sys/kern/kern_lock.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org>
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice(s), this list of conditions and the following disclaimer as
  12  *    the first lines of this file unmodified other than the possible
  13  *    addition of one or more copyright notices.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice(s), this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
  19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  21  * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
  22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  25  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  28  * DAMAGE.
  29  */
  30
  31 #include "opt_ddb.h"
  32 #include "opt_hwpmc_hooks.h"
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include <sys/param.h>
  38 #include <sys/kdb.h>
  39 #include <sys/ktr.h>
  40 #include <sys/lock.h>
  41 #include <sys/lock_profile.h>
  42 #include <sys/lockmgr.h>
  43 #include <sys/lockstat.h>
  44 #include <sys/mutex.h>
  45 #include <sys/proc.h>
  46 #include <sys/sleepqueue.h>
  47 #ifdef DEBUG_LOCKS
  48 #include <sys/stack.h>
  49 #endif
  50 #include <sys/sysctl.h>
  51 #include <sys/systm.h>
  52
  53 #include <machine/cpu.h>
  54
  55 #ifdef DDB
  56 #include <ddb/ddb.h>
  57 #endif
  58
  59 #ifdef HWPMC_HOOKS
  60 #include <sys/pmckern.h>
  61 PMC_SOFT_DECLARE( , , lock, failed);
  62 #endif
  63
  64 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
  65     (LK_ADAPTIVE | LK_NOSHARE));
  66 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
  67     ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
  68
  69 #define SQ_EXCLUSIVE_QUEUE      0
  70 #define SQ_SHARED_QUEUE         1
  71
  72 #ifndef INVARIANTS
  73 #define _lockmgr_assert(lk, what, file, line)
  74 #endif
  75
  76 #define TD_SLOCKS_INC(td)       ((td)->td_lk_slocks++)
  77 #define TD_SLOCKS_DEC(td)       ((td)->td_lk_slocks--)
  78
  79 #ifndef DEBUG_LOCKS
  80 #define STACK_PRINT(lk)
  81 #define STACK_SAVE(lk)
  82 #define STACK_ZERO(lk)
  83 #else
  84 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
  85 #define STACK_SAVE(lk)  stack_save(&(lk)->lk_stack)
  86 #define STACK_ZERO(lk)  stack_zero(&(lk)->lk_stack)
  87 #endif
  88
  89 #define LOCK_LOG2(lk, string, arg1, arg2)                               \
  90         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  91                 CTR2(KTR_LOCK, (string), (arg1), (arg2))
  92 #define LOCK_LOG3(lk, string, arg1, arg2, arg3)                         \
  93         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
  94                 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
  95
  96 #define GIANT_DECLARE                                                   \
  97         int _i = 0;                                                     \
  98         WITNESS_SAVE_DECL(Giant)
  99 #define GIANT_RESTORE() do {                                            \
 100         if (__predict_false(_i > 0)) {                                  \
 101                 while (_i--)                                            \
 102                         mtx_lock(&Giant);                               \
 103                 WITNESS_RESTORE(&Giant.lock_object, Giant);             \
 104         }                                                               \
 105 } while (0)
 106 #define GIANT_SAVE() do {                                               \
 107         if (__predict_false(mtx_owned(&Giant))) {                       \
 108                 WITNESS_SAVE(&Giant.lock_object, Giant);                \
 109                 while (mtx_owned(&Giant)) {                             \
 110                         _i++;                                           \
 111                         mtx_unlock(&Giant);                             \
 112                 }                                                       \
 113         }                                                               \
 114 } while (0)
 115
 116 static bool __always_inline
 117 LK_CAN_SHARE(uintptr_t x, int flags, bool fp)
 118 {
 119
 120         if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) ==
 121             LK_SHARE)
 122                 return (true);
 123         if (fp || (!(x & LK_SHARE)))
 124                 return (false);
 125         if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||
 126             (curthread->td_pflags & TDP_DEADLKTREAT))
 127                 return (true);
 128         return (false);
 129 }
 130
 131 #define LK_TRYOP(x)                                                     \
 132         ((x) & LK_NOWAIT)
 133
 134 #define LK_CAN_WITNESS(x)                                               \
 135         (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
 136 #define LK_TRYWIT(x)                                                    \
 137         (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
 138
 139 #define LK_CAN_ADAPT(lk, f)                                             \
 140         (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 &&             \
 141         ((f) & LK_SLEEPFAIL) == 0)
 142
 143 #define lockmgr_disowned(lk)                                            \
 144         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
 145
 146 #define lockmgr_xlocked_v(v)                                            \
 147         (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
 148
 149 #define lockmgr_xlocked(lk) lockmgr_xlocked_v((lk)->lk_lock)
 150
 151 static void     assert_lockmgr(const struct lock_object *lock, int how);
 152 #ifdef DDB
 153 static void     db_show_lockmgr(const struct lock_object *lock);
 154 #endif
 155 static void     lock_lockmgr(struct lock_object *lock, uintptr_t how);
 156 #ifdef KDTRACE_HOOKS
 157 static int      owner_lockmgr(const struct lock_object *lock,
 158                     struct thread **owner);
 159 #endif
 160 static uintptr_t unlock_lockmgr(struct lock_object *lock);
 161
 162 struct lock_class lock_class_lockmgr = {
 163         .lc_name = "lockmgr",
 164         .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
 165         .lc_assert = assert_lockmgr,
 166 #ifdef DDB
 167         .lc_ddb_show = db_show_lockmgr,
 168 #endif
 169         .lc_lock = lock_lockmgr,
 170         .lc_unlock = unlock_lockmgr,
 171 #ifdef KDTRACE_HOOKS
 172         .lc_owner = owner_lockmgr,
 173 #endif
 174 };
 175
 176 struct lockmgr_wait {
 177         const char *iwmesg;
 178         int ipri;
 179         int itimo;
 180 };
 181
 182 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
 183     int flags, bool fp);
 184 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp);
 185
 186 static void
 187 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper)
 188 {
 189         struct lock_class *class;
 190
 191         if (flags & LK_INTERLOCK) {
 192                 class = LOCK_CLASS(ilk);
 193                 class->lc_unlock(ilk);
 194         }
 195
 196         if (__predict_false(wakeup_swapper))
 197                 kick_proc0();
 198 }
 199
 200 static void
 201 lockmgr_note_shared_acquire(struct lock *lk, int contested,
 202     uint64_t waittime, const char *file, int line, int flags)
 203 {
 204
 205         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
 206             waittime, file, line, LOCKSTAT_READER);
 207         LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
 208         WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
 209         TD_LOCKS_INC(curthread);
 210         TD_SLOCKS_INC(curthread);
 211         STACK_SAVE(lk);
 212 }
 213
 214 static void
 215 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
 216 {
 217
 218         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
 219         WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
 220         LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
 221         TD_LOCKS_DEC(curthread);
 222         TD_SLOCKS_DEC(curthread);
 223 }
 224
 225 static void
 226 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
 227     uint64_t waittime, const char *file, int line, int flags)
 228 {
 229
 230         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
 231             waittime, file, line, LOCKSTAT_WRITER);
 232         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
 233         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
 234             line);
 235         TD_LOCKS_INC(curthread);
 236         STACK_SAVE(lk);
 237 }
 238
 239 static void
 240 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
 241 {
 242
 243         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_WRITER);
 244         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
 245             line);
 246         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
 247         TD_LOCKS_DEC(curthread);
 248 }
 249
 250 static __inline struct thread *
 251 lockmgr_xholder(const struct lock *lk)
 252 {
 253         uintptr_t x;
 254
 255         x = lk->lk_lock;
 256         return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
 257 }
 258
 259 /*
 260  * It assumes sleepq_lock held and returns with this one unheld.
