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

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    1 /*-
    2  * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 /*
   28  * This module holds the global variables and functions used to maintain
   29  * lock_object structures.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/11.1/sys/kern/subr_lock.c 315339 2017-03-16 00:51:24Z mjg $");
   34 
   35 #include "opt_ddb.h"
   36 #include "opt_mprof.h"
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h>
   40 #include <sys/kernel.h>
   41 #include <sys/ktr.h>
   42 #include <sys/lock.h>
   43 #include <sys/lock_profile.h>
   44 #include <sys/malloc.h>
   45 #include <sys/mutex.h>
   46 #include <sys/pcpu.h>
   47 #include <sys/proc.h>
   48 #include <sys/sbuf.h>
   49 #include <sys/sched.h>
   50 #include <sys/smp.h>
   51 #include <sys/sysctl.h>
   52 
   53 #ifdef DDB
   54 #include <ddb/ddb.h>
   55 #endif
   56 
   57 #include <machine/cpufunc.h>
   58 
   59 SDT_PROVIDER_DEFINE(lock);
   60 SDT_PROBE_DEFINE1(lock, , , starvation, "u_int");
   61 
   62 CTASSERT(LOCK_CLASS_MAX == 15);
   63 
   64 struct lock_class *lock_classes[LOCK_CLASS_MAX + 1] = {
   65         &lock_class_mtx_spin,
   66         &lock_class_mtx_sleep,
   67         &lock_class_sx,
   68         &lock_class_rm,
   69         &lock_class_rm_sleepable,
   70         &lock_class_rw,
   71         &lock_class_lockmgr,
   72 };
   73 
   74 void
   75 lock_init(struct lock_object *lock, struct lock_class *class, const char *name,
   76     const char *type, int flags)
   77 {
   78         int i;
   79 
   80         /* Check for double-init and zero object. */
   81         KASSERT(flags & LO_NEW || !lock_initialized(lock),
   82             ("lock \"%s\" %p already initialized", name, lock));
   83 
   84         /* Look up lock class to find its index. */
   85         for (i = 0; i < LOCK_CLASS_MAX; i++)
   86                 if (lock_classes[i] == class) {
   87                         lock->lo_flags = i << LO_CLASSSHIFT;
   88                         break;
   89                 }
   90         KASSERT(i < LOCK_CLASS_MAX, ("unknown lock class %p", class));
   91 
   92         /* Initialize the lock object. */
   93         lock->lo_name = name;
   94         lock->lo_flags |= flags | LO_INITIALIZED;
   95         LOCK_LOG_INIT(lock, 0);
   96         WITNESS_INIT(lock, (type != NULL) ? type : name);
   97 }
   98 
   99 void
  100 lock_destroy(struct lock_object *lock)
  101 {
  102 
  103         KASSERT(lock_initialized(lock), ("lock %p is not initialized", lock));
  104         WITNESS_DESTROY(lock);
  105         LOCK_LOG_DESTROY(lock, 0);
  106         lock->lo_flags &= ~LO_INITIALIZED;
  107 }
  108 
  109 static SYSCTL_NODE(_debug, OID_AUTO, lock, CTLFLAG_RD, NULL, "lock debugging");
  110 static SYSCTL_NODE(_debug_lock, OID_AUTO, delay, CTLFLAG_RD, NULL,
  111     "lock delay");
  112 
  113 static u_int __read_mostly starvation_limit = 131072;
  114 SYSCTL_INT(_debug_lock_delay, OID_AUTO, starvation_limit, CTLFLAG_RW,
  115     &starvation_limit, 0, "");
  116 
  117 static u_int __read_mostly restrict_starvation = 0;
  118 SYSCTL_INT(_debug_lock_delay, OID_AUTO, restrict_starvation, CTLFLAG_RW,
  119     &restrict_starvation, 0, "");
  120 
  121 void
  122 lock_delay(struct lock_delay_arg *la)
  123 {
  124         struct lock_delay_config *lc = la->config;
  125         u_int i;
  126 
  127         la->delay <<= 1;
  128         if (__predict_false(la->delay > lc->max))
  129                 la->delay = lc->max;
  130 
  131         for (i = la->delay; i > 0; i--)
  132                 cpu_spinwait();
  133 
  134         la->spin_cnt += la->delay;
  135         if (__predict_false(la->spin_cnt > starvation_limit)) {
  136                 SDT_PROBE1(lock, , , starvation, la->delay);
  137                 if (restrict_starvation)
  138                         la->delay = lc->base;
  139         }
  140 }
  141 
  142 static u_int
  143 lock_roundup_2(u_int val)
  144 {
  145         u_int res;
  146 
  147         for (res = 1; res <= val; res <<= 1)
  148                 continue;
  149 
  150         return (res);
