The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_lock.c

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    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/limits.h>
   41 #include <sys/lock.h>
   42 #include <sys/lock_profile.h>
   43 #include <sys/lockmgr.h>
   44 #include <sys/lockstat.h>
   45 #include <sys/mutex.h>
   46 #include <sys/proc.h>
   47 #include <sys/sleepqueue.h>
   48 #ifdef DEBUG_LOCKS
   49 #include <sys/stack.h>
   50 #endif
   51 #include <sys/sysctl.h>
   52 #include <sys/systm.h>
   53 
   54 #include <machine/cpu.h>
   55 
   56 #ifdef DDB
   57 #include <ddb/ddb.h>
   58 #endif
   59 
   60 #ifdef HWPMC_HOOKS
   61 #include <sys/pmckern.h>
   62 PMC_SOFT_DECLARE( , , lock, failed);
   63 #endif
   64 
   65 /*
   66  * Hack. There should be prio_t or similar so that this is not necessary.
   67  */
   68 _Static_assert((PRILASTFLAG * 2) - 1 <= USHRT_MAX,
   69     "prio flags wont fit in u_short pri in struct lock");
   70 
   71 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
   72     ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
   73 
   74 #define SQ_EXCLUSIVE_QUEUE      0
   75 #define SQ_SHARED_QUEUE         1
   76 
   77 #ifndef INVARIANTS
   78 #define _lockmgr_assert(lk, what, file, line)
   79 #endif
   80 
   81 #define TD_SLOCKS_INC(td)       ((td)->td_lk_slocks++)
   82 #define TD_SLOCKS_DEC(td)       ((td)->td_lk_slocks--)
   83 
   84 #ifndef DEBUG_LOCKS
   85 #define STACK_PRINT(lk)
   86 #define STACK_SAVE(lk)
   87 #define STACK_ZERO(lk)
   88 #else
   89 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
   90 #define STACK_SAVE(lk)  stack_save(&(lk)->lk_stack)
   91 #define STACK_ZERO(lk)  stack_zero(&(lk)->lk_stack)
   92 #endif
   93 
   94 #define LOCK_LOG2(lk, string, arg1, arg2)                               \
   95         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
   96                 CTR2(KTR_LOCK, (string), (arg1), (arg2))
   97 #define LOCK_LOG3(lk, string, arg1, arg2, arg3)                         \
   98         if (LOCK_LOG_TEST(&(lk)->lock_object, 0))                       \
   99                 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
  100 
  101 #define GIANT_DECLARE                                                   \
  102         int _i = 0;                                                     \
  103         WITNESS_SAVE_DECL(Giant)
  104 #define GIANT_RESTORE() do {                                            \
  105         if (__predict_false(_i > 0)) {                                  \
  106                 while (_i--)                                            \
  107                         mtx_lock(&Giant);                               \
  108                 WITNESS_RESTORE(&Giant.lock_object, Giant);             \
  109         }                                                               \
  110 } while (0)
  111 #define GIANT_SAVE() do {                                               \
  112         if (__predict_false(mtx_owned(&Giant))) {                       \
  113                 WITNESS_SAVE(&Giant.lock_object, Giant);                \
  114                 while (mtx_owned(&Giant)) {                             \
  115                         _i++;                                           \
  116                         mtx_unlock(&Giant);                             \
  117                 }                                                       \
  118         }                                                               \
  119 } while (0)
  120 
  121 static bool __always_inline
  122 LK_CAN_SHARE(uintptr_t x, int flags, bool fp)
  123 {
  124 
  125         if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) ==
  126             LK_SHARE)
  127                 return (true);
  128         if (fp || (!(x & LK_SHARE)))
  129                 return (false);
  130         if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||
  131             (curthread->td_pflags & TDP_DEADLKTREAT))
  132                 return (true);
  133         return (false);
  134 }
  135 
  136 #define LK_TRYOP(x)                                                     \
  137         ((x) & LK_NOWAIT)
  138 
  139 #define LK_CAN_WITNESS(x)                                               \
  140         (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
  141 #define LK_TRYWIT(x)                                                    \
  142         (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
  143 
  144 #define lockmgr_disowned(lk)                                            \
  145         (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
  146 
  147 #define lockmgr_xlocked_v(v)                                            \
  148         (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
  149 
  150 #define lockmgr_xlocked(lk) lockmgr_xlocked_v(lockmgr_read_value(lk))
  151 
  152 static void     assert_lockmgr(const struct lock_object *lock, int how);
  153 #ifdef DDB
  154 static void     db_show_lockmgr(const struct lock_object *lock);
  155 #endif
  156 static void     lock_lockmgr(struct lock_object *lock, uintptr_t how);
  157 #ifdef KDTRACE_HOOKS
  158 static int      owner_lockmgr(const struct lock_object *lock,
  159                     struct thread **owner);
  160 #endif
  161 static uintptr_t unlock_lockmgr(struct lock_object *lock);
  162 
  163 struct lock_class lock_class_lockmgr = {
  164         .lc_name = "lockmgr",
  165         .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
  166         .lc_assert = assert_lockmgr,
  167 #ifdef DDB
  168         .lc_ddb_show = db_show_lockmgr,
  169 #endif
  170         .lc_lock = lock_lockmgr,
  171         .lc_unlock = unlock_lockmgr,
  172 #ifdef KDTRACE_HOOKS
  173         .lc_owner = owner_lockmgr,
  174 #endif
  175 };
  176 
  177 static __read_mostly bool lk_adaptive = true;
  178 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, "lockmgr debugging");
  179 SYSCTL_BOOL(_debug_lockmgr, OID_AUTO, adaptive_spinning, CTLFLAG_RW, &lk_adaptive,
  180     0, "");
  181 #define lockmgr_delay  locks_delay
  182 
  183 struct lockmgr_wait {
  184         const char *iwmesg;
  185         int ipri;
  186         int itimo;
  187 };
  188 
  189 static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
  190     int flags, bool fp);
  191 static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp);
  192 
  193 static void
  194 lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper)
  195 {
  196         struct lock_class *class;
  197 
  198         if (flags & LK_INTERLOCK) {
  199                 class = LOCK_CLASS(ilk);
  200                 class->lc_unlock(ilk);
  201         }
  202 
  203         if (__predict_false(wakeup_swapper))
  204                 kick_proc0();
  205 }
  206 
  207 static void
  208 lockmgr_note_shared_acquire(struct lock *lk, int contested,
  209     uint64_t waittime, const char *file, int line, int flags)
  210 {
  211 
  212         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
  213             waittime, file, line, LOCKSTAT_READER);
  214         LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
  215         WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
  216         TD_LOCKS_INC(curthread);
  217         TD_SLOCKS_INC(curthread);
  218         STACK_SAVE(lk);
  219 }
  220 
  221 static void
  222 lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
  223 {
  224 
  225         WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
  226         LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
  227         TD_LOCKS_DEC(curthread);
  228         TD_SLOCKS_DEC(curthread);
  229 }
  230 
  231 static void
  232 lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
  233     uint64_t waittime, const char *file, int line, int flags)
  234 {
  235 
  236         LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested,
  237             waittime, file, line, LOCKSTAT_WRITER);
  238         LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
  239         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
  240             line);
  241         TD_LOCKS_INC(curthread);
  242         STACK_SAVE(lk);
  243 }
  244 
  245 static void
  246 lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
  247 {
  248 
  249         if (LK_HOLDER(lockmgr_read_value(lk)) != LK_KERNPROC) {
  250                 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
  251                 TD_LOCKS_DEC(curthread);
  252         }
  253         LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
  254             line);
  255 }
  256 
  257 static __inline struct thread *
  258 lockmgr_xholder(const struct lock *lk)
  259 {
  260         uintptr_t x;
  261 
  262         x = lockmgr_read_value(lk);
  263         return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
  264 }
  265 
  266 /*
  267  * It assumes sleepq_lock held and returns with this one unheld.
  268  * It also assumes the generic interlock is sane and previously checked.
  269  * If LK_INTERLOCK is specified the interlock is not reacquired after the
  270  * sleep.