 261  * It also assumes the generic interlock is sane and previously checked.
 262  * If LK_INTERLOCK is specified the interlock is not reacquired after the
 263  * sleep.
 264  */
 265 static __inline int
 266 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
 267     const char *wmesg, int pri, int timo, int queue)
 268 {
 269         GIANT_DECLARE;
 270         struct lock_class *class;
 271         int catch, error;
 272
 273         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 274         catch = pri & PCATCH;
 275         pri &= PRIMASK;
 276         error = 0;
 277
 278         LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
 279             (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
 280
 281         if (flags & LK_INTERLOCK)
 282                 class->lc_unlock(ilk);
 283         if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
 284                 lk->lk_exslpfail++;
 285         GIANT_SAVE();
 286         sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
 287             SLEEPQ_INTERRUPTIBLE : 0), queue);
 288         if ((flags & LK_TIMELOCK) && timo)
 289                 sleepq_set_timeout(&lk->lock_object, timo);
 290
 291         /*
 292          * Decisional switch for real sleeping.
 293          */
 294         if ((flags & LK_TIMELOCK) && timo && catch)
 295                 error = sleepq_timedwait_sig(&lk->lock_object, pri);
 296         else if ((flags & LK_TIMELOCK) && timo)
 297                 error = sleepq_timedwait(&lk->lock_object, pri);
 298         else if (catch)
 299                 error = sleepq_wait_sig(&lk->lock_object, pri);
 300         else
 301                 sleepq_wait(&lk->lock_object, pri);
 302         GIANT_RESTORE();
 303         if ((flags & LK_SLEEPFAIL) && error == 0)
 304                 error = ENOLCK;
 305
 306         return (error);
 307 }
 308
 309 static __inline int
 310 wakeupshlk(struct lock *lk, const char *file, int line)
 311 {
 312         uintptr_t v, x, orig_x;
 313         u_int realexslp;
 314         int queue, wakeup_swapper;
 315
 316         wakeup_swapper = 0;
 317         for (;;) {
 318                 x = lk->lk_lock;
 319                 if (lockmgr_sunlock_try(lk, &x))
 320                         break;
 321
 322                 /*
 323                  * We should have a sharer with waiters, so enter the hard
 324                  * path in order to handle wakeups correctly.
 325                  */
 326                 sleepq_lock(&lk->lock_object);
 327                 orig_x = lk->lk_lock;
 328 retry_sleepq:
 329                 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 330                 v = LK_UNLOCKED;
 331
 332                 /*
 333                  * If the lock has exclusive waiters, give them preference in
 334                  * order to avoid deadlock with shared runners up.
 335                  * If interruptible sleeps left the exclusive queue empty
 336                  * avoid a starvation for the threads sleeping on the shared
 337                  * queue by giving them precedence and cleaning up the
 338                  * exclusive waiters bit anyway.
 339                  * Please note that lk_exslpfail count may be lying about
 340                  * the real number of waiters with the LK_SLEEPFAIL flag on
 341                  * because they may be used in conjunction with interruptible
 342                  * sleeps so lk_exslpfail might be considered an 'upper limit'
 343                  * bound, including the edge cases.
 344                  */
 345                 realexslp = sleepq_sleepcnt(&lk->lock_object,
 346                     SQ_EXCLUSIVE_QUEUE);
 347                 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
 348                         if (lk->lk_exslpfail < realexslp) {
 349                                 lk->lk_exslpfail = 0;
 350                                 queue = SQ_EXCLUSIVE_QUEUE;
 351                                 v |= (x & LK_SHARED_WAITERS);
 352                         } else {
 353                                 lk->lk_exslpfail = 0;
 354                                 LOCK_LOG2(lk,
 355                                     "%s: %p has only LK_SLEEPFAIL sleepers",
 356                                     __func__, lk);
 357                                 LOCK_LOG2(lk,
 358                             "%s: %p waking up threads on the exclusive queue",
 359                                     __func__, lk);
 360                                 wakeup_swapper =
 361                                     sleepq_broadcast(&lk->lock_object,
 362                                     SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
 363                                 queue = SQ_SHARED_QUEUE;
 364                         }
 365
 366                 } else {
 367
 368                         /*
 369                          * Exclusive waiters sleeping with LK_SLEEPFAIL on
 370                          * and using interruptible sleeps/timeout may have
 371                          * left spourious lk_exslpfail counts on, so clean
 372                          * it up anyway.
 373                          */
 374                         lk->lk_exslpfail = 0;
 375                         queue = SQ_SHARED_QUEUE;
 376                 }
 377
 378                 if (lockmgr_sunlock_try(lk, &orig_x)) {
 379                         sleepq_release(&lk->lock_object);
 380                         break;
 381                 }
 382
 383                 x |= LK_SHARERS_LOCK(1);
 384                 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
 385                         orig_x = x;
 386                         goto retry_sleepq;
 387                 }
 388                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 389                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 390                     "exclusive");
 391                 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
 392                     0, queue);
 393                 sleepq_release(&lk->lock_object);
 394                 break;
 395         }
 396
 397         lockmgr_note_shared_release(lk, file, line);
 398         return (wakeup_swapper);
 399 }
 400
 401 static void
 402 assert_lockmgr(const struct lock_object *lock, int what)
 403 {
 404
 405         panic("lockmgr locks do not support assertions");
 406 }
 407
 408 static void
 409 lock_lockmgr(struct lock_object *lock, uintptr_t how)
 410 {
 411
 412         panic("lockmgr locks do not support sleep interlocking");
 413 }
 414
 415 static uintptr_t
 416 unlock_lockmgr(struct lock_object *lock)
 417 {
 418
 419         panic("lockmgr locks do not support sleep interlocking");
 420 }
 421
 422 #ifdef KDTRACE_HOOKS
 423 static int
 424 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
 425 {
 426
 427         panic("lockmgr locks do not support owner inquiring");
 428 }
 429 #endif
 430
 431 void
 432 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 433 {
 434         int iflags;
 435
 436         MPASS((flags & ~LK_INIT_MASK) == 0);
 437         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
 438             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
 439             &lk->lk_lock));
 440
 441         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
 442         if (flags & LK_CANRECURSE)
 443                 iflags |= LO_RECURSABLE;
 444         if ((flags & LK_NODUP) == 0)
 445                 iflags |= LO_DUPOK;
 446         if (flags & LK_NOPROFILE)
 447                 iflags |= LO_NOPROFILE;
 448         if ((flags & LK_NOWITNESS) == 0)
 449                 iflags |= LO_WITNESS;
 450         if (flags & LK_QUIET)
 451                 iflags |= LO_QUIET;
 452         if (flags & LK_IS_VNODE)
 453                 iflags |= LO_IS_VNODE;
 454         if (flags & LK_NEW)
 455                 iflags |= LO_NEW;
 456         iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
 457
 458         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
 459         lk->lk_lock = LK_UNLOCKED;
 460         lk->lk_recurse = 0;
 461         lk->lk_exslpfail = 0;
 462         lk->lk_timo = timo;
 463         lk->lk_pri = pri;
 464         STACK_ZERO(lk);
 465 }
 466
 467 /*
 468  * XXX: Gross hacks to manipulate external lock flags after
 469  * initialization.  Used for certain vnode and buf locks.
