The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_mutex.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Berkeley Software Design Inc's name may not be used to endorse or
   15  *    promote products derived from this software without specific prior
   16  *    written permission.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
   19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   21  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
   22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   25  * HOWEVER 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
   28  * SUCH DAMAGE.
   29  *
   30  *      from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
   31  *      and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
   32  */
   33 
   34 /*
   35  * Machine independent bits of mutex implementation.
   36  */
   37 
   38 #include <sys/cdefs.h>
   39 __FBSDID("$FreeBSD$");
   40 
   41 #include "opt_adaptive_mutexes.h"
   42 #include "opt_ddb.h"
   43 #include "opt_hwpmc_hooks.h"
   44 #include "opt_sched.h"
   45 
   46 #include <sys/param.h>
   47 #include <sys/systm.h>
   48 #include <sys/bus.h>
   49 #include <sys/conf.h>
   50 #include <sys/kdb.h>
   51 #include <sys/kernel.h>
   52 #include <sys/ktr.h>
   53 #include <sys/lock.h>
   54 #include <sys/malloc.h>
   55 #include <sys/mutex.h>
   56 #include <sys/proc.h>
   57 #include <sys/resourcevar.h>
   58 #include <sys/sched.h>
   59 #include <sys/sbuf.h>
   60 #include <sys/smp.h>
   61 #include <sys/sysctl.h>
   62 #include <sys/turnstile.h>
   63 #include <sys/vmmeter.h>
   64 #include <sys/lock_profile.h>
   65 
   66 #include <machine/atomic.h>
   67 #include <machine/bus.h>
   68 #include <machine/cpu.h>
   69 
   70 #include <ddb/ddb.h>
   71 
   72 #include <fs/devfs/devfs_int.h>
   73 
   74 #include <vm/vm.h>
   75 #include <vm/vm_extern.h>
   76 
   77 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
   78 #define ADAPTIVE_MUTEXES
   79 #endif
   80 
   81 #ifdef HWPMC_HOOKS
   82 #include <sys/pmckern.h>
   83 PMC_SOFT_DEFINE( , , lock, failed);
   84 #endif
   85 
   86 /*
   87  * Return the mutex address when the lock cookie address is provided.
   88  * This functionality assumes that struct mtx* have a member named mtx_lock.
   89  */
   90 #define mtxlock2mtx(c)  (__containerof(c, struct mtx, mtx_lock))
   91 
   92 /*
   93  * Internal utility macros.
   94  */
   95 #define mtx_unowned(m)  ((m)->mtx_lock == MTX_UNOWNED)
   96 
   97 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
   98 
   99 static void     assert_mtx(const struct lock_object *lock, int what);
  100 #ifdef DDB
  101 static void     db_show_mtx(const struct lock_object *lock);
  102 #endif
  103 static void     lock_mtx(struct lock_object *lock, uintptr_t how);
  104 static void     lock_spin(struct lock_object *lock, uintptr_t how);
  105 #ifdef KDTRACE_HOOKS
  106 static int      owner_mtx(const struct lock_object *lock,
  107                     struct thread **owner);
  108 #endif
  109 static uintptr_t unlock_mtx(struct lock_object *lock);
  110 static uintptr_t unlock_spin(struct lock_object *lock);
  111 
  112 /*
  113  * Lock classes for sleep and spin mutexes.
  114  */
  115 struct lock_class lock_class_mtx_sleep = {
  116         .lc_name = "sleep mutex",
  117         .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
  118         .lc_assert = assert_mtx,
  119 #ifdef DDB
  120         .lc_ddb_show = db_show_mtx,
  121 #endif
  122         .lc_lock = lock_mtx,
  123         .lc_unlock = unlock_mtx,
  124 #ifdef KDTRACE_HOOKS
  125         .lc_owner = owner_mtx,
  126 #endif
  127 };
  128 struct lock_class lock_class_mtx_spin = {
  129         .lc_name = "spin mutex",
  130         .lc_flags = LC_SPINLOCK | LC_RECURSABLE,
  131         .lc_assert = assert_mtx,
  132 #ifdef DDB
  133         .lc_ddb_show = db_show_mtx,
  134 #endif
  135         .lc_lock = lock_spin,
  136         .lc_unlock = unlock_spin,
  137 #ifdef KDTRACE_HOOKS
  138         .lc_owner = owner_mtx,
  139 #endif
  140 };
  141 
  142 #ifdef ADAPTIVE_MUTEXES
  143 static SYSCTL_NODE(_debug, OID_AUTO, mtx, CTLFLAG_RD, NULL, "mtx debugging");
  144 
  145 static struct lock_delay_config __read_frequently mtx_delay;
  146 
  147 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_base, CTLFLAG_RW, &mtx_delay.base,
  148     0, "");
  149 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_max, CTLFLAG_RW, &mtx_delay.max,
  150     0, "");
  151 
  152 LOCK_DELAY_SYSINIT_DEFAULT(mtx_delay);
  153 #endif
  154 
  155 static SYSCTL_NODE(_debug, OID_AUTO, mtx_spin, CTLFLAG_RD, NULL,
  156     "mtx spin debugging");
  157 
  158 static struct lock_delay_config __read_frequently mtx_spin_delay;
  159 
  160 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_base, CTLFLAG_RW,
  161     &mtx_spin_delay.base, 0, "");
  162 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_max, CTLFLAG_RW,
  163     &mtx_spin_delay.max, 0, "");
  164 
  165 LOCK_DELAY_SYSINIT_DEFAULT(mtx_spin_delay);
  166 
  167 /*
  168  * System-wide mutexes
  169  */
  170 struct mtx blocked_lock;
  171 struct mtx __exclusive_cache_line Giant;
  172 
  173 static void _mtx_lock_indefinite_check(struct mtx *, struct lock_delay_arg *);
  174 
  175 void
  176 assert_mtx(const struct lock_object *lock, int what)
  177 {
  178 
  179         /*
  180          * Treat LA_LOCKED as if LA_XLOCKED was asserted.
