kern_mutex.c

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    1 /*-
    2  * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  * 3. Berkeley Software Design Inc's name may not be used to endorse or
   13  *    promote products derived from this software without specific prior
   14  *    written permission.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  *
   28  *      from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
   29  *      and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
   30  */
   31 
   32 /*
   33  * Machine independent bits of mutex implementation.
   34  */
   35 
   36 #include <sys/cdefs.h>
   37 __FBSDID("$FreeBSD: releng/11.0/sys/kern/kern_mutex.c 303953 2016-08-11 09:28:49Z mjg $");
   38 
   39 #include "opt_adaptive_mutexes.h"
   40 #include "opt_ddb.h"
   41 #include "opt_hwpmc_hooks.h"
   42 #include "opt_sched.h"
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/bus.h>
   47 #include <sys/conf.h>
   48 #include <sys/kdb.h>
   49 #include <sys/kernel.h>
   50 #include <sys/ktr.h>
   51 #include <sys/lock.h>
   52 #include <sys/malloc.h>
   53 #include <sys/mutex.h>
   54 #include <sys/proc.h>
   55 #include <sys/resourcevar.h>
   56 #include <sys/sched.h>
   57 #include <sys/sbuf.h>
   58 #include <sys/smp.h>
   59 #include <sys/sysctl.h>
   60 #include <sys/turnstile.h>
   61 #include <sys/vmmeter.h>
   62 #include <sys/lock_profile.h>
   63 
   64 #include <machine/atomic.h>
   65 #include <machine/bus.h>
   66 #include <machine/cpu.h>
   67 
   68 #include <ddb/ddb.h>
   69 
   70 #include <fs/devfs/devfs_int.h>
   71 
   72 #include <vm/vm.h>
   73 #include <vm/vm_extern.h>
   74 
   75 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
   76 #define ADAPTIVE_MUTEXES
   77 #endif
   78 
   79 #ifdef HWPMC_HOOKS
   80 #include <sys/pmckern.h>
   81 PMC_SOFT_DEFINE( , , lock, failed);
   82 #endif
   83 
   84 /*
   85  * Return the mutex address when the lock cookie address is provided.
   86  * This functionality assumes that struct mtx* have a member named mtx_lock.
   87  */
   88 #define mtxlock2mtx(c)  (__containerof(c, struct mtx, mtx_lock))
   89 
   90 /*
   91  * Internal utility macros.
   92  */
   93 #define mtx_unowned(m)  ((m)->mtx_lock == MTX_UNOWNED)
   94 
   95 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
   96 
   97 #define mtx_owner(m)    ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK))
   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 mtx_delay = {
  146         .initial        = 1000,
  147         .step           = 500,
  148         .min            = 100,
  149         .max            = 5000,
  150 };
  151 
  152 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_initial, CTLFLAG_RW, &mtx_delay.initial,
  153     0, "");
  154 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_step, CTLFLAG_RW, &mtx_delay.step,
  155     0, "");
  156 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_min, CTLFLAG_RW, &mtx_delay.min,
  157     0, "");
  158 SYSCTL_INT(_debug_mtx, OID_AUTO, delay_max, CTLFLAG_RW, &mtx_delay.max,
  159     0, "");
  160 
  161 static void
  162 mtx_delay_sysinit(void *dummy)
  163 {
  164 
  165         mtx_delay.initial = mp_ncpus * 25;
  166         mtx_delay.step = (mp_ncpus * 25) / 2;
  167         mtx_delay.min = mp_ncpus * 5;
  168         mtx_delay.max = mp_ncpus * 25 * 10;
  169 }
  170 LOCK_DELAY_SYSINIT(mtx_delay_sysinit);
  171 #endif
  172 
  173 /*
  174  * System-wide mutexes
  175  */
  176 struct mtx blocked_lock;
  177 struct mtx Giant;
  178 
  179 void
  180 assert_mtx(const struct lock_object *lock, int what)
  181 {
  182 
  183         mtx_assert((const struct mtx *)lock, what);
  184 }
  185 
  186 void
  187 lock_mtx(struct lock_object *lock, uintptr_t how)
  188 {
  189 
  190         mtx_lock((struct mtx *)lock);
  191 }
  192 
  193 void
  194 lock_spin(struct lock_object *lock, uintptr_t how)
  195 {
  196 
  197         panic("spin locks can only use msleep_spin");
  198 }
  199 
  200 uintptr_t
  201 unlock_mtx(struct lock_object *lock)
  202 {
  203         struct mtx *m;
  204 
  205         m = (struct mtx *)lock;
  206         mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
  207         mtx_unlock(m);
  208         return (0);
  209 }
  210 
  211 uintptr_t
  212 unlock_spin(struct lock_object *lock)
  213 {
  214 
  215         panic("spin locks can only use msleep_spin");
  216 }
  217 
  218 #ifdef KDTRACE_HOOKS
  219 int
  220 owner_mtx(const struct lock_object *lock, struct thread **owner)
  221 {
  222         const struct mtx *m = (const struct mtx *)lock;
  223 
  224         *owner = mtx_owner(m);
  225         return (mtx_unowned(m) == 0);
  226 }
  227 #endif
  228 
  229 /*
  230  * Function versions of the inlined __mtx_* macros.  These are used by
  231  * modules and can also be called from assembly language if needed.
