOG2(lk,
 340                                     "%s: %p has only LK_SLEEPFAIL sleepers",
 341                                     __func__, lk);
 342                                 LOCK_LOG2(lk,
 343                             "%s: %p waking up threads on the exclusive queue",
 344                                     __func__, lk);
 345                                 wakeup_swapper =
 346                                     sleepq_broadcast(&lk->lock_object,
 347                                     SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
 348                                 queue = SQ_SHARED_QUEUE;
 349                         }
 350
 351                 } else {
 352
 353                         /*
 354                          * Exclusive waiters sleeping with LK_SLEEPFAIL on
 355                          * and using interruptible sleeps/timeout may have
 356                          * left spourious lk_exslpfail counts on, so clean
 357                          * it up anyway.
 358                          */
 359                         lk->lk_exslpfail = 0;
 360                         queue = SQ_SHARED_QUEUE;
 361                 }
 362
 363                 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
 364                     v)) {
 365                         sleepq_release(&lk->lock_object);
 366                         continue;
 367                 }
 368                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 369                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 370                     "exclusive");
 371                 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
 372                     0, queue);
 373                 sleepq_release(&lk->lock_object);
 374                 break;
 375         }
 376
 377         lockmgr_note_shared_release(lk, file, line);
 378         return (wakeup_swapper);
 379 }
 380
 381 static void
 382 assert_lockmgr(const struct lock_object *lock, int what)
 383 {
 384
 385         panic("lockmgr locks do not support assertions");
 386 }
 387
 388 static void
 389 lock_lockmgr(struct lock_object *lock, uintptr_t how)
 390 {
 391
 392         panic("lockmgr locks do not support sleep interlocking");
 393 }
 394
 395 static uintptr_t
 396 unlock_lockmgr(struct lock_object *lock)
 397 {
 398
 399         panic("lockmgr locks do not support sleep interlocking");
 400 }
 401
 402 #ifdef KDTRACE_HOOKS
 403 static int
 404 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
 405 {
 406
 407         panic("lockmgr locks do not support owner inquiring");
 408 }
 409 #endif
 410
 411 void
 412 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 413 {
 414         int iflags;
 415
 416         MPASS((flags & ~LK_INIT_MASK) == 0);
 417         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
 418             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
 419             &lk->lk_lock));
 420
 421         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
 422         if (flags & LK_CANRECURSE)
 423                 iflags |= LO_RECURSABLE;
 424         if ((flags & LK_NODUP) == 0)
 425                 iflags |= LO_DUPOK;
 426         if (flags & LK_NOPROFILE)
 427                 iflags |= LO_NOPROFILE;
 428         if ((flags & LK_NOWITNESS) == 0)
 429                 iflags |= LO_WITNESS;
 430         if (flags & LK_QUIET)
 431                 iflags |= LO_QUIET;
 432         if (flags & LK_IS_VNODE)
 433                 iflags |= LO_IS_VNODE;
 434         iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
 435
 436         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
 437         lk->lk_lock = LK_UNLOCKED;
 438         lk->lk_recurse = 0;
 439         lk->lk_exslpfail = 0;
 440         lk->lk_timo = timo;
 441         lk->lk_pri = pri;
 442         STACK_ZERO(lk);
 443 }
 444
 445 /*
 446  * XXX: Gross hacks to manipulate external lock flags after
 447  * initialization.  Used for certain vnode and buf locks.
 448  */
 449 void
 450 lockallowshare(struct lock *lk)
 451 {
 452
 453         lockmgr_assert(lk, KA_XLOCKED);
 454         lk->lock_object.lo_flags &= ~LK_NOSHARE;
 455 }
 456
 457 void
 458 lockdisableshare(struct lock *lk)
 459 {
 460
 461         lockmgr_assert(lk, KA_XLOCKED);
 462         lk->lock_object.lo_flags |= LK_NOSHARE;
 463 }
 464
 465 void
 466 lockallowrecurse(struct lock *lk)
 467 {
 468
 469         lockmgr_assert(lk, KA_XLOCKED);
 470         lk->lock_object.lo_flags |= LO_RECURSABLE;
 471 }
 472
 473 void
 474 lockdisablerecurse(struct lock *lk)
 475 {
 476
 477         lockmgr_assert(lk, KA_XLOCKED);
 478         lk->lock_object.lo_flags &= ~LO_RECURSABLE;
 479 }
 480
 481 void
 482 lockdestroy(struct lock *lk)
 483 {
 484
 485         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
 486         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
 487         KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
 488         lock_destroy(&lk->lock_object);
 489 }
 490
 491 static bool __always_inline
 492 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags)
 493 {
 494
 495         /*
 496          * If no other thread has an exclusive lock, or
 497          * no exclusive waiter is present, bump the count of
 498          * sharers.  Since we have to preserve the state of
 499          * waiters, if we fail to acquire the shared lock
 500          * loop back and retry.
 501          */
 502         *xp = lk->lk_lock;
 503         while (LK_CAN_SHARE(*xp, flags)) {
 504                 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
 505                     *xp + LK_ONE_SHARER)) {
 506                         return (true);
 507                 }
 508         }
 509         return (false);
 510 }
 511
 512 static bool __always_inline
 513 lockmgr_sunlock_try(struct lock *lk, uintptr_t x)
 514 {
 515
 516         for (;;) {
 517                 /*
 518                  * If there is more than one shared lock held, just drop one
 519                  * and return.
 520                  */
 521                 if (LK_SHARERS(x) > 1) {
 522                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x,
 523                             x - LK_ONE_SHARER))
 524                                 return (true);
 525                         continue;
 526                 }
 527
 528                 /*
 529                  * If there are not waiters on the exclusive queue, drop the
 530                  * lock quickly.