  181          *
  182          * Some callers of lc_assert uses LA_LOCKED to indicate that either
  183          * a shared lock or write lock was held, while other callers uses
  184          * the more strict LA_XLOCKED (used as MA_OWNED).
  185          *
  186          * Mutex is the only lock class that can not be shared, as a result,
  187          * we can reasonably consider the caller really intends to assert
  188          * LA_XLOCKED when they are asserting LA_LOCKED on a mutex object.
  189          */
  190         if (what & LA_LOCKED) {
  191                 what &= ~LA_LOCKED;
  192                 what |= LA_XLOCKED;
  193         }
  194         mtx_assert((const struct mtx *)lock, what);
  195 }
  196 
  197 void
  198 lock_mtx(struct lock_object *lock, uintptr_t how)
  199 {
  200 
  201         mtx_lock((struct mtx *)lock);
  202 }
  203 
  204 void
  205 lock_spin(struct lock_object *lock, uintptr_t how)
  206 {
  207 
  208         panic("spin locks can only use msleep_spin");
  209 }
  210 
  211 uintptr_t
  212 unlock_mtx(struct lock_object *lock)
  213 {
  214         struct mtx *m;
  215 
  216         m = (struct mtx *)lock;
  217         mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
  218         mtx_unlock(m);
  219         return (0);
  220 }
  221 
  222 uintptr_t
  223 unlock_spin(struct lock_object *lock)
  224 {
  225 
  226         panic("spin locks can only use msleep_spin");
  227 }
  228 
  229 #ifdef KDTRACE_HOOKS
  230 int
  231 owner_mtx(const struct lock_object *lock, struct thread **owner)
  232 {
  233         const struct mtx *m;
  234         uintptr_t x;
  235 
  236         m = (const struct mtx *)lock;
  237         x = m->mtx_lock;
  238         *owner = (struct thread *)(x & ~MTX_FLAGMASK);
  239         return (*owner != NULL);
  240 }
  241 #endif
  242 
  243 /*
  244  * Function versions of the inlined __mtx_* macros.  These are used by
  245  * modules and can also be called from assembly language if needed.
  246  */
  247 void
  248 __mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
  249 {
  250         struct mtx *m;
  251         uintptr_t tid, v;
  252 
  253         m = mtxlock2mtx(c);
  254 
  255         KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() ||
  256             !TD_IS_IDLETHREAD(curthread),
  257             ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d",
  258             curthread, m->lock_object.lo_name, file, line));
  259         KASSERT(m->mtx_lock != MTX_DESTROYED,
  260             ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
  261         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
  262             ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
  263             file, line));
  264         WITNESS_CHECKORDER(&m->lock_object, (opts & ~MTX_RECURSE) |
  265             LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
  266 
  267         tid = (uintptr_t)curthread;
  268         v = MTX_UNOWNED;
  269         if (!_mtx_obtain_lock_fetch(m, &v, tid))
  270                 _mtx_lock_sleep(m, v, opts, file, line);
  271         else
  272                 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
  273                     m, 0, 0, file, line);
  274         LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
  275             line);
  276         WITNESS_LOCK(&m->lock_object, (opts & ~MTX_RECURSE) | LOP_EXCLUSIVE,
  277             file, line);
  278         TD_LOCKS_INC(curthread);
  279 }
  280 
  281 void
  282 __mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
  283 {
  284         struct mtx *m;
  285 
  286         m = mtxlock2mtx(c);
  287 
  288         KASSERT(m->mtx_lock != MTX_DESTROYED,
  289             ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
  290         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
  291             ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
  292             file, line));
  293         WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  294         LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
  295             line);
  296         mtx_assert(m, MA_OWNED);
  297 
  298 #ifdef LOCK_PROFILING
  299         __mtx_unlock_sleep(c, (uintptr_t)curthread, opts, file, line);
  300 #else
  301         __mtx_unlock(m, curthread, opts, file, line);
  302 #endif
  303         TD_LOCKS_DEC(curthread);
  304 }
  305 
  306 void
  307 __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
  308     int line)
  309 {
  310         struct mtx *m;
  311 #ifdef SMP
  312         uintptr_t tid, v;
  313 #endif
  314 
  315         m = mtxlock2mtx(c);
  316 
  317         KASSERT(m->mtx_lock != MTX_DESTROYED,
  318             ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
  319         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  320             ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
  321             m->lock_object.lo_name, file, line));
  322         if (mtx_owned(m))
  323                 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
  324                     (opts & MTX_RECURSE) != 0,
  325             ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n",
  326                     m->lock_object.lo_name, file, line));
  327         opts &= ~MTX_RECURSE;
  328         WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
  329             file, line, NULL);
  330 #ifdef SMP
  331         spinlock_enter();
  332         tid = (uintptr_t)curthread;
  333         v = MTX_UNOWNED;
  334         if (!_mtx_obtain_lock_fetch(m, &v, tid))
  335                 _mtx_lock_spin(m, v, opts, file, line);
  336         else
  337                 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire,
  338                     m, 0, 0, file, line);
  339 #else
  340         __mtx_lock_spin(m, curthread, opts, file, line);
  341 #endif
  342         LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
  343             line);
  344         WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  345 }
  346 
  347 int
  348 __mtx_trylock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
  349     int line)
  350 {
  351         struct mtx *m;
  352 
  353         if (SCHEDULER_STOPPED())
  354                 return (1);
  355 
  356         m = mtxlock2mtx(c);
  357 
  358         KASSERT(m->mtx_lock != MTX_DESTROYED,
  359             ("mtx_trylock_spin() of destroyed mutex @ %s:%d", file, line));
  360         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  361             ("mtx_trylock_spin() of sleep mutex %s @ %s:%d",
  362             m->lock_object.lo_name, file, line));
  363         KASSERT((opts & MTX_RECURSE) == 0,
  364             ("mtx_trylock_spin: unsupp. opt MTX_RECURSE on mutex %s @ %s:%d\n",
  365             m->lock_object.lo_name, file, line));
  366         if (__mtx_trylock_spin(m, curthread, opts, file, line)) {
  367                 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 1, file, line);
  368                 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  369                 return (1);
  370         }
  371         LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 0, file, line);
  372         return (0);
  373 }
  374 
  375 void
  376 __mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
  377     int line)
  378 {
  379         struct mtx *m;
  380 
  381         m = mtxlock2mtx(c);
  382 
  383         KASSERT(m->mtx_lock != MTX_DESTROYED,
  384             ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
  385         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  386             ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
  387             m->lock_object.lo_name, file, line));
  388         WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  389         LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
  390             line);
  391         mtx_assert(m, MA_OWNED);
  392 
  393         __mtx_unlock_spin(m);
  394 }
  395 
  396 /*
  397  * The important part of mtx_trylock{,_flags}()
  398  * Tries to acquire lock `m.'  If this function is called on a mutex that
  399  * is already owned, it will recursively acquire the lock.