  232  */
  233 void
  234 __mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
  235 {
  236         struct mtx *m;
  237 
  238         if (SCHEDULER_STOPPED())
  239                 return;
  240 
  241         m = mtxlock2mtx(c);
  242 
  243         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
  244             ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d",
  245             curthread, m->lock_object.lo_name, file, line));
  246         KASSERT(m->mtx_lock != MTX_DESTROYED,
  247             ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
  248         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
  249             ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
  250             file, line));
  251         WITNESS_CHECKORDER(&m->lock_object, (opts & ~MTX_RECURSE) |
  252             LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
  253 
  254         __mtx_lock(m, curthread, opts, file, line);
  255         LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
  256             line);
  257         WITNESS_LOCK(&m->lock_object, (opts & ~MTX_RECURSE) | LOP_EXCLUSIVE,
  258             file, line);
  259         TD_LOCKS_INC(curthread);
  260 }
  261 
  262 void
  263 __mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
  264 {
  265         struct mtx *m;
  266 
  267         if (SCHEDULER_STOPPED())
  268                 return;
  269 
  270         m = mtxlock2mtx(c);
  271 
  272         KASSERT(m->mtx_lock != MTX_DESTROYED,
  273             ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
  274         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
  275             ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
  276             file, line));
  277         WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  278         LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
  279             line);
  280         mtx_assert(m, MA_OWNED);
  281 
  282         __mtx_unlock(m, curthread, opts, file, line);
  283         TD_LOCKS_DEC(curthread);
  284 }
  285 
  286 void
  287 __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
  288     int line)
  289 {
  290         struct mtx *m;
  291 
  292         if (SCHEDULER_STOPPED())
  293                 return;
  294 
  295         m = mtxlock2mtx(c);
  296 
  297         KASSERT(m->mtx_lock != MTX_DESTROYED,
  298             ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
  299         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  300             ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
  301             m->lock_object.lo_name, file, line));
  302         if (mtx_owned(m))
  303                 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
  304                     (opts & MTX_RECURSE) != 0,
  305             ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n",
  306                     m->lock_object.lo_name, file, line));
  307         opts &= ~MTX_RECURSE;
  308         WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
  309             file, line, NULL);
  310         __mtx_lock_spin(m, curthread, opts, file, line);
  311         LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
  312             line);
  313         WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  314 }
  315 
  316 int
  317 __mtx_trylock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
  318     int line)
  319 {
  320         struct mtx *m;
  321 
  322         if (SCHEDULER_STOPPED())
  323                 return (1);
  324 
  325         m = mtxlock2mtx(c);
  326 
  327         KASSERT(m->mtx_lock != MTX_DESTROYED,
  328             ("mtx_trylock_spin() of destroyed mutex @ %s:%d", file, line));
  329         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  330             ("mtx_trylock_spin() of sleep mutex %s @ %s:%d",
  331             m->lock_object.lo_name, file, line));
  332         KASSERT((opts & MTX_RECURSE) == 0,
  333             ("mtx_trylock_spin: unsupp. opt MTX_RECURSE on mutex %s @ %s:%d\n",
  334             m->lock_object.lo_name, file, line));
  335         if (__mtx_trylock_spin(m, curthread, opts, file, line)) {
  336                 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 1, file, line);
  337                 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  338                 return (1);
  339         }
  340         LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 0, file, line);
  341         return (0);
  342 }
  343 
  344 void
  345 __mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
  346     int line)
  347 {
  348         struct mtx *m;
  349 
  350         if (SCHEDULER_STOPPED())
  351                 return;
  352 
  353         m = mtxlock2mtx(c);
  354 
  355         KASSERT(m->mtx_lock != MTX_DESTROYED,
  356             ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
  357         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  358             ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
  359             m->lock_object.lo_name, file, line));
  360         WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  361         LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
  362             line);
  363         mtx_assert(m, MA_OWNED);
  364 
  365         __mtx_unlock_spin(m);
  366 }
  367 
  368 /*
  369  * The important part of mtx_trylock{,_flags}()
  370  * Tries to acquire lock `m.'  If this function is called on a mutex that
  371  * is already owned, it will recursively acquire the lock.
