sys/kern/kern_lock.c

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