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


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

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  * (c) UNIX System Laboratories, Inc.
    5  * All or some portions of this file are derived from material licensed
    6  * to the University of California by American Telephone and Telegraph
    7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
    8  * the permission of UNIX System Laboratories, Inc.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)kern_clock.c        8.5 (Berkeley) 1/21/94
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD$");
   39 
   40 #include "opt_device_polling.h"
   41 #include "opt_hwpmc_hooks.h"
   42 #include "opt_ntp.h"
   43 #include "opt_watchdog.h"
   44 
   45 #include <sys/param.h>
   46 #include <sys/systm.h>
   47 #include <sys/callout.h>
   48 #include <sys/kdb.h>
   49 #include <sys/kernel.h>
   50 #include <sys/lock.h>
   51 #include <sys/ktr.h>
   52 #include <sys/mutex.h>
   53 #include <sys/proc.h>
   54 #include <sys/resource.h>
   55 #include <sys/resourcevar.h>
   56 #include <sys/sched.h>
   57 #include <sys/signalvar.h>
   58 #include <sys/smp.h>
   59 #include <vm/vm.h>
   60 #include <vm/pmap.h>
   61 #include <vm/vm_map.h>
   62 #include <sys/sysctl.h>
   63 #include <sys/bus.h>
   64 #include <sys/interrupt.h>
   65 #include <sys/limits.h>
   66 #include <sys/timetc.h>
   67 
   68 #include <machine/cpu.h>
   69 
   70 #ifdef GPROF
   71 #include <sys/gmon.h>
   72 #endif
   73 
   74 #ifdef HWPMC_HOOKS
   75 #include <sys/pmckern.h>
   76 #endif
   77 
   78 #ifdef DEVICE_POLLING
   79 extern void hardclock_device_poll(void);
   80 #endif /* DEVICE_POLLING */
   81 
   82 static void initclocks(void *dummy);
   83 SYSINIT(clocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, initclocks, NULL)
   84 
   85 long cp_time[CPUSTATES];
   86 
   87 static int
   88 sysctl_kern_cp_time(SYSCTL_HANDLER_ARGS)
   89 {
   90         int error;
   91 #ifdef SCTL_MASK32
   92         int i;
   93         unsigned int cp_time32[CPUSTATES];
   94 #endif
   95 
   96 #ifdef SCTL_MASK32
   97         if (req->flags & SCTL_MASK32) {
   98                 if (!req->oldptr)
   99                         return SYSCTL_OUT(req, 0, sizeof(cp_time32));
  100                 for (i = 0; i < CPUSTATES; i++)
  101                         cp_time32[i] = (unsigned int)cp_time[i];
  102                 error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  103         } else
  104 #endif
  105         {
  106                 if (!req->oldptr)
  107                         return SYSCTL_OUT(req, 0, sizeof(cp_time));
  108                 error = SYSCTL_OUT(req, cp_time, sizeof(cp_time));
  109         }
  110         return error;
  111 }
  112 
  113 SYSCTL_PROC(_kern, OID_AUTO, cp_time, CTLTYPE_LONG|CTLFLAG_RD, 
  114     0,0, sysctl_kern_cp_time, "LU", "CPU time statistics");
  115 
  116 static long empty[CPUSTATES];
  117 
  118 static int
  119 sysctl_kern_cp_times(SYSCTL_HANDLER_ARGS)
  120 {
  121         struct pcpu *pcpu;
  122         int error;
  123         int c;
  124         long *cp_time;
  125 #ifdef SCTL_MASK32
  126         unsigned int cp_time32[CPUSTATES];
  127         int i;
  128 #endif
  129 
  130         if (!req->oldptr) {
  131 #ifdef SCTL_MASK32
  132                 if (req->flags & SCTL_MASK32)
  133                         return SYSCTL_OUT(req, 0, sizeof(cp_time32) * (mp_maxid + 1));
  134                 else
  135 #endif
  136                         return SYSCTL_OUT(req, 0, sizeof(long) * CPUSTATES * (mp_maxid + 1));
  137         }
  138         for (error = 0, c = 0; error == 0 && c <= mp_maxid; c++) {
