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