  372  */
  373 int
  374 _mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line)
  375 {
  376         struct mtx *m;
  377 #ifdef LOCK_PROFILING
  378         uint64_t waittime = 0;
  379         int contested = 0;
  380 #endif
  381         int rval;
  382 
  383         if (SCHEDULER_STOPPED())
  384                 return (1);
  385 
  386         m = mtxlock2mtx(c);
  387 
  388         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
  389             ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d",
  390             curthread, m->lock_object.lo_name, file, line));
  391         KASSERT(m->mtx_lock != MTX_DESTROYED,
  392             ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
  393         KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
  394             ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
  395             file, line));
  396 
  397         if (mtx_owned(m) && ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
  398             (opts & MTX_RECURSE) != 0)) {
  399                 m->mtx_recurse++;
  400                 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
  401                 rval = 1;
  402         } else
  403                 rval = _mtx_obtain_lock(m, (uintptr_t)curthread);
  404         opts &= ~MTX_RECURSE;
  405 
  406         LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
  407         if (rval) {
  408                 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
  409                     file, line);
  410                 TD_LOCKS_INC(curthread);
  411                 if (m->mtx_recurse == 0)
  412                         LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
  413                             m, contested, waittime, file, line);
  414 
  415         }
  416 
  417         return (rval);
  418 }
  419 
  420 /*
  421  * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
  422  *
  423  * We call this if the lock is either contested (i.e. we need to go to
  424  * sleep waiting for it), or if we need to recurse on it.
  425  */
  426 void
  427 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t tid, int opts,
  428     const char *file, int line)
  429 {
  430         struct mtx *m;
  431         struct turnstile *ts;
  432         uintptr_t v;
  433 #ifdef ADAPTIVE_MUTEXES
  434         volatile struct thread *owner;
  435 #endif
  436 #ifdef KTR
  437         int cont_logged = 0;
  438 #endif
  439 #ifdef LOCK_PROFILING
  440         int contested = 0;
  441         uint64_t waittime = 0;
  442 #endif
  443 #if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS)
  444         struct lock_delay_arg lda;
  445 #endif
  446 #ifdef KDTRACE_HOOKS
  447         u_int sleep_cnt = 0;
  448         int64_t sleep_time = 0;
  449         int64_t all_time = 0;
  450 #endif
  451 
  452         if (SCHEDULER_STOPPED())
  453                 return;
  454 
  455 #if defined(ADAPTIVE_MUTEXES)
  456         lock_delay_arg_init(&lda, &mtx_delay);
  457 #elif defined(KDTRACE_HOOKS)
  458         lock_delay_arg_init(&lda, NULL);
  459 #endif
  460         m = mtxlock2mtx(c);
  461 
  462         if (mtx_owned(m)) {
  463                 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
  464                     (opts & MTX_RECURSE) != 0,
  465             ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
  466                     m->lock_object.lo_name, file, line));
  467                 opts &= ~MTX_RECURSE;
  468                 m->mtx_recurse++;
  469                 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
  470                 if (LOCK_LOG_TEST(&m->lock_object, opts))
  471                         CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
  472                 return;
  473         }
  474         opts &= ~MTX_RECURSE;
  475 
  476 #ifdef HWPMC_HOOKS
  477         PMC_SOFT_CALL( , , lock, failed);
  478 #endif
  479         lock_profile_obtain_lock_failed(&m->lock_object,
  480                     &contested, &waittime);
  481         if (LOCK_LOG_TEST(&m->lock_object, opts))
  482                 CTR4(KTR_LOCK,
  483                     "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
  484                     m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
  485 #ifdef KDTRACE_HOOKS
  486         all_time -= lockstat_nsecs(&m->lock_object);
  487 #endif
  488 
  489         for (;;) {
  490                 if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid))
  491                         break;
  492 #ifdef KDTRACE_HOOKS
  493                 lda.spin_cnt++;
  494 #endif
  495 #ifdef ADAPTIVE_MUTEXES
  496                 /*
  497                  * If the owner is running on another CPU, spin until the
  498                  * owner stops running or the state of the lock changes.