  271  */
  272 static __inline int
  273 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
  274     const char *wmesg, int pri, int timo, int queue)
  275 {
  276         GIANT_DECLARE;
  277         struct lock_class *class;
  278         int catch, error;
  279 
  280         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
  281         catch = pri & PCATCH;
  282         pri &= PRIMASK;
  283         error = 0;
  284 
  285         LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
  286             (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
  287 
  288         if (flags & LK_INTERLOCK)
  289                 class->lc_unlock(ilk);
  290         if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) {
  291                 if (lk->lk_exslpfail < USHRT_MAX)
  292                         lk->lk_exslpfail++;
  293         }
  294         GIANT_SAVE();
  295         sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
  296             SLEEPQ_INTERRUPTIBLE : 0), queue);
  297         if ((flags & LK_TIMELOCK) && timo)
  298                 sleepq_set_timeout(&lk->lock_object, timo);
  299 
  300         /*
  301          * Decisional switch for real sleeping.
  302          */
  303         if ((flags & LK_TIMELOCK) && timo && catch)
  304                 error = sleepq_timedwait_sig(&lk->lock_object, pri);
  305         else if ((flags & LK_TIMELOCK) && timo)
  306                 error = sleepq_timedwait(&lk->lock_object, pri);
  307         else if (catch)
  308                 error = sleepq_wait_sig(&lk->lock_object, pri);
  309         else
  310                 sleepq_wait(&lk->lock_object, pri);
  311         GIANT_RESTORE();
  312         if ((flags & LK_SLEEPFAIL) && error == 0)
  313                 error = ENOLCK;
  314 
  315         return (error);
  316 }
  317 
  318 static __inline int
  319 wakeupshlk(struct lock *lk, const char *file, int line)
  320 {
  321         uintptr_t v, x, orig_x;
  322         u_int realexslp;
  323         int queue, wakeup_swapper;
  324 
  325         wakeup_swapper = 0;
  326         for (;;) {
  327                 x = lockmgr_read_value(lk);
  328                 if (lockmgr_sunlock_try(lk, &x))
  329                         break;
  330 
  331                 /*
  332                  * We should have a sharer with waiters, so enter the hard
  333                  * path in order to handle wakeups correctly.
  334                  */
  335                 sleepq_lock(&lk->lock_object);
  336                 orig_x = lockmgr_read_value(lk);
  337 retry_sleepq:
  338                 x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
  339                 v = LK_UNLOCKED;
  340 
  341                 /*
  342                  * If the lock has exclusive waiters, give them preference in
  343                  * order to avoid deadlock with shared runners up.
  344                  * If interruptible sleeps left the exclusive queue empty
  345                  * avoid a starvation for the threads sleeping on the shared
  346                  * queue by giving them precedence and cleaning up the
  347                  * exclusive waiters bit anyway.
  348                  * Please note that lk_exslpfail count may be lying about
  349                  * the real number of waiters with the LK_SLEEPFAIL flag on
  350                  * because they may be used in conjunction with interruptible
  351                  * sleeps so lk_exslpfail might be considered an 'upper limit'
  352                  * bound, including the edge cases.
  353                  */
  354                 realexslp = sleepq_sleepcnt(&lk->lock_object,
  355                     SQ_EXCLUSIVE_QUEUE);
  356                 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
  357                         if (lk->lk_exslpfail != USHRT_MAX && lk->lk_exslpfail < realexslp) {
  358                                 lk->lk_exslpfail = 0;
  359                                 queue = SQ_EXCLUSIVE_QUEUE;
  360                                 v |= (x & LK_SHARED_WAITERS);
  361                         } else {
  362                                 lk->lk_exslpfail = 0;
  363                                 LOCK_LOG2(lk,
  364                                     "%s: %p has only LK_SLEEPFAIL sleepers",
  365                                     __func__, lk);
  366                                 LOCK_LOG2(lk,
  367                             "%s: %p waking up threads on the exclusive queue",
  368                                     __func__, lk);
  369                                 wakeup_swapper =
  370                                     sleepq_broadcast(&lk->lock_object,
  371                                     SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
  372                                 queue = SQ_SHARED_QUEUE;
  373                         }
  374                 } else {
  375                         /*
  376                          * Exclusive waiters sleeping with LK_SLEEPFAIL on
  377                          * and using interruptible sleeps/timeout may have
  378                          * left spourious lk_exslpfail counts on, so clean
  379                          * it up anyway.
  380                          */
  381                         lk->lk_exslpfail = 0;
  382                         queue = SQ_SHARED_QUEUE;
  383                 }
  384 
  385                 if (lockmgr_sunlock_try(lk, &orig_x)) {
  386                         sleepq_release(&lk->lock_object);
  387                         break;
  388                 }
  389 
  390                 x |= LK_SHARERS_LOCK(1);
  391                 if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
  392                         orig_x = x;
  393                         goto retry_sleepq;
  394                 }
  395                 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
  396                     __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
  397                     "exclusive");
  398                 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
  399                     0, queue);
  400                 sleepq_release(&lk->lock_object);
  401                 break;
  402         }
  403 
  404         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
  405         return (wakeup_swapper);
  406 }
  407 
  408 static void
  409 assert_lockmgr(const struct lock_object *lock, int what)
  410 {
  411 
  412         panic("lockmgr locks do not support assertions");
  413 }
  414 
  415 static void
  416 lock_lockmgr(struct lock_object *lock, uintptr_t how)
  417 {
  418 
  419         panic("lockmgr locks do not support sleep interlocking");
  420 }
  421 
  422 static uintptr_t
  423 unlock_lockmgr(struct lock_object *lock)
  424 {
  425 
  426         panic("lockmgr locks do not support sleep interlocking");
  427 }
  428 
  429 #ifdef KDTRACE_HOOKS
  430 static int
  431 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
  432 {
  433 
  434         panic("lockmgr locks do not support owner inquiring");
  435 }
  436 #endif
  437 
  438 void
  439 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
  440 {
  441         int iflags;
  442 
  443         MPASS((flags & ~LK_INIT_MASK) == 0);
  444         ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
  445             ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
  446             &lk->lk_lock));
  447 
  448         iflags = LO_SLEEPABLE | LO_UPGRADABLE;
  449         if (flags & LK_CANRECURSE)
  450                 iflags |= LO_RECURSABLE;
  451         if ((flags & LK_NODUP) == 0)
  452                 iflags |= LO_DUPOK;
  453         if (flags & LK_NOPROFILE)
  454                 iflags |= LO_NOPROFILE;
  455         if ((flags & LK_NOWITNESS) == 0)
  456                 iflags |= LO_WITNESS;
  457         if (flags & LK_QUIET)
  458                 iflags |= LO_QUIET;
  459         if (flags & LK_IS_VNODE)
  460                 iflags |= LO_IS_VNODE;
  461         if (flags & LK_NEW)
  462                 iflags |= LO_NEW;
  463         iflags |= flags & LK_NOSHARE;
  464 
  465         lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
  466         lk->lk_lock = LK_UNLOCKED;
  467         lk->lk_recurse = 0;
  468         lk->lk_exslpfail = 0;
  469         lk->lk_timo = timo;
  470         lk->lk_pri = pri;
  471         STACK_ZERO(lk);
  472 }
  473 
  474 /*
  475  * XXX: Gross hacks to manipulate external lock flags after
  476  * initialization.  Used for certain vnode and buf locks.
  477  */
  478 void
  479 lockallowshare(struct lock *lk)
  480 {
  481 
  482         lockmgr_assert(lk, KA_XLOCKED);
  483         lk->lock_object.lo_flags &= ~LK_NOSHARE;
  484 }
  485 
  486 void
  487 lockdisableshare(struct lock *lk)
  488 {
  489 
  490         lockmgr_assert(lk, KA_XLOCKED);
  491         lk->lock_object.lo_flags |= LK_NOSHARE;
  492 }
  493 
  494 void
  495 lockallowrecurse(struct lock *lk)
  496 {
  497 
  498         lockmgr_assert(lk, KA_XLOCKED);
  499         lk->lock_object.lo_flags |= LO_RECURSABLE;
  500 }
  501 
  502 void
  503 lockdisablerecurse(struct lock *lk)
  504 {
  505 
  506         lockmgr_assert(lk, KA_XLOCKED);
  507         lk->lock_object.lo_flags &= ~LO_RECURSABLE;
  508 }
  509 
  510 void
  511 lockdestroy(struct lock *lk)
  512 {
  513 
  514         KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
  515         KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
  516         KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
  517         lock_destroy(&lk->lock_object);
  518 }
  519 
  520 static bool __always_inline
  521 lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
  522 {
  523 
  524         /*
  525          * If no other thread has an exclusive lock, or
  526          * no exclusive waiter is present, bump the count of
  527          * sharers.  Since we have to preserve the state of
  528          * waiters, if we fail to acquire the shared lock
  529          * loop back and retry.
