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  * 3. Neither the name of the author nor the names of any co-contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  */
   29 
   30 /*
   31  * This module holds the global variables and functions used to maintain
   32  * lock_object structures.
   33  */
   34 
   35 #include <sys/cdefs.h>
   36 __FBSDID("$FreeBSD: releng/9.2/sys/kern/subr_lock.c 248085 2013-03-09 02:36:32Z marius $");
   37 
   38 #include "opt_ddb.h"
   39 #include "opt_mprof.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/kernel.h>
   44 #include <sys/ktr.h>
   45 #include <sys/lock.h>
   46 #include <sys/lock_profile.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mutex.h>
   49 #include <sys/pcpu.h>
   50 #include <sys/proc.h>
   51 #include <sys/sbuf.h>
   52 #include <sys/sched.h>
   53 #include <sys/smp.h>
   54 #include <sys/sysctl.h>
   55 
   56 #ifdef DDB
   57 #include <ddb/ddb.h>
   58 #endif
   59 
   60 #include <machine/cpufunc.h>
   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_rw,
   70         &lock_class_lockmgr,
   71 };
   72 
   73 void
   74 lock_init(struct lock_object *lock, struct lock_class *class, const char *name,
   75     const char *type, int flags)
   76 {
   77         int i;
   78 
   79         /* Check for double-init and zero object. */
   80         KASSERT(!lock_initalized(lock), ("lock \"%s\" %p already initialized",
   81             name, lock));
   82 
   83         /* Look up lock class to find its index. */
   84         for (i = 0; i < LOCK_CLASS_MAX; i++)
   85                 if (lock_classes[i] == class) {
   86                         lock->lo_flags = i << LO_CLASSSHIFT;
   87                         break;
   88                 }
   89         KASSERT(i < LOCK_CLASS_MAX, ("unknown lock class %p", class));
   90 
   91         /* Initialize the lock object. */
   92         lock->lo_name = name;
   93         lock->lo_flags |= flags | LO_INITIALIZED;
   94         LOCK_LOG_INIT(lock, 0);
   95         WITNESS_INIT(lock, (type != NULL) ? type : name);
   96 }
   97 
   98 void
   99 lock_destroy(struct lock_object *lock)
  100 {
  101 
  102         KASSERT(lock_initalized(lock), ("lock %p is not initialized", lock));
  103         WITNESS_DESTROY(lock);
  104         LOCK_LOG_DESTROY(lock, 0);
  105         lock->lo_flags &= ~LO_INITIALIZED;
  106 }
  107 
  108 #ifdef DDB
  109 DB_SHOW_COMMAND(lock, db_show_lock)
  110 {
  111         struct lock_object *lock;
  112         struct lock_class *class;
  113 
  114         if (!have_addr)
  115                 return;
  116         lock = (struct lock_object *)addr;
  117         if (LO_CLASSINDEX(lock) > LOCK_CLASS_MAX) {
  118                 db_printf("Unknown lock class: %d\n", LO_CLASSINDEX(lock));
  119                 return;
  120         }
  121         class = LOCK_CLASS(lock);
  122         db_printf(" class: %s\n", class->lc_name);
  123         db_printf(" name: %s\n", lock->lo_name);
  124         class->lc_ddb_show(lock);
  125 }
  126 #endif
  127 
  128 #ifdef LOCK_PROFILING
  129 
  130 /*
  131  * One object per-thread for each lock the thread owns.  Tracks individual
  132  * lock instances.
  133  */
  134 struct lock_profile_object {
  135         LIST_ENTRY(lock_profile_object) lpo_link;
  136         struct lock_object *lpo_obj;
  137         const char      *lpo_file;
  138         int             lpo_line;
  139         uint16_t        lpo_ref;
  140         uint16_t        lpo_cnt;
  141         uint64_t        lpo_acqtime;
  142         uint64_t        lpo_waittime;
  143         u_int           lpo_contest_locking;
  144 };
  145 
  146 /*
  147  * One lock_prof for each (file, line, lock object) triple.
