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: releng/10.1/sys/kern/kern_clock.c 260817 2014-01-17 10:58:59Z avg $");
   39 
   40 #include "opt_kdb.h"
   41 #include "opt_device_polling.h"
   42 #include "opt_hwpmc_hooks.h"
   43 #include "opt_kdtrace.h"
   44 #include "opt_ntp.h"
   45 #include "opt_watchdog.h"
   46 
   47 #include <sys/param.h>
   48 #include <sys/systm.h>
   49 #include <sys/callout.h>
   50 #include <sys/kdb.h>
   51 #include <sys/kernel.h>
   52 #include <sys/kthread.h>
   53 #include <sys/ktr.h>
   54 #include <sys/lock.h>
   55 #include <sys/mutex.h>
   56 #include <sys/proc.h>
   57 #include <sys/resource.h>
   58 #include <sys/resourcevar.h>
   59 #include <sys/sched.h>
   60 #include <sys/sdt.h>
   61 #include <sys/signalvar.h>
   62 #include <sys/sleepqueue.h>
   63 #include <sys/smp.h>
   64 #include <vm/vm.h>
   65 #include <vm/pmap.h>
   66 #include <vm/vm_map.h>
   67 #include <sys/sysctl.h>
   68 #include <sys/bus.h>
   69 #include <sys/interrupt.h>
   70 #include <sys/limits.h>
   71 #include <sys/timetc.h>
   72 
   73 #ifdef GPROF
   74 #include <sys/gmon.h>
   75 #endif
   76 
   77 #ifdef HWPMC_HOOKS
   78 #include <sys/pmckern.h>
   79 PMC_SOFT_DEFINE( , , clock, hard);
   80 PMC_SOFT_DEFINE( , , clock, stat);
   81 PMC_SOFT_DEFINE_EX( , , clock, prof, \
   82     cpu_startprofclock, cpu_stopprofclock);
   83 #endif
   84 
   85 #ifdef DEVICE_POLLING
   86 extern void hardclock_device_poll(void);
   87 #endif /* DEVICE_POLLING */
   88 
   89 static void initclocks(void *dummy);
   90 SYSINIT(clocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, initclocks, NULL);
   91 
   92 /* Spin-lock protecting profiling statistics. */
   93 static struct mtx time_lock;
   94 
   95 SDT_PROVIDER_DECLARE(sched);
   96 SDT_PROBE_DEFINE2(sched, , , tick, "struct thread *", "struct proc *");
   97 
   98 static int
   99 sysctl_kern_cp_time(SYSCTL_HANDLER_ARGS)
  100 {
  101         int error;
  102         long cp_time[CPUSTATES];
  103 #ifdef SCTL_MASK32
  104         int i;
  105         unsigned int cp_time32[CPUSTATES];
  106 #endif
  107 
  108         read_cpu_time(cp_time);
  109 #ifdef SCTL_MASK32
  110         if (req->flags & SCTL_MASK32) {
  111                 if (!req->oldptr)
  112                         return SYSCTL_OUT(req, 0, sizeof(cp_time32));
  113                 for (i = 0; i < CPUSTATES; i++)
  114                         cp_time32[i] = (unsigned int)cp_time[i];
  115                 error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  116         } else
  117 #endif
  118         {
  119                 if (!req->oldptr)
  120                         return SYSCTL_OUT(req, 0, sizeof(cp_time));
  121                 error = SYSCTL_OUT(req, cp_time, sizeof(cp_time));
  122         }
  123         return error;
  124 }
  125 
  126 SYSCTL_PROC(_kern, OID_AUTO, cp_time, CTLTYPE_LONG|CTLFLAG_RD|CTLFLAG_MPSAFE,
  127     0,0, sysctl_kern_cp_time, "LU", "CPU time statistics");
  128 
  129 static long empty[CPUSTATES];
  130 
  131 static int
  132 sysctl_kern_cp_times(SYSCTL_HANDLER_ARGS)
  133 {
  134         struct pcpu *pcpu;
  135         int error;
  136         int c;
  137         long *cp_time;
  138 #ifdef SCTL_MASK32
  139         unsigned int cp_time32[CPUSTATES];
  140         int i;
  141 #endif
  142 
  143         if (!req->oldptr) {
  144 #ifdef SCTL_MASK32
  145                 if (req->flags & SCTL_MASK32)
  146                         return SYSCTL_OUT(req, 0, sizeof(cp_time32) * (mp_maxid + 1));
  147                 else
  148 #endif
  149                         return SYSCTL_OUT(req, 0, sizeof(long) * CPUSTATES * (mp_maxid + 1));
  150         }
  151         for (error = 0, c = 0; error == 0 && c <= mp_maxid; c++) {
  152                 if (!CPU_ABSENT(c)) {
  153                         pcpu = pcpu_find(c);
  154                         cp_time = pcpu->pc_cp_time;
  155                 } else {
  156                         cp_time = empty;
  157                 }
  158 #ifdef SCTL_MASK32
  159                 if (req->flags & SCTL_MASK32) {
  160                         for (i = 0; i < CPUSTATES; i++)