  530          */
  531         while (LK_CAN_SHARE(*xp, flags, fp)) {
  532                 if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
  533                     *xp + LK_ONE_SHARER)) {
  534                         return (true);
  535                 }
  536         }
  537         return (false);
  538 }
  539 
  540 static bool __always_inline
  541 lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
  542 {
  543 
  544         for (;;) {
  545                 if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
  546                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
  547                             *xp - LK_ONE_SHARER))
  548                                 return (true);
  549                         continue;
  550                 }
  551                 break;
  552         }
  553         return (false);
  554 }
  555 
  556 static bool
  557 lockmgr_slock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp,
  558     int flags)
  559 {
  560         struct thread *owner;
  561         uintptr_t x;
  562 
  563         x = *xp;
  564         MPASS(x != LK_UNLOCKED);
  565         owner = (struct thread *)LK_HOLDER(x);
  566         for (;;) {
  567                 MPASS(owner != curthread);
  568                 if (owner == (struct thread *)LK_KERNPROC)
  569                         return (false);
  570                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
  571                         return (false);
  572                 if (owner == NULL)
  573                         return (false);
  574                 if (!TD_IS_RUNNING(owner))
  575                         return (false);
  576                 if ((x & LK_ALL_WAITERS) != 0)
  577                         return (false);
  578                 lock_delay(lda);
  579                 x = lockmgr_read_value(lk);
  580                 if (LK_CAN_SHARE(x, flags, false)) {
  581                         *xp = x;
  582                         return (true);
  583                 }
  584                 owner = (struct thread *)LK_HOLDER(x);
  585         }
  586 }
  587 
  588 static __noinline int
  589 lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
  590     const char *file, int line, struct lockmgr_wait *lwa)
  591 {
  592         uintptr_t tid, x;
  593         int error = 0;
  594         const char *iwmesg;
  595         int ipri, itimo;
  596 
  597 #ifdef KDTRACE_HOOKS
  598         uint64_t sleep_time = 0;
  599 #endif
  600 #ifdef LOCK_PROFILING
  601         uint64_t waittime = 0;
  602         int contested = 0;
  603 #endif
  604         struct lock_delay_arg lda;
  605 
  606         if (KERNEL_PANICKED())
  607                 goto out;
  608 
  609         tid = (uintptr_t)curthread;
  610 
  611         if (LK_CAN_WITNESS(flags))
  612                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
  613                     file, line, flags & LK_INTERLOCK ? ilk : NULL);
  614         x = lockmgr_read_value(lk);
  615         lock_delay_arg_init(&lda, &lockmgr_delay);
  616         if (!lk_adaptive)
  617                 flags &= ~LK_ADAPTIVE;
  618         /*
  619          * The lock may already be locked exclusive by curthread,
  620          * avoid deadlock.
  621          */
  622         if (LK_HOLDER(x) == tid) {
  623                 LOCK_LOG2(lk,
  624                     "%s: %p already held in exclusive mode",
  625                     __func__, lk);
  626                 error = EDEADLK;
  627                 goto out;
  628         }
  629 
  630         for (;;) {
  631                 if (lockmgr_slock_try(lk, &x, flags, false))
  632                         break;
  633 
  634                 lock_profile_obtain_lock_failed(&lk->lock_object, false,
  635                     &contested, &waittime);
  636 
  637                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
  638                         if (lockmgr_slock_adaptive(&lda, lk, &x, flags))
  639                                 continue;
  640                 }
  641 
  642 #ifdef HWPMC_HOOKS
  643                 PMC_SOFT_CALL( , , lock, failed);
  644 #endif
  645 
  646                 /*
  647                  * If the lock is expected to not sleep just give up
  648                  * and return.
  649                  */
  650                 if (LK_TRYOP(flags)) {
  651                         LOCK_LOG2(lk, "%s: %p fails the try operation",
  652                             __func__, lk);
  653                         error = EBUSY;
  654                         break;
  655                 }
  656 
  657                 /*
  658                  * Acquire the sleepqueue chain lock because we
  659                  * probabilly will need to manipulate waiters flags.
  660                  */
  661                 sleepq_lock(&lk->lock_object);
  662                 x = lockmgr_read_value(lk);
  663 retry_sleepq:
  664 
  665                 /*
  666                  * if the lock can be acquired in shared mode, try
  667                  * again.
  668                  */
  669                 if (LK_CAN_SHARE(x, flags, false)) {
  670                         sleepq_release(&lk->lock_object);
  671                         continue;
  672                 }
  673 
  674                 /*
  675                  * Try to set the LK_SHARED_WAITERS flag.  If we fail,
  676                  * loop back and retry.
  677                  */
  678                 if ((x & LK_SHARED_WAITERS) == 0) {
  679                         if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
  680                             x | LK_SHARED_WAITERS)) {
  681                                 goto retry_sleepq;
  682                         }
  683                         LOCK_LOG2(lk, "%s: %p set shared waiters flag",
  684                             __func__, lk);
  685                 }
  686 
  687                 if (lwa == NULL) {
  688                         iwmesg = lk->lock_object.lo_name;
  689                         ipri = lk->lk_pri;
  690                         itimo = lk->lk_timo;
  691                 } else {
  692                         iwmesg = lwa->iwmesg;
  693                         ipri = lwa->ipri;
  694                         itimo = lwa->itimo;
  695                 }
  696 
  697                 /*
  698                  * As far as we have been unable to acquire the
  699                  * shared lock and the shared waiters flag is set,
  700                  * we will sleep.
  701                  */
  702 #ifdef KDTRACE_HOOKS
  703                 sleep_time -= lockstat_nsecs(&lk->lock_object);
  704 #endif
  705                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
  706                     SQ_SHARED_QUEUE);
  707 #ifdef KDTRACE_HOOKS
  708                 sleep_time += lockstat_nsecs(&lk->lock_object);
  709 #endif
  710                 flags &= ~LK_INTERLOCK;
  711                 if (error) {
  712                         LOCK_LOG3(lk,
  713                             "%s: interrupted sleep for %p with %d",
  714                             __func__, lk, error);
  715                         break;
  716                 }
  717                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
  718                     __func__, lk);
  719                 x = lockmgr_read_value(lk);
  720         }
  721         if (error == 0) {
  722 #ifdef KDTRACE_HOOKS
  723                 if (sleep_time != 0)
  724                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
  725                             LOCKSTAT_READER, (x & LK_SHARE) == 0,
  726                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
  727 #endif
  728 #ifdef LOCK_PROFILING
  729                 lockmgr_note_shared_acquire(lk, contested, waittime,
  730                     file, line, flags);
  731 #else
  732                 lockmgr_note_shared_acquire(lk, 0, 0, file, line,
  733                     flags);
  734 #endif
  735         }
  736 
  737 out:
  738         lockmgr_exit(flags, ilk, 0);
  739         return (error);
  740 }
  741 
  742 static bool
  743 lockmgr_xlock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp)
  744 {
  745         struct thread *owner;
  746         uintptr_t x;
  747 
  748         x = *xp;
  749         MPASS(x != LK_UNLOCKED);
  750         owner = (struct thread *)LK_HOLDER(x);
  751         for (;;) {
  752                 MPASS(owner != curthread);
  753                 if (owner == NULL)
  754                         return (false);
  755                 if ((x & LK_SHARE) && LK_SHARERS(x) > 0)
  756                         return (false);
  757                 if (owner == (struct thread *)LK_KERNPROC)
  758                         return (false);
  759                 if (!TD_IS_RUNNING(owner))
  760                         return (false);
  761                 if ((x & LK_ALL_WAITERS) != 0)
  762                         return (false);
  763                 lock_delay(lda);
  764                 x = lockmgr_read_value(lk);
  765                 if (x == LK_UNLOCKED) {
  766                         *xp = x;
  767                         return (true);
  768                 }
  769                 owner = (struct thread *)LK_HOLDER(x);
  770         }
  771 }
  772 
  773 static __noinline int
  774 lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
  775     const char *file, int line, struct lockmgr_wait *lwa)
  776 {
  777         struct lock_class *class;
  778         uintptr_t tid, x, v;
  779         int error = 0;
  780         const char *iwmesg;
  781         int ipri, itimo;
  782 
  783 #ifdef KDTRACE_HOOKS
  784         uint64_t sleep_time = 0;
  785 #endif
  786 #ifdef LOCK_PROFILING
  787         uint64_t waittime = 0;
  788         int contested = 0;
  789 #endif
  790         struct lock_delay_arg lda;
  791 
  792         if (KERNEL_PANICKED())
  793                 goto out;
  794 
  795         tid = (uintptr_t)curthread;
  796 
  797         if (LK_CAN_WITNESS(flags))
  798                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
  799                     LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
  800                     ilk : NULL);
  801 
  802         /*
  803          * If curthread already holds the lock and this one is
  804          * allowed to recurse, simply recurse on it.