  148  */
  149 struct lock_prof {
  150         SLIST_ENTRY(lock_prof) link;
  151         struct lock_class *class;
  152         const char      *file;
  153         const char      *name;
  154         int             line;
  155         int             ticks;
  156         uintmax_t       cnt_wait_max;
  157         uintmax_t       cnt_max;
  158         uintmax_t       cnt_tot;
  159         uintmax_t       cnt_wait;
  160         uintmax_t       cnt_cur;
  161         uintmax_t       cnt_contest_locking;
  162 };
  163 
  164 SLIST_HEAD(lphead, lock_prof);
  165 
  166 #define LPROF_HASH_SIZE         4096
  167 #define LPROF_HASH_MASK         (LPROF_HASH_SIZE - 1)
  168 #define LPROF_CACHE_SIZE        4096
  169 
  170 /*
  171  * Array of objects and profs for each type of object for each cpu.  Spinlocks
  172  * are handled separately because a thread may be preempted and acquire a
  173  * spinlock while in the lock profiling code of a non-spinlock.  In this way
  174  * we only need a critical section to protect the per-cpu lists.
  175  */
  176 struct lock_prof_type {
  177         struct lphead           lpt_lpalloc;
  178         struct lpohead          lpt_lpoalloc;
  179         struct lphead           lpt_hash[LPROF_HASH_SIZE];
  180         struct lock_prof        lpt_prof[LPROF_CACHE_SIZE];
  181         struct lock_profile_object lpt_objs[LPROF_CACHE_SIZE];
  182 };
  183 
  184 struct lock_prof_cpu {
  185         struct lock_prof_type   lpc_types[2]; /* One for spin one for other. */
  186 };
  187 
  188 struct lock_prof_cpu *lp_cpu[MAXCPU];
  189 
  190 volatile int lock_prof_enable = 0;
  191 static volatile int lock_prof_resetting;
  192 
  193 #define LPROF_SBUF_SIZE         256
  194 
  195 static int lock_prof_rejected;
  196 static int lock_prof_skipspin;
  197 static int lock_prof_skipcount;
  198 
  199 #ifndef USE_CPU_NANOSECONDS
  200 uint64_t
  201 nanoseconds(void)
  202 {
  203         struct bintime bt;
  204         uint64_t ns;
  205 
  206         binuptime(&bt);
  207         /* From bintime2timespec */
  208         ns = bt.sec * (uint64_t)1000000000;
  209         ns += ((uint64_t)1000000000 * (uint32_t)(bt.frac >> 32)) >> 32;
  210         return (ns);
  211 }
  212 #endif
  213 
  214 static void
  215 lock_prof_init_type(struct lock_prof_type *type)
  216 {
  217         int i;
  218 
  219         SLIST_INIT(&type->lpt_lpalloc);
  220         LIST_INIT(&type->lpt_lpoalloc);
  221         for (i = 0; i < LPROF_CACHE_SIZE; i++) {
  222                 SLIST_INSERT_HEAD(&type->lpt_lpalloc, &type->lpt_prof[i],
  223                     link);
  224                 LIST_INSERT_HEAD(&type->lpt_lpoalloc, &type->lpt_objs[i],
  225                     lpo_link);
  226         }
  227 }
  228 
  229 static void
  230 lock_prof_init(void *arg)
  231 {
  232         int cpu;
  233 
  234         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  235                 lp_cpu[cpu] = malloc(sizeof(*lp_cpu[cpu]), M_DEVBUF,
  236                     M_WAITOK | M_ZERO);
  237                 lock_prof_init_type(&lp_cpu[cpu]->lpc_types[0]);
  238                 lock_prof_init_type(&lp_cpu[cpu]->lpc_types[1]);
  239         }
  240 }
  241 SYSINIT(lockprof, SI_SUB_SMP, SI_ORDER_ANY, lock_prof_init, NULL);
  242 
  243 /*
  244  * To be certain that lock profiling has idled on all cpus before we
  245  * reset, we schedule the resetting thread on all active cpus.  Since
  246  * all operations happen within critical sections we can be sure that
  247  * it is safe to zero the profiling structures.
  248  */
  249 static void
  250 lock_prof_idle(void)
  251 {
  252         struct thread *td;
  253         int cpu;
  254 
  255         td = curthread;
  256         thread_lock(td);
  257         CPU_FOREACH(cpu) {
  258                 sched_bind(td, cpu);
  259         }
  260         sched_unbind(td);
  261         thread_unlock(td);
  262 }
  263 
  264 static void
  265 lock_prof_reset_wait(void)
  266 {
  267 
  268         /*
  269          * Spin relinquishing our cpu so that lock_prof_idle may
  270          * run on it.