  499                  */
  500                 v = m->mtx_lock;
  501                 if (v != MTX_UNOWNED) {
  502                         owner = (struct thread *)(v & ~MTX_FLAGMASK);
  503                         if (TD_IS_RUNNING(owner)) {
  504                                 if (LOCK_LOG_TEST(&m->lock_object, 0))
  505                                         CTR3(KTR_LOCK,
  506                                             "%s: spinning on %p held by %p",
  507                                             __func__, m, owner);
  508                                 KTR_STATE1(KTR_SCHED, "thread",
  509                                     sched_tdname((struct thread *)tid),
  510                                     "spinning", "lockname:\"%s\"",
  511                                     m->lock_object.lo_name);
  512                                 while (mtx_owner(m) == owner &&
  513                                     TD_IS_RUNNING(owner))
  514                                         lock_delay(&lda);
  515                                 KTR_STATE0(KTR_SCHED, "thread",
  516                                     sched_tdname((struct thread *)tid),
  517                                     "running");
  518                                 continue;
  519                         }
  520                 }
  521 #endif
  522 
  523                 ts = turnstile_trywait(&m->lock_object);
  524                 v = m->mtx_lock;
  525 
  526                 /*
  527                  * Check if the lock has been released while spinning for
  528                  * the turnstile chain lock.
  529                  */
  530                 if (v == MTX_UNOWNED) {
  531                         turnstile_cancel(ts);
  532                         continue;
  533                 }
  534 
  535 #ifdef ADAPTIVE_MUTEXES
  536                 /*
  537                  * The current lock owner might have started executing
  538                  * on another CPU (or the lock could have changed
  539                  * owners) while we were waiting on the turnstile
  540                  * chain lock.  If so, drop the turnstile lock and try
  541                  * again.
  542                  */
  543                 owner = (struct thread *)(v & ~MTX_FLAGMASK);
  544                 if (TD_IS_RUNNING(owner)) {
  545                         turnstile_cancel(ts);
  546                         continue;
  547                 }
  548 #endif
  549 
  550                 /*
  551                  * If the mutex isn't already contested and a failure occurs
  552                  * setting the contested bit, the mutex was either released
  553                  * or the state of the MTX_RECURSED bit changed.
  554                  */
  555                 if ((v & MTX_CONTESTED) == 0 &&
  556                     !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
  557                         turnstile_cancel(ts);
  558                         continue;
  559                 }
  560 
  561                 /*
  562                  * We definitely must sleep for this lock.
  563                  */
  564                 mtx_assert(m, MA_NOTOWNED);
  565 
  566 #ifdef KTR
  567                 if (!cont_logged) {
  568                         CTR6(KTR_CONTENTION,
  569                             "contention: %p at %s:%d wants %s, taken by %s:%d",
  570                             (void *)tid, file, line, m->lock_object.lo_name,
  571                             WITNESS_FILE(&m->lock_object),
  572                             WITNESS_LINE(&m->lock_object));
  573                         cont_logged = 1;
  574                 }
  575 #endif
  576 
  577                 /*
  578                  * Block on the turnstile.
  579                  */
  580 #ifdef KDTRACE_HOOKS
  581                 sleep_time -= lockstat_nsecs(&m->lock_object);
  582 #endif
  583                 turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
  584 #ifdef KDTRACE_HOOKS
  585                 sleep_time += lockstat_nsecs(&m->lock_object);
  586                 sleep_cnt++;
  587 #endif
  588         }
  589 #ifdef KDTRACE_HOOKS
  590         all_time += lockstat_nsecs(&m->lock_object);
  591 #endif
  592 #ifdef KTR
  593         if (cont_logged) {
  594                 CTR4(KTR_CONTENTION,
  595                     "contention end: %s acquired by %p at %s:%d",
  596                     m->lock_object.lo_name, (void *)tid, file, line);
  597         }
  598 #endif
  599         LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested,
  600             waittime, file, line);
  601 #ifdef KDTRACE_HOOKS
  602         if (sleep_time)
  603                 LOCKSTAT_RECORD1(adaptive__block, m, sleep_time);
  604 
  605         /*
  606          * Only record the loops spinning and not sleeping. 
