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/11.2/sys/kern/kern_clock.c 331722 2018-03-29 02:50:57Z eadler $");
   39 
   40 #include "opt_kdb.h"
   41 #include "opt_device_polling.h"
   42 #include "opt_hwpmc_hooks.h"
   43 #include "opt_ntp.h"
   44 #include "opt_watchdog.h"
   45 
   46 #include <sys/param.h>
   47 #include <sys/systm.h>
   48 #include <sys/callout.h>
   49 #include <sys/kdb.h>
   50 #include <sys/kernel.h>
   51 #include <sys/kthread.h>
   52 #include <sys/ktr.h>
   53 #include <sys/lock.h>
   54 #include <sys/mutex.h>
   55 #include <sys/proc.h>
   56 #include <sys/resource.h>
   57 #include <sys/resourcevar.h>
   58 #include <sys/sched.h>
   59 #include <sys/sdt.h>
   60 #include <sys/signalvar.h>
   61 #include <sys/sleepqueue.h>
   62 #include <sys/smp.h>
   63 #include <vm/vm.h>
   64 #include <vm/pmap.h>
   65 #include <vm/vm_map.h>
   66 #include <sys/sysctl.h>
   67 #include <sys/bus.h>
   68 #include <sys/interrupt.h>
   69 #include <sys/limits.h>
   70 #include <sys/timetc.h>
   71 
   72 #ifdef GPROF
   73 #include <sys/gmon.h>
   74 #endif
   75 
   76 #ifdef HWPMC_HOOKS
   77 #include <sys/pmckern.h>
   78 PMC_SOFT_DEFINE( , , clock, hard);
   79 PMC_SOFT_DEFINE( , , clock, stat);
   80 PMC_SOFT_DEFINE_EX( , , clock, prof, \
   81     cpu_startprofclock, cpu_stopprofclock);
   82 #endif
   83 
   84 #ifdef DEVICE_POLLING
   85 extern void hardclock_device_poll(void);
   86 #endif /* DEVICE_POLLING */
   87 
   88 static void initclocks(void *dummy);
   89 SYSINIT(clocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, initclocks, NULL);
   90 
   91 /* Spin-lock protecting profiling statistics. */
   92 static struct mtx time_lock;
   93 
   94 SDT_PROVIDER_DECLARE(sched);
   95 SDT_PROBE_DEFINE2(sched, , , tick, "struct thread *", "struct proc *");
   96 
   97 static int
   98 sysctl_kern_cp_time(SYSCTL_HANDLER_ARGS)
   99 {
  100         int error;
  101         long cp_time[CPUSTATES];
  102 #ifdef SCTL_MASK32
  103         int i;
  104         unsigned int cp_time32[CPUSTATES];
  105 #endif
  106 
  107         read_cpu_time(cp_time);
  108 #ifdef SCTL_MASK32
  109         if (req->flags & SCTL_MASK32) {
  110                 if (!req->oldptr)
  111                         return SYSCTL_OUT(req, 0, sizeof(cp_time32));
  112                 for (i = 0; i < CPUSTATES; i++)
  113                         cp_time32[i] = (unsigned int)cp_time[i];
  114                 error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  115         } else
  116 #endif
  117         {
  118                 if (!req->oldptr)
  119                         return SYSCTL_OUT(req, 0, sizeof(cp_time));
  120                 error = SYSCTL_OUT(req, cp_time, sizeof(cp_time));
  121         }
  122         return error;
  123 }
  124 
  125 SYSCTL_PROC(_kern, OID_AUTO, cp_time, CTLTYPE_LONG|CTLFLAG_RD|CTLFLAG_MPSAFE,
  126     0,0, sysctl_kern_cp_time, "LU", "CPU time statistics");
  127 
  128 static long empty[CPUSTATES];
  129 
  130 static int
  131 sysctl_kern_cp_times(SYSCTL_HANDLER_ARGS)
  132 {
  133         struct pcpu *pcpu;
  134         int error;
  135         int c;
  136         long *cp_time;
  137 #ifdef SCTL_MASK32
  138         unsigned int cp_time32[CPUSTATES];
  139         int i;
  140 #endif
  141 
  142         if (!req->oldptr) {
  143 #ifdef SCTL_MASK32
  144                 if (req->flags & SCTL_MASK32)
  145                         return SYSCTL_OUT(req, 0, sizeof(cp_time32) * (mp_maxid + 1));
  146                 else
  147 #endif
  148                         return SYSCTL_OUT(req, 0, sizeof(long) * CPUSTATES * (mp_maxid + 1));
  149         }
  150         for (error = 0, c = 0; error == 0 && c <= mp_maxid; c++) {
  151                 if (!CPU_ABSENT(c)) {
  152                         pcpu = pcpu_find(c);
  153                         cp_time = pcpu->pc_cp_time;
  154                 } else {
  155                         cp_time = empty;
  156                 }
  157 #ifdef SCTL_MASK32
  158                 if (req->flags & SCTL_MASK32) {
  159                         for (i = 0; i < CPUSTATES; i++)