  271          */
  272         while (lock_prof_resetting)
  273                 sched_relinquish(curthread);
  274 }
  275 
  276 static void
  277 lock_prof_reset(void)
  278 {
  279         struct lock_prof_cpu *lpc;
  280         int enabled, i, cpu;
  281 
  282         /*
  283          * We not only race with acquiring and releasing locks but also
  284          * thread exit.  To be certain that threads exit without valid head
  285          * pointers they must see resetting set before enabled is cleared.
  286          * Otherwise a lock may not be removed from a per-thread list due
  287          * to disabled being set but not wait for reset() to remove it below.
  288          */
  289         atomic_store_rel_int(&lock_prof_resetting, 1);
  290         enabled = lock_prof_enable;
  291         lock_prof_enable = 0;
  292         lock_prof_idle();
  293         /*
  294          * Some objects may have migrated between CPUs.  Clear all links
  295          * before we zero the structures.  Some items may still be linked
  296          * into per-thread lists as well.
  297          */
  298         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  299                 lpc = lp_cpu[cpu];
  300                 for (i = 0; i < LPROF_CACHE_SIZE; i++) {
  301                         LIST_REMOVE(&lpc->lpc_types[0].lpt_objs[i], lpo_link);
  302                         LIST_REMOVE(&lpc->lpc_types[1].lpt_objs[i], lpo_link);
  303                 }
  304         }
  305         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  306                 lpc = lp_cpu[cpu];
  307                 bzero(lpc, sizeof(*lpc));
  308                 lock_prof_init_type(&lpc->lpc_types[0]);
  309                 lock_prof_init_type(&lpc->lpc_types[1]);
  310         }
  311         atomic_store_rel_int(&lock_prof_resetting, 0);
  312         lock_prof_enable = enabled;
  313 }
  314 
  315 static void
  316 lock_prof_output(struct lock_prof *lp, struct sbuf *sb)
  317 {
  318         const char *p;
  319 
  320         for (p = lp->file; p != NULL && strncmp(p, "../", 3) == 0; p += 3);
  321         sbuf_printf(sb,
  322             "%8ju %9ju %11ju %11ju %11ju %6ju %6ju %2ju %6ju %s:%d (%s:%s)\n",
  323             lp->cnt_max / 1000, lp->cnt_wait_max / 1000, lp->cnt_tot / 1000,
  324             lp->cnt_wait / 1000, lp->cnt_cur,
  325             lp->cnt_cur == 0 ? (uintmax_t)0 :
  326             lp->cnt_tot / (lp->cnt_cur * 1000),
  327             lp->cnt_cur == 0 ? (uintmax_t)0 :
  328             lp->cnt_wait / (lp->cnt_cur * 1000),
  329             (uintmax_t)0, lp->cnt_contest_locking,
  330             p, lp->line, lp->class->lc_name, lp->name);
  331 }
  332 
  333 static void
  334 lock_prof_sum(struct lock_prof *match, struct lock_prof *dst, int hash,
  335     int spin, int t)
  336 {
  337         struct lock_prof_type *type;
  338         struct lock_prof *l;
  339         int cpu;
  340 
  341         dst->file = match->file;
  342         dst->line = match->line;
  343         dst->class = match->class;
  344         dst->name = match->name;
  345 
  346         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  347                 if (lp_cpu[cpu] == NULL)
  348                         continue;
  349                 type = &lp_cpu[cpu]->lpc_types[spin];
  350                 SLIST_FOREACH(l, &type->lpt_hash[hash], link) {
  351                         if (l->ticks == t)
  352                                 continue;
  353                         if (l->file != match->file || l->line != match->line ||
  354                             l->name != match->name)
  355                                 continue;
  356                         l->ticks = t;
  357                         if (l->cnt_max > dst->cnt_max)
  358                                 dst->cnt_max = l->cnt_max;
  359                         if (l->cnt_wait_max > dst->cnt_wait_max)