  161                                 cp_time32[i] = (unsigned int)cp_time[i];
  162                         error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  163                 } else
  164 #endif
  165                         error = SYSCTL_OUT(req, cp_time, sizeof(long) * CPUSTATES);
  166         }
  167         return error;
  168 }
  169 
  170 SYSCTL_PROC(_kern, OID_AUTO, cp_times, CTLTYPE_LONG|CTLFLAG_RD|CTLFLAG_MPSAFE,
  171     0,0, sysctl_kern_cp_times, "LU", "per-CPU time statistics");
  172 
  173 #ifdef DEADLKRES
  174 static const char *blessed[] = {
  175         "getblk",
  176         "so_snd_sx",
  177         "so_rcv_sx",
  178         NULL
  179 };
  180 static int slptime_threshold = 1800;
  181 static int blktime_threshold = 900;
  182 static int sleepfreq = 3;
  183 
  184 static void
  185 deadlkres(void)
  186 {
  187         struct proc *p;
  188         struct thread *td;
  189         void *wchan;
  190         int blkticks, i, slpticks, slptype, tryl, tticks;
  191 
  192         tryl = 0;
  193         for (;;) {
  194                 blkticks = blktime_threshold * hz;
  195                 slpticks = slptime_threshold * hz;
  196 
  197                 /*
  198                  * Avoid to sleep on the sx_lock in order to avoid a possible
  199                  * priority inversion problem leading to starvation.
  200                  * If the lock can't be held after 100 tries, panic.
  201                  */
  202                 if (!sx_try_slock(&allproc_lock)) {
  203                         if (tryl > 100)
  204                 panic("%s: possible deadlock detected on allproc_lock\n",
  205                                     __func__);
  206                         tryl++;
  207                         pause("allproc", sleepfreq * hz);
  208                         continue;
  209                 }
  210                 tryl = 0;
  211                 FOREACH_PROC_IN_SYSTEM(p) {
  212                         PROC_LOCK(p);
  213                         if (p->p_state == PRS_NEW) {
  214                                 PROC_UNLOCK(p);
  215                                 continue;
  216                         }
  217                         FOREACH_THREAD_IN_PROC(p, td) {
  218 
  219                                 thread_lock(td);
  220                                 if (TD_ON_LOCK(td)) {
  221 
  222                                         /*
  223                                          * The thread should be blocked on a
  224                                          * turnstile, simply check if the
  225                                          * turnstile channel is in good state.
  226                                          */
  227                                         MPASS(td->td_blocked != NULL);
  228 
  229                                         tticks = ticks - td->td_blktick;
  230                                         thread_unlock(td);
  231                                         if (tticks > blkticks) {
  232 
  233                                                 /*
  234                                                  * Accordingly with provided
  235                                                  * thresholds, this thread is
  236                                                  * stuck for too long on a
  237                                                  * turnstile.
  238                                                  */
  239                                                 PROC_UNLOCK(p);
  240                                                 sx_sunlock(&allproc_lock);
  241         panic("%s: possible deadlock detected for %p, blocked for %d ticks\n",
  242                                                     __func__, td, tticks);
  243                                         }
  244                                 } else if (TD_IS_SLEEPING(td) &&
  245                                     TD_ON_SLEEPQ(td)) {
  246 
  247                                         /*
  248                                          * Check if the thread is sleeping on a
  249                                          * lock, otherwise skip the check.