  400  */
  401 int
  402 _mtx_trylock_flags_int(struct mtx *m, int opts LOCK_FILE_LINE_ARG_DEF)
  403 {
  404         struct thread *td;
  405         uintptr_t tid, v;
  406 #ifdef LOCK_PROFILING
  407         uint64_t waittime = 0;
  408         int contested = 0;
  409 #endif
  410         int rval;
  411         bool recursed;
  412 
  413         td = curthread;
  414         tid = (uintptr_t)td;
  415         if (SCHEDULER_STOPPED_TD(td))
  416                 return (1);
  417 
  418         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td),
  419             ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d",
  420             curthread, m->lock_object.lo_name, file, line));
  421         KASSERT(m->mtx_lock != MTX_DESTROYED,
  422             ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
  423         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
  424             ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
  425             file, line));
  426 
  427         rval = 1;
  428         recursed = false;
  429         v = MTX_UNOWNED;
  430         for (;;) {
  431                 if (_mtx_obtain_lock_fetch(m, &v, tid))
  432                         break;
  433                 if (v == MTX_UNOWNED)
  434                         continue;
  435                 if (v == tid &&
  436                     ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
  437                     (opts & MTX_RECURSE) != 0)) {
  438                         m->mtx_recurse++;
  439                         atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
  440                         recursed = true;
  441                         break;
  442                 }
  443                 rval = 0;
  444                 break;
  445         }
  446 
  447         opts &= ~MTX_RECURSE;
  448 
  449         LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
  450         if (rval) {
  451                 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
  452                     file, line);
  453                 TD_LOCKS_INC(curthread);
  454                 if (!recursed)
  455                         LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
  456                             m, contested, waittime, file, line);
  457         }
  458 
  459         return (rval);
  460 }
  461 
  462 int
  463 _mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line)
  464 {
  465         struct mtx *m;
  466 
  467         m = mtxlock2mtx(c);
  468         return (_mtx_trylock_flags_int(m, opts LOCK_FILE_LINE_ARG));
  469 }
  470 
  471 /*
  472  * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
  473  *
  474  * We call this if the lock is either contested (i.e. we need to go to
  475  * sleep waiting for it), or if we need to recurse on it.
  476  */
  477 #if LOCK_DEBUG > 0
  478 void
  479 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, int opts, const char *file,
  480     int line)
  481 #else
  482 void
  483 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v)
  484 #endif
  485 {
  486         struct thread *td;
  487         struct mtx *m;
  488         struct turnstile *ts;
  489         uintptr_t tid;
  490         struct thread *owner;
  491 #ifdef LOCK_PROFILING
  492         int contested = 0;
  493         uint64_t waittime = 0;
  494 #endif
  495 #if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS)
  496         struct lock_delay_arg lda;
  497 #endif
  498 #ifdef KDTRACE_HOOKS
  499         u_int sleep_cnt = 0;
  500         int64_t sleep_time = 0;
  501         int64_t all_time = 0;
  502 #endif
  503 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
  504         int doing_lockprof = 0;
  505 #endif
  506 
  507         td = curthread;
  508         tid = (uintptr_t)td;
  509         m = mtxlock2mtx(c);
  510 
  511 #ifdef KDTRACE_HOOKS
  512         if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) {
  513                 while (v == MTX_UNOWNED) {
  514                         if (_mtx_obtain_lock_fetch(m, &v, tid))
  515                                 goto out_lockstat;
  516                 }
  517                 doing_lockprof = 1;
  518                 all_time -= lockstat_nsecs(&m->lock_object);
  519         }
  520 #endif
  521 #ifdef LOCK_PROFILING
  522         doing_lockprof = 1;
  523 #endif
  524 
  525         if (SCHEDULER_STOPPED_TD(td))
  526                 return;
  527 
  528 #if defined(ADAPTIVE_MUTEXES)
  529         lock_delay_arg_init(&lda, &mtx_delay);
  530 #elif defined(KDTRACE_HOOKS)
  531         lock_delay_arg_init(&lda, NULL);
  532 #endif
  533 
  534         if (__predict_false(v == MTX_UNOWNED))
  535                 v = MTX_READ_VALUE(m);
  536 
  537         if (__predict_false(lv_mtx_owner(v) == td)) {
  538                 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
  539                     (opts & MTX_RECURSE) != 0,
  540             ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
  541                     m->lock_object.lo_name, file, line));
  542 #if LOCK_DEBUG > 0
  543                 opts &= ~MTX_RECURSE;
  544 #endif
  545                 m->mtx_recurse++;
  546                 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
  547                 if (LOCK_LOG_TEST(&m->lock_object, opts))
  548                         CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
  549                 return;
  550         }
  551 #if LOCK_DEBUG > 0
  552         opts &= ~MTX_RECURSE;
  553 #endif
  554 
  555 #ifdef HWPMC_HOOKS
  556         PMC_SOFT_CALL( , , lock, failed);
  557 #endif
  558         lock_profile_obtain_lock_failed(&m->lock_object,
  559                     &contested, &waittime);
  560         if (LOCK_LOG_TEST(&m->lock_object, opts))
  561                 CTR4(KTR_LOCK,
  562                     "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
  563                     m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
  564 
  565         for (;;) {
  566                 if (v == MTX_UNOWNED) {
  567                         if (_mtx_obtain_lock_fetch(m, &v, tid))
  568                                 break;
  569                         continue;
  570                 }
  571 #ifdef KDTRACE_HOOKS
  572                 lda.spin_cnt++;
  573 #endif
  574 #ifdef ADAPTIVE_MUTEXES
  575                 /*
  576                  * If the owner is running on another CPU, spin until the
  577                  * owner stops running or the state of the lock changes.