  607          */
  608         if (lda.spin_cnt > sleep_cnt)
  609                 LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time);
  610 #endif
  611 }
  612 
  613 static void
  614 _mtx_lock_spin_failed(struct mtx *m)
  615 {
  616         struct thread *td;
  617 
  618         td = mtx_owner(m);
  619 
  620         /* If the mutex is unlocked, try again. */
  621         if (td == NULL)
  622                 return;
  623 
  624         printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
  625             m, m->lock_object.lo_name, td, td->td_tid);
  626 #ifdef WITNESS
  627         witness_display_spinlock(&m->lock_object, td, printf);
  628 #endif
  629         panic("spin lock held too long");
  630 }
  631 
  632 #ifdef SMP
  633 /*
  634  * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock.
  635  *
  636  * This is only called if we need to actually spin for the lock. Recursion
  637  * is handled inline.
  638  */
  639 void
  640 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t tid, int opts,
  641     const char *file, int line)
  642 {
  643         struct mtx *m;
  644         int i = 0;
  645 #ifdef LOCK_PROFILING
  646         int contested = 0;
  647         uint64_t waittime = 0;
  648 #endif
  649 #ifdef KDTRACE_HOOKS
  650         int64_t spin_time = 0;
  651 #endif
  652 
  653         if (SCHEDULER_STOPPED())
  654                 return;
  655 
  656         m = mtxlock2mtx(c);
  657 
  658         if (LOCK_LOG_TEST(&m->lock_object, opts))
  659                 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
  660         KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
  661             "spinning", "lockname:\"%s\"", m->lock_object.lo_name);
  662 
  663 #ifdef HWPMC_HOOKS
  664         PMC_SOFT_CALL( , , lock, failed);
  665 #endif
  666         lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
  667 #ifdef KDTRACE_HOOKS
  668         spin_time -= lockstat_nsecs(&m->lock_object);
  669 #endif
  670         for (;;) {
  671                 if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid))
  672                         break;
  673                 /* Give interrupts a chance while we spin. */
  674                 spinlock_exit();
  675                 while (m->mtx_lock != MTX_UNOWNED) {
  676                         if (i++ < 10000000) {
  677                                 cpu_spinwait();
  678                                 continue;
  679                         }
  680                         if (i < 60000000 || kdb_active || panicstr != NULL)
  681                                 DELAY(1);
  682                         else
  683                                 _mtx_lock_spin_failed(m);
  684                         cpu_spinwait();
  685                 }
  686                 spinlock_enter();
  687         }
  688 #ifdef KDTRACE_HOOKS
  689         spin_time += lockstat_nsecs(&m->lock_object);
  690 #endif
  691 
  692         if (LOCK_LOG_TEST(&m->lock_object, opts))
  693                 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
  694         KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
  695             "running");
  696 
  697 #ifdef KDTRACE_HOOKS
  698         LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
  699             contested, waittime, file, line);
  700         if (spin_time != 0)
  701                 LOCKSTAT_RECORD1(spin__spin, m, spin_time);
  702 #endif
  703 }
  704 #endif /* SMP */
  705 
  706 void
  707 thread_lock_flags_(struct thread *td, int opts, const char *file, int line)
  708 {
  709         struct mtx *m;
  710         uintptr_t tid;
  711         int i;
  712 #ifdef LOCK_PROFILING
  713         int contested = 0;
  714         uint64_t waittime = 0;
  715 #endif
  716 #ifdef KDTRACE_HOOKS
  717         int64_t spin_time = 0;
  718 #endif
  719 
  720         i = 0;
  721         tid = (uintptr_t)curthread;
  722 
  723         if (SCHEDULER_STOPPED()) {
  724                 /*
  725                  * Ensure that spinlock sections are balanced even when the
  726                  * scheduler is stopped, since we may otherwise inadvertently
  727                  * re-enable interrupts while dumping core.