  139                 if (!CPU_ABSENT(c)) {
  140                         pcpu = pcpu_find(c);
  141                         cp_time = pcpu->pc_cp_time;
  142                 } else {
  143                         cp_time = empty;
  144                 }
  145 #ifdef SCTL_MASK32
  146                 if (req->flags & SCTL_MASK32) {
  147                         for (i = 0; i < CPUSTATES; i++)
  148                                 cp_time32[i] = (unsigned int)cp_time[i];
  149                         error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  150                 } else
  151 #endif
  152                         error = SYSCTL_OUT(req, cp_time, sizeof(long) * CPUSTATES);
  153         }
  154         return error;
  155 }
  156 
  157 SYSCTL_PROC(_kern, OID_AUTO, cp_times, CTLTYPE_LONG|CTLFLAG_RD,
  158     0,0, sysctl_kern_cp_times, "LU", "per-CPU time statistics");
  159 
  160 void
  161 read_cpu_time(long *cp_time)
  162 {
  163         struct pcpu *pc;
  164         int i, j;
  165 
  166         /* Sum up global cp_time[]. */
  167         bzero(cp_time, sizeof(long) * CPUSTATES);
  168         for (i = 0; i <= mp_maxid; i++) {
  169                 if (CPU_ABSENT(i))
  170                         continue;
  171                 pc = pcpu_find(i);
  172                 for (j = 0; j < CPUSTATES; j++)
  173                         cp_time[j] += pc->pc_cp_time[j];
  174         }
  175 }
  176 
  177 #ifdef SW_WATCHDOG
  178 #include <sys/watchdog.h>
  179 
  180 static int watchdog_ticks;
  181 static int watchdog_enabled;
  182 static void watchdog_fire(void);
  183 static void watchdog_config(void *, u_int, int *);
  184 #endif /* SW_WATCHDOG */
  185 
  186 /*
  187  * Clock handling routines.
  188  *
  189  * This code is written to operate with two timers that run independently of
  190  * each other.
  191  *
  192  * The main timer, running hz times per second, is used to trigger interval
  193  * timers, timeouts and rescheduling as needed.
  194  *
  195  * The second timer handles kernel and user profiling,
  196  * and does resource use estimation.  If the second timer is programmable,
  197  * it is randomized to avoid aliasing between the two clocks.  For example,
  198  * the randomization prevents an adversary from always giving up the cpu
  199  * just before its quantum expires.  Otherwise, it would never accumulate
  200  * cpu ticks.  The mean frequency of the second timer is stathz.
  201  *
  202  * If no second timer exists, stathz will be zero; in this case we drive
  203  * profiling and statistics off the main clock.  This WILL NOT be accurate;
  204  * do not do it unless absolutely necessary.
  205  *
  206  * The statistics clock may (or may not) be run at a higher rate while
  207  * profiling.  This profile clock runs at profhz.  We require that profhz
  208  * be an integral multiple of stathz.
  209  *
  210  * If the statistics clock is running fast, it must be divided by the ratio
  211  * profhz/stathz for statistics.  (For profiling, every tick counts.)
  212  *
  213  * Time-of-day is maintained using a "timecounter", which may or may
  214  * not be related to the hardware generating the above mentioned
  215  * interrupts.
  216  */
  217 
  218 int     stathz;
  219 int     profhz;
  220 int     profprocs;
  221 int     ticks;
  222 int     psratio;
  223 
  224 /*
  225  * Initialize clock frequencies and start both clocks running.
  226  */
  227 /* ARGSUSED*/
  228 static void
  229 initclocks(dummy)
  230         void *dummy;
  231 {
  232         register int i;
  233 
  234         /*
  235          * Set divisors to 1 (normal case) and let the machine-specific
  236          * code do its bit.