  250                                          * Drop the thread lock in order to
  251                                          * avoid a LOR with the sleepqueue
  252                                          * spinlock.
  253                                          */
  254                                         wchan = td->td_wchan;
  255                                         tticks = ticks - td->td_slptick;
  256                                         thread_unlock(td);
  257                                         slptype = sleepq_type(wchan);
  258                                         if ((slptype == SLEEPQ_SX ||
  259                                             slptype == SLEEPQ_LK) &&
  260                                             tticks > slpticks) {
  261 
  262                                                 /*
  263                                                  * Accordingly with provided
  264                                                  * thresholds, this thread is
  265                                                  * stuck for too long on a
  266                                                  * sleepqueue.
  267                                                  * However, being on a
  268                                                  * sleepqueue, we might still
  269                                                  * check for the blessed
  270                                                  * list.
  271                                                  */
  272                                                 tryl = 0;
  273                                                 for (i = 0; blessed[i] != NULL;
  274                                                     i++) {
  275                                                         if (!strcmp(blessed[i],
  276                                                             td->td_wmesg)) {
  277                                                                 tryl = 1;
  278                                                                 break;
  279                                                         }
  280                                                 }
  281                                                 if (tryl != 0) {
  282                                                         tryl = 0;
  283                                                         continue;
  284                                                 }
  285                                                 PROC_UNLOCK(p);
  286                                                 sx_sunlock(&allproc_lock);
  287         panic("%s: possible deadlock detected for %p, blocked for %d ticks\n",
  288                                                     __func__, td, tticks);
  289                                         }
  290                                 } else
  291                                         thread_unlock(td);
  292                         }
  293                         PROC_UNLOCK(p);
  294                 }
  295                 sx_sunlock(&allproc_lock);
  296 
  297                 /* Sleep for sleepfreq seconds. */
  298                 pause("-", sleepfreq * hz);
  299         }
  300 }
  301 
  302 static struct kthread_desc deadlkres_kd = {
  303         "deadlkres",
  304         deadlkres,
  305         (struct thread **)NULL
  306 };
  307 
  308 SYSINIT(deadlkres, SI_SUB_CLOCKS, SI_ORDER_ANY, kthread_start, &deadlkres_kd);
  309 
  310 static SYSCTL_NODE(_debug, OID_AUTO, deadlkres, CTLFLAG_RW, 0,
  311     "Deadlock resolver");
  312 SYSCTL_INT(_debug_deadlkres, OID_AUTO, slptime_threshold, CTLFLAG_RW,
  313     &slptime_threshold, 0,
  314     "Number of seconds within is valid to sleep on a sleepqueue");
  315 SYSCTL_INT(_debug_deadlkres, OID_AUTO, blktime_threshold, CTLFLAG_RW,
  316     &blktime_threshold, 0,
  317     "Number of seconds within is valid to block on a turnstile");
  318 SYSCTL_INT(_debug_deadlkres, OID_AUTO, sleepfreq, CTLFLAG_RW, &sleepfreq, 0,
  319     "Number of seconds between any deadlock resolver thread run");
  320 #endif  /* DEADLKRES */
  321 
  322 void
  323 read_cpu_time(long *cp_time)
  324 {
  325         struct pcpu *pc;
  326         int i, j;
  327 
  328         /* Sum up global cp_time[]. */
  329         bzero(cp_time, sizeof(long) * CPUSTATES);
  330         CPU_FOREACH(i) {
  331                 pc = pcpu_find(i);
  332                 for (j = 0; j < CPUSTATES; j++)
  333                         cp_time[j] += pc->pc_cp_time[j];
  334         }
  335 }
  336 
  337 #ifdef SW_WATCHDOG
  338 #include <sys/watchdog.h>
  339 
  340 static int watchdog_ticks;
  341 static int watchdog_enabled;
  342 static void watchdog_fire(void);
  343 static void watchdog_config(void *, u_int, int *);
  344 #endif /* SW_WATCHDOG */
  345 
  346 /*
  347  * Clock handling routines.