  578                  */
  579                 owner = lv_mtx_owner(v);
  580                 if (TD_IS_RUNNING(owner)) {
  581                         if (LOCK_LOG_TEST(&m->lock_object, 0))
  582                                 CTR3(KTR_LOCK,
  583                                     "%s: spinning on %p held by %p",
  584                                     __func__, m, owner);
  585                         KTR_STATE1(KTR_SCHED, "thread",
  586                             sched_tdname((struct thread *)tid),
  587                             "spinning", "lockname:\"%s\"",
  588                             m->lock_object.lo_name);
  589                         do {
  590                                 lock_delay(&lda);
  591                                 v = MTX_READ_VALUE(m);
  592                                 owner = lv_mtx_owner(v);
  593                         } while (v != MTX_UNOWNED && TD_IS_RUNNING(owner));
  594                         KTR_STATE0(KTR_SCHED, "thread",
  595                             sched_tdname((struct thread *)tid),
  596                             "running");
  597                         continue;
  598                 }
  599 #endif
  600 
  601                 ts = turnstile_trywait(&m->lock_object);
  602                 v = MTX_READ_VALUE(m);
  603 retry_turnstile:
  604 
  605                 /*
  606                  * Check if the lock has been released while spinning for
  607                  * the turnstile chain lock.
  608                  */
  609                 if (v == MTX_UNOWNED) {
  610                         turnstile_cancel(ts);
  611                         continue;
  612                 }
  613 
  614 #ifdef ADAPTIVE_MUTEXES
  615                 /*
  616                  * The current lock owner might have started executing
  617                  * on another CPU (or the lock could have changed
  618                  * owners) while we were waiting on the turnstile
  619                  * chain lock.  If so, drop the turnstile lock and try
  620                  * again.
  621                  */
  622                 owner = lv_mtx_owner(v);
  623                 if (TD_IS_RUNNING(owner)) {
  624                         turnstile_cancel(ts);
  625                         continue;
  626                 }
  627 #endif
  628 
  629                 /*
  630                  * If the mutex isn't already contested and a failure occurs
  631                  * setting the contested bit, the mutex was either released
  632                  * or the state of the MTX_RECURSED bit changed.
  633                  */
  634                 if ((v & MTX_CONTESTED) == 0 &&
  635                     !atomic_fcmpset_ptr(&m->mtx_lock, &v, v | MTX_CONTESTED)) {
  636                         goto retry_turnstile;
  637                 }
  638 
  639                 /*
  640                  * We definitely must sleep for this lock.
  641                  */
  642                 mtx_assert(m, MA_NOTOWNED);
  643 
  644                 /*
  645                  * Block on the turnstile.
  646                  */
  647 #ifdef KDTRACE_HOOKS
  648                 sleep_time -= lockstat_nsecs(&m->lock_object);
  649 #endif
  650 #ifndef ADAPTIVE_MUTEXES
  651                 owner = mtx_owner(m);
  652 #endif
  653                 MPASS(owner == mtx_owner(m));
  654                 turnstile_wait(ts, owner, TS_EXCLUSIVE_QUEUE);
  655 #ifdef KDTRACE_HOOKS
  656                 sleep_time += lockstat_nsecs(&m->lock_object);
  657                 sleep_cnt++;
  658 #endif
  659                 v = MTX_READ_VALUE(m);
  660         }
  661 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
  662         if (__predict_true(!doing_lockprof))
  663                 return;
  664 #endif
  665 #ifdef KDTRACE_HOOKS
  666         all_time += lockstat_nsecs(&m->lock_object);
  667         if (sleep_time)
  668                 LOCKSTAT_RECORD1(adaptive__block, m, sleep_time);
  669 
  670         /*
  671          * Only record the loops spinning and not sleeping.
  672          */
  673         if (lda.spin_cnt > sleep_cnt)
  674                 LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time);
  675 out_lockstat:
  676 #endif
  677         LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested,
  678             waittime, file, line);
  679 }
  680 
  681 #ifdef SMP
  682 /*
  683  * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock.