  237          */
  238         cpu_initclocks();
  239 
  240         /*
  241          * Compute profhz/stathz, and fix profhz if needed.
  242          */
  243         i = stathz ? stathz : hz;
  244         if (profhz == 0)
  245                 profhz = i;
  246         psratio = profhz / i;
  247 #ifdef SW_WATCHDOG
  248         EVENTHANDLER_REGISTER(watchdog_list, watchdog_config, NULL, 0);
  249 #endif
  250 }
  251 
  252 /*
  253  * Each time the real-time timer fires, this function is called on all CPUs.
  254  * Note that hardclock() calls hardclock_process() for the boot CPU, so only
  255  * the other CPUs in the system need to call this function.
  256  */
  257 void
  258 hardclock_process(frame)
  259         register struct clockframe *frame;
  260 {
  261         struct pstats *pstats;
  262         struct thread *td = curthread;
  263         struct proc *p = td->td_proc;
  264 
  265         /*
  266          * Run current process's virtual and profile time, as needed.
  267          */
  268         mtx_lock_spin_flags(&sched_lock, MTX_QUIET);
  269         if (p->p_flag & P_SA) {
  270                 /* XXXKSE What to do? */
  271         } else {
  272                 pstats = p->p_stats;
  273                 if (CLKF_USERMODE(frame) &&
  274                     timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value) &&
  275                     itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0) {
  276                         p->p_sflag |= PS_ALRMPEND;
  277                         td->td_flags |= TDF_ASTPENDING;
  278                 }
  279                 if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value) &&
  280                     itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0) {
  281                         p->p_sflag |= PS_PROFPEND;
  282                         td->td_flags |= TDF_ASTPENDING;
  283                 }
  284         }
  285         mtx_unlock_spin_flags(&sched_lock, MTX_QUIET);
  286 
  287 #ifdef  HWPMC_HOOKS
  288         if (PMC_CPU_HAS_SAMPLES(PCPU_GET(cpuid)))
  289                 PMC_CALL_HOOK_UNLOCKED(curthread, PMC_FN_DO_SAMPLES, NULL);
  290 #endif
  291 }
  292 
  293 /*
  294  * The real-time timer, interrupting hz times per second.
  295  */
  296 void
  297 hardclock(frame)
  298         register struct clockframe *frame;
  299 {
  300         int need_softclock = 0;
  301 
  302         CTR0(KTR_CLK, "hardclock fired");
  303         hardclock_process(frame);
  304 
  305         tc_ticktock();
  306         /*
  307          * If no separate statistics clock is available, run it from here.
  308          *
  309          * XXX: this only works for UP
  310          */
  311         if (stathz == 0) {
  312                 profclock(frame);
  313                 statclock(frame);
  314         }
  315 
  316 #ifdef DEVICE_POLLING
  317         hardclock_device_poll();        /* this is very short and quick */
  318 #endif /* DEVICE_POLLING */
  319 
  320         /*
  321          * Process callouts at a very low cpu priority, so we don't keep the
  322          * relatively high clock interrupt priority any longer than necessary.
  323          */
  324         mtx_lock_spin_flags(&callout_lock, MTX_QUIET);
  325         ticks++;
  326         if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) {
  327                 need_softclock = 1;
  328         } else if (softticks + 1 == ticks)
  329                 ++softticks;
  330         mtx_unlock_spin_flags(&callout_lock, MTX_QUIET);
  331 
  332         /*
  333          * swi_sched acquires sched_lock, so we don't want to call it with
  334          * callout_lock held; incorrect locking order.
  335          */
  336         if (need_softclock)
  337                 swi_sched(softclock_ih, 0);
  338 
  339 #ifdef SW_WATCHDOG
  340         if (watchdog_enabled > 0 && --watchdog_ticks <= 0)
  341                 watchdog_fire();
  342 #endif /* SW_WATCHDOG */
  343 }
  344 
  345 /*
  346  * Compute number of ticks in the specified amount of time.