 531                  */
 532                 if ((x & LK_ALL_WAITERS) == 0) {
 533                         MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
 534                             LK_SHARERS_LOCK(1));
 535                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &x,
 536                             LK_UNLOCKED))
 537                                 return (true);
 538                         continue;
 539                 }
 540                 break;
 541         }
 542         return (false);
 543 }
 544
 545 int
 546 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk,
 547     const char *file, int line)
 548 {
 549         struct lock_class *class;
 550         uintptr_t x, v, tid;
 551         u_int op;
 552         bool locked;
 553
 554         op = flags & LK_TYPE_MASK;
 555         locked = false;
 556         switch (op) {
 557         case LK_SHARED:
 558                 if (LK_CAN_WITNESS(flags))
 559                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 560                             file, line, flags & LK_INTERLOCK ? ilk : NULL);
 561                 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
 562                         break;
 563                 if (lockmgr_slock_try(lk, &x, flags)) {
 564                         lockmgr_note_shared_acquire(lk, 0, 0,
 565                             file, line, flags);
 566                         locked = true;
 567                 }
 568                 break;
 569         case LK_EXCLUSIVE:
 570                 if (LK_CAN_WITNESS(flags))
 571                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 572                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 573                             ilk : NULL);
 574                 tid = (uintptr_t)curthread;
 575                 if (lk->lk_lock == LK_UNLOCKED &&
 576                     atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
 577                         lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 578                             flags);
 579                         locked = true;
 580                 }
 581                 break;
 582         case LK_UPGRADE:
 583         case LK_TRYUPGRADE:
 584                 _lockmgr_assert(lk, KA_SLOCKED, file, line);
 585                 tid = (uintptr_t)curthread;
 586                 v = lk->lk_lock;
 587                 x = v & LK_ALL_WAITERS;
 588                 v &= LK_EXCLUSIVE_SPINNERS;
 589                 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
 590                     tid | x)) {
 591                         lockmgr_note_exclusive_upgrade(lk, file, line, flags);
 592                         locked = true;
 593                 }
 594                 break;
 595         default:
 596                 break;
 597         }
 598         if (__predict_true(locked)) {
 599                 if (__predict_false(flags & LK_INTERLOCK)) {
 600                         class = LOCK_CLASS(ilk);
 601                         class->lc_unlock(ilk);
 602                 }
 603                 return (0);
 604         } else {
 605                 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
 606                     LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
 607         }
 608 }
 609
 610 int
 611 lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk)
 612 {
 613         struct lock_class *class;
 614         uintptr_t x, tid;
 615         bool unlocked;
 616         const char *file;
 617         int line;
 618
 619         file = __FILE__;
 620         line = __LINE__;
 621
 622         _lockmgr_assert(lk, KA_LOCKED, file, line);
 623         unlocked = false;
 624         x = lk->lk_lock;
 625         if (__predict_true(x & LK_SHARE) != 0) {
 626                 if (lockmgr_sunlock_try(lk, x)) {
 627                         lockmgr_note_shared_release(lk, file, line);
 628                         unlocked = true;
 629                 }
 630         } else {
 631                 tid = (uintptr_t)curthread;
 632                 if (!lockmgr_recursed(lk) &&
 633                     atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
 634                         lockmgr_note_exclusive_release(lk, file, line);
 635                         unlocked = true;
 636                 }
 637         }
 638         if (__predict_true(unlocked)) {
 639                 if (__predict_false(flags & LK_INTERLOCK)) {
 640                         class = LOCK_CLASS(ilk);
 641                         class->lc_unlock(ilk);
 642                 }
 643                 return (0);
 644         } else {
 645                 return (__lockmgr_args(lk, flags | LK_RELEASE, ilk, LK_WMESG_DEFAULT,
 646                     LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, LOCK_FILE, LOCK_LINE));
 647         }
 648 }
 649
 650 int
 651 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
 652     const char *wmesg, int pri, int timo, const char *file, int line)
 653 {
 654         GIANT_DECLARE;
 655         struct lock_class *class;
 656         const char *iwmesg;
 657         uintptr_t tid, v, x;
 658         u_int op, realexslp;
 659         int error, ipri, itimo, queue, wakeup_swapper;
 660 #ifdef LOCK_PROFILING
 661         uint64_t waittime = 0;
 662         int contested = 0;
 663 #endif
 664 #ifdef ADAPTIVE_LOCKMGRS
 665         volatile struct thread *owner;
 666         u_int i, spintries = 0;
 667 #endif
 668
 669         error = 0;
 670         tid = (uintptr_t)curthread;
 671         op = (flags & LK_TYPE_MASK);
 672         iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
 673         ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
 674         itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
 675
 676         MPASS((flags & ~LK_TOTAL_MASK) == 0);
 677         KASSERT((op & (op - 1)) == 0,
 678             ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
 679         KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
 680             (op != LK_DOWNGRADE && op != LK_RELEASE),
 681             ("%s: Invalid flags in regard of the operation desired @ %s:%d",
 682             __func__, file, line));
 683         KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
 684             ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
 685             __func__, file, line));
 686         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 687             ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
 688             lk->lock_object.lo_name, file, line));
 689
 690         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 691         if (panicstr != NULL) {
 692                 if (flags & LK_INTERLOCK)
 693                         class->lc_unlock(ilk);
 694                 return (0);
 695         }
 696
 697         if (lk->lock_object.lo_flags & LK_NOSHARE) {
 698                 switch (op) {
 699                 case LK_SHARED:
 700                         op = LK_EXCLUSIVE;
 701                         break;
 702                 case LK_UPGRADE:
 703                 case LK_TRYUPGRADE:
 704                 case LK_DOWNGRADE:
 705                         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
 706                             file, line);
 707                         if (flags & LK_INTERLOCK)
 708                                 class->lc_unlock(ilk);
 709                         return (0);
 710                 }
 711         }
 712
 713         wakeup_swapper = 0;
 714         switch (op) {
 715         case LK_SHARED:
 716                 if (LK_CAN_WITNESS(flags))
 717                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 718                             file, line, flags & LK_INTERLOCK ? ilk : NULL);
 719                 for (;;) {
 720                         if (lockmgr_slock_try(lk, &x, flags))
 721                                 break;
 722 #ifdef HWPMC_HOOKS
 723                         PMC_SOFT_CALL( , , lock, failed);
 724 #endif
 725                         lock_profile_obtain_lock_failed(&lk->lock_object,
 726                             &contested, &waittime);
 727
 728                         /*
 729                          * If the lock is already held by curthread in
 730                          * exclusive way avoid a deadlock.