 470  */
 471 void
 472 lockallowshare(struct lock *lk)
 473 {
 474
 475         lockmgr_assert(lk, KA_XLOCKED);
 476         lk->lock_object.lo_flags &= ~LK_NOSHARE;
 477 }
 478
 479 void
 480 lockdisableshare(struct lock *lk)
 481 {
 482
 483         lockmgr_assert(lk, KA_XLOCKED);
 484         lk->lock_object.lo_flags |= LK_NOSHARE;
 485 }
 486
 487 void
 488 lockallowrecurse(struct lock *lk)
 489 {
 490
 491         lockmgr_assert(lk, KA_XLOCKED);
 492         lk->lock_object.lo_flags |= LO_RECURSABLE;
 493 }
 494
 495 void
 496 lockdisablerecurse(struct lock *lk)
 497 {
 498
 499         lockmgr_assert(lk, KA_XLOCKED);
 500         lk->lock_object.lo_flags &= ~LO_RECURSABLE;
 501 }
 502
 503 void
 504 lockdestroy(struct lock *lk)
 505 {
 506
 507         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
 508         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
 509         KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
 510         lock_destroy(&lk->lock_object);
 511 }
 512
 513 static bool __always_inline
 514 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
 515 {
 516
 517         /*
 518          * If no other thread has an exclusive lock, or
 519          * no exclusive waiter is present, bump the count of
 520          * sharers.  Since we have to preserve the state of
 521          * waiters, if we fail to acquire the shared lock
 522          * loop back and retry.
 523          */
 524         *xp = lk->lk_lock;
 525         while (LK_CAN_SHARE(*xp, flags, fp)) {
 526                 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
 527                     *xp + LK_ONE_SHARER)) {
 528                         return (true);
 529                 }
 530         }
 531         return (false);
 532 }
 533
 534 static bool __always_inline
 535 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
 536 {
 537
 538         for (;;) {
 539                 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
 540                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
 541                             *xp - LK_ONE_SHARER))
 542                                 return (true);
 543                         continue;
 544                 }
 545                 break;
 546         }
 547         return (false);
 548 }
 549
 550 static __noinline int
 551 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 552     const char *file, int line, struct lockmgr_wait *lwa)
 553 {
 554         uintptr_t tid, x;
 555         int error = 0;
 556         const char *iwmesg;
 557         int ipri, itimo;
 558
 559 #ifdef KDTRACE_HOOKS
 560         uint64_t sleep_time = 0;
 561 #endif
 562 #ifdef LOCK_PROFILING
 563         uint64_t waittime = 0;
 564         int contested = 0;
 565 #endif
 566
 567         if (__predict_false(panicstr != NULL))
 568                 goto out;
 569
 570         tid = (uintptr_t)curthread;
 571
 572         if (LK_CAN_WITNESS(flags))
 573                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 574                     file, line, flags & LK_INTERLOCK ? ilk : NULL);
 575         for (;;) {
 576                 if (lockmgr_slock_try(lk, &x, flags, false))
 577                         break;
 578 #ifdef HWPMC_HOOKS
 579                 PMC_SOFT_CALL( , , lock, failed);
 580 #endif
 581                 lock_profile_obtain_lock_failed(&lk->lock_object,
 582                     &contested, &waittime);
 583
 584                 /*
 585                  * If the lock is already held by curthread in
 586                  * exclusive way avoid a deadlock.
 587                  */
 588                 if (LK_HOLDER(x) == tid) {
 589                         LOCK_LOG2(lk,
 590                             "%s: %p already held in exclusive mode",
 591                             __func__, lk);
 592                         error = EDEADLK;
 593                         break;
 594                 }
 595
 596                 /*
 597                  * If the lock is expected to not sleep just give up
 598                  * and return.
 599                  */
 600                 if (LK_TRYOP(flags)) {
 601                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 602                             __func__, lk);
 603                         error = EBUSY;
 604                         break;
 605                 }
 606
 607                 /*
 608                  * Acquire the sleepqueue chain lock because we
 609                  * probabilly will need to manipulate waiters flags.
 610                  */
 611                 sleepq_lock(&lk->lock_object);
 612                 x = lk->lk_lock;
 613 retry_sleepq:
 614
 615                 /*
 616                  * if the lock can be acquired in shared mode, try
 617                  * again.
 618                  */
 619                 if (LK_CAN_SHARE(x, flags, false)) {
 620                         sleepq_release(&lk->lock_object);
 621                         continue;
 622                 }
 623
 624                 /*
 625                  * Try to set the LK_SHARED_WAITERS flag.  If we fail,
 626                  * loop back and retry.
 627                  */
 628                 if ((x & LK_SHARED_WAITERS) == 0) {
 629                         if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 630                             x | LK_SHARED_WAITERS)) {
 631                                 goto retry_sleepq;
 632                         }
 633                         LOCK_LOG2(lk, "%s: %p set shared waiters flag",
 634                             __func__, lk);
 635                 }
 636
 637                 if (lwa == NULL) {
 638                         iwmesg = lk->lock_object.lo_name;
 639                         ipri = lk->lk_pri;
 640                         itimo = lk->lk_timo;
 641                 } else {
 642                         iwmesg = lwa->iwmesg;
 643                         ipri = lwa->ipri;
 644                         itimo = lwa->itimo;
 645                 }
 646
 647                 /*
 648                  * As far as we have been unable to acquire the
 649                  * shared lock and the shared waiters flag is set,
 650                  * we will sleep.