  360                                 dst->cnt_wait_max = l->cnt_wait_max;
  361                         dst->cnt_tot += l->cnt_tot;
  362                         dst->cnt_wait += l->cnt_wait;
  363                         dst->cnt_cur += l->cnt_cur;
  364                         dst->cnt_contest_locking += l->cnt_contest_locking;
  365                 }
  366         }
  367         
  368 }
  369 
  370 static void
  371 lock_prof_type_stats(struct lock_prof_type *type, struct sbuf *sb, int spin,
  372     int t)
  373 {
  374         struct lock_prof *l;
  375         int i;
  376 
  377         for (i = 0; i < LPROF_HASH_SIZE; ++i) {
  378                 SLIST_FOREACH(l, &type->lpt_hash[i], link) {
  379                         struct lock_prof lp = {};
  380 
  381                         if (l->ticks == t)
  382                                 continue;
  383                         lock_prof_sum(l, &lp, i, spin, t);
  384                         lock_prof_output(&lp, sb);
  385                 }
  386         }
  387 }
  388 
  389 static int
  390 dump_lock_prof_stats(SYSCTL_HANDLER_ARGS)
  391 {
  392         struct sbuf *sb;
  393         int error, cpu, t;
  394         int enabled;
  395 
  396         error = sysctl_wire_old_buffer(req, 0);
  397         if (error != 0)
  398                 return (error);
  399         sb = sbuf_new_for_sysctl(NULL, NULL, LPROF_SBUF_SIZE, req);
  400         sbuf_printf(sb, "\n%8s %9s %11s %11s %11s %6s %6s %2s %6s %s\n",
  401             "max", "wait_max", "total", "wait_total", "count", "avg", "wait_avg", "cnt_hold", "cnt_lock", "name");
  402         enabled = lock_prof_enable;
  403         lock_prof_enable = 0;
  404         lock_prof_idle();
  405         t = ticks;
  406         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  407                 if (lp_cpu[cpu] == NULL)
  408                         continue;
  409                 lock_prof_type_stats(&lp_cpu[cpu]->lpc_types[0], sb, 0, t);
  410                 lock_prof_type_stats(&lp_cpu[cpu]->lpc_types[1], sb, 1, t);
  411         }
  412         lock_prof_enable = enabled;
  413 
  414         error = sbuf_finish(sb);
  415         /* Output a trailing NUL. */
  416         if (error == 0)
  417                 error = SYSCTL_OUT(req, "", 1);
  418         sbuf_delete(sb);
  419         return (error);
  420 }
  421 
  422 static int
  423 enable_lock_prof(SYSCTL_HANDLER_ARGS)
  424 {
  425         int error, v;
  426 
  427         v = lock_prof_enable;
  428         error = sysctl_handle_int(oidp, &v, v, req);
  429         if (error)
  430                 return (error);
  431         if (req->newptr == NULL)
  432                 return (error);
  433         if (v == lock_prof_enable)
  434                 return (0);
  435         if (v == 1)
  436                 lock_prof_reset();
  437         lock_prof_enable = !!v;
  438 
  439         return (0);
  440 }
  441 
  442 static int
  443 reset_lock_prof_stats(SYSCTL_HANDLER_ARGS)
  444 {
  445         int error, v;
  446 
  447         v = 0;
  448         error = sysctl_handle_int(oidp, &v, 0, req);
  449         if (error)
  450                 return (error);
  451         if (req->newptr == NULL)
  452                 return (error);
  453         if (v == 0)
  454                 return (0);
  455         lock_prof_reset();
  456 
  457         return (0);
  458 }
  459 
  460 static struct lock_prof *
  461 lock_profile_lookup(struct lock_object *lo, int spin, const char *file,
  462     int line)
  463 {
  464         const char *unknown = "(unknown)";
  465         struct lock_prof_type *type;
  466         struct lock_prof *lp;
  467         struct lphead *head;
  468         const char *p;
  469         u_int hash;
  470 
  471         p = file;
  472         if (p == NULL || *p == '\0')
  473                 p = unknown;