  151 }
  152 
  153 void
  154 lock_delay_default_init(struct lock_delay_config *lc)
  155 {
  156 
  157         lc->base = lock_roundup_2(mp_ncpus) / 4;
  158         lc->max = lc->base * 1024;
  159 }
  160 
  161 #ifdef DDB
  162 DB_SHOW_COMMAND(lock, db_show_lock)
  163 {
  164         struct lock_object *lock;
  165         struct lock_class *class;
  166 
  167         if (!have_addr)
  168                 return;
  169         lock = (struct lock_object *)addr;
  170         if (LO_CLASSINDEX(lock) > LOCK_CLASS_MAX) {
  171                 db_printf("Unknown lock class: %d\n", LO_CLASSINDEX(lock));
  172                 return;
  173         }
  174         class = LOCK_CLASS(lock);
  175         db_printf(" class: %s\n", class->lc_name);
  176         db_printf(" name: %s\n", lock->lo_name);
  177         class->lc_ddb_show(lock);
  178 }
  179 #endif
  180 
  181 #ifdef LOCK_PROFILING
  182 
  183 /*
  184  * One object per-thread for each lock the thread owns.  Tracks individual
  185  * lock instances.
  186  */
  187 struct lock_profile_object {
  188         LIST_ENTRY(lock_profile_object) lpo_link;
  189         struct lock_object *lpo_obj;
  190         const char      *lpo_file;
  191         int             lpo_line;
  192         uint16_t        lpo_ref;
  193         uint16_t        lpo_cnt;
  194         uint64_t        lpo_acqtime;
  195         uint64_t        lpo_waittime;
  196         u_int           lpo_contest_locking;
  197 };
  198 
  199 /*
  200  * One lock_prof for each (file, line, lock object) triple.
  201  */
  202 struct lock_prof {
  203         SLIST_ENTRY(lock_prof) link;
  204         struct lock_class *class;
  205         const char      *file;
  206         const char      *name;
  207         int             line;
  208         int             ticks;
  209         uintmax_t       cnt_wait_max;
  210         uintmax_t       cnt_max;
  211         uintmax_t       cnt_tot;
  212         uintmax_t       cnt_wait;
  213         uintmax_t       cnt_cur;
  214         uintmax_t       cnt_contest_locking;
  215 };
  216 
  217 SLIST_HEAD(lphead, lock_prof);
  218 
  219 #define LPROF_HASH_SIZE         4096
  220 #define LPROF_HASH_MASK         (LPROF_HASH_SIZE - 1)
  221 #define LPROF_CACHE_SIZE        4096
  222 
  223 /*
  224  * Array of objects and profs for each type of object for each cpu.  Spinlocks
  225  * are handled separately because a thread may be preempted and acquire a
  226  * spinlock while in the lock profiling code of a non-spinlock.  In this way
  227  * we only need a critical section to protect the per-cpu lists.
  228  */
  229 struct lock_prof_type {
  230         struct lphead           lpt_lpalloc;
  231         struct lpohead          lpt_lpoalloc;
  232         struct lphead           lpt_hash[LPROF_HASH_SIZE];
  233         struct lock_prof        lpt_prof[LPROF_CACHE_SIZE];
  234         struct lock_profile_object lpt_objs[LPROF_CACHE_SIZE];
  235 };
  236 
  237 struct lock_prof_cpu {
  238         struct lock_prof_type   lpc_types[2]; /* One for spin one for other. */
  239 };
  240 
  241 struct lock_prof_cpu *lp_cpu[MAXCPU];
  242 
  243 volatile int __read_mostly lock_prof_enable;
  244 static volatile int lock_prof_resetting;
  245 
  246 #define LPROF_SBUF_SIZE         256
  247 
  248 static int lock_prof_rejected;
  249 static int lock_prof_skipspin;
  250 static int lock_prof_skipcount;
  251 
  252 #ifndef USE_CPU_NANOSECONDS
  253 uint64_t
  254 nanoseconds(void)
  255 {
  256         struct bintime bt;
  257         uint64_t ns;
  258 
  259         binuptime(&bt);
  260         /* From bintime2timespec */
  261         ns = bt.sec * (uint64_t)1000000000;
  262         ns += ((uint64_t)1000000000 * (uint32_t)(bt.frac >> 32)) >> 32;
  263         return (ns);
  264 }
  265 #endif
  266 
  267 static void
  268 lock_prof_init_type(struct lock_prof_type *type)
  269 {
  270         int i;
  271 
  272         SLIST_INIT(&type->lpt_lpalloc);
  273         LIST_INIT(&type->lpt_lpoalloc);
  274         for (i = 0; i < LPROF_CACHE_SIZE; i++) {
  275                 SLIST_INSERT_HEAD(&type->lpt_lpalloc, &type->lpt_prof[i],
  276                     link);