 651                  */
 652 #ifdef KDTRACE_HOOKS
 653                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 654 #endif
 655                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 656                     SQ_SHARED_QUEUE);
 657 #ifdef KDTRACE_HOOKS
 658                 sleep_time += lockstat_nsecs(&lk->lock_object);
 659 #endif
 660                 flags &= ~LK_INTERLOCK;
 661                 if (error) {
 662                         LOCK_LOG3(lk,
 663                             "%s: interrupted sleep for %p with %d",
 664                             __func__, lk, error);
 665                         break;
 666                 }
 667                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 668                     __func__, lk);
 669         }
 670         if (error == 0) {
 671 #ifdef KDTRACE_HOOKS
 672                 if (sleep_time != 0)
 673                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 674                             LOCKSTAT_READER, (x & LK_SHARE) == 0,
 675                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 676 #endif
 677 #ifdef LOCK_PROFILING
 678                 lockmgr_note_shared_acquire(lk, contested, waittime,
 679                     file, line, flags);
 680 #else
 681                 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
 682                     flags);
 683 #endif
 684         }
 685
 686 out:
 687         lockmgr_exit(flags, ilk, 0);
 688         return (error);
 689 }
 690
 691 static __noinline int
 692 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
 693     const char *file, int line, struct lockmgr_wait *lwa)
 694 {
 695         struct lock_class *class;
 696         uintptr_t tid, x, v;
 697         int error = 0;
 698         const char *iwmesg;
 699         int ipri, itimo;
 700
 701 #ifdef KDTRACE_HOOKS
 702         uint64_t sleep_time = 0;
 703 #endif
 704 #ifdef LOCK_PROFILING
 705         uint64_t waittime = 0;
 706         int contested = 0;
 707 #endif
 708
 709         if (__predict_false(panicstr != NULL))
 710                 goto out;
 711
 712         tid = (uintptr_t)curthread;
 713
 714         if (LK_CAN_WITNESS(flags))
 715                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 716                     LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 717                     ilk : NULL);
 718
 719         /*
 720          * If curthread already holds the lock and this one is
 721          * allowed to recurse, simply recurse on it.
 722          */
 723         if (lockmgr_xlocked(lk)) {
 724                 if ((flags & LK_CANRECURSE) == 0 &&
 725                     (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
 726                         /*
 727                          * If the lock is expected to not panic just
 728                          * give up and return.
 729                          */
 730                         if (LK_TRYOP(flags)) {
 731                                 LOCK_LOG2(lk,
 732                                     "%s: %p fails the try operation",
 733                                     __func__, lk);
 734                                 error = EBUSY;
 735                                 goto out;
 736                         }
 737                         if (flags & LK_INTERLOCK) {
 738                                 class = LOCK_CLASS(ilk);
 739                                 class->lc_unlock(ilk);
 740                         }
 741                         panic("%s: recursing on non recursive lockmgr %p "
 742                             "@ %s:%d\n", __func__, lk, file, line);
 743                 }
 744                 lk->lk_recurse++;
 745                 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
 746                 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
 747                     lk->lk_recurse, file, line);
 748                 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 749                     LK_TRYWIT(flags), file, line);
 750                 TD_LOCKS_INC(curthread);
 751                 goto out;
 752         }
 753
 754         for (;;) {
 755                 if (lk->lk_lock == LK_UNLOCKED &&
 756                     atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
 757                         break;
 758 #ifdef HWPMC_HOOKS
 759                 PMC_SOFT_CALL( , , lock, failed);
 760 #endif
 761                 lock_profile_obtain_lock_failed(&lk->lock_object,
 762                     &contested, &waittime);
 763
 764                 /*
 765                  * If the lock is expected to not sleep just give up
 766                  * and return.
 767                  */
 768                 if (LK_TRYOP(flags)) {
 769                         LOCK_LOG2(lk, "%s: %p fails the try operation",
 770                             __func__, lk);
 771                         error = EBUSY;
 772                         break;
 773                 }
 774
 775                 /*
 776                  * Acquire the sleepqueue chain lock because we
 777                  * probabilly will need to manipulate waiters flags.
 778                  */
 779                 sleepq_lock(&lk->lock_object);
 780                 x = lk->lk_lock;
 781 retry_sleepq:
 782
 783                 /*
 784                  * if the lock has been released while we spun on
 785                  * the sleepqueue chain lock just try again.
 786                  */
 787                 if (x == LK_UNLOCKED) {
 788                         sleepq_release(&lk->lock_object);
 789                         continue;
 790                 }
 791
 792                 /*
 793                  * The lock can be in the state where there is a
 794                  * pending queue of waiters, but still no owner.
 795                  * This happens when the lock is contested and an
 796                  * owner is going to claim the lock.
 797                  * If curthread is the one successfully acquiring it
 798                  * claim lock ownership and return, preserving waiters
 799                  * flags.
 800                  */
 801                 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 802                 if ((x & ~v) == LK_UNLOCKED) {
 803                         v &= ~LK_EXCLUSIVE_SPINNERS;
 804                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
 805                             tid | v)) {
 806                                 sleepq_release(&lk->lock_object);
 807                                 LOCK_LOG2(lk,
 808                                     "%s: %p claimed by a new writer",
 809                                     __func__, lk);
 810                                 break;
 811                         }
 812                         goto retry_sleepq;
 813                 }
 814
 815                 /*
 816                  * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
 817                  * fail, loop back and retry.
 818                  */
 819                 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
 820                         if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
 821                             x | LK_EXCLUSIVE_WAITERS)) {
 822                                 goto retry_sleepq;
 823                         }
 824                         LOCK_LOG2(lk, "%s: %p set excl waiters flag",
 825                             __func__, lk);
 826                 }
 827
 828                 if (lwa == NULL) {
 829                         iwmesg = lk->lock_object.lo_name;
 830                         ipri = lk->lk_pri;
 831                         itimo = lk->lk_timo;
 832                 } else {
 833                         iwmesg = lwa->iwmesg;
 834                         ipri = lwa->ipri;
 835                         itimo = lwa->itimo;
 836                 }
 837
 838                 /*
 839                  * As far as we have been unable to acquire the
 840                  * exclusive lock and the exclusive waiters flag
 841                  * is set, we will sleep.
 842                  */
 843 #ifdef KDTRACE_HOOKS
 844                 sleep_time -= lockstat_nsecs(&lk->lock_object);
 845 #endif
 846                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
 847                     SQ_EXCLUSIVE_QUEUE);
 848 #ifdef KDTRACE_HOOKS
 849                 sleep_time += lockstat_nsecs(&lk->lock_object);
 850 #endif
 851                 flags &= ~LK_INTERLOCK;
 852                 if (error) {
 853                         LOCK_LOG3(lk,
 854                             "%s: interrupted sleep for %p with %d",
 855                             __func__, lk, error);
 856                         break;
 857                 }
 858                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 859                     __func__, lk);
 860         }
 861         if (error == 0) {
 862 #ifdef KDTRACE_HOOKS
 863                 if (sleep_time != 0)
 864                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
 865                             LOCKSTAT_WRITER, (x & LK_SHARE) == 0,
 866                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
 867 #endif
 868 #ifdef LOCK_PROFILING
 869                 lockmgr_note_exclusive_acquire(lk, contested, waittime,
 870                     file, line, flags);
 871 #else
 872                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 873                     flags);
 874 #endif
 875         }
 876
 877 out:
 878         lockmgr_exit(flags, ilk, 0);
 879         return (error);
 880 }
 881
 882 static __noinline int
 883 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
 884     const char *file, int line, struct lockmgr_wait *lwa)
 885 {
 886         uintptr_t tid, x, v;
 887         int error = 0;
 888         int wakeup_swapper = 0;
 889         int op;
 890
 891         if (__predict_false(panicstr != NULL))
 892                 goto out;
 893
 894         tid = (uintptr_t)curthread;
 895
 896         _lockmgr_assert(lk, KA_SLOCKED, file, line);
 897         v = lk->lk_lock;
 898         x = v & LK_ALL_WAITERS;
 899         v &= LK_EXCLUSIVE_SPINNERS;
 900
 901         /*
 902          * Try to switch from one shared lock to an exclusive one.