  474         hash = (uintptr_t)lo->lo_name * 31 + (uintptr_t)p * 31 + line;
  475         hash &= LPROF_HASH_MASK;
  476         type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
  477         head = &type->lpt_hash[hash];
  478         SLIST_FOREACH(lp, head, link) {
  479                 if (lp->line == line && lp->file == p &&
  480                     lp->name == lo->lo_name)
  481                         return (lp);
  482 
  483         }
  484         lp = SLIST_FIRST(&type->lpt_lpalloc);
  485         if (lp == NULL) {
  486                 lock_prof_rejected++;
  487                 return (lp);
  488         }
  489         SLIST_REMOVE_HEAD(&type->lpt_lpalloc, link);
  490         lp->file = p;
  491         lp->line = line;
  492         lp->class = LOCK_CLASS(lo);
  493         lp->name = lo->lo_name;
  494         SLIST_INSERT_HEAD(&type->lpt_hash[hash], lp, link);
  495         return (lp);
  496 }
  497 
  498 static struct lock_profile_object *
  499 lock_profile_object_lookup(struct lock_object *lo, int spin, const char *file,
  500     int line)
  501 {
  502         struct lock_profile_object *l;
  503         struct lock_prof_type *type;
  504         struct lpohead *head;
  505 
  506         head = &curthread->td_lprof[spin];
  507         LIST_FOREACH(l, head, lpo_link)
  508                 if (l->lpo_obj == lo && l->lpo_file == file &&
  509                     l->lpo_line == line)
  510                         return (l);
  511         type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
  512         l = LIST_FIRST(&type->lpt_lpoalloc);
  513         if (l == NULL) {
  514                 lock_prof_rejected++;
  515                 return (NULL);
  516         }
  517         LIST_REMOVE(l, lpo_link);
  518         l->lpo_obj = lo;
  519         l->lpo_file = file;
  520         l->lpo_line = line;
  521         l->lpo_cnt = 0;
  522         LIST_INSERT_HEAD(head, l, lpo_link);
  523 
  524         return (l);
  525 }
  526 
  527 void
  528 lock_profile_obtain_lock_success(struct lock_object *lo, int contested,
  529     uint64_t waittime, const char *file, int line)
  530 {
  531         static int lock_prof_count;
  532         struct lock_profile_object *l;
  533         int spin;
  534 
  535         if (SCHEDULER_STOPPED())
  536                 return;
  537 
  538         /* don't reset the timer when/if recursing */
  539         if (!lock_prof_enable || (lo->lo_flags & LO_NOPROFILE))
  540                 return;
  541         if (lock_prof_skipcount &&
  542             (++lock_prof_count % lock_prof_skipcount) != 0)
  543                 return;
  544         spin = (LOCK_CLASS(lo)->lc_flags & LC_SPINLOCK) ? 1 : 0;
  545         if (spin && lock_prof_skipspin == 1)
  546                 return;
  547         critical_enter();
  548         /* Recheck enabled now that we're in a critical section. */
  549         if (lock_prof_enable == 0)
  550                 goto out;
  551         l = lock_profile_object_lookup(lo, spin, file, line);
  552         if (l == NULL)
  553                 goto out;
  554         l->lpo_cnt++;
  555         if (++l->lpo_ref > 1)
  556                 goto out;
  557         l->lpo_contest_locking = contested;
  558         l->lpo_acqtime = nanoseconds(); 
  559         if (waittime && (l->lpo_acqtime > waittime))
  560                 l->lpo_waittime = l->lpo_acqtime - waittime;
  561         else
  562                 l->lpo_waittime = 0;
  563 out:
  564         critical_exit();
  565 }
  566 
  567 void
  568 lock_profile_thread_exit(struct thread *td)
  569 {
  570 #ifdef INVARIANTS
  571         struct lock_profile_object *l;
  572 
  573         MPASS(curthread->td_critnest == 0);
  574 #endif
  575         /*
  576          * If lock profiling was disabled we have to wait for reset to
  577          * clear our pointers before we can exit safely.