  348  *
  349  * This code is written to operate with two timers that run independently of
  350  * each other.
  351  *
  352  * The main timer, running hz times per second, is used to trigger interval
  353  * timers, timeouts and rescheduling as needed.
  354  *
  355  * The second timer handles kernel and user profiling,
  356  * and does resource use estimation.  If the second timer is programmable,
  357  * it is randomized to avoid aliasing between the two clocks.  For example,
  358  * the randomization prevents an adversary from always giving up the cpu
  359  * just before its quantum expires.  Otherwise, it would never accumulate
  360  * cpu ticks.  The mean frequency of the second timer is stathz.
  361  *
  362  * If no second timer exists, stathz will be zero; in this case we drive
  363  * profiling and statistics off the main clock.  This WILL NOT be accurate;
  364  * do not do it unless absolutely necessary.
  365  *
  366  * The statistics clock may (or may not) be run at a higher rate while
  367  * profiling.  This profile clock runs at profhz.  We require that profhz
  368  * be an integral multiple of stathz.
  369  *
  370  * If the statistics clock is running fast, it must be divided by the ratio
  371  * profhz/stathz for statistics.  (For profiling, every tick counts.)
  372  *
  373  * Time-of-day is maintained using a "timecounter", which may or may
  374  * not be related to the hardware generating the above mentioned
  375  * interrupts.
  376  */
  377 
  378 int     stathz;
  379 int     profhz;
  380 int     profprocs;
  381 volatile int    ticks;
  382 int     psratio;
  383 
  384 static DPCPU_DEFINE(int, pcputicks);    /* Per-CPU version of ticks. */
  385 static int global_hardclock_run = 0;
  386 
  387 /*
  388  * Initialize clock frequencies and start both clocks running.
  389  */
  390 /* ARGSUSED*/
  391 static void
  392 initclocks(dummy)
  393         void *dummy;
  394 {
  395         register int i;
  396 
  397         /*
  398          * Set divisors to 1 (normal case) and let the machine-specific
  399          * code do its bit.
  400          */
  401         mtx_init(&time_lock, "time lock", NULL, MTX_DEF);
  402         cpu_initclocks();
  403 
  404         /*
  405          * Compute profhz/stathz, and fix profhz if needed.
  406          */
  407         i = stathz ? stathz : hz;
  408         if (profhz == 0)
  409                 profhz = i;
  410         psratio = profhz / i;
  411 #ifdef SW_WATCHDOG
  412         EVENTHANDLER_REGISTER(watchdog_list, watchdog_config, NULL, 0);
  413 #endif
  414 }
  415 
  416 /*
  417  * Each time the real-time timer fires, this function is called on all CPUs.
  418  * Note that hardclock() calls hardclock_cpu() for the boot CPU, so only
  419  * the other CPUs in the system need to call this function.
  420  */
  421 void
  422 hardclock_cpu(int usermode)
  423 {
  424         struct pstats *pstats;
  425         struct thread *td = curthread;
  426         struct proc *p = td->td_proc;
  427         int flags;
  428 
  429         /*
  430          * Run current process's virtual and profile time, as needed.
  431          */
  432         pstats = p->p_stats;
  433         flags = 0;
  434         if (usermode &&
  435             timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value)) {
  436                 PROC_SLOCK(p);
  437                 if (itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0)
  438                         flags |= TDF_ALRMPEND | TDF_ASTPENDING;
  439                 PROC_SUNLOCK(p);
  440         }
  441         if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value)) {
  442                 PROC_SLOCK(p);
  443                 if (itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0)
  444                         flags |= TDF_PROFPEND | TDF_ASTPENDING;
  445                 PROC_SUNLOCK(p);
  446         }
  447         thread_lock(td);
  448         sched_tick(1);
  449         td->td_flags |= flags;
  450         thread_unlock(td);
  451 
  452 #ifdef HWPMC_HOOKS
  453         if (PMC_CPU_HAS_SAMPLES(PCPU_GET(cpuid)))
  454                 PMC_CALL_HOOK_UNLOCKED(curthread, PMC_FN_DO_SAMPLES, NULL);
  455         if (td->td_intr_frame != NULL)
  456                 PMC_SOFT_CALL_TF( , , clock, hard, td->td_intr_frame);
  457 #endif
  458         callout_process(sbinuptime());
  459 }
  460 
  461 /*
  462  * The real-time timer, interrupting hz times per second.