  728                  */
  729                 spinlock_enter();
  730                 return;
  731         }
  732 
  733 #ifdef KDTRACE_HOOKS
  734         spin_time -= lockstat_nsecs(&td->td_lock->lock_object);
  735 #endif
  736         for (;;) {
  737 retry:
  738                 spinlock_enter();
  739                 m = td->td_lock;
  740                 KASSERT(m->mtx_lock != MTX_DESTROYED,
  741                     ("thread_lock() of destroyed mutex @ %s:%d", file, line));
  742                 KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
  743                     ("thread_lock() of sleep mutex %s @ %s:%d",
  744                     m->lock_object.lo_name, file, line));
  745                 if (mtx_owned(m))
  746                         KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
  747             ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
  748                             m->lock_object.lo_name, file, line));
  749                 WITNESS_CHECKORDER(&m->lock_object,
  750                     opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
  751                 for (;;) {
  752                         if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid))
  753                                 break;
  754                         if (m->mtx_lock == tid) {
  755                                 m->mtx_recurse++;
  756                                 break;
  757                         }
  758 #ifdef HWPMC_HOOKS
  759                         PMC_SOFT_CALL( , , lock, failed);
  760 #endif
  761                         lock_profile_obtain_lock_failed(&m->lock_object,
  762                             &contested, &waittime);
  763                         /* Give interrupts a chance while we spin. */
  764                         spinlock_exit();
  765                         while (m->mtx_lock != MTX_UNOWNED) {
  766                                 if (i++ < 10000000)
  767                                         cpu_spinwait();
  768                                 else if (i < 60000000 ||
  769                                     kdb_active || panicstr != NULL)
  770                                         DELAY(1);
  771                                 else
  772                                         _mtx_lock_spin_failed(m);
  773                                 cpu_spinwait();
  774                                 if (m != td->td_lock)
  775                                         goto retry;
  776                         }
  777                         spinlock_enter();
  778                 }
  779                 if (m == td->td_lock)
  780                         break;
  781                 __mtx_unlock_spin(m);   /* does spinlock_exit() */
  782         }
  783 #ifdef KDTRACE_HOOKS
  784         spin_time += lockstat_nsecs(&m->lock_object);
  785 #endif
  786         if (m->mtx_recurse == 0)
  787                 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
  788                     contested, waittime, file, line);
  789         LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
  790             line);
  791         WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
  792 #ifdef KDTRACE_HOOKS
  793         if (spin_time != 0)
  794                 LOCKSTAT_RECORD1(thread__spin, m, spin_time);
  795 #endif
  796 }
  797 
  798 struct mtx *
  799 thread_lock_block(struct thread *td)
  800 {
  801         struct mtx *lock;
  802 
  803         THREAD_LOCK_ASSERT(td, MA_OWNED);
  804         lock = td->td_lock;
  805         td->td_lock = &blocked_lock;
  806         mtx_unlock_spin(lock);
  807 
  808         return (lock);
  809 }
  810 
  811 void
  812 thread_lock_unblock(struct thread *td, struct mtx *new)
  813 {
  814         mtx_assert(new, MA_OWNED);
  815         MPASS(td->td_lock == &blocked_lock);
  816         atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
  817 }
  818 
  819 void
  820 thread_lock_set(struct thread *td, struct mtx *new)
  821 {
  822         struct mtx *lock;
  823 
  824         mtx_assert(new, MA_OWNED);
  825         THREAD_LOCK_ASSERT(td, MA_OWNED);
  826         lock = td->td_lock;
  827         td->td_lock = new;
  828         mtx_unlock_spin(lock);
  829 }
  830 
  831 /*
  832  * __mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
  833  *
  834  * We are only called here if the lock is recursed or contested (i.e. we
  835  * need to wake up a blocked thread).
  836  */
  837 void
  838 __mtx_unlock_sleep(volatile uintptr_t *c, int opts, const char *file, int line)
  839 {
  840         struct mtx *m;
  841         struct turnstile *ts;
  842 
  843         if (SCHEDULER_STOPPED())
  844                 return;
  845 
  846         m = mtxlock2mtx(c);
  847 
  848         if (mtx_recursed(m)) {
  849                 if (--(m->mtx_recurse) == 0)
  850                         atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
  851                 if (LOCK_LOG_TEST(&m->lock_object, opts))
  852                         CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
  853                 return;
  854         }
  855 
  856         /*
  857          * We have to lock the chain before the turnstile so this turnstile
  858          * can be removed from the hash list if it is empty.