 903          * We need to preserve waiters flags during the operation.
 904          */
 905         if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
 906             tid | x)) {
 907                 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
 908                     line);
 909                 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
 910                     LK_TRYWIT(flags), file, line);
 911                 LOCKSTAT_RECORD0(lockmgr__upgrade, lk);
 912                 TD_SLOCKS_DEC(curthread);
 913                 goto out;
 914         }
 915
 916         op = flags & LK_TYPE_MASK;
 917
 918         /*
 919          * In LK_TRYUPGRADE mode, do not drop the lock,
 920          * returning EBUSY instead.
 921          */
 922         if (op == LK_TRYUPGRADE) {
 923                 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
 924                     __func__, lk);
 925                 error = EBUSY;
 926                 goto out;
 927         }
 928
 929         /*
 930          * We have been unable to succeed in upgrading, so just
 931          * give up the shared lock.
 932          */
 933         wakeup_swapper |= wakeupshlk(lk, file, line);
 934         error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
 935         flags &= ~LK_INTERLOCK;
 936 out:
 937         lockmgr_exit(flags, ilk, wakeup_swapper);
 938         return (error);
 939 }
 940
 941 int
 942 lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk,
 943     const char *file, int line)
 944 {
 945         struct lock_class *class;
 946         uintptr_t x, tid;
 947         u_int op;
 948         bool locked;
 949
 950         if (__predict_false(panicstr != NULL))
 951                 return (0);
 952
 953         op = flags & LK_TYPE_MASK;
 954         locked = false;
 955         switch (op) {
 956         case LK_SHARED:
 957                 if (LK_CAN_WITNESS(flags))
 958                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 959                             file, line, flags & LK_INTERLOCK ? ilk : NULL);
 960                 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
 961                         break;
 962                 if (lockmgr_slock_try(lk, &x, flags, true)) {
 963                         lockmgr_note_shared_acquire(lk, 0, 0,
 964                             file, line, flags);
 965                         locked = true;
 966                 } else {
 967                         return (lockmgr_slock_hard(lk, flags, ilk, file, line,
 968                             NULL));
 969                 }
 970                 break;
 971         case LK_EXCLUSIVE:
 972                 if (LK_CAN_WITNESS(flags))
 973                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 974                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 975                             ilk : NULL);
 976                 tid = (uintptr_t)curthread;
 977                 if (lk->lk_lock == LK_UNLOCKED &&
 978                     atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
 979                         lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 980                             flags);
 981                         locked = true;
 982                 } else {
 983                         return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
 984                             NULL));
 985                 }
 986                 break;
 987         case LK_UPGRADE:
 988         case LK_TRYUPGRADE:
 989                 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
 990         default:
 991                 break;
 992         }
 993         if (__predict_true(locked)) {
 994                 if (__predict_false(flags & LK_INTERLOCK)) {
 995                         class = LOCK_CLASS(ilk);
 996                         class->lc_unlock(ilk);
 997                 }
 998                 return (0);
 999         } else {
1000                 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
1001                     LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
1002         }
1003 }
1004
1005 static __noinline int
1006 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1007     const char *file, int line)
1008
1009 {
1010         int wakeup_swapper = 0;
1011
1012         if (__predict_false(panicstr != NULL))
1013                 goto out;
1014
1015         wakeup_swapper = wakeupshlk(lk, file, line);
1016
1017 out:
1018         lockmgr_exit(flags, ilk, wakeup_swapper);
1019         return (0);
1020 }
1021
1022 static __noinline int
1023 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
1024     const char *file, int line)
1025 {
1026         uintptr_t tid, v;
1027         int wakeup_swapper = 0;
1028         u_int realexslp;
1029         int queue;
1030
1031         if (__predict_false(panicstr != NULL))
1032                 goto out;
1033
1034         tid = (uintptr_t)curthread;
1035
1036         /*
1037          * As first option, treact the lock as if it has not
1038          * any waiter.
1039          * Fix-up the tid var if the lock has been disowned.
1040          */
1041         if (LK_HOLDER(x) == LK_KERNPROC)
1042                 tid = LK_KERNPROC;
1043         else {
1044                 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1045                 TD_LOCKS_DEC(curthread);
1046         }
1047         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
1048
1049         /*
1050          * The lock is held in exclusive mode.
1051          * If the lock is recursed also, then unrecurse it.
1052          */
1053         if (lockmgr_xlocked_v(x) && lockmgr_recursed(lk)) {
1054                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
1055                 lk->lk_recurse--;
1056                 goto out;
1057         }
1058         if (tid != LK_KERNPROC)
1059                 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,
1060                     LOCKSTAT_WRITER);
1061
1062         if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
1063                 goto out;
1064
1065         sleepq_lock(&lk->lock_object);
1066         x = lk->lk_lock;
1067         v = LK_UNLOCKED;
1068
1069         /*
1070          * If the lock has exclusive waiters, give them
1071          * preference in order to avoid deadlock with
1072          * shared runners up.
1073          * If interruptible sleeps left the exclusive queue
1074          * empty avoid a starvation for the threads sleeping
1075          * on the shared queue by giving them precedence
1076          * and cleaning up the exclusive waiters bit anyway.
1077          * Please note that lk_exslpfail count may be lying
1078          * about the real number of waiters with the
1079          * LK_SLEEPFAIL flag on because they may be used in
1080          * conjunction with interruptible sleeps so
1081          * lk_exslpfail might be considered an 'upper limit'
1082          * bound, including the edge cases.
1083          */
1084         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1085         realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
1086         if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1087                 if (lk->lk_exslpfail < realexslp) {
1088                         lk->lk_exslpfail = 0;
1089                         queue = SQ_EXCLUSIVE_QUEUE;
1090                         v |= (x & LK_SHARED_WAITERS);
1091                 } else {
1092                         lk->lk_exslpfail = 0;
1093                         LOCK_LOG2(lk,
1094                             "%s: %p has only LK_SLEEPFAIL sleepers",
1095                             __func__, lk);
1096                         LOCK_LOG2(lk,
1097                             "%s: %p waking up threads on the exclusive queue",
1098                             __func__, lk);
1099                         wakeup_swapper = sleepq_broadcast(&lk->lock_object,
1100                             SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1101                         queue = SQ_SHARED_QUEUE;
1102                 }
1103         } else {
1104
1105                 /*
1106                  * Exclusive waiters sleeping with LK_SLEEPFAIL
1107                  * on and using interruptible sleeps/timeout
1108                  * may have left spourious lk_exslpfail counts
1109                  * on, so clean it up anyway.