  160                                 cp_time32[i] = (unsigned int)cp_time[i];
  161                         error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  162                 } else
  163 #endif
  164                         error = SYSCTL_OUT(req, cp_time, sizeof(long) * CPUSTATES);
  165         }
  166         return error;
  167 }
  168 
  169 SYSCTL_PROC(_kern, OID_AUTO, cp_times, CTLTYPE_LONG|CTLFLAG_RD|CTLFLAG_MPSAFE,
  170     0,0, sysctl_kern_cp_times, "LU", "per-CPU time statistics");
  171 
  172 #ifdef DEADLKRES
  173 static const char *blessed[] = {
  174         "getblk",
  175         "so_snd_sx",
  176         "so_rcv_sx",
  177         NULL
  178 };
  179 static int slptime_threshold = 1800;
  180 static int blktime_threshold = 900;
  181 static int sleepfreq = 3;
  182 
  183 static void
  184 deadlkres(void)
  185 {
  186         struct proc *p;
  187         struct thread *td;
  188         void *wchan;
  189         int blkticks, i, slpticks, slptype, tryl, tticks;
  190 
  191         tryl = 0;
  192         for (;;) {
  193                 blkticks = blktime_threshold * hz;
  194                 slpticks = slptime_threshold * hz;
  195 
  196                 /*
  197                  * Avoid to sleep on the sx_lock in order to avoid a possible
  198                  * priority inversion problem leading to starvation.
  199                  * If the lock can't be held after 100 tries, panic.
  200                  */
  201                 if (!sx_try_slock(&allproc_lock)) {
  202                         if (tryl > 100)
  203                 panic("%s: possible deadlock detected on allproc_lock\n",
  204                                     __func__);
  205                         tryl++;
  206                         pause("allproc", sleepfreq * hz);
  207                         continue;
  208                 }
  209                 tryl = 0;
  210                 FOREACH_PROC_IN_SYSTEM(p) {
  211                         PROC_LOCK(p);
  212                         if (p->p_state == PRS_NEW) {
  213                                 PROC_UNLOCK(p);
  214                                 continue;
  215                         }
  216                         FOREACH_THREAD_IN_PROC(p, td) {
  217 
  218                                 thread_lock(td);
  219                                 if (TD_ON_LOCK(td)) {
  220 
  221                                         /*
  222                                          * The thread should be blocked on a
  223                                          * turnstile, simply check if the
  224                                          * turnstile channel is in good state.
  225                                          */
  226                                         MPASS(td->td_blocked != NULL);
  227 
  228                                         tticks = ticks - td->td_blktick;
  229                                         thread_unlock(td);
  230                                         if (tticks > blkticks) {
  231 
  232                                                 /*
  233                                                  * Accordingly with provided
  234                                                  * thresholds, this thread is
  235                                                  * stuck for too long on a
  236                                                  * turnstile.
  237                                                  */
  238                                                 PROC_UNLOCK(p);
  239                                                 sx_sunlock(&allproc_lock);
  240         panic("%s: possible deadlock detected for %p, blocked for %d ticks\n",
  241                                                     __func__, td, tticks);
  242                                         }
  243                                 } else if (TD_IS_SLEEPING(td) &&
  244                                     TD_ON_SLEEPQ(td)) {
  245 
  246                                         /*
  247                                          * Check if the thread is sleeping on a
  248                                          * lock, otherwise skip the check.