  347  */
  348 int
  349 tvtohz(tv)
  350         struct timeval *tv;
  351 {
  352         register unsigned long ticks;
  353         register long sec, usec;
  354 
  355         /*
  356          * If the number of usecs in the whole seconds part of the time
  357          * difference fits in a long, then the total number of usecs will
  358          * fit in an unsigned long.  Compute the total and convert it to
  359          * ticks, rounding up and adding 1 to allow for the current tick
  360          * to expire.  Rounding also depends on unsigned long arithmetic
  361          * to avoid overflow.
  362          *
  363          * Otherwise, if the number of ticks in the whole seconds part of
  364          * the time difference fits in a long, then convert the parts to
  365          * ticks separately and add, using similar rounding methods and
  366          * overflow avoidance.  This method would work in the previous
  367          * case but it is slightly slower and assumes that hz is integral.
  368          *
  369          * Otherwise, round the time difference down to the maximum
  370          * representable value.
  371          *
  372          * If ints have 32 bits, then the maximum value for any timeout in
  373          * 10ms ticks is 248 days.
  374          */
  375         sec = tv->tv_sec;
  376         usec = tv->tv_usec;
  377         if (usec < 0) {
  378                 sec--;
  379                 usec += 1000000;
  380         }
  381         if (sec < 0) {
  382 #ifdef DIAGNOSTIC
  383                 if (usec > 0) {
  384                         sec++;
  385                         usec -= 1000000;
  386                 }
  387                 printf("tvotohz: negative time difference %ld sec %ld usec\n",
  388                        sec, usec);
  389 #endif
  390                 ticks = 1;
  391         } else if (sec <= LONG_MAX / 1000000)
  392                 ticks = (sec * 1000000 + (unsigned long)usec + (tick - 1))
  393                         / tick + 1;
  394         else if (sec <= LONG_MAX / hz)
  395                 ticks = sec * hz
  396                         + ((unsigned long)usec + (tick - 1)) / tick + 1;
  397         else
  398                 ticks = LONG_MAX;
  399         if (ticks > INT_MAX)
  400                 ticks = INT_MAX;
  401         return ((int)ticks);
  402 }
  403 
  404 /*
  405  * Start profiling on a process.
  406  *
  407  * Kernel profiling passes proc0 which never exits and hence
  408  * keeps the profile clock running constantly.
  409  */
  410 void
  411 startprofclock(p)
  412         register struct proc *p;
  413 {
  414 
  415         /*
  416          * XXX; Right now sched_lock protects statclock(), but perhaps
  417          * it should be protected later on by a time_lock, which would
  418          * cover psdiv, etc. as well.
  419          */
  420         PROC_LOCK_ASSERT(p, MA_OWNED);
  421         if (p->p_flag & P_STOPPROF)
  422                 return;
  423         if ((p->p_flag & P_PROFIL) == 0) {
  424                 mtx_lock_spin(&sched_lock);
  425                 p->p_flag |= P_PROFIL;
  426                 if (++profprocs == 1)
  427                         cpu_startprofclock();
  428                 mtx_unlock_spin(&sched_lock);
  429         }
  430 }
  431 
  432 /*
  433  * Stop profiling on a process.