1110                  */
1111                 lk->lk_exslpfail = 0;
1112                 queue = SQ_SHARED_QUEUE;
1113         }
1114
1115         LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
1116             __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1117             "exclusive");
1118         atomic_store_rel_ptr(&lk->lk_lock, v);
1119         wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue);
1120         sleepq_release(&lk->lock_object);
1121
1122 out:
1123         lockmgr_exit(flags, ilk, wakeup_swapper);
1124         return (0);
1125 }
1126
1127 int
1128 lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk)
1129 {
1130         struct lock_class *class;
1131         uintptr_t x, tid;
1132         const char *file;
1133         int line;
1134
1135         if (__predict_false(panicstr != NULL))
1136                 return (0);
1137
1138         file = __FILE__;
1139         line = __LINE__;
1140
1141         _lockmgr_assert(lk, KA_LOCKED, file, line);
1142         x = lk->lk_lock;
1143         if (__predict_true(x & LK_SHARE) != 0) {
1144                 if (lockmgr_sunlock_try(lk, &x)) {
1145                         lockmgr_note_shared_release(lk, file, line);
1146                 } else {
1147                         return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1148                 }
1149         } else {
1150                 tid = (uintptr_t)curthread;
1151                 if (!lockmgr_recursed(lk) &&
1152                     atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
1153                         lockmgr_note_exclusive_release(lk, file, line);
1154                 } else {
1155                         return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1156                 }
1157         }
1158         if (__predict_false(flags & LK_INTERLOCK)) {
1159                 class = LOCK_CLASS(ilk);
1160                 class->lc_unlock(ilk);
1161         }
1162         return (0);
1163 }
1164
1165 int
1166 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
1167     const char *wmesg, int pri, int timo, const char *file, int line)
1168 {
1169         GIANT_DECLARE;
1170         struct lockmgr_wait lwa;
1171         struct lock_class *class;
1172         const char *iwmesg;
1173         uintptr_t tid, v, x;
1174         u_int op, realexslp;
1175         int error, ipri, itimo, queue, wakeup_swapper;
1176 #ifdef LOCK_PROFILING
1177         uint64_t waittime = 0;
1178         int contested = 0;
1179 #endif
1180
1181         if (panicstr != NULL)
1182                 return (0);
1183
1184         error = 0;
1185         tid = (uintptr_t)curthread;
1186         op = (flags & LK_TYPE_MASK);
1187         iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
1188         ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
1189         itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
1190
1191         lwa.iwmesg = iwmesg;
1192         lwa.ipri = ipri;
1193         lwa.itimo = itimo;
1194
1195         MPASS((flags & ~LK_TOTAL_MASK) == 0);
1196         KASSERT((op & (op - 1)) == 0,
1197             ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
1198         KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
1199             (op != LK_DOWNGRADE && op != LK_RELEASE),
1200             ("%s: Invalid flags in regard of the operation desired @ %s:%d",
1201             __func__, file, line));
1202         KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
1203             ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
1204             __func__, file, line));
1205         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
1206             ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
1207             lk->lock_object.lo_name, file, line));
1208
1209         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
1210
1211         if (lk->lock_object.lo_flags & LK_NOSHARE) {
1212                 switch (op) {
1213                 case LK_SHARED:
1214                         op = LK_EXCLUSIVE;
1215                         break;
1216                 case LK_UPGRADE:
1217                 case LK_TRYUPGRADE:
1218                 case LK_DOWNGRADE:
1219                         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
1220                             file, line);
1221                         if (flags & LK_INTERLOCK)
1222                                 class->lc_unlock(ilk);
1223                         return (0);
1224                 }
1225         }
1226
1227         wakeup_swapper = 0;
1228         switch (op) {
1229         case LK_SHARED:
1230                 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa));
1231                 break;
1232         case LK_UPGRADE:
1233         case LK_TRYUPGRADE:
1234                 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa));
1235                 break;
1236         case LK_EXCLUSIVE:
1237                 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa));
1238                 break;
1239         case LK_DOWNGRADE:
1240                 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1241                 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
1242
1243                 /*
1244                  * Panic if the lock is recursed.
1245                  */
1246                 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1247                         if (flags & LK_INTERLOCK)
1248                                 class->lc_unlock(ilk);
1249                         panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
1250                             __func__, iwmesg, file, line);
1251                 }
1252                 TD_SLOCKS_INC(curthread);
1253
1254                 /*
1255                  * In order to preserve waiters flags, just spin.
1256                  */
1257                 for (;;) {
1258                         x = lk->lk_lock;
1259                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1260                         x &= LK_ALL_WAITERS;
1261                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1262                             LK_SHARERS_LOCK(1) | x))
1263                                 break;
1264                         cpu_spinwait();
1265                 }
1266                 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
1267                 LOCKSTAT_RECORD0(lockmgr__downgrade, lk);
1268                 break;
1269         case LK_RELEASE:
1270                 _lockmgr_assert(lk, KA_LOCKED, file, line);
1271                 x = lk->lk_lock;
1272
1273                 if (__predict_true(x & LK_SHARE) != 0) {
1274                         return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
1275                 } else {
1276                         return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
1277                 }
1278                 break;
1279         case LK_DRAIN:
1280                 if (LK_CAN_WITNESS(flags))
1281                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1282                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1283                             ilk : NULL);
1284
1285                 /*
1286                  * Trying to drain a lock we already own will result in a
1287                  * deadlock.
1288                  */
1289                 if (lockmgr_xlocked(lk)) {
1290                         if (flags & LK_INTERLOCK)
1291                                 class->lc_unlock(ilk);
1292                         panic("%s: draining %s with the lock held @ %s:%d\n",
1293                             __func__, iwmesg, file, line);
1294                 }
1295
1296                 for (;;) {
1297                         if (lk->lk_lock == LK_UNLOCKED &&
1298                             atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
1299                                 break;
1300
1301 #ifdef HWPMC_HOOKS
1302                         PMC_SOFT_CALL( , , lock, failed);
1303 #endif
1304                         lock_profile_obtain_lock_failed(&lk->lock_object,
1305                             &contested, &waittime);
1306
1307                         /*
1308                          * If the lock is expected to not sleep just give up
1309                          * and return.
1310                          */
1311                         if (LK_TRYOP(flags)) {
1312                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
1313                                     __func__, lk);
1314                                 error = EBUSY;
1315                                 break;
1316                         }
1317
1318                         /*
1319                          * Acquire the sleepqueue chain lock because we
1320                          * probabilly will need to manipulate waiters flags.
1321                          */
1322                         sleepq_lock(&lk->lock_object);
1323                         x = lk->lk_lock;
1324
1325                         /*
1326                          * if the lock has been released while we spun on
1327                          * the sleepqueue chain lock just try again.