  277                 LIST_INSERT_HEAD(&type->lpt_lpoalloc, &type->lpt_objs[i],
  278                     lpo_link);
  279         }
  280 }
  281 
  282 static void
  283 lock_prof_init(void *arg)
  284 {
  285         int cpu;
  286 
  287         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  288                 lp_cpu[cpu] = malloc(sizeof(*lp_cpu[cpu]), M_DEVBUF,
  289                     M_WAITOK | M_ZERO);
  290                 lock_prof_init_type(&lp_cpu[cpu]->lpc_types[0]);
  291                 lock_prof_init_type(&lp_cpu[cpu]->lpc_types[1]);
  292         }
  293 }
  294 SYSINIT(lockprof, SI_SUB_SMP, SI_ORDER_ANY, lock_prof_init, NULL);
  295 
  296 static void
  297 lock_prof_reset_wait(void)
  298 {
  299 
  300         /*
  301          * Spin relinquishing our cpu so that quiesce_all_cpus may
  302          * complete.
  303          */
  304         while (lock_prof_resetting)
  305                 sched_relinquish(curthread);
  306 }
  307 
  308 static void
  309 lock_prof_reset(void)
  310 {
  311         struct lock_prof_cpu *lpc;
  312         int enabled, i, cpu;
  313 
  314         /*
  315          * We not only race with acquiring and releasing locks but also
  316          * thread exit.  To be certain that threads exit without valid head
  317          * pointers they must see resetting set before enabled is cleared.
  318          * Otherwise a lock may not be removed from a per-thread list due
  319          * to disabled being set but not wait for reset() to remove it below.
  320          */
  321         atomic_store_rel_int(&lock_prof_resetting, 1);
  322         enabled = lock_prof_enable;
  323         lock_prof_enable = 0;
  324         quiesce_all_cpus("profreset", 0);
  325         /*
  326          * Some objects may have migrated between CPUs.  Clear all links
  327          * before we zero the structures.  Some items may still be linked
  328          * into per-thread lists as well.
  329          */
  330         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  331                 lpc = lp_cpu[cpu];
  332                 for (i = 0; i < LPROF_CACHE_SIZE; i++) {
  333                         LIST_REMOVE(&lpc->lpc_types[0].lpt_objs[i], lpo_link);
  334                         LIST_REMOVE(&lpc->lpc_types[1].lpt_objs[i], lpo_link);
  335                 }
  336         }
  337         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  338                 lpc = lp_cpu[cpu];
  339                 bzero(lpc, sizeof(*lpc));
  340                 lock_prof_init_type(&lpc->lpc_types[0]);
  341                 lock_prof_init_type(&lpc->lpc_types[1]);
  342         }
  343         atomic_store_rel_int(&lock_prof_resetting, 0);
  344         lock_prof_enable = enabled;
  345 }
  346 
  347 static void
  348 lock_prof_output(struct lock_prof *lp, struct sbuf *sb)
  349 {
  350         const char *p;
  351 
  352         for (p = lp->file; p != NULL && strncmp(p, "../", 3) == 0; p += 3);
  353         sbuf_printf(sb,
  354             "%8ju %9ju %11ju %11ju %11ju %6ju %6ju %2ju %6ju %s:%d (%s:%s)\n",
  355             lp->cnt_max / 1000, lp->cnt_wait_max / 1000, lp->cnt_tot / 1000,
  356             lp->cnt_wait / 1000, lp->cnt_cur,
  357             lp->cnt_cur == 0 ? (uintmax_t)0 :
  358             lp->cnt_tot / (lp->cnt_cur * 1000),
  359             lp->cnt_cur == 0 ? (uintmax_t)0 :
  360             lp->cnt_wait / (lp->cnt_cur * 1000),
  361             (uintmax_t)0, lp->cnt_contest_locking,
  362             p, lp->line, lp->class->lc_name, lp->name);
  363 }
  364 
  365 static void
  366 lock_prof_sum(struct lock_prof *match, struct lock_prof *dst, int hash,
  367     int spin, int t)
  368 {
  369         struct lock_prof_type *type;
  370         struct lock_prof *l;
  371         int cpu;
  372 
  373         dst->file = match->file;
  374         dst->line = match->line;
  375         dst->class = match->class;
  376         dst->name = match->name;
  377 
  378         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  379                 if (lp_cpu[cpu] == NULL)
  380                         continue;
  381                 type = &lp_cpu[cpu]->lpc_types[spin];