  805          */
  806         if (lockmgr_xlocked(lk)) {
  807                 if ((flags & LK_CANRECURSE) == 0 &&
  808                     (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
  809                         /*
  810                          * If the lock is expected to not panic just
  811                          * give up and return.
  812                          */
  813                         if (LK_TRYOP(flags)) {
  814                                 LOCK_LOG2(lk,
  815                                     "%s: %p fails the try operation",
  816                                     __func__, lk);
  817                                 error = EBUSY;
  818                                 goto out;
  819                         }
  820                         if (flags & LK_INTERLOCK) {
  821                                 class = LOCK_CLASS(ilk);
  822                                 class->lc_unlock(ilk);
  823                         }
  824                         STACK_PRINT(lk);
  825                         panic("%s: recursing on non recursive lockmgr %p "
  826                             "@ %s:%d\n", __func__, lk, file, line);
  827                 }
  828                 atomic_set_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
  829                 lk->lk_recurse++;
  830                 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
  831                 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
  832                     lk->lk_recurse, file, line);
  833                 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
  834                     LK_TRYWIT(flags), file, line);
  835                 TD_LOCKS_INC(curthread);
  836                 goto out;
  837         }
  838 
  839         x = LK_UNLOCKED;
  840         lock_delay_arg_init(&lda, &lockmgr_delay);
  841         if (!lk_adaptive)
  842                 flags &= ~LK_ADAPTIVE;
  843         for (;;) {
  844                 if (x == LK_UNLOCKED) {
  845                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, tid))
  846                                 break;
  847                         continue;
  848                 }
  849 
  850                 lock_profile_obtain_lock_failed(&lk->lock_object, false,
  851                     &contested, &waittime);
  852 
  853                 if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) {
  854                         if (lockmgr_xlock_adaptive(&lda, lk, &x))
  855                                 continue;
  856                 }
  857 #ifdef HWPMC_HOOKS
  858                 PMC_SOFT_CALL( , , lock, failed);
  859 #endif
  860 
  861                 /*
  862                  * If the lock is expected to not sleep just give up
  863                  * and return.
  864                  */
  865                 if (LK_TRYOP(flags)) {
  866                         LOCK_LOG2(lk, "%s: %p fails the try operation",
  867                             __func__, lk);
  868                         error = EBUSY;
  869                         break;
  870                 }
  871 
  872                 /*
  873                  * Acquire the sleepqueue chain lock because we
  874                  * probabilly will need to manipulate waiters flags.
  875                  */
  876                 sleepq_lock(&lk->lock_object);
  877                 x = lockmgr_read_value(lk);
  878 retry_sleepq:
  879 
  880                 /*
  881                  * if the lock has been released while we spun on
  882                  * the sleepqueue chain lock just try again.
  883                  */
  884                 if (x == LK_UNLOCKED) {
  885                         sleepq_release(&lk->lock_object);
  886                         continue;
  887                 }
  888 
  889                 /*
  890                  * The lock can be in the state where there is a
  891                  * pending queue of waiters, but still no owner.
  892                  * This happens when the lock is contested and an
  893                  * owner is going to claim the lock.
  894                  * If curthread is the one successfully acquiring it
  895                  * claim lock ownership and return, preserving waiters
  896                  * flags.
  897                  */
  898                 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
  899                 if ((x & ~v) == LK_UNLOCKED) {
  900                         v &= ~LK_EXCLUSIVE_SPINNERS;
  901                         if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
  902                             tid | v)) {
  903                                 sleepq_release(&lk->lock_object);
  904                                 LOCK_LOG2(lk,
  905                                     "%s: %p claimed by a new writer",
  906                                     __func__, lk);
  907                                 break;
  908                         }
  909                         goto retry_sleepq;
  910                 }
  911 
  912                 /*
  913                  * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
  914                  * fail, loop back and retry.
  915                  */
  916                 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
  917                         if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
  918                             x | LK_EXCLUSIVE_WAITERS)) {
  919                                 goto retry_sleepq;
  920                         }
  921                         LOCK_LOG2(lk, "%s: %p set excl waiters flag",
  922                             __func__, lk);
  923                 }
  924 
  925                 if (lwa == NULL) {
  926                         iwmesg = lk->lock_object.lo_name;
  927                         ipri = lk->lk_pri;
  928                         itimo = lk->lk_timo;
  929                 } else {
  930                         iwmesg = lwa->iwmesg;
  931                         ipri = lwa->ipri;
  932                         itimo = lwa->itimo;
  933                 }
  934 
  935                 /*
  936                  * As far as we have been unable to acquire the
  937                  * exclusive lock and the exclusive waiters flag
  938                  * is set, we will sleep.
  939                  */
  940 #ifdef KDTRACE_HOOKS
  941                 sleep_time -= lockstat_nsecs(&lk->lock_object);
  942 #endif
  943                 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
  944                     SQ_EXCLUSIVE_QUEUE);
  945 #ifdef KDTRACE_HOOKS
  946                 sleep_time += lockstat_nsecs(&lk->lock_object);
  947 #endif
  948                 flags &= ~LK_INTERLOCK;
  949                 if (error) {
  950                         LOCK_LOG3(lk,
  951                             "%s: interrupted sleep for %p with %d",
  952                             __func__, lk, error);
  953                         break;
  954                 }
  955                 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
  956                     __func__, lk);
  957                 x = lockmgr_read_value(lk);
  958         }
  959         if (error == 0) {
  960 #ifdef KDTRACE_HOOKS
  961                 if (sleep_time != 0)
  962                         LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time,
  963                             LOCKSTAT_WRITER, (x & LK_SHARE) == 0,
  964                             (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x));
  965 #endif
  966 #ifdef LOCK_PROFILING
  967                 lockmgr_note_exclusive_acquire(lk, contested, waittime,
  968                     file, line, flags);
  969 #else
  970                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
  971                     flags);
  972 #endif
  973         }
  974 
  975 out:
  976         lockmgr_exit(flags, ilk, 0);
  977         return (error);
  978 }
  979 
  980 static __noinline int
  981 lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
  982     const char *file, int line, struct lockmgr_wait *lwa)
  983 {
  984         uintptr_t tid, v, setv;
  985         int error = 0;
  986         int op;
  987 
  988         if (KERNEL_PANICKED())
  989                 goto out;
  990 
  991         tid = (uintptr_t)curthread;
  992 
  993         _lockmgr_assert(lk, KA_SLOCKED, file, line);
  994 
  995         op = flags & LK_TYPE_MASK;
  996         v = lockmgr_read_value(lk);
  997         for (;;) {
  998                 if (LK_SHARERS(v) > 1) {
  999                         if (op == LK_TRYUPGRADE) {
 1000                                 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
 1001                                     __func__, lk);
 1002                                 error = EBUSY;
 1003                                 goto out;
 1004                         }
 1005                         if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &v,
 1006                             v - LK_ONE_SHARER)) {
 1007                                 lockmgr_note_shared_release(lk, file, line);
 1008                                 goto out_xlock;
 1009                         }
 1010                         continue;
 1011                 }
 1012                 MPASS((v & ~LK_ALL_WAITERS) == LK_SHARERS_LOCK(1));
 1013 
 1014                 setv = tid;
 1015                 setv |= (v & LK_ALL_WAITERS);
 1016 
 1017                 /*
 1018                  * Try to switch from one shared lock to an exclusive one.