  463  */
  464 void
  465 hardclock(int usermode, uintfptr_t pc)
  466 {
  467 
  468         atomic_add_int(&ticks, 1);
  469         hardclock_cpu(usermode);
  470         tc_ticktock(1);
  471         cpu_tick_calibration();
  472         /*
  473          * If no separate statistics clock is available, run it from here.
  474          *
  475          * XXX: this only works for UP
  476          */
  477         if (stathz == 0) {
  478                 profclock(usermode, pc);
  479                 statclock(usermode);
  480         }
  481 #ifdef DEVICE_POLLING
  482         hardclock_device_poll();        /* this is very short and quick */
  483 #endif /* DEVICE_POLLING */
  484 #ifdef SW_WATCHDOG
  485         if (watchdog_enabled > 0 && --watchdog_ticks <= 0)
  486                 watchdog_fire();
  487 #endif /* SW_WATCHDOG */
  488 }
  489 
  490 void
  491 hardclock_cnt(int cnt, int usermode)
  492 {
  493         struct pstats *pstats;
  494         struct thread *td = curthread;
  495         struct proc *p = td->td_proc;
  496         int *t = DPCPU_PTR(pcputicks);
  497         int flags, global, newticks;
  498 #ifdef SW_WATCHDOG
  499         int i;
  500 #endif /* SW_WATCHDOG */
  501 
  502         /*
  503          * Update per-CPU and possibly global ticks values.
  504          */
  505         *t += cnt;
  506         do {
  507                 global = ticks;
  508                 newticks = *t - global;
  509                 if (newticks <= 0) {
  510                         if (newticks < -1)
  511                                 *t = global - 1;
  512                         newticks = 0;
  513                         break;
  514                 }
  515         } while (!atomic_cmpset_int(&ticks, global, *t));
  516 
  517         /*
  518          * Run current process's virtual and profile time, as needed.
  519          */
  520         pstats = p->p_stats;
  521         flags = 0;
  522         if (usermode &&
  523             timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value)) {
  524                 PROC_SLOCK(p);
  525                 if (itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL],
  526                     tick * cnt) == 0)
  527                         flags |= TDF_ALRMPEND | TDF_ASTPENDING;
  528                 PROC_SUNLOCK(p);
  529         }
  530         if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value)) {
  531                 PROC_SLOCK(p);
  532                 if (itimerdecr(&pstats->p_timer[ITIMER_PROF],
  533                     tick * cnt) == 0)
  534                         flags |= TDF_PROFPEND | TDF_ASTPENDING;
  535                 PROC_SUNLOCK(p);
  536         }
  537         thread_lock(td);
  538         sched_tick(cnt);
  539         td->td_flags |= flags;
  540         thread_unlock(td);
  541 
  542 #ifdef  HWPMC_HOOKS
  543         if (PMC_CPU_HAS_SAMPLES(PCPU_GET(cpuid)))
  544                 PMC_CALL_HOOK_UNLOCKED(curthread, PMC_FN_DO_SAMPLES, NULL);
  545         if (td->td_intr_frame != NULL)
  546                 PMC_SOFT_CALL_TF( , , clock, hard, td->td_intr_frame);
  547 #endif
  548         /* We are in charge to handle this tick duty. */
  549         if (newticks > 0) {
  550                 /* Dangerous and no need to call these things concurrently. */
  551                 if (atomic_cmpset_acq_int(&global_hardclock_run, 0, 1)) {
  552                         tc_ticktock(newticks);
  553 #ifdef DEVICE_POLLING
  554                         /* This is very short and quick. */
  555                         hardclock_device_poll();
  556 #endif /* DEVICE_POLLING */
  557                         atomic_store_rel_int(&global_hardclock_run, 0);
  558                 }
  559 #ifdef SW_WATCHDOG
  560                 if (watchdog_enabled > 0) {
  561                         i = atomic_fetchadd_int(&watchdog_ticks, -newticks);
  562                         if (i > 0 && i <= newticks)
  563                                 watchdog_fire();
  564                 }
  565 #endif /* SW_WATCHDOG */
  566         }
  567         if (curcpu == CPU_FIRST())
  568                 cpu_tick_calibration();
  569 }
  570 
  571 void
  572 hardclock_sync(int cpu)
  573 {
  574         int     *t = DPCPU_ID_PTR(cpu, pcputicks);
  575 
  576         *t = ticks;
  577 }
  578 
  579 /*
  580  * Compute number of ticks in the specified amount of time.