  684  *
  685  * This is only called if we need to actually spin for the lock. Recursion
  686  * is handled inline.
  687  */
  688 #if LOCK_DEBUG > 0
  689 void
  690 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, int opts,
  691     const char *file, int line)
  692 #else
  693 void
  694 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v)
  695 #endif
  696 {
  697         struct mtx *m;
  698         struct lock_delay_arg lda;
  699         uintptr_t tid;
  700 #ifdef LOCK_PROFILING
  701         int contested = 0;
  702         uint64_t waittime = 0;
  703 #endif
  704 #ifdef KDTRACE_HOOKS
  705         int64_t spin_time = 0;
  706 #endif
  707 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
  708         int doing_lockprof = 0;
  709 #endif
  710 
  711         tid = (uintptr_t)curthread;
  712         m = mtxlock2mtx(c);
  713 
  714 #ifdef KDTRACE_HOOKS
  715         if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) {
  716                 while (v == MTX_UNOWNED) {
  717                         if (_mtx_obtain_lock_fetch(m, &v, tid))
  718                                 goto out_lockstat;
  719                 }
  720                 doing_lockprof = 1;
  721                 spin_time -= lockstat_nsecs(&m->lock_object);
  722         }
  723 #endif
  724 #ifdef LOCK_PROFILING
  725         doing_lockprof = 1;
  726 #endif
  727 
  728         if (__predict_false(v == MTX_UNOWNED))
  729                 v = MTX_READ_VALUE(m);
  730 
  731         if (__predict_false(v == tid)) {
  732                 m->mtx_recurse++;
  733                 return;
  734         }
  735 
  736         if (SCHEDULER_STOPPED())
  737                 return;
  738 
  739         lock_delay_arg_init(&lda, &mtx_spin_delay);
  740 
  741         if (LOCK_LOG_TEST(&m->lock_object, opts))
  742                 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
  743         KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
  744             "spinning", "lockname:\"%s\"", m->lock_object.lo_name);
  745 
  746 #ifdef HWPMC_HOOKS
  747         PMC_SOFT_CALL( , , lock, failed);
  748 #endif
  749         lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
  750 
  751         for (;;) {
  752                 if (v == MTX_UNOWNED) {
  753                         if (_mtx_obtain_lock_fetch(m, &v, tid))
  754                                 break;
  755                         continue;
  756                 }
  757                 /* Give interrupts a chance while we spin. */
  758                 spinlock_exit();
  759                 do {
  760                         if (__predict_true(lda.spin_cnt < 10000000)) {
  761                                 lock_delay(&lda);
  762                         } else {
  763                                 _mtx_lock_indefinite_check(m, &lda);
  764                         }
  765                         v = MTX_READ_VALUE(m);
  766                 } while (v != MTX_UNOWNED);
  767                 spinlock_enter();
  768         }
  769 
  770         if (LOCK_LOG_TEST(&m->lock_object, opts))
  771                 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
  772         KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
  773             "running");
  774 
  775 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
  776         if (__predict_true(!doing_lockprof))
  777                 return;
  778 #endif
  779 #ifdef KDTRACE_HOOKS
  780         spin_time += lockstat_nsecs(&m->lock_object);
  781         if (lda.spin_cnt != 0)
  782                 LOCKSTAT_RECORD1(spin__spin, m, spin_time);
  783 out_lockstat:
  784 #endif
  785         LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
  786             contested, waittime, file, line);
  787 }
  788 #endif /* SMP */
  789 
  790 #ifdef INVARIANTS
  791 static void
  792 thread_lock_validate(struct mtx *m, int opts, const char *file, int line)
  793 {
  794 
  795         KASSERT(m->mtx_lock != MTX_DESTROYED,
  796             ("thread_lock() of destroyed mutex @ %s:%d", file, line));
  797         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  798             ("thread_lock() of sleep mutex %s @ %s:%d",
  799             m->lock_object.lo_name, file, line));
  800         if (mtx_owned(m))
  801                 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
  802                     ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
  803                     m->lock_object.lo_name, file, line));
  804         WITNESS_CHECKORDER(&m->lock_object,
  805             opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
  806 }
  807 #else
  808 #define thread_lock_validate(m, opts, file, line) do { } while (0)
  809 #endif
  810 
  811 #ifndef LOCK_PROFILING
  812 #if LOCK_DEBUG > 0
  813 void
  814 _thread_lock(struct thread *td, int opts, const char *file, int line)
  815 #else
  816 void
  817 _thread_lock(struct thread *td)
  818 #endif
  819 {
  820         struct mtx *m;
  821         uintptr_t tid, v;
  822 
  823         tid = (uintptr_t)curthread;
  824 
  825         if (__predict_false(LOCKSTAT_PROFILE_ENABLED(spin__acquire)))
  826                 goto slowpath_noirq;
  827         spinlock_enter();
  828         m = td->td_lock;
  829         thread_lock_validate(m, 0, file, line);
  830         v = MTX_READ_VALUE(m);
  831         if (__predict_true(v == MTX_UNOWNED)) {
  832                 if (__predict_false(!_mtx_obtain_lock(m, tid)))
  833                         goto slowpath_unlocked;
  834         } else if (v == tid) {
  835                 m->mtx_recurse++;
  836         } else
  837                 goto slowpath_unlocked;
  838         if (__predict_true(m == td->td_lock)) {
  839                 WITNESS_LOCK(&m->lock_object, LOP_EXCLUSIVE, file, line);
  840                 return;
  841         }
  842         MPASS(m->mtx_recurse == 0);
  843         _mtx_release_lock_quick(m);
  844 slowpath_unlocked:
  845         spinlock_exit();
  846 slowpath_noirq:
  847 #if LOCK_DEBUG > 0
  848         thread_lock_flags_(td, opts, file, line);
  849 #else
  850         thread_lock_flags_(td, 0, 0, 0);
  851 #endif
  852 }
  853 #endif
  854 
  855 void
  856 thread_lock_flags_(struct thread *td, int opts, const char *file, int line)
  857 {
  858         struct mtx *m;
  859         uintptr_t tid, v;
  860         struct lock_delay_arg lda;
  861 #ifdef LOCK_PROFILING
  862         int contested = 0;
  863         uint64_t waittime = 0;
  864 #endif
  865 #ifdef KDTRACE_HOOKS
  866         int64_t spin_time = 0;
  867 #endif
  868 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
  869         int doing_lockprof = 1;
  870 #endif
  871 
  872         tid = (uintptr_t)curthread;
  873 
  874         if (SCHEDULER_STOPPED()) {
  875                 /*
  876                  * Ensure that spinlock sections are balanced even when the
  877                  * scheduler is stopped, since we may otherwise inadvertently
  878                  * re-enable interrupts while dumping core.