1328                          */
1329                         if (x == LK_UNLOCKED) {
1330                                 sleepq_release(&lk->lock_object);
1331                                 continue;
1332                         }
1333
1334                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1335                         if ((x & ~v) == LK_UNLOCKED) {
1336                                 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1337
1338                                 /*
1339                                  * If interruptible sleeps left the exclusive
1340                                  * queue empty avoid a starvation for the
1341                                  * threads sleeping on the shared queue by
1342                                  * giving them precedence and cleaning up the
1343                                  * exclusive waiters bit anyway.
1344                                  * Please note that lk_exslpfail count may be
1345                                  * lying about the real number of waiters with
1346                                  * the LK_SLEEPFAIL flag on because they may
1347                                  * be used in conjunction with interruptible
1348                                  * sleeps so lk_exslpfail might be considered
1349                                  * an 'upper limit' bound, including the edge
1350                                  * cases.
1351                                  */
1352                                 if (v & LK_EXCLUSIVE_WAITERS) {
1353                                         queue = SQ_EXCLUSIVE_QUEUE;
1354                                         v &= ~LK_EXCLUSIVE_WAITERS;
1355                                 } else {
1356
1357                                         /*
1358                                          * Exclusive waiters sleeping with
1359                                          * LK_SLEEPFAIL on and using
1360                                          * interruptible sleeps/timeout may
1361                                          * have left spourious lk_exslpfail
1362                                          * counts on, so clean it up anyway.
1363                                          */
1364                                         MPASS(v & LK_SHARED_WAITERS);
1365                                         lk->lk_exslpfail = 0;
1366                                         queue = SQ_SHARED_QUEUE;
1367                                         v &= ~LK_SHARED_WAITERS;
1368                                 }
1369                                 if (queue == SQ_EXCLUSIVE_QUEUE) {
1370                                         realexslp =
1371                                             sleepq_sleepcnt(&lk->lock_object,
1372                                             SQ_EXCLUSIVE_QUEUE);
1373                                         if (lk->lk_exslpfail >= realexslp) {
1374                                                 lk->lk_exslpfail = 0;
1375                                                 queue = SQ_SHARED_QUEUE;
1376                                                 v &= ~LK_SHARED_WAITERS;
1377                                                 if (realexslp != 0) {
1378                                                         LOCK_LOG2(lk,
1379                                         "%s: %p has only LK_SLEEPFAIL sleepers",
1380                                                             __func__, lk);
1381                                                         LOCK_LOG2(lk,
1382                         "%s: %p waking up threads on the exclusive queue",
1383                                                             __func__, lk);
1384                                                         wakeup_swapper =
1385                                                             sleepq_broadcast(
1386                                                             &lk->lock_object,
1387                                                             SLEEPQ_LK, 0,
1388                                                             SQ_EXCLUSIVE_QUEUE);
1389                                                 }
1390                                         } else
1391                                                 lk->lk_exslpfail = 0;
1392                                 }
1393                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1394                                         sleepq_release(&lk->lock_object);
1395                                         continue;
1396                                 }
1397                                 LOCK_LOG3(lk,
1398                                 "%s: %p waking up all threads on the %s queue",
1399                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
1400                                     "shared" : "exclusive");
1401                                 wakeup_swapper |= sleepq_broadcast(
1402                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
1403
1404                                 /*
1405                                  * If shared waiters have been woken up we need
1406                                  * to wait for one of them to acquire the lock
1407                                  * before to set the exclusive waiters in
1408                                  * order to avoid a deadlock.
1409                                  */
1410                                 if (queue == SQ_SHARED_QUEUE) {
1411                                         for (v = lk->lk_lock;
1412                                             (v & LK_SHARE) && !LK_SHARERS(v);
1413                                             v = lk->lk_lock)
1414                                                 cpu_spinwait();
1415                                 }
1416                         }
1417
1418                         /*
1419                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
1420                          * fail, loop back and retry.
1421                          */
1422                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1423                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1424                                     x | LK_EXCLUSIVE_WAITERS)) {
1425                                         sleepq_release(&lk->lock_object);
1426                                         continue;
1427                                 }
1428                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1429                                     __func__, lk);
1430                         }
1431
1432                         /*
1433                          * As far as we have been unable to acquire the
1434                          * exclusive lock and the exclusive waiters flag
1435                          * is set, we will sleep.
1436                          */
1437                         if (flags & LK_INTERLOCK) {
1438                                 class->lc_unlock(ilk);
1439                                 flags &= ~LK_INTERLOCK;
1440                         }
1441                         GIANT_SAVE();
1442                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1443                             SQ_EXCLUSIVE_QUEUE);
1444                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1445                         GIANT_RESTORE();
1446                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1447                             __func__, lk);
1448                 }
1449
1450                 if (error == 0) {
1451                         lock_profile_obtain_lock_success(&lk->lock_object,
1452                             contested, waittime, file, line);
1453                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1454                             lk->lk_recurse, file, line);
1455                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1456                             LK_TRYWIT(flags), file, line);
1457                         TD_LOCKS_INC(curthread);
1458                         STACK_SAVE(lk);
1459                 }
1460                 break;
1461         default:
1462                 if (flags & LK_INTERLOCK)
1463                         class->lc_unlock(ilk);
1464                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1465         }
1466
1467         if (flags & LK_INTERLOCK)
1468                 class->lc_unlock(ilk);
1469         if (wakeup_swapper)
1470                 kick_proc0();
1471
1472         return (error);
1473 }
1474
1475 void
1476 _lockmgr_disown(struct lock *lk, const char *file, int line)
1477 {
1478         uintptr_t tid, x;
1479
1480         if (SCHEDULER_STOPPED())
1481                 return;
1482
1483         tid = (uintptr_t)curthread;
1484         _lockmgr_assert(lk, KA_XLOCKED, file, line);
1485
1486         /*
1487          * Panic if the lock is recursed.
1488          */
1489         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1490                 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1491                     __func__,  file, line);
1492
1493         /*
1494          * If the owner is already LK_KERNPROC just skip the whole operation.
1495          */
1496         if (LK_HOLDER(lk->lk_lock) != tid)
1497                 return;
1498         lock_profile_release_lock(&lk->lock_object);
1499         LOCKSTAT_RECORD1(lockmgr__disown, lk, LOCKSTAT_WRITER);
1500         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1501         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1502         TD_LOCKS_DEC(curthread);
1503         STACK_SAVE(lk);
1504
1505         /*
1506          * In order to preserve waiters flags, just spin.