  581  */
  582 int
  583 tvtohz(tv)
  584         struct timeval *tv;
  585 {
  586         register unsigned long ticks;
  587         register long sec, usec;
  588 
  589         /*
  590          * If the number of usecs in the whole seconds part of the time
  591          * difference fits in a long, then the total number of usecs will
  592          * fit in an unsigned long.  Compute the total and convert it to
  593          * ticks, rounding up and adding 1 to allow for the current tick
  594          * to expire.  Rounding also depends on unsigned long arithmetic
  595          * to avoid overflow.
  596          *
  597          * Otherwise, if the number of ticks in the whole seconds part of
  598          * the time difference fits in a long, then convert the parts to
  599          * ticks separately and add, using similar rounding methods and
  600          * overflow avoidance.  This method would work in the previous
  601          * case but it is slightly slower and assumes that hz is integral.
  602          *
  603          * Otherwise, round the time difference down to the maximum
  604          * representable value.
  605          *
  606          * If ints have 32 bits, then the maximum value for any timeout in
  607          * 10ms ticks is 248 days.
  608          */
  609         sec = tv->tv_sec;
  610         usec = tv->tv_usec;
  611         if (usec < 0) {
  612                 sec--;
  613                 usec += 1000000;
  614         }
  615         if (sec < 0) {
  616 #ifdef DIAGNOSTIC
  617                 if (usec > 0) {
  618                         sec++;
  619                         usec -= 1000000;
  620                 }
  621                 printf("tvotohz: negative time difference %ld sec %ld usec\n",
  622                        sec, usec);
  623 #endif
  624                 ticks = 1;
  625         } else if (sec <= LONG_MAX / 1000000)
  626                 ticks = (sec * 1000000 + (unsigned long)usec + (tick - 1))
  627                         / tick + 1;
  628         else if (sec <= LONG_MAX / hz)
  629                 ticks = sec * hz
  630                         + ((unsigned long)usec + (tick - 1)) / tick + 1;
  631         else
  632                 ticks = LONG_MAX;
  633         if (ticks > INT_MAX)
  634                 ticks = INT_MAX;
  635         return ((int)ticks);
  636 }
  637 
  638 /*
  639  * Start profiling on a process.
  640  *
  641  * Kernel profiling passes proc0 which never exits and hence
  642  * keeps the profile clock running constantly.
  643  */
  644 void
  645 startprofclock(p)
  646         register struct proc *p;
  647 {
  648 
  649         PROC_LOCK_ASSERT(p, MA_OWNED);
  650         if (p->p_flag & P_STOPPROF)
  651                 return;
  652         if ((p->p_flag & P_PROFIL) == 0) {
  653                 p->p_flag |= P_PROFIL;
  654                 mtx_lock(&time_lock);
  655                 if (++profprocs == 1)
  656                         cpu_startprofclock();
  657                 mtx_unlock(&time_lock);
  658         }
  659 }
  660 
  661 /*
  662  * Stop profiling on a process.