  879                  */
  880                 spinlock_enter();
  881                 return;
  882         }
  883 
  884         lock_delay_arg_init(&lda, &mtx_spin_delay);
  885 
  886 #ifdef HWPMC_HOOKS
  887         PMC_SOFT_CALL( , , lock, failed);
  888 #endif
  889 
  890 #ifdef LOCK_PROFILING
  891         doing_lockprof = 1;
  892 #elif defined(KDTRACE_HOOKS)
  893         doing_lockprof = lockstat_enabled;
  894         if (__predict_false(doing_lockprof))
  895                 spin_time -= lockstat_nsecs(&td->td_lock->lock_object);
  896 #endif
  897         spinlock_enter();
  898 
  899         for (;;) {
  900 retry:
  901                 m = td->td_lock;
  902                 thread_lock_validate(m, opts, file, line);
  903                 v = MTX_READ_VALUE(m);
  904                 for (;;) {
  905                         if (v == MTX_UNOWNED) {
  906                                 if (_mtx_obtain_lock_fetch(m, &v, tid))
  907                                         break;
  908                                 continue;
  909                         }
  910                         if (v == tid) {
  911                                 m->mtx_recurse++;
  912                                 MPASS(m == td->td_lock);
  913                                 break;
  914                         }
  915                         lock_profile_obtain_lock_failed(&m->lock_object,
  916                             &contested, &waittime);
  917                         /* Give interrupts a chance while we spin. */
  918                         spinlock_exit();
  919                         do {
  920                                 if (__predict_true(lda.spin_cnt < 10000000)) {
  921                                         lock_delay(&lda);
  922                                 } else {
  923                                         _mtx_lock_indefinite_check(m, &lda);
  924                                 }
  925                                 if (m != td->td_lock) {
  926                                         spinlock_enter();
  927                                         goto retry;
  928                                 }
  929                                 v = MTX_READ_VALUE(m);
  930                         } while (v != MTX_UNOWNED);
  931                         spinlock_enter();
  932                 }
  933                 if (m == td->td_lock)
  934                         break;
  935                 MPASS(m->mtx_recurse == 0);
  936                 _mtx_release_lock_quick(m);
  937         }
  938         LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
  939             line);
  940         WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  941 
  942 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
  943         if (__predict_true(!doing_lockprof))
  944                 return;
  945 #endif
  946 #ifdef KDTRACE_HOOKS
  947         spin_time += lockstat_nsecs(&m->lock_object);
  948 #endif
  949         if (m->mtx_recurse == 0)
  950                 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
  951                     contested, waittime, file, line);
  952 #ifdef KDTRACE_HOOKS
  953         if (lda.spin_cnt != 0)
  954                 LOCKSTAT_RECORD1(thread__spin, m, spin_time);
  955 #endif
  956 }
  957 
  958 struct mtx *
  959 thread_lock_block(struct thread *td)
  960 {
  961         struct mtx *lock;
  962 
  963         THREAD_LOCK_ASSERT(td, MA_OWNED);
  964         lock = td->td_lock;
  965         td->td_lock = &blocked_lock;
  966         mtx_unlock_spin(lock);
  967 
  968         return (lock);
  969 }
  970 
  971 void
  972 thread_lock_unblock(struct thread *td, struct mtx *new)
  973 {
  974         mtx_assert(new, MA_OWNED);
  975         MPASS(td->td_lock == &blocked_lock);
  976         atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
  977 }
  978 
  979 void
  980 thread_lock_set(struct thread *td, struct mtx *new)
  981 {
  982         struct mtx *lock;
  983 
  984         mtx_assert(new, MA_OWNED);
  985         THREAD_LOCK_ASSERT(td, MA_OWNED);
  986         lock = td->td_lock;
  987         td->td_lock = new;
  988         mtx_unlock_spin(lock);
  989 }
  990 
  991 /*
  992  * __mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
  993  *
  994  * We are only called here if the lock is recursed, contested (i.e. we
  995  * need to wake up a blocked thread) or lockstat probe is active.