 1019                  * We need to preserve waiters flags during the operation.
 1020                  */
 1021                 if (atomic_fcmpset_ptr(&lk->lk_lock, &v, setv)) {
 1022                         LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
 1023                             line);
 1024                         WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
 1025                             LK_TRYWIT(flags), file, line);
 1026                         LOCKSTAT_RECORD0(lockmgr__upgrade, lk);
 1027                         TD_SLOCKS_DEC(curthread);
 1028                         goto out;
 1029                 }
 1030         }
 1031 
 1032 out_xlock:
 1033         error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
 1034         flags &= ~LK_INTERLOCK;
 1035 out:
 1036         lockmgr_exit(flags, ilk, 0);
 1037         return (error);
 1038 }
 1039 
 1040 int
 1041 lockmgr_lock_flags(struct lock *lk, u_int flags, struct lock_object *ilk,
 1042     const char *file, int line)
 1043 {
 1044         struct lock_class *class;
 1045         uintptr_t x, tid;
 1046         u_int op;
 1047         bool locked;
 1048 
 1049         if (KERNEL_PANICKED())
 1050                 return (0);
 1051 
 1052         op = flags & LK_TYPE_MASK;
 1053         locked = false;
 1054         switch (op) {
 1055         case LK_SHARED:
 1056                 if (LK_CAN_WITNESS(flags))
 1057                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 1058                             file, line, flags & LK_INTERLOCK ? ilk : NULL);
 1059                 if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
 1060                         break;
 1061                 x = lockmgr_read_value(lk);
 1062                 if (lockmgr_slock_try(lk, &x, flags, true)) {
 1063                         lockmgr_note_shared_acquire(lk, 0, 0,
 1064                             file, line, flags);
 1065                         locked = true;
 1066                 } else {
 1067                         return (lockmgr_slock_hard(lk, flags, ilk, file, line,
 1068                             NULL));
 1069                 }
 1070                 break;
 1071         case LK_EXCLUSIVE:
 1072                 if (LK_CAN_WITNESS(flags))
 1073                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 1074                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 1075                             ilk : NULL);
 1076                 tid = (uintptr_t)curthread;
 1077                 if (lockmgr_read_value(lk) == LK_UNLOCKED &&
 1078                     atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
 1079                         lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 1080                             flags);
 1081                         locked = true;
 1082                 } else {
 1083                         return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
 1084                             NULL));
 1085                 }
 1086                 break;
 1087         case LK_UPGRADE:
 1088         case LK_TRYUPGRADE:
 1089                 return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
 1090         default:
 1091                 break;
 1092         }
 1093         if (__predict_true(locked)) {
 1094                 if (__predict_false(flags & LK_INTERLOCK)) {
 1095                         class = LOCK_CLASS(ilk);
 1096                         class->lc_unlock(ilk);
 1097                 }
 1098                 return (0);
 1099         } else {
 1100                 return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
 1101                     LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
 1102         }
 1103 }
 1104 
 1105 static __noinline int
 1106 lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
 1107     const char *file, int line)
 1108 
 1109 {
 1110         int wakeup_swapper = 0;
 1111 
 1112         if (KERNEL_PANICKED())
 1113                 goto out;
 1114 
 1115         wakeup_swapper = wakeupshlk(lk, file, line);
 1116 
 1117 out:
 1118         lockmgr_exit(flags, ilk, wakeup_swapper);
 1119         return (0);
 1120 }
 1121 
 1122 static __noinline int
 1123 lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
 1124     const char *file, int line)
 1125 {
 1126         uintptr_t tid, v;
 1127         int wakeup_swapper = 0;
 1128         u_int realexslp;
 1129         int queue;
 1130 
 1131         if (KERNEL_PANICKED())
 1132                 goto out;
 1133 
 1134         tid = (uintptr_t)curthread;
 1135 
 1136         /*
 1137          * As first option, treact the lock as if it has not
 1138          * any waiter.
 1139          * Fix-up the tid var if the lock has been disowned.
 1140          */
 1141         if (LK_HOLDER(x) == LK_KERNPROC)
 1142                 tid = LK_KERNPROC;
 1143 
 1144         /*
 1145          * The lock is held in exclusive mode.
 1146          * If the lock is recursed also, then unrecurse it.
 1147          */
 1148         if (lockmgr_recursed_v(x)) {
 1149                 LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
 1150                 lk->lk_recurse--;
 1151                 if (lk->lk_recurse == 0)
 1152                         atomic_clear_ptr(&lk->lk_lock, LK_WRITER_RECURSED);
 1153                 goto out;
 1154         }
 1155         if (tid != LK_KERNPROC)
 1156                 LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,
 1157                     LOCKSTAT_WRITER);
 1158 
 1159         if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
 1160                 goto out;
 1161 
 1162         sleepq_lock(&lk->lock_object);
 1163         x = lockmgr_read_value(lk);
 1164         v = LK_UNLOCKED;
 1165 
 1166         /*
 1167          * If the lock has exclusive waiters, give them
 1168          * preference in order to avoid deadlock with
 1169          * shared runners up.
 1170          * If interruptible sleeps left the exclusive queue
 1171          * empty avoid a starvation for the threads sleeping
 1172          * on the shared queue by giving them precedence
 1173          * and cleaning up the exclusive waiters bit anyway.
 1174          * Please note that lk_exslpfail count may be lying
 1175          * about the real number of waiters with the
 1176          * LK_SLEEPFAIL flag on because they may be used in
 1177          * conjunction with interruptible sleeps so
 1178          * lk_exslpfail might be considered an 'upper limit'
 1179          * bound, including the edge cases.
 1180          */
 1181         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
 1182         realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
 1183         if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
 1184                 if (lk->lk_exslpfail != USHRT_MAX && lk->lk_exslpfail < realexslp) {
 1185                         lk->lk_exslpfail = 0;
 1186                         queue = SQ_EXCLUSIVE_QUEUE;
 1187                         v |= (x & LK_SHARED_WAITERS);
 1188                 } else {
 1189                         lk->lk_exslpfail = 0;
 1190                         LOCK_LOG2(lk,
 1191                             "%s: %p has only LK_SLEEPFAIL sleepers",
 1192                             __func__, lk);
 1193                         LOCK_LOG2(lk,
 1194                             "%s: %p waking up threads on the exclusive queue",
 1195                             __func__, lk);
 1196                         wakeup_swapper = sleepq_broadcast(&lk->lock_object,
 1197                             SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
 1198                         queue = SQ_SHARED_QUEUE;
 1199                 }
 1200         } else {
 1201                 /*
 1202                  * Exclusive waiters sleeping with LK_SLEEPFAIL
 1203                  * on and using interruptible sleeps/timeout
 1204                  * may have left spourious lk_exslpfail counts
 1205                  * on, so clean it up anyway.
 1206                  */
 1207                 lk->lk_exslpfail = 0;
 1208                 queue = SQ_SHARED_QUEUE;
 1209         }
 1210 
 1211         LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
 1212             __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
 1213             "exclusive");
 1214         atomic_store_rel_ptr(&lk->lk_lock, v);
 1215         wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue);
 1216         sleepq_release(&lk->lock_object);
 1217 
 1218 out:
 1219         lockmgr_exit(flags, ilk, wakeup_swapper);
 1220         return (0);
 1221 }
 1222 
 1223 /*
 1224  * Lightweight entry points for common operations.
 1225  *
 1226  * Functionality is similar to sx locks, in that none of the additional lockmgr
 1227  * features are supported. To be clear, these are NOT supported:
 1228  * 1. shared locking disablement
 1229  * 2. returning with an error after sleep
 1230  * 3. unlocking the interlock
 1231  *
 1232  * If in doubt, use lockmgr_lock_flags.