  382                 SLIST_FOREACH(l, &type->lpt_hash[hash], link) {
  383                         if (l->ticks == t)
  384                                 continue;
  385                         if (l->file != match->file || l->line != match->line ||
  386                             l->name != match->name)
  387                                 continue;
  388                         l->ticks = t;
  389                         if (l->cnt_max > dst->cnt_max)
  390                                 dst->cnt_max = l->cnt_max;
  391                         if (l->cnt_wait_max > dst->cnt_wait_max)
  392                                 dst->cnt_wait_max = l->cnt_wait_max;
  393                         dst->cnt_tot += l->cnt_tot;
  394                         dst->cnt_wait += l->cnt_wait;
  395                         dst->cnt_cur += l->cnt_cur;
  396                         dst->cnt_contest_locking += l->cnt_contest_locking;
  397                 }
  398         }
  399         
  400 }
  401 
  402 static void
  403 lock_prof_type_stats(struct lock_prof_type *type, struct sbuf *sb, int spin,
  404     int t)
  405 {
  406         struct lock_prof *l;
  407         int i;
  408 
  409         for (i = 0; i < LPROF_HASH_SIZE; ++i) {
  410                 SLIST_FOREACH(l, &type->lpt_hash[i], link) {
  411                         struct lock_prof lp = {};
  412 
  413                         if (l->ticks == t)
  414                                 continue;
  415                         lock_prof_sum(l, &lp, i, spin, t);
  416                         lock_prof_output(&lp, sb);
  417                 }
  418         }
  419 }
  420 
  421 static int
  422 dump_lock_prof_stats(SYSCTL_HANDLER_ARGS)
  423 {
  424         struct sbuf *sb;
  425         int error, cpu, t;
  426         int enabled;
  427 
  428         error = sysctl_wire_old_buffer(req, 0);
  429         if (error != 0)
  430                 return (error);
  431         sb = sbuf_new_for_sysctl(NULL, NULL, LPROF_SBUF_SIZE, req);
  432         sbuf_printf(sb, "\n%8s %9s %11s %11s %11s %6s %6s %2s %6s %s\n",
  433             "max", "wait_max", "total", "wait_total", "count", "avg", "wait_avg", "cnt_hold", "cnt_lock", "name");
  434         enabled = lock_prof_enable;
  435         lock_prof_enable = 0;
  436         quiesce_all_cpus("profstat", 0);
  437         t = ticks;
  438         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  439                 if (lp_cpu[cpu] == NULL)
  440                         continue;
  441                 lock_prof_type_stats(&lp_cpu[cpu]->lpc_types[0], sb, 0, t);
  442                 lock_prof_type_stats(&lp_cpu[cpu]->lpc_types[1], sb, 1, t);
  443         }
  444         lock_prof_enable = enabled;
  445 
  446         error = sbuf_finish(sb);
  447         /* Output a trailing NUL. */
  448         if (error == 0)
  449                 error = SYSCTL_OUT(req, "", 1);
  450         sbuf_delete(sb);
  451         return (error);
  452 }
  453 
  454 static int
  455 enable_lock_prof(SYSCTL_HANDLER_ARGS)
  456 {
  457         int error, v;
  458 
  459         v = lock_prof_enable;
  460         error = sysctl_handle_int(oidp, &v, v, req);
  461         if (error)
  462                 return (error);
  463         if (req->newptr == NULL)
  464                 return (error);
  465         if (v == lock_prof_enable)
  466                 return (0);
  467         if (v == 1)
  468                 lock_prof_reset();
  469         lock_prof_enable = !!v;
  470 
  471         return (0);
  472 }
  473 
  474 static int
  475 reset_lock_prof_stats(SYSCTL_HANDLER_ARGS)
  476 {
  477         int error, v;
  478 
  479         v = 0;
  480         error = sysctl_handle_int(oidp, &v, 0, req);
  481         if (error)
  482                 return (error);
  483         if (req->newptr == NULL)
  484                 return (error);
  485         if (v == 0)
  486                 return (0);
  487         lock_prof_reset();
  488 
  489         return (0);
  490 }
  491 
  492 static struct lock_prof *
  493 lock_profile_lookup(struct lock_object *lo, int spin, const char *file,
  494     int line)
  495 {
  496         const char *unknown = "(unknown)";