  249                                          * Drop the thread lock in order to
  250                                          * avoid a LOR with the sleepqueue
  251                                          * spinlock.
  252                                          */
  253                                         wchan = td->td_wchan;
  254                                         tticks = ticks - td->td_slptick;
  255                                         thread_unlock(td);
  256                                         slptype = sleepq_type(wchan);
  257                                         if ((slptype == SLEEPQ_SX ||
  258                                             slptype == SLEEPQ_LK) &&
  259                                             tticks > slpticks) {
  260 
  261                                                 /*
  262                                                  * Accordingly with provided
  263                                                  * thresholds, this thread is
  264                                                  * stuck for too long on a
  265                                                  * sleepqueue.
  266                                                  * However, being on a
  267                                                  * sleepqueue, we might still
  268                                                  * check for the blessed
  269                                                  * list.
  270                                                  */
  271                                                 tryl = 0;
  272                                                 for (i = 0; blessed[i] != NULL;
  273                                                     i++) {
  274                                                         if (!strcmp(blessed[i],
  275                                                             td->td_wmesg)) {
  276                                                                 tryl = 1;
  277                                                                 break;
  278                                                         }
  279                                                 }
  280                                                 if (tryl != 0) {
  281                                                         tryl = 0;
  282                                                         continue;
  283                                                 }
  284                                                 PROC_UNLOCK(p);
  285                                                 sx_sunlock(&allproc_lock);
  286         panic("%s: possible deadlock detected for %p, blocked for %d ticks\n",
  287                                                     __func__, td, tticks);
  288                                         }
  289                                 } else
  290                                         thread_unlock(td);
  291                         }
  292                         PROC_UNLOCK(p);
  293                 }
  294                 sx_sunlock(&allproc_lock);
  295 
  296                 /* Sleep for sleepfreq seconds. */
  297                 pause("-", sleepfreq * hz);
  298         }
  299 }
  300 
  301 static struct kthread_desc deadlkres_kd = {
  302         "deadlkres",
  303         deadlkres,
  304         (struct thread **)NULL
  305 };
  306 
  307 SYSINIT(deadlkres, SI_SUB_CLOCKS, SI_ORDER_ANY, kthread_start, &deadlkres_kd);
  308 
  309 static SYSCTL_NODE(_debug, OID_AUTO, deadlkres, CTLFLAG_RW, 0,
  310     "Deadlock resolver");
  311 SYSCTL_INT(_debug_deadlkres, OID_AUTO, slptime_threshold, CTLFLAG_RW,
  312     &slptime_threshold, 0,
  313     "Number of seconds within is valid to sleep on a sleepqueue");
  314 SYSCTL_INT(_debug_deadlkres, OID_AUTO, blktime_threshold, CTLFLAG_RW,
  315     &blktime_threshold, 0,
  316     "Number of seconds within is valid to block on a turnstile");
  317 SYSCTL_INT(_debug_deadlkres, OID_AUTO, sleepfreq, CTLFLAG_RW, &sleepfreq, 0,
  318     "Number of seconds between any deadlock resolver thread run");
  319 #endif  /* DEADLKRES */
  320 
  321 void
  322 read_cpu_time(long *cp_time)
  323 {
  324         struct pcpu *pc;
  325         int i, j;
  326 
  327         /* Sum up global cp_time[]. */
  328         bzero(cp_time, sizeof(long) * CPUSTATES);
  329         CPU_FOREACH(i) {
  330                 pc = pcpu_find(i);
  331                 for (j = 0; j < CPUSTATES; j++)
  332                         cp_time[j] += pc->pc_cp_time[j];
  333         }
  334 }
  335 
  336 #include <sys/watchdog.h>
  337 
  338 static int watchdog_ticks;
  339 static int watchdog_enabled;
  340 static void watchdog_fire(void);
  341 static void watchdog_config(void *, u_int, int *);
  342 
  343 static void
  344 watchdog_attach(void)
  345 {
  346         EVENTHANDLER_REGISTER(watchdog_list, watchdog_config, NULL, 0);
  347 }
  348 
  349 /*
  350  * Clock handling routines.