  663  */
  664 void
  665 stopprofclock(p)
  666         register struct proc *p;
  667 {
  668 
  669         PROC_LOCK_ASSERT(p, MA_OWNED);
  670         if (p->p_flag & P_PROFIL) {
  671                 if (p->p_profthreads != 0) {
  672                         p->p_flag |= P_STOPPROF;
  673                         while (p->p_profthreads != 0)
  674                                 msleep(&p->p_profthreads, &p->p_mtx, PPAUSE,
  675                                     "stopprof", 0);
  676                         p->p_flag &= ~P_STOPPROF;
  677                 }
  678                 if ((p->p_flag & P_PROFIL) == 0)
  679                         return;
  680                 p->p_flag &= ~P_PROFIL;
  681                 mtx_lock(&time_lock);
  682                 if (--profprocs == 0)
  683                         cpu_stopprofclock();
  684                 mtx_unlock(&time_lock);
  685         }
  686 }
  687 
  688 /*
  689  * Statistics clock.  Updates rusage information and calls the scheduler
  690  * to adjust priorities of the active thread.
  691  *
  692  * This should be called by all active processors.
  693  */
  694 void
  695 statclock(int usermode)
  696 {
  697 
  698         statclock_cnt(1, usermode);
  699 }
  700 
  701 void
  702 statclock_cnt(int cnt, int usermode)
  703 {
  704         struct rusage *ru;
  705         struct vmspace *vm;
  706         struct thread *td;
  707         struct proc *p;
  708         long rss;
  709         long *cp_time;
  710 
  711         td = curthread;
  712         p = td->td_proc;
  713 
  714         cp_time = (long *)PCPU_PTR(cp_time);
  715         if (usermode) {
  716                 /*
  717                  * Charge the time as appropriate.
  718                  */
  719                 td->td_uticks += cnt;
  720                 if (p->p_nice > NZERO)
  721                         cp_time[CP_NICE] += cnt;
  722                 else
  723                         cp_time[CP_USER] += cnt;
  724         } else {
  725                 /*
  726                  * Came from kernel mode, so we were:
  727                  * - handling an interrupt,
  728                  * - doing syscall or trap work on behalf of the current
  729                  *   user process, or
  730                  * - spinning in the idle loop.
  731                  * Whichever it is, charge the time as appropriate.
  732                  * Note that we charge interrupts to the current process,
  733                  * regardless of whether they are ``for'' that process,
  734                  * so that we know how much of its real time was spent
  735                  * in ``non-process'' (i.e., interrupt) work.
  736                  */
  737                 if ((td->td_pflags & TDP_ITHREAD) ||
  738                     td->td_intr_nesting_level >= 2) {
  739                         td->td_iticks += cnt;
  740                         cp_time[CP_INTR] += cnt;
  741                 } else {
  742                         td->td_pticks += cnt;
  743                         td->td_sticks += cnt;
  744                         if (!TD_IS_IDLETHREAD(td))
  745                                 cp_time[CP_SYS] += cnt;
  746                         else
  747                                 cp_time[CP_IDLE] += cnt;
  748                 }
  749         }
  750 
  751         /* Update resource usage integrals and maximums. */
  752         MPASS(p->p_vmspace != NULL);
  753         vm = p->p_vmspace;
  754         ru = &td->td_ru;
  755         ru->ru_ixrss += pgtok(vm->vm_tsize) * cnt;
  756         ru->ru_idrss += pgtok(vm->vm_dsize) * cnt;
  757         ru->ru_isrss += pgtok(vm->vm_ssize) * cnt;
  758         rss = pgtok(vmspace_resident_count(vm));
  759         if (ru->ru_maxrss < rss)
  760                 ru->ru_maxrss = rss;
  761         KTR_POINT2(KTR_SCHED, "thread", sched_tdname(td), "statclock",
  762             "prio:%d", td->td_priority, "stathz:%d", (stathz)?stathz:hz);
  763         SDT_PROBE2(sched, , , tick, td, td->td_proc);
  764         thread_lock_flags(td, MTX_QUIET);
  765         for ( ; cnt > 0; cnt--)
  766                 sched_clock(td);
  767         thread_unlock(td);
  768 #ifdef HWPMC_HOOKS
  769         if (td->td_intr_frame != NULL)
  770                 PMC_SOFT_CALL_TF( , , clock, stat, td->td_intr_frame);
  771 #endif
  772 }
  773 
  774 void
  775 profclock(int usermode, uintfptr_t pc)
  776 {
  777 
  778         profclock_cnt(1, usermode, pc);
  779 }
  780 
  781 void
  782 profclock_cnt(int cnt, int usermode, uintfptr_t pc)
  783 {
  784         struct thread *td;
  785 #ifdef GPROF
  786         struct gmonparam *g;
  787         uintfptr_t i;
  788 #endif
  789 
  790         td = curthread;
  791         if (usermode) {
  792                 /*
  793                  * Came from user mode; CPU was in user state.