 731                          */
 732                         if (LK_HOLDER(x) == tid) {
 733                                 LOCK_LOG2(lk,
 734                                     "%s: %p already held in exclusive mode",
 735                                     __func__, lk);
 736                                 error = EDEADLK;
 737                                 break;
 738                         }
 739
 740                         /*
 741                          * If the lock is expected to not sleep just give up
 742                          * and return.
 743                          */
 744                         if (LK_TRYOP(flags)) {
 745                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 746                                     __func__, lk);
 747                                 error = EBUSY;
 748                                 break;
 749                         }
 750
 751 #ifdef ADAPTIVE_LOCKMGRS
 752                         /*
 753                          * If the owner is running on another CPU, spin until
 754                          * the owner stops running or the state of the lock
 755                          * changes.  We need a double-state handle here
 756                          * because for a failed acquisition the lock can be
 757                          * either held in exclusive mode or shared mode
 758                          * (for the writer starvation avoidance technique).
 759                          */
 760                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 761                             LK_HOLDER(x) != LK_KERNPROC) {
 762                                 owner = (struct thread *)LK_HOLDER(x);
 763                                 if (LOCK_LOG_TEST(&lk->lock_object, 0))
 764                                         CTR3(KTR_LOCK,
 765                                             "%s: spinning on %p held by %p",
 766                                             __func__, lk, owner);
 767                                 KTR_STATE1(KTR_SCHED, "thread",
 768                                     sched_tdname(td), "spinning",
 769                                     "lockname:\"%s\"", lk->lock_object.lo_name);
 770
 771                                 /*
 772                                  * If we are holding also an interlock drop it
 773                                  * in order to avoid a deadlock if the lockmgr
 774                                  * owner is adaptively spinning on the
 775                                  * interlock itself.
 776                                  */
 777                                 if (flags & LK_INTERLOCK) {
 778                                         class->lc_unlock(ilk);
 779                                         flags &= ~LK_INTERLOCK;
 780                                 }
 781                                 GIANT_SAVE();
 782                                 while (LK_HOLDER(lk->lk_lock) ==
 783                                     (uintptr_t)owner && TD_IS_RUNNING(owner))
 784                                         cpu_spinwait();
 785                                 KTR_STATE0(KTR_SCHED, "thread",
 786                                     sched_tdname(td), "running");
 787                                 GIANT_RESTORE();
 788                                 continue;
 789                         } else if (LK_CAN_ADAPT(lk, flags) &&
 790                             (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
 791                             spintries < alk_retries) {
 792                                 KTR_STATE1(KTR_SCHED, "thread",
 793                                     sched_tdname(td), "spinning",
 794                                     "lockname:\"%s\"", lk->lock_object.lo_name);
 795                                 if (flags & LK_INTERLOCK) {
 796                                         class->lc_unlock(ilk);
 797                                         flags &= ~LK_INTERLOCK;
 798                                 }
 799                                 GIANT_SAVE();
 800                                 spintries++;
 801                                 for (i = 0; i < alk_loops; i++) {
 802                                         if (LOCK_LOG_TEST(&lk->lock_object, 0))
 803                                                 CTR4(KTR_LOCK,
 804                                     "%s: shared spinning on %p with %u and %u",
 805                                                     __func__, lk, spintries, i);
 806                                         x = lk->lk_lock;
 807                                         if ((x & LK_SHARE) == 0 ||
 808                                             LK_CAN_SHARE(x, flags) != 0)
 809                                                 break;
 810                                         cpu_spinwait();
 811                                 }
 812                                 KTR_STATE0(KTR_SCHED, "thread",
 813                                     sched_tdname(td), "running");
 814                                 GIANT_RESTORE();
 815                                 if (i != alk_loops)
 816                                         continue;
 817                         }
 818 #endif
 819
 820                         /*
 821                          * Acquire the sleepqueue chain lock because we
 822                          * probabilly will need to manipulate waiters flags.
 823                          */
 824                         sleepq_lock(&lk->lock_object);
 825                         x = lk->lk_lock;
 826
 827                         /*
 828                          * if the lock can be acquired in shared mode, try
 829                          * again.
 830                          */
 831                         if (LK_CAN_SHARE(x, flags)) {
 832                                 sleepq_release(&lk->lock_object);
 833                                 continue;
 834                         }
 835
 836 #ifdef ADAPTIVE_LOCKMGRS
 837                         /*
 838                          * The current lock owner might have started executing
 839                          * on another CPU (or the lock could have changed
 840                          * owner) while we were waiting on the turnstile
 841                          * chain lock.  If so, drop the turnstile lock and try
 842                          * again.
 843                          */
 844                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
 845                             LK_HOLDER(x) != LK_KERNPROC) {
 846                                 owner = (struct thread *)LK_HOLDER(x);
 847                                 if (TD_IS_RUNNING(owner)) {
 848                                         sleepq_release(&lk->lock_object);
 849                                         continue;
 850                                 }
 851                         }
 852 #endif
 853
 854                         /*
 855                          * Try to set the LK_SHARED_WAITERS flag.  If we fail,
 856                          * loop back and retry.
 857                          */
 858                         if ((x & LK_SHARED_WAITERS) == 0) {
 859                                 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
 860                                     x | LK_SHARED_WAITERS)) {
 861                                         sleepq_release(&lk->lock_object);
 862                                         continue;
 863                                 }
 864                                 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
 865                                     __func__, lk);
 866                         }
 867
 868                         /*
 869                          * As far as we have been unable to acquire the
 870                          * shared lock and the shared waiters flag is set,
 871                          * we will sleep.