  434  */
  435 void
  436 stopprofclock(p)
  437         register struct proc *p;
  438 {
  439 
  440         PROC_LOCK_ASSERT(p, MA_OWNED);
  441         if (p->p_flag & P_PROFIL) {
  442                 if (p->p_profthreads != 0) {
  443                         p->p_flag |= P_STOPPROF;
  444                         while (p->p_profthreads != 0)
  445                                 msleep(&p->p_profthreads, &p->p_mtx, PPAUSE,
  446                                     "stopprof", 0);
  447                         p->p_flag &= ~P_STOPPROF;
  448                 }
  449                 if ((p->p_flag & P_PROFIL) == 0)
  450                         return;
  451                 mtx_lock_spin(&sched_lock);
  452                 p->p_flag &= ~P_PROFIL;
  453                 if (--profprocs == 0)
  454                         cpu_stopprofclock();
  455                 mtx_unlock_spin(&sched_lock);
  456         }
  457 }
  458 
  459 /*
  460  * Statistics clock.  Grab profile sample, and if divider reaches 0,
  461  * do process and kernel statistics.  Most of the statistics are only
  462  * used by user-level statistics programs.  The main exceptions are
  463  * ke->ke_uticks, p->p_rux.rux_sticks, p->p_rux.rux_iticks, and p->p_estcpu.
  464  * This should be called by all active processors.
  465  */
  466 void
  467 statclock(frame)
  468         register struct clockframe *frame;
  469 {
  470         struct rusage *ru;
  471         struct vmspace *vm;
  472         struct thread *td;
  473         struct proc *p;
  474         long rss;
  475         long *pcp_time;
  476 
  477         td = curthread;
  478         p = td->td_proc;
  479 
  480         mtx_lock_spin_flags(&sched_lock, MTX_QUIET);
  481         pcp_time = (long *)PCPU_PTR(cp_time);
  482         if (CLKF_USERMODE(frame)) {
  483                 /*
  484                  * Charge the time as appropriate.
  485                  */
  486                 if (p->p_flag & P_SA)
  487                         thread_statclock(1);
  488                 p->p_rux.rux_uticks++;
  489                 if (p->p_nice > NZERO) {
  490                         cp_time[CP_NICE]++;
  491                         pcp_time[CP_NICE]++;
  492                 } else {
  493                         cp_time[CP_USER]++;
  494                         pcp_time[CP_USER]++;
  495                 }
  496         } else {
  497                 /*
  498                  * Came from kernel mode, so we were:
  499                  * - handling an interrupt,
  500                  * - doing syscall or trap work on behalf of the current
  501                  *   user process, or
  502                  * - spinning in the idle loop.
  503                  * Whichever it is, charge the time as appropriate.
  504                  * Note that we charge interrupts to the current process,
  505                  * regardless of whether they are ``for'' that process,
  506                  * so that we know how much of its real time was spent
  507                  * in ``non-process'' (i.e., interrupt) work.
  508                  */
  509                 if ((td->td_pflags & TDP_ITHREAD) ||
  510                     td->td_intr_nesting_level >= 2) {
  511                         p->p_rux.rux_iticks++;
  512                         cp_time[CP_INTR]++;
  513                         pcp_time[CP_INTR]++;
  514                 } else {
  515                         if (p->p_flag & P_SA)
  516                                 thread_statclock(0);
  517                         td->td_sticks++;
  518                         p->p_rux.rux_sticks++;
  519                         if (td != PCPU_GET(idlethread)) {
  520                                 cp_time[CP_SYS]++;
  521                                 pcp_time[CP_SYS]++;
  522                         } else {
  523                                 cp_time[CP_IDLE]++;
  524                                 pcp_time[CP_IDLE]++;
  525                         }
  526                 }
  527         }
  528         CTR4(KTR_SCHED, "statclock: %p(%s) prio %d stathz %d",
  529             td, td->td_proc->p_comm, td->td_priority, (stathz)?stathz:hz);
  530 
  531         sched_clock(td);
  532 
  533         /* Update resource usage integrals and maximums. */
  534         MPASS(p->p_stats != NULL);
  535         MPASS(p->p_vmspace != NULL);
  536         vm = p->p_vmspace;
  537         ru = &p->p_stats->p_ru;
  538         ru->ru_ixrss += pgtok(vm->vm_tsize);
  539         ru->ru_idrss += pgtok(vm->vm_dsize);
  540         ru->ru_isrss += pgtok(vm->vm_ssize);
  541         rss = pgtok(vmspace_resident_count(vm));
  542         if (ru->ru_maxrss < rss)
  543                 ru->ru_maxrss = rss;
  544         mtx_unlock_spin_flags(&sched_lock, MTX_QUIET);
  545 }
  546 
  547 void
  548 profclock(frame)
  549         register struct clockframe *frame;
  550 {
  551         struct thread *td;
  552 #ifdef GPROF
  553         struct gmonparam *g;
  554         int i;
  555 #endif
  556 
  557         td = curthread;
  558         if (CLKF_USERMODE(frame)) {
  559                 /*
  560                  * Came from user mode; CPU was in user state.