  578          */
  579         lock_prof_reset_wait();
  580 #ifdef INVARIANTS
  581         LIST_FOREACH(l, &td->td_lprof[0], lpo_link)
  582                 printf("thread still holds lock acquired at %s:%d\n",
  583                     l->lpo_file, l->lpo_line);
  584         LIST_FOREACH(l, &td->td_lprof[1], lpo_link)
  585                 printf("thread still holds lock acquired at %s:%d\n",
  586                     l->lpo_file, l->lpo_line);
  587 #endif
  588         MPASS(LIST_FIRST(&td->td_lprof[0]) == NULL);
  589         MPASS(LIST_FIRST(&td->td_lprof[1]) == NULL);
  590 }
  591 
  592 void
  593 lock_profile_release_lock(struct lock_object *lo)
  594 {
  595         struct lock_profile_object *l;
  596         struct lock_prof_type *type;
  597         struct lock_prof *lp;
  598         uint64_t curtime, holdtime;
  599         struct lpohead *head;
  600         int spin;
  601 
  602         if (SCHEDULER_STOPPED())
  603                 return;
  604         if (lo->lo_flags & LO_NOPROFILE)
  605                 return;
  606         spin = (LOCK_CLASS(lo)->lc_flags & LC_SPINLOCK) ? 1 : 0;
  607         head = &curthread->td_lprof[spin];
  608         if (LIST_FIRST(head) == NULL)
  609                 return;
  610         critical_enter();
  611         /* Recheck enabled now that we're in a critical section. */
  612         if (lock_prof_enable == 0 && lock_prof_resetting == 1)
  613                 goto out;
  614         /*
  615          * If lock profiling is not enabled we still want to remove the
  616          * lpo from our queue.
  617          */
  618         LIST_FOREACH(l, head, lpo_link)
  619                 if (l->lpo_obj == lo)
  620                         break;
  621         if (l == NULL)
  622                 goto out;
  623         if (--l->lpo_ref > 0)
  624                 goto out;
  625         lp = lock_profile_lookup(lo, spin, l->lpo_file, l->lpo_line);
  626         if (lp == NULL)
  627                 goto release;
  628         curtime = nanoseconds();
  629         if (curtime < l->lpo_acqtime)
  630                 goto release;
  631         holdtime = curtime - l->lpo_acqtime;
  632 
  633         /*
  634          * Record if the lock has been held longer now than ever
  635          * before.
  636          */
  637         if (holdtime > lp->cnt_max)
  638                 lp->cnt_max = holdtime;
  639         if (l->lpo_waittime > lp->cnt_wait_max)
  640                 lp->cnt_wait_max = l->lpo_waittime;
  641         lp->cnt_tot += holdtime;
  642         lp->cnt_wait += l->lpo_waittime;
  643         lp->cnt_contest_locking += l->lpo_contest_locking;
  644         lp->cnt_cur += l->lpo_cnt;
  645 release:
  646         LIST_REMOVE(l, lpo_link);
  647         type = &lp_cpu[PCPU_GET(cpuid)]->lpc_types[spin];
  648         LIST_INSERT_HEAD(&type->lpt_lpoalloc, l, lpo_link);
  649 out:
  650         critical_exit();
  651 }
  652 
  653 static SYSCTL_NODE(_debug, OID_AUTO, lock, CTLFLAG_RD, NULL, "lock debugging");
  654 static SYSCTL_NODE(_debug_lock, OID_AUTO, prof, CTLFLAG_RD, NULL,
  655     "lock profiling");
  656 SYSCTL_INT(_debug_lock_prof, OID_AUTO, skipspin, CTLFLAG_RW,
  657     &lock_prof_skipspin, 0, "Skip profiling on spinlocks.");
  658 SYSCTL_INT(_debug_lock_prof, OID_AUTO, skipcount, CTLFLAG_RW,
  659     &lock_prof_skipcount, 0, "Sample approximately every N lock acquisitions.");
  660 SYSCTL_INT(_debug_lock_prof, OID_AUTO, rejected, CTLFLAG_RD,
  661     &lock_prof_rejected, 0, "Number of rejected profiling records");
  662 SYSCTL_PROC(_debug_lock_prof, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
  663     NULL, 0, dump_lock_prof_stats, "A", "Lock profiling statistics");
  664 SYSCTL_PROC(_debug_lock_prof, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
  665     NULL, 0, reset_lock_prof_stats, "I", "Reset lock profiling statistics");
  666 SYSCTL_PROC(_debug_lock_prof, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
  667     NULL, 0, enable_lock_prof, "I", "Enable lock profiling");
  668 
  669 #endif

Cache object: 122985a2c9be3ff02ee4146577f2cf7a


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