 872                          */
 873                         error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 874                             SQ_SHARED_QUEUE);
 875                         flags &= ~LK_INTERLOCK;
 876                         if (error) {
 877                                 LOCK_LOG3(lk,
 878                                     "%s: interrupted sleep for %p with %d",
 879                                     __func__, lk, error);
 880                                 break;
 881                         }
 882                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 883                             __func__, lk);
 884                 }
 885                 if (error == 0) {
 886 #ifdef LOCK_PROFILING
 887                         lockmgr_note_shared_acquire(lk, contested, waittime,
 888                             file, line, flags);
 889 #else
 890                         lockmgr_note_shared_acquire(lk, 0, 0, file, line,
 891                             flags);
 892 #endif
 893                 }
 894                 break;
 895         case LK_UPGRADE:
 896         case LK_TRYUPGRADE:
 897                 _lockmgr_assert(lk, KA_SLOCKED, file, line);
 898                 v = lk->lk_lock;
 899                 x = v & LK_ALL_WAITERS;
 900                 v &= LK_EXCLUSIVE_SPINNERS;
 901
 902                 /*
 903                  * Try to switch from one shared lock to an exclusive one.
 904                  * We need to preserve waiters flags during the operation.
 905                  */
 906                 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
 907                     tid | x)) {
 908                         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
 909                             line);
 910                         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
 911                             LK_TRYWIT(flags), file, line);
 912                         TD_SLOCKS_DEC(curthread);
 913                         break;
 914                 }
 915
 916                 /*
 917                  * In LK_TRYUPGRADE mode, do not drop the lock,
 918                  * returning EBUSY instead.
 919                  */
 920                 if (op == LK_TRYUPGRADE) {
 921                         LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
 922                             __func__, lk);
 923                         error = EBUSY;
 924                         break;
 925                 }
 926
 927                 /*
 928                  * We have been unable to succeed in upgrading, so just
 929                  * give up the shared lock.
 930                  */
 931                 wakeup_swapper |= wakeupshlk(lk, file, line);
 932
 933                 /* FALLTHROUGH */
 934         case LK_EXCLUSIVE:
 935                 if (LK_CAN_WITNESS(flags))
 936                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 937                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 938                             ilk : NULL);
 939
 940                 /*
 941                  * If curthread already holds the lock and this one is
 942                  * allowed to recurse, simply recurse on it.
 943                  */
 944                 if (lockmgr_xlocked(lk)) {
 945                         if ((flags & LK_CANRECURSE) == 0 &&
 946                             (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
 947
 948                                 /*
 949                                  * If the lock is expected to not panic just
 950                                  * give up and return.
 951                                  */
 952                                 if (LK_TRYOP(flags)) {
 953                                         LOCK_LOG2(lk,
 954                                             "%s: %p fails the try operation",
 955                                             __func__, lk);
 956                                         error = EBUSY;
 957                                         break;
 958                                 }
 959                                 if (flags & LK_INTERLOCK)
 960                                         class->lc_unlock(ilk);
 961                 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
 962                                     __func__, iwmesg, file, line);
 963                         }
 964                         lk->lk_recurse++;
 965                         LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
 966                         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 967                             lk->lk_recurse, file, line);
 968                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 969                             LK_TRYWIT(flags), file, line);
 970                         TD_LOCKS_INC(curthread);
 971                         break;
 972                 }
 973
 974                 for (;;) {
 975                         if (lk->lk_lock == LK_UNLOCKED &&
 976                             atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
 977                                 break;
 978 #ifdef HWPMC_HOOKS
 979                         PMC_SOFT_CALL( , , lock, failed);
 980 #endif
 981                         lock_profile_obtain_lock_failed(&lk->lock_object,
 982                             &contested, &waittime);
 983
 984                         /*
 985                          * If the lock is expected to not sleep just give up
 986                          * and return.
 987                          */
 988                         if (LK_TRYOP(flags)) {
 989                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 990                                     __func__, lk);
 991                                 error = EBUSY;
 992                                 break;
 993                         }
 994
 995 #ifdef ADAPTIVE_LOCKMGRS
 996                         /*
 997                          * If the owner is running on another CPU, spin until
 998                          * the owner stops running or the state of the lock
 999                          * changes.
1000                          */
1001                         x = lk->lk_lock;
1002                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
1003                             LK_HOLDER(x) != LK_KERNPROC) {
1004                                 owner = (struct thread *)LK_HOLDER(x);
1005                                 if (LOCK_LOG_TEST(&lk->lock_object, 0))
1006                                         CTR3(KTR_LOCK,
1007                                             "%s: spinning on %p held by %p",
1008                                             __func__, lk, owner);
1009                                 KTR_STATE1(KTR_SCHED, "thread",
1010                                     sched_tdname(td), "spinning",
1011                                     "lockname:\"%s\"", lk->lock_object.lo_name);
1012
1013                                 /*
1014                                  * If we are holding also an interlock drop it
1015                                  * in order to avoid a deadlock if the lockmgr
1016                                  * owner is adaptively spinning on the
1017                                  * interlock itself.
1018                                  */
1019                                 if (flags & LK_INTERLOCK) {
1020                                         class->lc_unlock(ilk);
1021                                         flags &= ~LK_INTERLOCK;
1022                                 }
1023                                 GIANT_SAVE();
1024                                 while (LK_HOLDER(lk->lk_lock) ==
1025                                     (uintptr_t)owner && TD_IS_RUNNING(owner))
1026                                         cpu_spinwait();
1027                                 KTR_STATE0(KTR_SCHED, "thread",
1028                                     sched_tdname(td), "running");
1029                                 GIANT_RESTORE();
1030                                 continue;
1031                         } else if (LK_CAN_ADAPT(lk, flags) &&
1032                             (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
1033                             spintries < alk_retries) {
1034                                 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
1035                                     !atomic_cmpset_ptr(&lk->lk_lock, x,
1036                                     x | LK_EXCLUSIVE_SPINNERS))
1037                                         continue;
1038                                 KTR_STATE1(KTR_SCHED, "thread",
1039                                     sched_tdname(td), "spinning",
1040                                     "lockname:\"%s\"", lk->lock_object.lo_name);
1041                                 if (flags & LK_INTERLOCK) {
1042                                         class->lc_unlock(ilk);
1043                                         flags &= ~LK_INTERLOCK;
1044                                 }
1045                                 GIANT_SAVE();
1046                                 spintries++;
1047                                 for (i = 0; i < alk_loops; i++) {
1048                                         if (LOCK_LOG_TEST(&lk->lock_object, 0))
1049                                                 CTR4(KTR_LOCK,
1050                                     "%s: shared spinning on %p with %u and %u",
1051                                                     __func__, lk, spintries, i);
1052                                         if ((lk->lk_lock &
1053                                             LK_EXCLUSIVE_SPINNERS) == 0)
1054                                                 break;
1055                                         cpu_spinwait();
1056                                 }
1057                                 KTR_STATE0(KTR_SCHED, "thread",
1058                                     sched_tdname(td), "running");
1059                                 GIANT_RESTORE();
1060                                 if (i != alk_loops)
1061                                         continue;
1062                         }
1063 #endif
1064
1065                         /*
1066                          * Acquire the sleepqueue chain lock because we
1067                          * probabilly will need to manipulate waiters flags.