  859          */
  860         turnstile_chain_lock(&m->lock_object);
  861         ts = turnstile_lookup(&m->lock_object);
  862         if (LOCK_LOG_TEST(&m->lock_object, opts))
  863                 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
  864         MPASS(ts != NULL);
  865         turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
  866         _mtx_release_lock_quick(m);
  867 
  868         /*
  869          * This turnstile is now no longer associated with the mutex.  We can
  870          * unlock the chain lock so a new turnstile may take it's place.
  871          */
  872         turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
  873         turnstile_chain_unlock(&m->lock_object);
  874 }
  875 
  876 /*
  877  * All the unlocking of MTX_SPIN locks is done inline.
  878  * See the __mtx_unlock_spin() macro for the details.
  879  */
  880 
  881 /*
  882  * The backing function for the INVARIANTS-enabled mtx_assert()
  883  */
  884 #ifdef INVARIANT_SUPPORT
  885 void
  886 __mtx_assert(const volatile uintptr_t *c, int what, const char *file, int line)
  887 {
  888         const struct mtx *m;
  889 
  890         if (panicstr != NULL || dumping)
  891                 return;
  892 
  893         m = mtxlock2mtx(c);
  894 
  895         switch (what) {
  896         case MA_OWNED:
  897         case MA_OWNED | MA_RECURSED:
  898         case MA_OWNED | MA_NOTRECURSED:
  899                 if (!mtx_owned(m))
  900                         panic("mutex %s not owned at %s:%d",
  901                             m->lock_object.lo_name, file, line);
  902                 if (mtx_recursed(m)) {
  903                         if ((what & MA_NOTRECURSED) != 0)
  904                                 panic("mutex %s recursed at %s:%d",
  905                                     m->lock_object.lo_name, file, line);
  906                 } else if ((what & MA_RECURSED) != 0) {
  907                         panic("mutex %s unrecursed at %s:%d",
  908                             m->lock_object.lo_name, file, line);
  909                 }
  910                 break;
  911         case MA_NOTOWNED:
  912                 if (mtx_owned(m))
  913                         panic("mutex %s owned at %s:%d",
  914                             m->lock_object.lo_name, file, line);
  915                 break;
  916         default:
  917                 panic("unknown mtx_assert at %s:%d", file, line);
  918         }
  919 }
  920 #endif
  921 
  922 /*
  923  * General init routine used by the MTX_SYSINIT() macro.
  924  */
  925 void
  926 mtx_sysinit(void *arg)
  927 {
  928         struct mtx_args *margs = arg;
  929 
  930         mtx_init((struct mtx *)margs->ma_mtx, margs->ma_desc, NULL,
  931             margs->ma_opts);
  932 }
  933 
  934 /*
  935  * Mutex initialization routine; initialize lock `m' of type contained in
  936  * `opts' with options contained in `opts' and name `name.'  The optional
  937  * lock type `type' is used as a general lock category name for use with
  938  * witness.
  939  */
  940 void
  941 _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts)
  942 {
  943         struct mtx *m;
  944         struct lock_class *class;
  945         int flags;
  946 
  947         m = mtxlock2mtx(c);
  948 
  949         MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
  950             MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE | MTX_NEW)) == 0);
  951         ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
  952             ("%s: mtx_lock not aligned for %s: %p", __func__, name,
  953             &m->mtx_lock));
  954 
  955         /* Determine lock class and lock flags. */
  956         if (opts & MTX_SPIN)
  957                 class = &lock_class_mtx_spin;
  958         else
  959                 class = &lock_class_mtx_sleep;
  960         flags = 0;
  961         if (opts & MTX_QUIET)
  962                 flags |= LO_QUIET;
  963         if (opts & MTX_RECURSE)
  964                 flags |= LO_RECURSABLE;
  965         if ((opts & MTX_NOWITNESS) == 0)
  966                 flags |= LO_WITNESS;
  967         if (opts & MTX_DUPOK)
  968                 flags |= LO_DUPOK;
  969         if (opts & MTX_NOPROFILE)
  970                 flags |= LO_NOPROFILE;
  971         if (opts & MTX_NEW)
  972                 flags |= LO_NEW;
  973 
  974         /* Initialize mutex. */
  975         lock_init(&m->lock_object, class, name, type, flags);
  976 
  977         m->mtx_lock = MTX_UNOWNED;
  978         m->mtx_recurse = 0;
  979 }
  980 
  981 /*
  982  * Remove lock `m' from all_mtx queue.  We don't allow MTX_QUIET to be
  983  * passed in as a flag here because if the corresponding mtx_init() was
  984  * called with MTX_QUIET set, then it will already be set in the mutex's
  985  * flags.