 1233  */
 1234 int
 1235 lockmgr_slock(struct lock *lk, u_int flags, const char *file, int line)
 1236 {
 1237         uintptr_t x;
 1238 
 1239         MPASS((flags & LK_TYPE_MASK) == LK_SHARED);
 1240         MPASS((flags & LK_INTERLOCK) == 0);
 1241         MPASS((lk->lock_object.lo_flags & LK_NOSHARE) == 0);
 1242 
 1243         if (LK_CAN_WITNESS(flags))
 1244                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
 1245                     file, line, NULL);
 1246         x = lockmgr_read_value(lk);
 1247         if (__predict_true(lockmgr_slock_try(lk, &x, flags, true))) {
 1248                 lockmgr_note_shared_acquire(lk, 0, 0, file, line, flags);
 1249                 return (0);
 1250         }
 1251 
 1252         return (lockmgr_slock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL));
 1253 }
 1254 
 1255 int
 1256 lockmgr_xlock(struct lock *lk, u_int flags, const char *file, int line)
 1257 {
 1258         uintptr_t tid;
 1259 
 1260         MPASS((flags & LK_TYPE_MASK) == LK_EXCLUSIVE);
 1261         MPASS((flags & LK_INTERLOCK) == 0);
 1262 
 1263         if (LK_CAN_WITNESS(flags))
 1264                 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 1265                     LOP_EXCLUSIVE, file, line, NULL);
 1266         tid = (uintptr_t)curthread;
 1267         if (atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
 1268                 lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
 1269                     flags);
 1270                 return (0);
 1271         }
 1272 
 1273         return (lockmgr_xlock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL));
 1274 }
 1275 
 1276 int
 1277 lockmgr_unlock(struct lock *lk)
 1278 {
 1279         uintptr_t x, tid;
 1280         const char *file;
 1281         int line;
 1282 
 1283         file = __FILE__;
 1284         line = __LINE__;
 1285 
 1286         _lockmgr_assert(lk, KA_LOCKED, file, line);
 1287         x = lockmgr_read_value(lk);
 1288         if (__predict_true(x & LK_SHARE) != 0) {
 1289                 lockmgr_note_shared_release(lk, file, line);
 1290                 if (lockmgr_sunlock_try(lk, &x)) {
 1291                         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER);
 1292                 } else {
 1293                         return (lockmgr_sunlock_hard(lk, x, LK_RELEASE, NULL, file, line));
 1294                 }
 1295         } else {
 1296                 tid = (uintptr_t)curthread;
 1297                 lockmgr_note_exclusive_release(lk, file, line);
 1298                 if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
 1299                         LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,LOCKSTAT_WRITER);
 1300                 } else {
 1301                         return (lockmgr_xunlock_hard(lk, x, LK_RELEASE, NULL, file, line));
 1302                 }
 1303         }
 1304         return (0);
 1305 }
 1306 
 1307 int
 1308 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
 1309     const char *wmesg, int pri, int timo, const char *file, int line)
 1310 {
 1311         GIANT_DECLARE;
 1312         struct lockmgr_wait lwa;
 1313         struct lock_class *class;
 1314         const char *iwmesg;
 1315         uintptr_t tid, v, x;
 1316         u_int op, realexslp;
 1317         int error, ipri, itimo, queue, wakeup_swapper;
 1318 #ifdef LOCK_PROFILING
 1319         uint64_t waittime = 0;
 1320         int contested = 0;
 1321 #endif
 1322 
 1323         if (KERNEL_PANICKED())
 1324                 return (0);
 1325 
 1326         error = 0;
 1327         tid = (uintptr_t)curthread;
 1328         op = (flags & LK_TYPE_MASK);
 1329         iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
 1330         ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
 1331         itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
 1332 
 1333         lwa.iwmesg = iwmesg;
 1334         lwa.ipri = ipri;
 1335         lwa.itimo = itimo;
 1336 
 1337         MPASS((flags & ~LK_TOTAL_MASK) == 0);
 1338         KASSERT((op & (op - 1)) == 0,
 1339             ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
 1340         KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
 1341             (op != LK_DOWNGRADE && op != LK_RELEASE),
 1342             ("%s: Invalid flags in regard of the operation desired @ %s:%d",
 1343             __func__, file, line));
 1344         KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
 1345             ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
 1346             __func__, file, line));
 1347         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
 1348             ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
 1349             lk->lock_object.lo_name, file, line));
 1350 
 1351         class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
 1352 
 1353         if (lk->lock_object.lo_flags & LK_NOSHARE) {
 1354                 switch (op) {
 1355                 case LK_SHARED:
 1356                         op = LK_EXCLUSIVE;
 1357                         break;
 1358                 case LK_UPGRADE:
 1359                 case LK_TRYUPGRADE:
 1360                 case LK_DOWNGRADE:
 1361                         _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
 1362                             file, line);
 1363                         if (flags & LK_INTERLOCK)
 1364                                 class->lc_unlock(ilk);
 1365                         return (0);
 1366                 }
 1367         }
 1368 
 1369         wakeup_swapper = 0;
 1370         switch (op) {
 1371         case LK_SHARED:
 1372                 return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa));
 1373                 break;
 1374         case LK_UPGRADE:
 1375         case LK_TRYUPGRADE:
 1376                 return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa));
 1377                 break;
 1378         case LK_EXCLUSIVE:
 1379                 return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa));
 1380                 break;
 1381         case LK_DOWNGRADE:
 1382                 _lockmgr_assert(lk, KA_XLOCKED, file, line);
 1383                 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
 1384 
 1385                 /*
 1386                  * Panic if the lock is recursed.
 1387                  */
 1388                 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
 1389                         if (flags & LK_INTERLOCK)
 1390                                 class->lc_unlock(ilk);
 1391                         panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
 1392                             __func__, iwmesg, file, line);
 1393                 }
 1394                 TD_SLOCKS_INC(curthread);
 1395 
 1396                 /*
 1397                  * In order to preserve waiters flags, just spin.
 1398                  */
 1399                 for (;;) {
 1400                         x = lockmgr_read_value(lk);
 1401                         MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
 1402                         x &= LK_ALL_WAITERS;
 1403                         if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
 1404                             LK_SHARERS_LOCK(1) | x))
 1405                                 break;
 1406                         cpu_spinwait();
 1407                 }
 1408                 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
 1409                 LOCKSTAT_RECORD0(lockmgr__downgrade, lk);
 1410                 break;
 1411         case LK_RELEASE:
 1412                 _lockmgr_assert(lk, KA_LOCKED, file, line);
 1413                 x = lockmgr_read_value(lk);
 1414 
 1415                 if (__predict_true(x & LK_SHARE) != 0) {
 1416                         lockmgr_note_shared_release(lk, file, line);
 1417                         return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
 1418                 } else {
 1419                         lockmgr_note_exclusive_release(lk, file, line);
 1420                         return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
 1421                 }
 1422                 break;
 1423         case LK_DRAIN:
 1424                 if (LK_CAN_WITNESS(flags))
 1425                         WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
 1426                             LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
 1427                             ilk : NULL);
 1428 
 1429                 /*
 1430                  * Trying to drain a lock we already own will result in a
 1431                  * deadlock.
 1432                  */
 1433                 if (lockmgr_xlocked(lk)) {
 1434                         if (flags & LK_INTERLOCK)
 1435                                 class->lc_unlock(ilk);
 1436                         panic("%s: draining %s with the lock held @ %s:%d\n",
 1437                             __func__, iwmesg, file, line);
 1438                 }
 1439 
 1440                 for (;;) {
 1441                         if (lk->lk_lock == LK_UNLOCKED &&
 1442                             atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
 1443                                 break;
 1444 
 1445 #ifdef HWPMC_HOOKS
 1446                         PMC_SOFT_CALL( , , lock, failed);
 1447 #endif
 1448                         lock_profile_obtain_lock_failed(&lk->lock_object, false,
 1449                             &contested, &waittime);
 1450 
 1451                         /*
 1452                          * If the lock is expected to not sleep just give up
 1453                          * and return.