  351  *
  352  * This code is written to operate with two timers that run independently of
  353  * each other.
  354  *
  355  * The main timer, running hz times per second, is used to trigger interval
  356  * timers, timeouts and rescheduling as needed.
  357  *
  358  * The second timer handles kernel and user profiling,
  359  * and does resource use estimation.  If the second timer is programmable,
  360  * it is randomized to avoid aliasing between the two clocks.  For example,
  361  * the randomization prevents an adversary from always giving up the cpu
  362  * just before its quantum expires.  Otherwise, it would never accumulate
  363  * cpu ticks.  The mean frequency of the second timer is stathz.
  364  *
  365  * If no second timer exists, stathz will be zero; in this case we drive
  366  * profiling and statistics off the main clock.  This WILL NOT be accurate;
  367  * do not do it unless absolutely necessary.
  368  *
  369  * The statistics clock may (or may not) be run at a higher rate while
  370  * profiling.  This profile clock runs at profhz.  We require that profhz
  371  * be an integral multiple of stathz.
  372  *
  373  * If the statistics clock is running fast, it must be divided by the ratio
  374  * profhz/stathz for statistics.  (For profiling, every tick counts.)
  375  *
  376  * Time-of-day is maintained using a "timecounter", which may or may
  377  * not be related to the hardware generating the above mentioned
  378  * interrupts.
  379  */
  380 
  381 int     stathz;
  382 int     profhz;
  383 int     profprocs;
  384 volatile int    ticks;
  385 int     psratio;
  386 
  387 static DPCPU_DEFINE(int, pcputicks);    /* Per-CPU version of ticks. */
  388 #ifdef DEVICE_POLLING
  389 static int devpoll_run = 0;
  390 #endif
  391 
  392 /*
  393  * Initialize clock frequencies and start both clocks running.
  394  */
  395 /* ARGSUSED*/
  396 static void
  397 initclocks(void *dummy)
  398 {
  399         int i;
  400 
  401         /*
  402          * Set divisors to 1 (normal case) and let the machine-specific
  403          * code do its bit.
  404          */
  405         mtx_init(&time_lock, "time lock", NULL, MTX_DEF);
  406         cpu_initclocks();
  407 
  408         /*
  409          * Compute profhz/stathz, and fix profhz if needed.
  410          */
  411         i = stathz ? stathz : hz;
  412         if (profhz == 0)
  413                 profhz = i;
  414         psratio = profhz / i;
  415 
  416 #ifdef SW_WATCHDOG
  417         /* Enable hardclock watchdog now, even if a hardware watchdog exists. */
  418         watchdog_attach();
  419 #else
  420         /* Volunteer to run a software watchdog. */
  421         if (wdog_software_attach == NULL)
  422                 wdog_software_attach = watchdog_attach;
  423 #endif
  424 }
  425 
  426 /*
  427  * Each time the real-time timer fires, this function is called on all CPUs.
  428  * Note that hardclock() calls hardclock_cpu() for the boot CPU, so only
  429  * the other CPUs in the system need to call this function.
  430  */
  431 void
  432 hardclock_cpu(int usermode)
  433 {
  434         struct pstats *pstats;
  435         struct thread *td = curthread;
  436         struct proc *p = td->td_proc;
  437         int flags;
  438 
  439         /*
  440          * Run current process's virtual and profile time, as needed.