  996  */
  997 #if LOCK_DEBUG > 0
  998 void
  999 __mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v, int opts,
 1000     const char *file, int line)
 1001 #else
 1002 void
 1003 __mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v)
 1004 #endif
 1005 {
 1006         struct mtx *m;
 1007         struct turnstile *ts;
 1008         uintptr_t tid;
 1009 
 1010         if (SCHEDULER_STOPPED())
 1011                 return;
 1012 
 1013         tid = (uintptr_t)curthread;
 1014         m = mtxlock2mtx(c);
 1015 
 1016         if (__predict_false(v == tid))
 1017                 v = MTX_READ_VALUE(m);
 1018 
 1019         if (__predict_false(v & MTX_RECURSED)) {
 1020                 if (--(m->mtx_recurse) == 0)
 1021                         atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
 1022                 if (LOCK_LOG_TEST(&m->lock_object, opts))
 1023                         CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
 1024                 return;
 1025         }
 1026 
 1027         LOCKSTAT_PROFILE_RELEASE_LOCK(adaptive__release, m);
 1028         if (v == tid && _mtx_release_lock(m, tid))
 1029                 return;
 1030 
 1031         /*
 1032          * We have to lock the chain before the turnstile so this turnstile
 1033          * can be removed from the hash list if it is empty.
 1034          */
 1035         turnstile_chain_lock(&m->lock_object);
 1036         _mtx_release_lock_quick(m);
 1037         ts = turnstile_lookup(&m->lock_object);
 1038         MPASS(ts != NULL);
 1039         if (LOCK_LOG_TEST(&m->lock_object, opts))
 1040                 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
 1041         turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
 1042 
 1043         /*
 1044          * This turnstile is now no longer associated with the mutex.  We can
 1045          * unlock the chain lock so a new turnstile may take it's place.
 1046          */
 1047         turnstile_unpend(ts);
 1048         turnstile_chain_unlock(&m->lock_object);
 1049 }
 1050 
 1051 /*
 1052  * All the unlocking of MTX_SPIN locks is done inline.
 1053  * See the __mtx_unlock_spin() macro for the details.
 1054  */
 1055 
 1056 /*
 1057  * The backing function for the INVARIANTS-enabled mtx_assert()
 1058  */
 1059 #ifdef INVARIANT_SUPPORT
 1060 void
 1061 __mtx_assert(const volatile uintptr_t *c, int what, const char *file, int line)
 1062 {
 1063         const struct mtx *m;
 1064 
 1065         if (panicstr != NULL || dumping || SCHEDULER_STOPPED())
 1066                 return;
 1067 
 1068         m = mtxlock2mtx(c);
 1069 
 1070         switch (what) {
 1071         case MA_OWNED:
 1072         case MA_OWNED | MA_RECURSED:
 1073         case MA_OWNED | MA_NOTRECURSED:
 1074                 if (!mtx_owned(m))
 1075                         panic("mutex %s not owned at %s:%d",
 1076                             m->lock_object.lo_name, file, line);
 1077                 if (mtx_recursed(m)) {
 1078                         if ((what & MA_NOTRECURSED) != 0)
 1079                                 panic("mutex %s recursed at %s:%d",
 1080                                     m->lock_object.lo_name, file, line);
 1081                 } else if ((what & MA_RECURSED) != 0) {
 1082                         panic("mutex %s unrecursed at %s:%d",
 1083                             m->lock_object.lo_name, file, line);
 1084                 }
 1085                 break;
 1086         case MA_NOTOWNED:
 1087                 if (mtx_owned(m))
 1088                         panic("mutex %s owned at %s:%d",
 1089                             m->lock_object.lo_name, file, line);
 1090                 break;
 1091         default:
 1092                 panic("unknown mtx_assert at %s:%d", file, line);
 1093         }
 1094 }
 1095 #endif
 1096 
 1097 /*
 1098  * General init routine used by the MTX_SYSINIT() macro.
 1099  */
 1100 void
 1101 mtx_sysinit(void *arg)
 1102 {
 1103         struct mtx_args *margs = arg;
 1104 
 1105         mtx_init((struct mtx *)margs->ma_mtx, margs->ma_desc, NULL,
 1106             margs->ma_opts);
 1107 }
 1108 
 1109 /*
 1110  * Mutex initialization routine; initialize lock `m' of type contained in
 1111  * `opts' with options contained in `opts' and name `name.'  The optional
 1112  * lock type `type' is used as a general lock category name for use with
 1113  * witness.
 1114  */
 1115 void
 1116 _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts)
 1117 {
 1118         struct mtx *m;
 1119         struct lock_class *class;
 1120         int flags;
 1121 
 1122         m = mtxlock2mtx(c);
 1123 
 1124         MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
 1125             MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE | MTX_NEW)) == 0);
 1126         ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
 1127             ("%s: mtx_lock not aligned for %s: %p", __func__, name,
 1128             &m->mtx_lock));
 1129 
 1130         /* Determine lock class and lock flags. */
 1131         if (opts & MTX_SPIN)
 1132                 class = &lock_class_mtx_spin;
 1133         else
 1134                 class = &lock_class_mtx_sleep;
 1135         flags = 0;
 1136         if (opts & MTX_QUIET)
 1137                 flags |= LO_QUIET;
 1138         if (opts & MTX_RECURSE)
 1139                 flags |= LO_RECURSABLE;
 1140         if ((opts & MTX_NOWITNESS) == 0)
 1141                 flags |= LO_WITNESS;
 1142         if (opts & MTX_DUPOK)
 1143                 flags |= LO_DUPOK;
 1144         if (opts & MTX_NOPROFILE)
 1145                 flags |= LO_NOPROFILE;
 1146         if (opts & MTX_NEW)
 1147                 flags |= LO_NEW;
 1148 
 1149         /* Initialize mutex. */
 1150         lock_init(&m->lock_object, class, name, type, flags);
 1151 
 1152         m->mtx_lock = MTX_UNOWNED;
 1153         m->mtx_recurse = 0;
 1154 }
 1155 
 1156 /*
 1157  * Remove lock `m' from all_mtx queue.  We don't allow MTX_QUIET to be
 1158  * passed in as a flag here because if the corresponding mtx_init() was
 1159  * called with MTX_QUIET set, then it will already be set in the mutex's
 1160  * flags.