 1454                          */
 1455                         if (LK_TRYOP(flags)) {
 1456                                 LOCK_LOG2(lk, "%s: %p fails the try operation",
 1457                                     __func__, lk);
 1458                                 error = EBUSY;
 1459                                 break;
 1460                         }
 1461 
 1462                         /*
 1463                          * Acquire the sleepqueue chain lock because we
 1464                          * probabilly will need to manipulate waiters flags.
 1465                          */
 1466                         sleepq_lock(&lk->lock_object);
 1467                         x = lockmgr_read_value(lk);
 1468 
 1469                         /*
 1470                          * if the lock has been released while we spun on
 1471                          * the sleepqueue chain lock just try again.
 1472                          */
 1473                         if (x == LK_UNLOCKED) {
 1474                                 sleepq_release(&lk->lock_object);
 1475                                 continue;
 1476                         }
 1477 
 1478                         v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
 1479                         if ((x & ~v) == LK_UNLOCKED) {
 1480                                 v = (x & ~LK_EXCLUSIVE_SPINNERS);
 1481 
 1482                                 /*
 1483                                  * If interruptible sleeps left the exclusive
 1484                                  * queue empty avoid a starvation for the
 1485                                  * threads sleeping on the shared queue by
 1486                                  * giving them precedence and cleaning up the
 1487                                  * exclusive waiters bit anyway.
 1488                                  * Please note that lk_exslpfail count may be
 1489                                  * lying about the real number of waiters with
 1490                                  * the LK_SLEEPFAIL flag on because they may
 1491                                  * be used in conjunction with interruptible
 1492                                  * sleeps so lk_exslpfail might be considered
 1493                                  * an 'upper limit' bound, including the edge
 1494                                  * cases.
 1495                                  */
 1496                                 if (v & LK_EXCLUSIVE_WAITERS) {
 1497                                         queue = SQ_EXCLUSIVE_QUEUE;
 1498                                         v &= ~LK_EXCLUSIVE_WAITERS;
 1499                                 } else {
 1500                                         /*
 1501                                          * Exclusive waiters sleeping with
 1502                                          * LK_SLEEPFAIL on and using
 1503                                          * interruptible sleeps/timeout may
 1504                                          * have left spourious lk_exslpfail
 1505                                          * counts on, so clean it up anyway.
 1506                                          */
 1507                                         MPASS(v & LK_SHARED_WAITERS);
 1508                                         lk->lk_exslpfail = 0;
 1509                                         queue = SQ_SHARED_QUEUE;
 1510                                         v &= ~LK_SHARED_WAITERS;
 1511                                 }
 1512                                 if (queue == SQ_EXCLUSIVE_QUEUE) {
 1513                                         realexslp =
 1514                                             sleepq_sleepcnt(&lk->lock_object,
 1515                                             SQ_EXCLUSIVE_QUEUE);
 1516                                         if (lk->lk_exslpfail >= realexslp) {
 1517                                                 lk->lk_exslpfail = 0;
 1518                                                 queue = SQ_SHARED_QUEUE;
 1519                                                 v &= ~LK_SHARED_WAITERS;
 1520                                                 if (realexslp != 0) {
 1521                                                         LOCK_LOG2(lk,
 1522                                         "%s: %p has only LK_SLEEPFAIL sleepers",
 1523                                                             __func__, lk);
 1524                                                         LOCK_LOG2(lk,
 1525                         "%s: %p waking up threads on the exclusive queue",
 1526                                                             __func__, lk);
 1527                                                         wakeup_swapper =
 1528                                                             sleepq_broadcast(
 1529                                                             &lk->lock_object,
 1530                                                             SLEEPQ_LK, 0,
 1531                                                             SQ_EXCLUSIVE_QUEUE);
 1532                                                 }
 1533                                         } else
 1534                                                 lk->lk_exslpfail = 0;
 1535                                 }
 1536                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
 1537                                         sleepq_release(&lk->lock_object);
 1538                                         continue;
 1539                                 }
 1540                                 LOCK_LOG3(lk,
 1541                                 "%s: %p waking up all threads on the %s queue",
 1542                                     __func__, lk, queue == SQ_SHARED_QUEUE ?
 1543                                     "shared" : "exclusive");
 1544                                 wakeup_swapper |= sleepq_broadcast(
 1545                                     &lk->lock_object, SLEEPQ_LK, 0, queue);
 1546 
 1547                                 /*
 1548                                  * If shared waiters have been woken up we need
 1549                                  * to wait for one of them to acquire the lock
 1550                                  * before to set the exclusive waiters in
 1551                                  * order to avoid a deadlock.
 1552                                  */
 1553                                 if (queue == SQ_SHARED_QUEUE) {
 1554                                         for (v = lk->lk_lock;
 1555                                             (v & LK_SHARE) && !LK_SHARERS(v);
 1556                                             v = lk->lk_lock)
 1557                                                 cpu_spinwait();
 1558                                 }
 1559                         }
 1560 
 1561                         /*
 1562                          * Try to set the LK_EXCLUSIVE_WAITERS flag.  If we
 1563                          * fail, loop back and retry.
 1564                          */
 1565                         if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
 1566                                 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
 1567                                     x | LK_EXCLUSIVE_WAITERS)) {
 1568                                         sleepq_release(&lk->lock_object);
 1569                                         continue;
 1570                                 }
 1571                                 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
 1572                                     __func__, lk);
 1573                         }
 1574 
 1575                         /*
 1576                          * As far as we have been unable to acquire the
 1577                          * exclusive lock and the exclusive waiters flag
 1578                          * is set, we will sleep.
 1579                          */
 1580                         if (flags & LK_INTERLOCK) {
 1581                                 class->lc_unlock(ilk);
 1582                                 flags &= ~LK_INTERLOCK;
 1583                         }
 1584                         GIANT_SAVE();
 1585                         sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
 1586                             SQ_EXCLUSIVE_QUEUE);
 1587                         sleepq_wait(&lk->lock_object, ipri & PRIMASK);
 1588                         GIANT_RESTORE();
 1589                         LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
 1590                             __func__, lk);
 1591                 }
 1592 
 1593                 if (error == 0) {
 1594                         lock_profile_obtain_lock_success(&lk->lock_object,
 1595                             false, contested, waittime, file, line);
 1596                         LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
 1597                             lk->lk_recurse, file, line);
 1598                         WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
 1599                             LK_TRYWIT(flags), file, line);
 1600                         TD_LOCKS_INC(curthread);
 1601                         STACK_SAVE(lk);
 1602                 }
 1603                 break;
 1604         default:
 1605                 if (flags & LK_INTERLOCK)
 1606                         class->lc_unlock(ilk);
 1607                 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
 1608         }
 1609 
 1610         if (flags & LK_INTERLOCK)
 1611                 class->lc_unlock(ilk);
 1612         if (wakeup_swapper)
 1613                 kick_proc0();
 1614 
 1615         return (error);
 1616 }
 1617 
 1618 void
 1619 _lockmgr_disown(struct lock *lk, const char *file, int line)
 1620 {
 1621         uintptr_t tid, x;
 1622 
 1623         if (SCHEDULER_STOPPED())
 1624                 return;
 1625 
 1626         tid = (uintptr_t)curthread;
 1627         _lockmgr_assert(lk, KA_XLOCKED, file, line);
 1628 
 1629         /*
 1630          * Panic if the lock is recursed.
 1631          */
 1632         if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
 1633                 panic("%s: disown a recursed lockmgr @ %s:%d\n",
 1634                     __func__,  file, line);
 1635 
 1636         /*
 1637          * If the owner is already LK_KERNPROC just skip the whole operation.
 1638          */
 1639         if (LK_HOLDER(lk->lk_lock) != tid)
 1640                 return;
 1641         lock_profile_release_lock(&lk->lock_object, false);
 1642         LOCKSTAT_RECORD1(lockmgr__disown, lk, LOCKSTAT_WRITER);
 1643         LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
 1644         WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
 1645         TD_LOCKS_DEC(curthread);
 1646         STACK_SAVE(lk);
 1647 
 1648         /*
 1649          * In order to preserve waiters flags, just spin.