  497         struct lock_prof_type *type;
  498         struct lock_prof *lp;
  499         struct lphead *head;
  500         const char *p;
  501         u_int hash;
  502 
  503         p = file;
  504         if (p == NULL || *p == '\0')
  505                 p = unknown;
  506         hash = (uintptr_t)lo->lo_name * 31 + (uintptr_t)p * 31 + line;
  507         hash &= LPROF_HASH_MASK;
  508         type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
  509         head = &type->lpt_hash[hash];
  510         SLIST_FOREACH(lp, head, link) {
  511                 if (lp->line == line && lp->file == p &&
  512                     lp->name == lo->lo_name)
  513                         return (lp);
  514 
  515         }
  516         lp = SLIST_FIRST(&type->lpt_lpalloc);
  517         if (lp == NULL) {
  518                 lock_prof_rejected++;
  519                 return (lp);
  520         }
  521         SLIST_REMOVE_HEAD(&type->lpt_lpalloc, link);
  522         lp->file = p;
  523         lp->line = line;
  524         lp->class = LOCK_CLASS(lo);
  525         lp->name = lo->lo_name;
  526         SLIST_INSERT_HEAD(&type->lpt_hash[hash], lp, link);
  527         return (lp);
  528 }
  529 
  530 static struct lock_profile_object *
  531 lock_profile_object_lookup(struct lock_object *lo, int spin, const char *file,
  532     int line)
  533 {
  534         struct lock_profile_object *l;
  535         struct lock_prof_type *type;
  536         struct lpohead *head;
  537 
  538         head = &curthread->td_lprof[spin];
  539         LIST_FOREACH(l, head, lpo_link)
  540                 if (l->lpo_obj == lo && l->lpo_file == file &&
  541                     l->lpo_line == line)
  542                         return (l);
  543         type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
  544         l = LIST_FIRST(&type->lpt_lpoalloc);
  545         if (l == NULL) {
  546                 lock_prof_rejected++;
  547                 return (NULL);
  548         }
  549         LIST_REMOVE(l, lpo_link);
  550         l->lpo_obj = lo;
  551         l->lpo_file = file;
  552         l->lpo_line = line;
  553         l->lpo_cnt = 0;
  554         LIST_INSERT_HEAD(head, l, lpo_link);
  555 
  556         return (l);
  557 }
  558 
  559 void
  560 lock_profile_obtain_lock_success(struct lock_object *lo, int contested,
  561     uint64_t waittime, const char *file, int line)
  562 {
  563         static int lock_prof_count;
  564         struct lock_profile_object *l;
  565         int spin;
  566 
  567         if (SCHEDULER_STOPPED())
  568                 return;
  569 
  570         /* don't reset the timer when/if recursing */
  571         if (!lock_prof_enable || (lo->lo_flags & LO_NOPROFILE))
  572                 return;
  573         if (lock_prof_skipcount &&
  574             (++lock_prof_count % lock_prof_skipcount) != 0)
  575                 return;
  576         spin = (LOCK_CLASS(lo)->lc_flags & LC_SPINLOCK) ? 1 : 0;
  577         if (spin && lock_prof_skipspin == 1)
  578                 return;
  579         critical_enter();
  580         /* Recheck enabled now that we're in a critical section. */
  581         if (lock_prof_enable == 0)
  582                 goto out;
  583         l = lock_profile_object_lookup(lo, spin, file, line);
  584         if (l == NULL)
  585                 goto out;
  586         l->lpo_cnt++;
  587         if (++l->lpo_ref > 1)
  588                 goto out;
  589         l->lpo_contest_locking = contested;
  590         l->lpo_acqtime = nanoseconds(); 
  591         if (waittime && (l->lpo_acqtime > waittime))
  592                 l->lpo_waittime = l->lpo_acqtime - waittime;
  593         else
  594                 l->lpo_waittime = 0;
  595 out:
  596         critical_exit();
  597 }
  598 
  599 void
  600 lock_profile_thread_exit(struct thread *td)
  601 {
  602 #ifdef INVARIANTS
  603         struct lock_profile_object *l;
  604 
  605         MPASS(curthread->td_critnest == 0);
  606 #endif
  607         /*
  608          * If lock profiling was disabled we have to wait for reset to
  609          * clear our pointers before we can exit safely.