1507          */
1508         for (;;) {
1509                 x = lk->lk_lock;
1510                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1511                 x &= LK_ALL_WAITERS;
1512                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1513                     LK_KERNPROC | x))
1514                         return;
1515                 cpu_spinwait();
1516         }
1517 }
1518
1519 void
1520 lockmgr_printinfo(const struct lock *lk)
1521 {
1522         struct thread *td;
1523         uintptr_t x;
1524
1525         if (lk->lk_lock == LK_UNLOCKED)
1526                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1527         else if (lk->lk_lock & LK_SHARE)
1528                 printf("lock type %s: SHARED (count %ju)\n",
1529                     lk->lock_object.lo_name,
1530                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1531         else {
1532                 td = lockmgr_xholder(lk);
1533                 if (td == (struct thread *)LK_KERNPROC)
1534                         printf("lock type %s: EXCL by KERNPROC\n",
1535                             lk->lock_object.lo_name);
1536                 else
1537                         printf("lock type %s: EXCL by thread %p "
1538                             "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
1539                             td, td->td_proc->p_pid, td->td_proc->p_comm,
1540                             td->td_tid);
1541         }
1542
1543         x = lk->lk_lock;
1544         if (x & LK_EXCLUSIVE_WAITERS)
1545                 printf(" with exclusive waiters pending\n");
1546         if (x & LK_SHARED_WAITERS)
1547                 printf(" with shared waiters pending\n");
1548         if (x & LK_EXCLUSIVE_SPINNERS)
1549                 printf(" with exclusive spinners pending\n");
1550
1551         STACK_PRINT(lk);
1552 }
1553
1554 int
1555 lockstatus(const struct lock *lk)
1556 {
1557         uintptr_t v, x;
1558         int ret;
1559
1560         ret = LK_SHARED;
1561         x = lk->lk_lock;
1562         v = LK_HOLDER(x);
1563
1564         if ((x & LK_SHARE) == 0) {
1565                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1566                         ret = LK_EXCLUSIVE;
1567                 else
1568                         ret = LK_EXCLOTHER;
1569         } else if (x == LK_UNLOCKED)
1570                 ret = 0;
1571
1572         return (ret);
1573 }
1574
1575 #ifdef INVARIANT_SUPPORT
1576
1577 FEATURE(invariant_support,
1578     "Support for modules compiled with INVARIANTS option");
1579
1580 #ifndef INVARIANTS
1581 #undef  _lockmgr_assert
1582 #endif
1583
1584 void
1585 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1586 {
1587         int slocked = 0;
1588
1589         if (panicstr != NULL)
1590                 return;
1591         switch (what) {
1592         case KA_SLOCKED:
1593         case KA_SLOCKED | KA_NOTRECURSED:
1594         case KA_SLOCKED | KA_RECURSED:
1595                 slocked = 1;
1596         case KA_LOCKED:
1597         case KA_LOCKED | KA_NOTRECURSED:
1598         case KA_LOCKED | KA_RECURSED:
1599 #ifdef WITNESS
1600
1601                 /*
1602                  * We cannot trust WITNESS if the lock is held in exclusive
1603                  * mode and a call to lockmgr_disown() happened.
1604                  * Workaround this skipping the check if the lock is held in
1605                  * exclusive mode even for the KA_LOCKED case.
1606                  */
1607                 if (slocked || (lk->lk_lock & LK_SHARE)) {
1608                         witness_assert(&lk->lock_object, what, file, line);
1609                         break;
1610                 }
1611 #endif
1612                 if (lk->lk_lock == LK_UNLOCKED ||
1613                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1614                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1615                         panic("Lock %s not %slocked @ %s:%d\n",
1616                             lk->lock_object.lo_name, slocked ? "share" : "",
1617                             file, line);
1618
1619                 if ((lk->lk_lock & LK_SHARE) == 0) {
1620                         if (lockmgr_recursed(lk)) {
1621                                 if (what & KA_NOTRECURSED)
1622                                         panic("Lock %s recursed @ %s:%d\n",
1623                                             lk->lock_object.lo_name, file,
1624                                             line);
1625                         } else if (what & KA_RECURSED)
1626                                 panic("Lock %s not recursed @ %s:%d\n",
1627                                     lk->lock_object.lo_name, file, line);
1628                 }
1629                 break;
1630         case KA_XLOCKED:
1631         case KA_XLOCKED | KA_NOTRECURSED:
1632         case KA_XLOCKED | KA_RECURSED:
1633                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1634                         panic("Lock %s not exclusively locked @ %s:%d\n",
1635                             lk->lock_object.lo_name, file, line);
1636                 if (lockmgr_recursed(lk)) {
1637                         if (what & KA_NOTRECURSED)
1638                                 panic("Lock %s recursed @ %s:%d\n",
1639                                     lk->lock_object.lo_name, file, line);
1640                 } else if (what & KA_RECURSED)
1641                         panic("Lock %s not recursed @ %s:%d\n",
1642                             lk->lock_object.lo_name, file, line);
1643                 break;
1644         case KA_UNLOCKED:
1645                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1646                         panic("Lock %s exclusively locked @ %s:%d\n",
1647                             lk->lock_object.lo_name, file, line);
1648                 break;
1649         default:
1650                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1651                     line);
1652         }
1653 }
1654 #endif
1655
1656 #ifdef DDB
1657 int
1658 lockmgr_chain(struct thread *td, struct thread **ownerp)
1659 {
1660         struct lock *lk;
1661
1662         lk = td->td_wchan;
1663
1664         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1665                 return (0);
1666         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1667         if (lk->lk_lock & LK_SHARE)
1668                 db_printf("SHARED (count %ju)\n",
1669                     (uintmax_t)LK_SHARERS(lk->lk_lock));
1670         else
1671                 db_printf("EXCL\n");
1672         *ownerp = lockmgr_xholder(lk);
1673
1674         return (1);
1675 }
1676
1677 static void
1678 db_show_lockmgr(const struct lock_object *lock)
1679 {
1680         struct thread *td;
1681         const struct lock *lk;
1682
1683         lk = (const struct lock *)lock;
1684
1685         db_printf(" state: ");
1686         if (lk->lk_lock == LK_UNLOCKED)
1687                 db_printf("UNLOCKED\n");
1688         else if (lk->lk_lock & LK_SHARE)
1689                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1690         else {
1691                 td = lockmgr_xholder(lk);
1692                 if (td == (struct thread *)LK_KERNPROC)
1693                         db_printf("XLOCK: LK_KERNPROC\n");
1694                 else
1695                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1696                             td->td_tid, td->td_proc->p_pid,
1697                             td->td_proc->p_comm);
1698                 if (lockmgr_recursed(lk))
1699                         db_printf(" recursed: %d\n", lk->lk_recurse);
1700         }
1701         db_printf(" waiters: ");
1702         switch (lk->lk_lock & LK_ALL_WAITERS) {
1703         case LK_SHARED_WAITERS:
1704                 db_printf("shared\n");
1705                 break;
1706         case LK_EXCLUSIVE_WAITERS:
1707                 db_printf("exclusive\n");
1708                 break;
1709         case LK_ALL_WAITERS:
1710                 db_printf("shared and exclusive\n");
1711                 break;
1712         default:
1713                 db_printf("none\n");
1714         }
1715         db_printf(" spinners: ");
1716         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1717                 db_printf("exclusive\n");
1718         else
1719                 db_printf("none\n");
1720 }
1721 #endif