1068                          */
1069                         sleepq_lock(&lk->lock_object);
1070                         x = lk->lk_lock;
1071
1072                         /*
1073                          * if the lock has been released while we spun on
1074                          * the sleepqueue chain lock just try again.
1075                          */
1076                         if (x == LK_UNLOCKED) {
1077                                 sleepq_release(&lk->lock_object);
1078                                 continue;
1079                         }
1080
1081 #ifdef ADAPTIVE_LOCKMGRS
1082                         /*
1083                          * The current lock owner might have started executing
1084                          * on another CPU (or the lock could have changed
1085                          * owner) while we were waiting on the turnstile
1086                          * chain lock.  If so, drop the turnstile lock and try
1087                          * again.
1088                          */
1089                         if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
1090                             LK_HOLDER(x) != LK_KERNPROC) {
1091                                 owner = (struct thread *)LK_HOLDER(x);
1092                                 if (TD_IS_RUNNING(owner)) {
1093                                         sleepq_release(&lk->lock_object);
1094                                         continue;
1095                                 }
1096                         }
1097 #endif
1098
1099                         /*
1100                          * The lock can be in the state where there is a
1101                          * pending queue of waiters, but still no owner.
1102                          * This happens when the lock is contested and an
1103                          * owner is going to claim the lock.
1104                          * If curthread is the one successfully acquiring it
1105                          * claim lock ownership and return, preserving waiters
1106                          * flags.
1107                          */
1108                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1109                         if ((x & ~v) == LK_UNLOCKED) {
1110                                 v &= ~LK_EXCLUSIVE_SPINNERS;
1111                                 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
1112                                     tid | v)) {
1113                                         sleepq_release(&lk->lock_object);
1114                                         LOCK_LOG2(lk,
1115                                             "%s: %p claimed by a new writer",
1116                                             __func__, lk);
1117                                         break;
1118                                 }
1119                                 sleepq_release(&lk->lock_object);
1120                                 continue;
1121                         }
1122
1123                         /*
1124                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1125                          * fail, loop back and retry.
1126                          */
1127                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1128                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1129                                     x | LK_EXCLUSIVE_WAITERS)) {
1130                                         sleepq_release(&lk->lock_object);
1131                                         continue;
1132                                 }
1133                                 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
1134                                     __func__, lk);
1135                         }
1136
1137                         /*
1138                          * As far as we have been unable to acquire the
1139                          * exclusive lock and the exclusive waiters flag
1140                          * is set, we will sleep.
1141                          */
1142                         error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
1143                             SQ_EXCLUSIVE_QUEUE);
1144                         flags &= ~LK_INTERLOCK;
1145                         if (error) {
1146                                 LOCK_LOG3(lk,
1147                                     "%s: interrupted sleep for %p with %d",
1148                                     __func__, lk, error);
1149                                 break;
1150                         }
1151                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1152                             __func__, lk);
1153                 }
1154                 if (error == 0) {
1155 #ifdef LOCK_PROFILING
1156                         lockmgr_note_exclusive_acquire(lk, contested, waittime,
1157                             file, line, flags);
1158 #else
1159                         lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
1160                             flags);
1161 #endif
1162                 }
1163                 break;
1164         case LK_DOWNGRADE:
1165                 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1166                 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
1167                 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
1168
1169                 /*
1170                  * Panic if the lock is recursed.
1171                  */
1172                 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1173                         if (flags & LK_INTERLOCK)
1174                                 class->lc_unlock(ilk);
1175                         panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
1176                             __func__, iwmesg, file, line);
1177                 }
1178                 TD_SLOCKS_INC(curthread);
1179
1180                 /*
1181                  * In order to preserve waiters flags, just spin.
1182                  */
1183                 for (;;) {
1184                         x = lk->lk_lock;
1185                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1186                         x &= LK_ALL_WAITERS;
1187                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1188                             LK_SHARERS_LOCK(1) | x))
1189                                 break;
1190                         cpu_spinwait();
1191                 }
1192                 break;
1193         case LK_RELEASE:
1194                 _lockmgr_assert(lk, KA_LOCKED, file, line);
1195                 x = lk->lk_lock;
1196
1197                 if ((x & LK_SHARE) == 0) {
1198
1199                         /*
1200                          * As first option, treact the lock as if it has not
1201                          * any waiter.
1202                          * Fix-up the tid var if the lock has been disowned.
1203                          */
1204                         if (LK_HOLDER(x) == LK_KERNPROC)
1205                                 tid = LK_KERNPROC;
1206                         else {
1207                                 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
1208                                     file, line);
1209                                 TD_LOCKS_DEC(curthread);
1210                         }
1211                         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
1212                             lk->lk_recurse, file, line);
1213
1214                         /*
1215                          * The lock is held in exclusive mode.
1216                          * If the lock is recursed also, then unrecurse it.