  610          */
  611         lock_prof_reset_wait();
  612 #ifdef INVARIANTS
  613         LIST_FOREACH(l, &td->td_lprof[0], lpo_link)
  614                 printf("thread still holds lock acquired at %s:%d\n",
  615                     l->lpo_file, l->lpo_line);
  616         LIST_FOREACH(l, &td->td_lprof[1], lpo_link)
  617                 printf("thread still holds lock acquired at %s:%d\n",
  618                     l->lpo_file, l->lpo_line);
  619 #endif
  620         MPASS(LIST_FIRST(&td->td_lprof[0]) == NULL);
  621         MPASS(LIST_FIRST(&td->td_lprof[1]) == NULL);
  622 }
  623 
  624 void
  625 lock_profile_release_lock(struct lock_object *lo)
  626 {
  627         struct lock_profile_object *l;
  628         struct lock_prof_type *type;
  629         struct lock_prof *lp;
  630         uint64_t curtime, holdtime;
  631         struct lpohead *head;
  632         int spin;
  633 
  634         if (SCHEDULER_STOPPED())
  635                 return;
  636         if (lo->lo_flags & LO_NOPROFILE)
  637                 return;
  638         spin = (LOCK_CLASS(lo)->lc_flags & LC_SPINLOCK) ? 1 : 0;
  639         head = &curthread->td_lprof[spin];
  640         if (LIST_FIRST(head) == NULL)
  641                 return;
  642         critical_enter();
  643         /* Recheck enabled now that we're in a critical section. */
  644         if (lock_prof_enable == 0 && lock_prof_resetting == 1)
  645                 goto out;
  646         /*
  647          * If lock profiling is not enabled we still want to remove the
  648          * lpo from our queue.
  649          */
  650         LIST_FOREACH(l, head, lpo_link)
  651                 if (l->lpo_obj == lo)
  652                         break;
  653         if (l == NULL)
  654                 goto out;
  655         if (--l->lpo_ref > 0)
  656                 goto out;
  657         lp = lock_profile_lookup(lo, spin, l->lpo_file, l->lpo_line);
  658         if (lp == NULL)
  659                 goto release;
  660         curtime = nanoseconds();
  661         if (curtime < l->lpo_acqtime)
  662                 goto release;
  663         holdtime = curtime - l->lpo_acqtime;
  664 
  665         /*
  666          * Record if the lock has been held longer now than ever
  667          * before.
  668          */
  669         if (holdtime > lp->cnt_max)
  670                 lp->cnt_max = holdtime;
  671         if (l->lpo_waittime > lp->cnt_wait_max)
  672                 lp->cnt_wait_max = l->lpo_waittime;
  673         lp->cnt_tot += holdtime;
  674         lp->cnt_wait += l->lpo_waittime;
  675         lp->cnt_contest_locking += l->lpo_contest_locking;
  676         lp->cnt_cur += l->lpo_cnt;
  677 release:
  678         LIST_REMOVE(l, lpo_link);
  679         type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
  680         LIST_INSERT_HEAD(&type->lpt_lpoalloc, l, lpo_link);
  681 out:
  682         critical_exit();
  683 }
  684 
  685 static SYSCTL_NODE(_debug_lock, OID_AUTO, prof, CTLFLAG_RD, NULL,
  686     "lock profiling");
  687 SYSCTL_INT(_debug_lock_prof, OID_AUTO, skipspin, CTLFLAG_RW,
  688     &lock_prof_skipspin, 0, "Skip profiling on spinlocks.");
  689 SYSCTL_INT(_debug_lock_prof, OID_AUTO, skipcount, CTLFLAG_RW,
  690     &lock_prof_skipcount, 0, "Sample approximately every N lock acquisitions.");
  691 SYSCTL_INT(_debug_lock_prof, OID_AUTO, rejected, CTLFLAG_RD,
  692     &lock_prof_rejected, 0, "Number of rejected profiling records");
  693 SYSCTL_PROC(_debug_lock_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
  694     NULL, 0, dump_lock_prof_stats, "A", "Lock profiling statistics");
  695 SYSCTL_PROC(_debug_lock_prof, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
  696     NULL, 0, reset_lock_prof_stats, "I", "Reset lock profiling statistics");
  697 SYSCTL_PROC(_debug_lock_prof, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
  698     NULL, 0, enable_lock_prof, "I", "Enable lock profiling");
  699 
  700 #endif

Cache object: 540ed89036ed6b608d715b687c6022a9


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