 1161  */
 1162 void
 1163 _mtx_destroy(volatile uintptr_t *c)
 1164 {
 1165         struct mtx *m;
 1166 
 1167         m = mtxlock2mtx(c);
 1168 
 1169         if (!mtx_owned(m))
 1170                 MPASS(mtx_unowned(m));
 1171         else {
 1172                 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
 1173 
 1174                 /* Perform the non-mtx related part of mtx_unlock_spin(). */
 1175                 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin)
 1176                         spinlock_exit();
 1177                 else
 1178                         TD_LOCKS_DEC(curthread);
 1179 
 1180                 lock_profile_release_lock(&m->lock_object);
 1181                 /* Tell witness this isn't locked to make it happy. */
 1182                 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
 1183                     __LINE__);
 1184         }
 1185 
 1186         m->mtx_lock = MTX_DESTROYED;
 1187         lock_destroy(&m->lock_object);
 1188 }
 1189 
 1190 /*
 1191  * Intialize the mutex code and system mutexes.  This is called from the MD
 1192  * startup code prior to mi_startup().  The per-CPU data space needs to be
 1193  * setup before this is called.
 1194  */
 1195 void
 1196 mutex_init(void)
 1197 {
 1198 
 1199         /* Setup turnstiles so that sleep mutexes work. */
 1200         init_turnstiles();
 1201 
 1202         /*
 1203          * Initialize mutexes.
 1204          */
 1205         mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
 1206         mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
 1207         blocked_lock.mtx_lock = 0xdeadc0de;     /* Always blocked. */
 1208         mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
 1209         mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN);
 1210         mtx_init(&proc0.p_statmtx, "pstatl", NULL, MTX_SPIN);
 1211         mtx_init(&proc0.p_itimmtx, "pitiml", NULL, MTX_SPIN);
 1212         mtx_init(&proc0.p_profmtx, "pprofl", NULL, MTX_SPIN);
 1213         mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
 1214         mtx_lock(&Giant);
 1215 }
 1216 
 1217 static void __noinline
 1218 _mtx_lock_indefinite_check(struct mtx *m, struct lock_delay_arg *ldap)
 1219 {
 1220         struct thread *td;
 1221 
 1222         ldap->spin_cnt++;
 1223         if (ldap->spin_cnt < 60000000 || kdb_active || panicstr != NULL)
 1224                 cpu_lock_delay();
 1225         else {
 1226                 td = mtx_owner(m);
 1227 
 1228                 /* If the mutex is unlocked, try again. */
 1229                 if (td == NULL)
 1230                         return;
 1231 
 1232                 printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
 1233                     m, m->lock_object.lo_name, td, td->td_tid);
 1234 #ifdef WITNESS
 1235                 witness_display_spinlock(&m->lock_object, td, printf);
 1236 #endif
 1237                 panic("spin lock held too long");
 1238         }
 1239         cpu_spinwait();
 1240 }
 1241 
 1242 void
 1243 mtx_spin_wait_unlocked(struct mtx *m)
 1244 {
 1245         struct lock_delay_arg lda;
 1246 
 1247         KASSERT(m->mtx_lock != MTX_DESTROYED,
 1248             ("%s() of destroyed mutex %p", __func__, m));
 1249         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
 1250             ("%s() of sleep mutex %p (%s)", __func__, m,
 1251             m->lock_object.lo_name));
 1252         KASSERT(!mtx_owned(m), ("%s() waiting on myself on lock %p (%s)", __func__, m,
 1253             m->lock_object.lo_name));
 1254 
 1255         lda.spin_cnt = 0;
 1256 
 1257         while (atomic_load_acq_ptr(&m->mtx_lock) != MTX_UNOWNED) {
 1258                 if (__predict_true(lda.spin_cnt < 10000000)) {
 1259                         cpu_spinwait();
 1260                         lda.spin_cnt++;
 1261                 } else {
 1262                         _mtx_lock_indefinite_check(m, &lda);
 1263                 }
 1264         }
 1265 }
 1266 
 1267 #ifdef DDB
 1268 void
 1269 db_show_mtx(const struct lock_object *lock)
 1270 {
 1271         struct thread *td;
 1272         const struct mtx *m;
 1273 
 1274         m = (const struct mtx *)lock;
 1275 
 1276         db_printf(" flags: {");
 1277         if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
 1278                 db_printf("SPIN");
 1279         else
 1280                 db_printf("DEF");
 1281         if (m->lock_object.lo_flags & LO_RECURSABLE)
 1282                 db_printf(", RECURSE");
 1283         if (m->lock_object.lo_flags & LO_DUPOK)
 1284                 db_printf(", DUPOK");
 1285         db_printf("}\n");
 1286         db_printf(" state: {");
 1287         if (mtx_unowned(m))
 1288                 db_printf("UNOWNED");
 1289         else if (mtx_destroyed(m))
 1290                 db_printf("DESTROYED");
 1291         else {
 1292                 db_printf("OWNED");
 1293                 if (m->mtx_lock & MTX_CONTESTED)
 1294                         db_printf(", CONTESTED");
 1295                 if (m->mtx_lock & MTX_RECURSED)
 1296                         db_printf(", RECURSED");
 1297         }
 1298         db_printf("}\n");
 1299         if (!mtx_unowned(m) && !mtx_destroyed(m)) {
 1300                 td = mtx_owner(m);
 1301                 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
 1302                     td->td_tid, td->td_proc->p_pid, td->td_name);
 1303                 if (mtx_recursed(m))
 1304                         db_printf(" recursed: %d\n", m->mtx_recurse);
 1305         }
 1306 }
 1307 #endif

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