  794                  * If this process is being profiled, record the tick.
  795                  * if there is no related user location yet, don't
  796                  * bother trying to count it.
  797                  */
  798                 if (td->td_proc->p_flag & P_PROFIL)
  799                         addupc_intr(td, pc, cnt);
  800         }
  801 #ifdef GPROF
  802         else {
  803                 /*
  804                  * Kernel statistics are just like addupc_intr, only easier.
  805                  */
  806                 g = &_gmonparam;
  807                 if (g->state == GMON_PROF_ON && pc >= g->lowpc) {
  808                         i = PC_TO_I(g, pc);
  809                         if (i < g->textsize) {
  810                                 KCOUNT(g, i) += cnt;
  811                         }
  812                 }
  813         }
  814 #endif
  815 #ifdef HWPMC_HOOKS
  816         if (td->td_intr_frame != NULL)
  817                 PMC_SOFT_CALL_TF( , , clock, prof, td->td_intr_frame);
  818 #endif
  819 }
  820 
  821 /*
  822  * Return information about system clocks.
  823  */
  824 static int
  825 sysctl_kern_clockrate(SYSCTL_HANDLER_ARGS)
  826 {
  827         struct clockinfo clkinfo;
  828         /*
  829          * Construct clockinfo structure.
  830          */
  831         bzero(&clkinfo, sizeof(clkinfo));
  832         clkinfo.hz = hz;
  833         clkinfo.tick = tick;
  834         clkinfo.profhz = profhz;
  835         clkinfo.stathz = stathz ? stathz : hz;
  836         return (sysctl_handle_opaque(oidp, &clkinfo, sizeof clkinfo, req));
  837 }
  838 
  839 SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate,
  840         CTLTYPE_STRUCT|CTLFLAG_RD|CTLFLAG_MPSAFE,
  841         0, 0, sysctl_kern_clockrate, "S,clockinfo",
  842         "Rate and period of various kernel clocks");
  843 
  844 #ifdef SW_WATCHDOG
  845 
  846 static void
  847 watchdog_config(void *unused __unused, u_int cmd, int *error)
  848 {
  849         u_int u;
  850 
  851         u = cmd & WD_INTERVAL;
  852         if (u >= WD_TO_1SEC) {
  853                 watchdog_ticks = (1 << (u - WD_TO_1SEC)) * hz;
  854                 watchdog_enabled = 1;
  855                 *error = 0;
  856         } else {
  857                 watchdog_enabled = 0;
  858         }
  859 }
  860 
  861 /*
  862  * Handle a watchdog timeout by dumping interrupt information and
  863  * then either dropping to DDB or panicking.
  864  */
  865 static void
  866 watchdog_fire(void)
  867 {
  868         int nintr;
  869         uint64_t inttotal;
  870         u_long *curintr;
  871         char *curname;
  872 
  873         curintr = intrcnt;
  874         curname = intrnames;
  875         inttotal = 0;
  876         nintr = sintrcnt / sizeof(u_long);
  877 
  878         printf("interrupt                   total\n");
  879         while (--nintr >= 0) {
  880                 if (*curintr)
  881                         printf("%-12s %20lu\n", curname, *curintr);
  882                 curname += strlen(curname) + 1;
  883                 inttotal += *curintr++;
  884         }
  885         printf("Total        %20ju\n", (uintmax_t)inttotal);
  886 
  887 #if defined(KDB) && !defined(KDB_UNATTENDED)
  888         kdb_backtrace();
  889         kdb_enter(KDB_WHY_WATCHDOG, "watchdog timeout");
  890 #else
  891         panic("watchdog timeout");
  892 #endif
  893 }
  894 
  895 #endif /* SW_WATCHDOG */

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