1217                          */
1218                         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1219                                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
1220                                     lk);
1221                                 lk->lk_recurse--;
1222                                 break;
1223                         }
1224                         if (tid != LK_KERNPROC)
1225                                 lock_profile_release_lock(&lk->lock_object);
1226
1227                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
1228                             LK_UNLOCKED))
1229                                 break;
1230
1231                         sleepq_lock(&lk->lock_object);
1232                         x = lk->lk_lock;
1233                         v = LK_UNLOCKED;
1234
1235                         /*
1236                          * If the lock has exclusive waiters, give them
1237                          * preference in order to avoid deadlock with
1238                          * shared runners up.
1239                          * If interruptible sleeps left the exclusive queue
1240                          * empty avoid a starvation for the threads sleeping
1241                          * on the shared queue by giving them precedence
1242                          * and cleaning up the exclusive waiters bit anyway.
1243                          * Please note that lk_exslpfail count may be lying
1244                          * about the real number of waiters with the
1245                          * LK_SLEEPFAIL flag on because they may be used in
1246                          * conjunction with interruptible sleeps so
1247                          * lk_exslpfail might be considered an 'upper limit'
1248                          * bound, including the edge cases.
1249                          */
1250                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1251                         realexslp = sleepq_sleepcnt(&lk->lock_object,
1252                             SQ_EXCLUSIVE_QUEUE);
1253                         if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1254                                 if (lk->lk_exslpfail < realexslp) {
1255                                         lk->lk_exslpfail = 0;
1256                                         queue = SQ_EXCLUSIVE_QUEUE;
1257                                         v |= (x & LK_SHARED_WAITERS);
1258                                 } else {
1259                                         lk->lk_exslpfail = 0;
1260                                         LOCK_LOG2(lk,
1261                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1262                                             __func__, lk);
1263                                         LOCK_LOG2(lk,
1264                         "%s: %p waking up threads on the exclusive queue",
1265                                             __func__, lk);
1266                                         wakeup_swapper =
1267                                             sleepq_broadcast(&lk->lock_object,
1268                                             SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1269                                         queue = SQ_SHARED_QUEUE;
1270                                 }
1271                         } else {
1272
1273                                 /*
1274                                  * Exclusive waiters sleeping with LK_SLEEPFAIL
1275                                  * on and using interruptible sleeps/timeout
1276                                  * may have left spourious lk_exslpfail counts
1277                                  * on, so clean it up anyway.
1278                                  */
1279                                 lk->lk_exslpfail = 0;
1280                                 queue = SQ_SHARED_QUEUE;
1281                         }
1282
1283                         LOCK_LOG3(lk,
1284                             "%s: %p waking up threads on the %s queue",
1285                             __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1286                             "exclusive");
1287                         atomic_store_rel_ptr(&lk->lk_lock, v);
1288                         wakeup_swapper |= sleepq_broadcast(&lk->lock_object,
1289                             SLEEPQ_LK, 0, queue);
1290                         sleepq_release(&lk->lock_object);
1291                         break;
1292                 } else
1293                         wakeup_swapper = wakeupshlk(lk, file, line);
1294                 break;
1295         case LK_DRAIN:
1296                 if (LK_CAN_WITNESS(flags))
1297                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1298                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1299                             ilk : NULL);
1300
1301                 /*
1302                  * Trying to drain a lock we already own will result in a
1303                  * deadlock.
1304                  */
1305                 if (lockmgr_xlocked(lk)) {
1306                         if (flags & LK_INTERLOCK)
1307                                 class->lc_unlock(ilk);
1308                         panic("%s: draining %s with the lock held @ %s:%d\n",
1309                             __func__, iwmesg, file, line);
1310                 }
1311
1312                 for (;;) {
1313                         if (lk->lk_lock == LK_UNLOCKED &&
1314                             atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
1315                                 break;
1316
1317 #ifdef HWPMC_HOOKS
1318                         PMC_SOFT_CALL( , , lock, failed);
1319 #endif
1320                         lock_profile_obtain_lock_failed(&lk->lock_object,
1321                             &contested, &waittime);
1322
1323                         /*
1324                          * If the lock is expected to not sleep just give up
1325                          * and return.
1326                          */
1327                         if (LK_TRYOP(flags)) {
1328                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
1329                                     __func__, lk);
1330                                 error = EBUSY;
1331                                 break;
1332                         }
1333
1334                         /*
1335                          * Acquire the sleepqueue chain lock because we
1336                          * probabilly will need to manipulate waiters flags.
1337                          */
1338                         sleepq_lock(&lk->lock_object);
1339                         x = lk->lk_lock;
1340
1341                         /*
1342                          * if the lock has been released while we spun on
1343                          * the sleepqueue chain lock just try again.
1344                          */
1345                         if (x == LK_UNLOCKED) {
1346                                 sleepq_release(&lk->lock_object);
1347                                 continue;
1348                         }
1349
1350                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1351                         if ((x & ~v) == LK_UNLOCKED) {
1352                                 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1353
1354                                 /*
1355                                  * If interruptible sleeps left the exclusive
1356                                  * queue empty avoid a starvation for the
1357                                  * threads sleeping on the shared queue by
1358                                  * giving them precedence and cleaning up the
1359                                  * exclusive waiters bit anyway.
1360                                  * Please note that lk_exslpfail count may be
1361                                  * lying about the real number of waiters with
1362                                  * the LK_SLEEPFAIL flag on because they may
1363                                  * be used in conjunction with interruptible
1364                                  * sleeps so lk_exslpfail might be considered
1365                                  * an 'upper limit' bound, including the edge
1366                                  * cases.
1367                                  */
1368                                 if (v & LK_EXCLUSIVE_WAITERS) {
1369                                         queue = SQ_EXCLUSIVE_QUEUE;
1370                                         v &= ~LK_EXCLUSIVE_WAITERS;
1371                                 } else {
1372
1373                                         /*
1374                                          * Exclusive waiters sleeping with
1375                                          * LK_SLEEPFAIL on and using
1376                                          * interruptible sleeps/timeout may
1377                                          * have left spourious lk_exslpfail
1378                                          * counts on, so clean it up anyway.