  561                  * If this process is being profiled, record the tick.
  562                  * if there is no related user location yet, don't
  563                  * bother trying to count it.
  564                  */
  565                 if (td->td_proc->p_flag & P_PROFIL)
  566                         addupc_intr(td, CLKF_PC(frame), 1);
  567         }
  568 #ifdef GPROF
  569         else {
  570                 /*
  571                  * Kernel statistics are just like addupc_intr, only easier.
  572                  */
  573                 g = &_gmonparam;
  574                 if (g->state == GMON_PROF_ON) {
  575                         i = CLKF_PC(frame) - g->lowpc;
  576                         if (i < g->textsize) {
  577                                 i /= HISTFRACTION * sizeof(*g->kcount);
  578                                 g->kcount[i]++;
  579                         }
  580                 }
  581         }
  582 #endif
  583 }
  584 
  585 /*
  586  * Return information about system clocks.
  587  */
  588 static int
  589 sysctl_kern_clockrate(SYSCTL_HANDLER_ARGS)
  590 {
  591         struct clockinfo clkinfo;
  592         /*
  593          * Construct clockinfo structure.
  594          */
  595         bzero(&clkinfo, sizeof(clkinfo));
  596         clkinfo.hz = hz;
  597         clkinfo.tick = tick;
  598         clkinfo.profhz = profhz;
  599         clkinfo.stathz = stathz ? stathz : hz;
  600         return (sysctl_handle_opaque(oidp, &clkinfo, sizeof clkinfo, req));
  601 }
  602 
  603 SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD,
  604         0, 0, sysctl_kern_clockrate, "S,clockinfo",
  605         "Rate and period of various kernel clocks");
  606 
  607 #ifdef SW_WATCHDOG
  608 
  609 static void
  610 watchdog_config(void *unused __unused, u_int cmd, int *error)
  611 {
  612         u_int u;
  613 
  614         u = cmd & WD_INTERVAL;
  615         if (u >= WD_TO_1SEC) {
  616                 watchdog_ticks = (1 << (u - WD_TO_1SEC)) * hz;
  617                 watchdog_enabled = 1;
  618                 *error = 0;
  619         } else {
  620                 watchdog_enabled = 0;
  621         }
  622 }
  623 
  624 /*
  625  * Handle a watchdog timeout by dumping interrupt information and
  626  * then either dropping to DDB or panicing.
  627  */
  628 static void
  629 watchdog_fire(void)
  630 {
  631         int nintr;
  632         u_int64_t inttotal;
  633         u_long *curintr;
  634         char *curname;
  635 
  636         curintr = intrcnt;
  637         curname = intrnames;
  638         inttotal = 0;
  639         nintr = eintrcnt - intrcnt;
  640         
  641         printf("interrupt                   total\n");
  642         while (--nintr >= 0) {
  643                 if (*curintr)
  644                         printf("%-12s %20lu\n", curname, *curintr);
  645                 curname += strlen(curname) + 1;
  646                 inttotal += *curintr++;
  647         }
  648         printf("Total        %20ju\n", (uintmax_t)inttotal);
  649 
  650 #ifdef KDB
  651         kdb_backtrace();
  652         kdb_enter("watchdog timeout");
  653 #else
  654         panic("watchdog timeout");
  655 #endif /* KDB */
  656 }
  657 
  658 #endif /* SW_WATCHDOG */

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