 1650          */
 1651         for (;;) {
 1652                 x = lockmgr_read_value(lk);
 1653                 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
 1654                 x &= LK_ALL_WAITERS;
 1655                 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
 1656                     LK_KERNPROC | x))
 1657                         return;
 1658                 cpu_spinwait();
 1659         }
 1660 }
 1661 
 1662 void
 1663 lockmgr_printinfo(const struct lock *lk)
 1664 {
 1665         struct thread *td;
 1666         uintptr_t x;
 1667 
 1668         if (lk->lk_lock == LK_UNLOCKED)
 1669                 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
 1670         else if (lk->lk_lock & LK_SHARE)
 1671                 printf("lock type %s: SHARED (count %ju)\n",
 1672                     lk->lock_object.lo_name,
 1673                     (uintmax_t)LK_SHARERS(lk->lk_lock));
 1674         else {
 1675                 td = lockmgr_xholder(lk);
 1676                 if (td == (struct thread *)LK_KERNPROC)
 1677                         printf("lock type %s: EXCL by KERNPROC\n",
 1678                             lk->lock_object.lo_name);
 1679                 else
 1680                         printf("lock type %s: EXCL by thread %p "
 1681                             "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
 1682                             td, td->td_proc->p_pid, td->td_proc->p_comm,
 1683                             td->td_tid);
 1684         }
 1685 
 1686         x = lk->lk_lock;
 1687         if (x & LK_EXCLUSIVE_WAITERS)
 1688                 printf(" with exclusive waiters pending\n");
 1689         if (x & LK_SHARED_WAITERS)
 1690                 printf(" with shared waiters pending\n");
 1691         if (x & LK_EXCLUSIVE_SPINNERS)
 1692                 printf(" with exclusive spinners pending\n");
 1693 
 1694         STACK_PRINT(lk);
 1695 }
 1696 
 1697 int
 1698 lockstatus(const struct lock *lk)
 1699 {
 1700         uintptr_t v, x;
 1701         int ret;
 1702 
 1703         ret = LK_SHARED;
 1704         x = lockmgr_read_value(lk);
 1705         v = LK_HOLDER(x);
 1706 
 1707         if ((x & LK_SHARE) == 0) {
 1708                 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
 1709                         ret = LK_EXCLUSIVE;
 1710                 else
 1711                         ret = LK_EXCLOTHER;
 1712         } else if (x == LK_UNLOCKED)
 1713                 ret = 0;
 1714 
 1715         return (ret);
 1716 }
 1717 
 1718 #ifdef INVARIANT_SUPPORT
 1719 
 1720 FEATURE(invariant_support,
 1721     "Support for modules compiled with INVARIANTS option");
 1722 
 1723 #ifndef INVARIANTS
 1724 #undef  _lockmgr_assert
 1725 #endif
 1726 
 1727 void
 1728 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
 1729 {
 1730         int slocked = 0;
 1731 
 1732         if (KERNEL_PANICKED())
 1733                 return;
 1734         switch (what) {
 1735         case KA_SLOCKED:
 1736         case KA_SLOCKED | KA_NOTRECURSED:
 1737         case KA_SLOCKED | KA_RECURSED:
 1738                 slocked = 1;
 1739         case KA_LOCKED:
 1740         case KA_LOCKED | KA_NOTRECURSED:
 1741         case KA_LOCKED | KA_RECURSED:
 1742 #ifdef WITNESS
 1743 
 1744                 /*
 1745                  * We cannot trust WITNESS if the lock is held in exclusive
 1746                  * mode and a call to lockmgr_disown() happened.
 1747                  * Workaround this skipping the check if the lock is held in
 1748                  * exclusive mode even for the KA_LOCKED case.
 1749                  */
 1750                 if (slocked || (lk->lk_lock & LK_SHARE)) {
 1751                         witness_assert(&lk->lock_object, what, file, line);
 1752                         break;
 1753                 }
 1754 #endif
 1755                 if (lk->lk_lock == LK_UNLOCKED ||
 1756                     ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
 1757                     (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
 1758                         panic("Lock %s not %slocked @ %s:%d\n",
 1759                             lk->lock_object.lo_name, slocked ? "share" : "",
 1760                             file, line);
 1761 
 1762                 if ((lk->lk_lock & LK_SHARE) == 0) {
 1763                         if (lockmgr_recursed(lk)) {
 1764                                 if (what & KA_NOTRECURSED)
 1765                                         panic("Lock %s recursed @ %s:%d\n",
 1766                                             lk->lock_object.lo_name, file,
 1767                                             line);
 1768                         } else if (what & KA_RECURSED)
 1769                                 panic("Lock %s not recursed @ %s:%d\n",
 1770                                     lk->lock_object.lo_name, file, line);
 1771                 }
 1772                 break;
 1773         case KA_XLOCKED:
 1774         case KA_XLOCKED | KA_NOTRECURSED:
 1775         case KA_XLOCKED | KA_RECURSED:
 1776                 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
 1777                         panic("Lock %s not exclusively locked @ %s:%d\n",
 1778                             lk->lock_object.lo_name, file, line);
 1779                 if (lockmgr_recursed(lk)) {
 1780                         if (what & KA_NOTRECURSED)
 1781                                 panic("Lock %s recursed @ %s:%d\n",
 1782                                     lk->lock_object.lo_name, file, line);
 1783                 } else if (what & KA_RECURSED)
 1784                         panic("Lock %s not recursed @ %s:%d\n",
 1785                             lk->lock_object.lo_name, file, line);
 1786                 break;
 1787         case KA_UNLOCKED:
 1788                 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
 1789                         panic("Lock %s exclusively locked @ %s:%d\n",
 1790                             lk->lock_object.lo_name, file, line);
 1791                 break;
 1792         default:
 1793                 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
 1794                     line);
 1795         }
 1796 }
 1797 #endif
 1798 
 1799 #ifdef DDB
 1800 int
 1801 lockmgr_chain(struct thread *td, struct thread **ownerp)
 1802 {
 1803         const struct lock *lk;
 1804 
 1805         lk = td->td_wchan;
 1806 
 1807         if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
 1808                 return (0);
 1809         db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
 1810         if (lk->lk_lock & LK_SHARE)
 1811                 db_printf("SHARED (count %ju)\n",
 1812                     (uintmax_t)LK_SHARERS(lk->lk_lock));
 1813         else
 1814                 db_printf("EXCL\n");
 1815         *ownerp = lockmgr_xholder(lk);
 1816 
 1817         return (1);
 1818 }
 1819 
 1820 static void
 1821 db_show_lockmgr(const struct lock_object *lock)
 1822 {
 1823         struct thread *td;
 1824         const struct lock *lk;
 1825 
 1826         lk = (const struct lock *)lock;
 1827 
 1828         db_printf(" state: ");
 1829         if (lk->lk_lock == LK_UNLOCKED)
 1830                 db_printf("UNLOCKED\n");
 1831         else if (lk->lk_lock & LK_SHARE)
 1832                 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
 1833         else {
 1834                 td = lockmgr_xholder(lk);
 1835                 if (td == (struct thread *)LK_KERNPROC)
 1836                         db_printf("XLOCK: LK_KERNPROC\n");
 1837                 else
 1838                         db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
 1839                             td->td_tid, td->td_proc->p_pid,
 1840                             td->td_proc->p_comm);
 1841                 if (lockmgr_recursed(lk))
 1842                         db_printf(" recursed: %d\n", lk->lk_recurse);
 1843         }
 1844         db_printf(" waiters: ");
 1845         switch (lk->lk_lock & LK_ALL_WAITERS) {
 1846         case LK_SHARED_WAITERS:
 1847                 db_printf("shared\n");
 1848                 break;
 1849         case LK_EXCLUSIVE_WAITERS:
 1850                 db_printf("exclusive\n");
 1851                 break;
 1852         case LK_ALL_WAITERS:
 1853                 db_printf("shared and exclusive\n");
 1854                 break;
 1855         default:
 1856                 db_printf("none\n");
 1857         }
 1858         db_printf(" spinners: ");
 1859         if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
 1860                 db_printf("exclusive\n");
 1861         else
 1862                 db_printf("none\n");
 1863 }
 1864 #endif

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