1379                                          */
1380                                         MPASS(v & LK_SHARED_WAITERS);
1381                                         lk->lk_exslpfail = 0;
1382                                         queue = SQ_SHARED_QUEUE;
1383                                         v &= ~LK_SHARED_WAITERS;
1384                                 }
1385                                 if (queue == SQ_EXCLUSIVE_QUEUE) {
1386                                         realexslp =
1387                                             sleepq_sleepcnt(&lk->lock_object,
1388                                             SQ_EXCLUSIVE_QUEUE);
1389                                         if (lk->lk_exslpfail >= realexslp) {
1390                                                 lk->lk_exslpfail = 0;
1391                                                 queue = SQ_SHARED_QUEUE;
1392                                                 v &= ~LK_SHARED_WAITERS;
1393                                                 if (realexslp != 0) {
1394                                                         LOCK_LOG2(lk,
1395                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1396                                                             __func__, lk);
1397                                                         LOCK_LOG2(lk,
1398                         "%s: %p waking up threads on the exclusive queue",
1399                                                             __func__, lk);
1400                                                         wakeup_swapper =
1401                                                             sleepq_broadcast(
1402                                                             &lk->lock_object,
1403                                                             SLEEPQ_LK, 0,
1404                                                             SQ_EXCLUSIVE_QUEUE);
1405                                                 }
1406                                         } else
1407                                                 lk->lk_exslpfail = 0;
1408                                 }
1409                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1410                                         sleepq_release(&lk->lock_object);
1411                                         continue;
1412                                 }
1413                                 LOCK_LOG3(lk,
1414                                 "%s: %p waking up all threads on the %s queue",
1415                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
1416                                     "shared" : "exclusive");
1417                                 wakeup_swapper |= sleepq_broadcast(
1418                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
1419
1420                                 /*
1421                                  * If shared waiters have been woken up we need
1422                                  * to wait for one of them to acquire the lock
1423                                  * before to set the exclusive waiters in
1424                                  * order to avoid a deadlock.
1425                                  */
1426                                 if (queue == SQ_SHARED_QUEUE) {
1427                                         for (v = lk->lk_lock;
1428                                             (v & LK_SHARE) && !LK_SHARERS(v);
1429                                             v = lk->lk_lock)
1430                                                 cpu_spinwait();
1431                                 }
1432                         }
1433
1434                         /*
1435                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1436                          * fail, loop back and retry.
1437                          */
1438                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1439                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1440                                     x | LK_EXCLUSIVE_WAITERS)) {
1441                                         sleepq_release(&lk->lock_object);
1442                                         continue;
1443                                 }
1444                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1445                                     __func__, lk);
1446                         }
1447
1448                         /*
1449                          * As far as we have been unable to acquire the
1450                          * exclusive lock and the exclusive waiters flag
1451                          * is set, we will sleep.
1452                          */
1453                         if (flags & LK_INTERLOCK) {
1454                                 class->lc_unlock(ilk);
1455                                 flags &= ~LK_INTERLOCK;
1456                         }
1457                         GIANT_SAVE();
1458                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1459                             SQ_EXCLUSIVE_QUEUE);
1460                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1461                         GIANT_RESTORE();
1462                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1463                             __func__, lk);
1464                 }
1465
1466                 if (error == 0) {
1467                         lock_profile_obtain_lock_success(&lk->lock_object,
1468                             contested, waittime, file, line);
1469                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1470                             lk->lk_recurse, file, line);
1471                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1472                             LK_TRYWIT(flags), file, line);
1473                         TD_LOCKS_INC(curthread);
1474                         STACK_SAVE(lk);
1475                 }
1476                 break;
1477         default:
1478                 if (flags & LK_INTERLOCK)
1479                         class->lc_unlock(ilk);
1480                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1481         }
1482
1483         if (flags & LK_INTERLOCK)
1484                 class->lc_unlock(ilk);
1485         if (wakeup_swapper)
1486                 kick_proc0();
1487
1488         return (error);
1489 }
1490
1491 void
1492 _lockmgr_disown(struct lock *lk, const char *file, int line)
1493 {
1494         uintptr_t tid, x;
1495
1496         if (SCHEDULER_STOPPED())
1497                 return;
1498
1499         tid = (uintptr_t)curthread;
1500         _lockmgr_assert(lk, KA_XLOCKED, file, line);
1501
1502         /*
1503          * Panic if the lock is recursed.
1504          */
1505         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1506                 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1507                     __func__,  file, line);
1508
1509         /*
1510          * If the owner is already LK_KERNPROC just skip the whole operation.
1511          */
1512         if (LK_HOLDER(lk->lk_lock) != tid)
1513                 return;
1514         lock_profile_release_lock(&lk->lock_object);
1515         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1516         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1517         TD_LOCKS_DEC(curthread);
1518         STACK_SAVE(lk);
1519
1520         /*
1521          * In order to preserve waiters flags, just spin.