  986  */
  987 void
  988 _mtx_destroy(volatile uintptr_t *c)
  989 {
  990         struct mtx *m;
  991 
  992         m = mtxlock2mtx(c);
  993 
  994         if (!mtx_owned(m))
  995                 MPASS(mtx_unowned(m));
  996         else {
  997                 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
  998 
  999                 /* Perform the non-mtx related part of mtx_unlock_spin(). */
 1000                 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin)
 1001                         spinlock_exit();
 1002                 else
 1003                         TD_LOCKS_DEC(curthread);
 1004 
 1005                 lock_profile_release_lock(&m->lock_object);
 1006                 /* Tell witness this isn't locked to make it happy. */
 1007                 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
 1008                     __LINE__);
 1009         }
 1010 
 1011         m->mtx_lock = MTX_DESTROYED;
 1012         lock_destroy(&m->lock_object);
 1013 }
 1014 
 1015 /*
 1016  * Intialize the mutex code and system mutexes.  This is called from the MD
 1017  * startup code prior to mi_startup().  The per-CPU data space needs to be
 1018  * setup before this is called.
 1019  */
 1020 void
 1021 mutex_init(void)
 1022 {
 1023 
 1024         /* Setup turnstiles so that sleep mutexes work. */
 1025         init_turnstiles();
 1026 
 1027         /*
 1028          * Initialize mutexes.
 1029          */
 1030         mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
 1031         mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
 1032         blocked_lock.mtx_lock = 0xdeadc0de;     /* Always blocked. */
 1033         mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
 1034         mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN);
 1035         mtx_init(&proc0.p_statmtx, "pstatl", NULL, MTX_SPIN);
 1036         mtx_init(&proc0.p_itimmtx, "pitiml", NULL, MTX_SPIN);
 1037         mtx_init(&proc0.p_profmtx, "pprofl", NULL, MTX_SPIN);
 1038         mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
 1039         mtx_lock(&Giant);
 1040 }
 1041 
 1042 #ifdef DDB
 1043 void
 1044 db_show_mtx(const struct lock_object *lock)
 1045 {
 1046         struct thread *td;
 1047         const struct mtx *m;
 1048 
 1049         m = (const struct mtx *)lock;
 1050 
 1051         db_printf(" flags: {");
 1052         if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
 1053                 db_printf("SPIN");
 1054         else
 1055                 db_printf("DEF");
 1056         if (m->lock_object.lo_flags & LO_RECURSABLE)
 1057                 db_printf(", RECURSE");
 1058         if (m->lock_object.lo_flags & LO_DUPOK)
 1059                 db_printf(", DUPOK");
 1060         db_printf("}\n");
 1061         db_printf(" state: {");
 1062         if (mtx_unowned(m))
 1063                 db_printf("UNOWNED");
 1064         else if (mtx_destroyed(m))
 1065                 db_printf("DESTROYED");
 1066         else {
 1067                 db_printf("OWNED");
 1068                 if (m->mtx_lock & MTX_CONTESTED)
 1069                         db_printf(", CONTESTED");
 1070                 if (m->mtx_lock & MTX_RECURSED)
 1071                         db_printf(", RECURSED");
 1072         }
 1073         db_printf("}\n");
 1074         if (!mtx_unowned(m) && !mtx_destroyed(m)) {
 1075                 td = mtx_owner(m);
 1076                 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
 1077                     td->td_tid, td->td_proc->p_pid, td->td_name);
 1078                 if (mtx_recursed(m))
 1079                         db_printf(" recursed: %d\n", m->mtx_recurse);
 1080         }
 1081 }
 1082 #endif
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_mutex.c

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