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