1522          */
1523         for (;;) {
1524                 x = lk->lk_lock;
1525                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1526                 x &= LK_ALL_WAITERS;
1527                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1528                     LK_KERNPROC | x))
1529                         return;
1530                 cpu_spinwait();
1531         }
1532 }
1533
1534 void
1535 lockmgr_printinfo(const struct lock *lk)
1536 {
1537         struct thread *td;
1538         uintptr_t x;
1539
1540         if (lk->lk_lock == LK_UNLOCKED)
1541                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1542         else if (lk->lk_lock & LK_SHARE)
1543                 printf("lock type %s: SHARED (count %ju)\n",
1544                     lk->lock_object.lo_name,
1545                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1546         else {
1547                 td = lockmgr_xholder(lk);
1548                 if (td == (struct thread *)LK_KERNPROC)
1549                         printf("lock type %s: EXCL by KERNPROC\n",
1550                             lk->lock_object.lo_name);
1551                 else
1552                         printf("lock type %s: EXCL by thread %p "
1553                             "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1554                             td, td->td_proc->p_pid, td->td_proc->p_comm,
1555                             td->td_tid);
1556         }
1557
1558         x = lk->lk_lock;
1559         if (x & LK_EXCLUSIVE_WAITERS)
1560                 printf(" with exclusive waiters pending\n");
1561         if (x & LK_SHARED_WAITERS)
1562                 printf(" with shared waiters pending\n");
1563         if (x & LK_EXCLUSIVE_SPINNERS)
1564                 printf(" with exclusive spinners pending\n");
1565
1566         STACK_PRINT(lk);
1567 }
1568
1569 int
1570 lockstatus(const struct lock *lk)
1571 {
1572         uintptr_t v, x;
1573         int ret;
1574
1575         ret = LK_SHARED;
1576         x = lk->lk_lock;
1577         v = LK_HOLDER(x);
1578
1579         if ((x & LK_SHARE) == 0) {
1580                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1581                         ret = LK_EXCLUSIVE;
1582                 else
1583                         ret = LK_EXCLOTHER;
1584         } else if (x == LK_UNLOCKED)
1585                 ret = 0;
1586
1587         return (ret);
1588 }
1589
1590 #ifdef INVARIANT_SUPPORT
1591
1592 FEATURE(invariant_support,
1593     "Support for modules compiled with INVARIANTS option");
1594
1595 #ifndef INVARIANTS
1596 #undef  _lockmgr_assert
1597 #endif
1598
1599 void
1600 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1601 {
1602         int slocked = 0;
1603
1604         if (panicstr != NULL)
1605                 return;
1606         switch (what) {
1607         case KA_SLOCKED:
1608         case KA_SLOCKED | KA_NOTRECURSED:
1609         case KA_SLOCKED | KA_RECURSED:
1610                 slocked = 1;
1611         case KA_LOCKED:
1612         case KA_LOCKED | KA_NOTRECURSED:
1613         case KA_LOCKED | KA_RECURSED:
1614 #ifdef WITNESS
1615
1616                 /*
1617                  * We cannot trust WITNESS if the lock is held in exclusive
1618                  * mode and a call to lockmgr_disown() happened.
1619                  * Workaround this skipping the check if the lock is held in
1620                  * exclusive mode even for the KA_LOCKED case.
1621                  */
1622                 if (slocked || (lk->lk_lock & LK_SHARE)) {
1623                         witness_assert(&lk->lock_object, what, file, line);
1624                         break;
1625                 }
1626 #endif
1627                 if (lk->lk_lock == LK_UNLOCKED ||
1628                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1629                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1630                         panic("Lock %s not %slocked @ %s:%d\n",
1631                             lk->lock_object.lo_name, slocked ? "share" : "",
1632                             file, line);
1633
1634                 if ((lk->lk_lock & LK_SHARE) == 0) {
1635                         if (lockmgr_recursed(lk)) {
1636                                 if (what & KA_NOTRECURSED)
1637                                         panic("Lock %s recursed @ %s:%d\n",
1638                                             lk->lock_object.lo_name, file,
1639                                             line);
1640                         } else if (what & KA_RECURSED)
1641                                 panic("Lock %s not recursed @ %s:%d\n",
1642                                     lk->lock_object.lo_name, file, line);
1643                 }
1644                 break;
1645         case KA_XLOCKED:
1646         case KA_XLOCKED | KA_NOTRECURSED:
1647         case KA_XLOCKED | KA_RECURSED:
1648                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1649                         panic("Lock %s not exclusively locked @ %s:%d\n",
1650                             lk->lock_object.lo_name, file, line);
1651                 if (lockmgr_recursed(lk)) {
1652                         if (what & KA_NOTRECURSED)
1653                                 panic("Lock %s recursed @ %s:%d\n",
1654                                     lk->lock_object.lo_name, file, line);
1655                 } else if (what & KA_RECURSED)
1656                         panic("Lock %s not recursed @ %s:%d\n",
1657                             lk->lock_object.lo_name, file, line);
1658                 break;
1659         case KA_UNLOCKED:
1660                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1661                         panic("Lock %s exclusively locked @ %s:%d\n",
1662                             lk->lock_object.lo_name, file, line);
1663                 break;
1664         default:
1665                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1666                     line);
1667         }
1668 }
1669 #endif
1670
1671 #ifdef DDB
1672 int
1673 lockmgr_chain(struct thread *td, struct thread **ownerp)
1674 {
1675         struct lock *lk;
1676
1677         lk = td->td_wchan;
1678
1679         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1680                 return (0);
1681         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1682         if (lk->lk_lock & LK_SHARE)
1683                 db_printf("SHARED (count %ju)\n",
1684                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1685         else
1686                 db_printf("EXCL\n");
1687         *ownerp = lockmgr_xholder(lk);
1688
1689         return (1);
1690 }
1691
1692 static void
1693 db_show_lockmgr(const struct lock_object *lock)
1694 {
1695         struct thread *td;
1696         const struct lock *lk;
1697
1698         lk = (const struct lock *)lock;
1699
1700         db_printf(" state: ");
1701         if (lk->lk_lock == LK_UNLOCKED)
1702                 db_printf("UNLOCKED\n");
1703         else if (lk->lk_lock & LK_SHARE)
1704                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1705         else {
1706                 td = lockmgr_xholder(lk);
1707                 if (td == (struct thread *)LK_KERNPROC)
1708                         db_printf("XLOCK: LK_KERNPROC\n");
1709                 else
1710                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1711                             td->td_tid, td->td_proc->p_pid,
1712                             td->td_proc->p_comm);
1713                 if (lockmgr_recursed(lk))
1714                         db_printf(" recursed: %d\n", lk->lk_recurse);
1715         }
1716         db_printf(" waiters: ");
1717         switch (lk->lk_lock & LK_ALL_WAITERS) {
1718         case LK_SHARED_WAITERS:
1719                 db_printf("shared\n");
1720                 break;
1721         case LK_EXCLUSIVE_WAITERS:
1722                 db_printf("exclusive\n");
1723                 break;
1724         case LK_ALL_WAITERS:
1725                 db_printf("shared and exclusive\n");
1726                 break;
1727         default:
1728                 db_printf("none\n");
1729         }
1730         db_printf(" spinners: ");
1731         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1732                 db_printf("exclusive\n");
1733         else
1734                 db_printf("none\n");
1735 }
1736 #endif