  441          */
  442         pstats = p->p_stats;
  443         flags = 0;
  444         if (usermode &&
  445             timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value)) {
  446                 PROC_ITIMLOCK(p);
  447                 if (itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0)
  448                         flags |= TDF_ALRMPEND | TDF_ASTPENDING;
  449                 PROC_ITIMUNLOCK(p);
  450         }
  451         if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value)) {
  452                 PROC_ITIMLOCK(p);
  453                 if (itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0)
  454                         flags |= TDF_PROFPEND | TDF_ASTPENDING;
  455                 PROC_ITIMUNLOCK(p);
  456         }
  457         thread_lock(td);
  458         td->td_flags |= flags;
  459         thread_unlock(td);
  460 
  461 #ifdef HWPMC_HOOKS
  462         if (PMC_CPU_HAS_SAMPLES(PCPU_GET(cpuid)))
  463                 PMC_CALL_HOOK_UNLOCKED(curthread, PMC_FN_DO_SAMPLES, NULL);
  464         if (td->td_intr_frame != NULL)
  465                 PMC_SOFT_CALL_TF( , , clock, hard, td->td_intr_frame);
  466 #endif
  467         callout_process(sbinuptime());
  468 }
  469 
  470 /*
  471  * The real-time timer, interrupting hz times per second.
  472  */
  473 void
  474 hardclock(int usermode, uintfptr_t pc)
  475 {
  476 
  477         atomic_add_int(&ticks, 1);
  478         hardclock_cpu(usermode);
  479         tc_ticktock(1);
  480         cpu_tick_calibration();
  481         /*
  482          * If no separate statistics clock is available, run it from here.
  483          *
  484          * XXX: this only works for UP
  485          */
  486         if (stathz == 0) {
  487                 profclock(usermode, pc);
  488                 statclock(usermode);
  489         }
  490 #ifdef DEVICE_POLLING
  491         hardclock_device_poll();        /* this is very short and quick */
  492 #endif /* DEVICE_POLLING */
  493         if (watchdog_enabled > 0 && --watchdog_ticks <= 0)
  494                 watchdog_fire();
  495 }
  496 
  497 void
  498 hardclock_cnt(int cnt, int usermode)
  499 {
  500         struct pstats *pstats;
  501         struct thread *td = curthread;
  502         struct proc *p = td->td_proc;
  503         int *t = DPCPU_PTR(pcputicks);
  504         int flags, global, newticks;
  505         int i;
  506 
  507         /*
  508          * Update per-CPU and possibly global ticks values.
  509          */
  510         *t += cnt;
  511         do {
  512                 global = ticks;
  513                 newticks = *t - global;
  514                 if (newticks <= 0) {
  515                         if (newticks < -1)
  516                                 *t = global - 1;
  517                         newticks = 0;
  518                         break;
  519                 }
  520         } while (!atomic_cmpset_int(&ticks, global, *t));
  521 
  522         /*
  523          * Run current process's virtual and profile time, as needed.
  524          */
  525         pstats = p->p_stats;
  526         flags = 0;
  527         if (usermode &&
  528             timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value)) {
  529                 PROC_ITIMLOCK(p);
  530                 if (itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL],
  531                     tick * cnt) == 0)
  532                         flags |= TDF_ALRMPEND | TDF_ASTPENDING;
  533                 PROC_ITIMUNLOCK(p);
  534         }
  535         if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value)) {
  536                 PROC_ITIMLOCK(p);
  537                 if (itimerdecr(&pstats->p_timer[ITIMER_PROF],
  538                     tick * cnt) == 0)
  539                         flags |= TDF_PROFPEND | TDF_ASTPENDING;
  540                 PROC_ITIMUNLOCK(p);
  541         }
  542         if (flags != 0) {
  543                 thread_lock(td);
  544                 td->td_flags |= flags;
  545                 thread_unlock(td);
  546         }
  547 
  548 #ifdef  HWPMC_HOOKS
  549         if (PMC_CPU_HAS_SAMPLES(PCPU_GET(cpuid)))
  550                 PMC_CALL_HOOK_UNLOCKED(curthread, PMC_FN_DO_SAMPLES, NULL);
  551         if (td->td_intr_frame != NULL)
  552                 PMC_SOFT_CALL_TF( , , clock, hard, td->td_intr_frame);
  553 #endif
  554         /* We are in charge to handle this tick duty. */
  555         if (newticks > 0) {
  556                 tc_ticktock(newticks);
  557 #ifdef DEVICE_POLLING
  558                 /* Dangerous and no need to call these things concurrently. */
  559                 if (atomic_cmpset_acq_int(&devpoll_run, 0, 1)) {
  560                         /* This is very short and quick. */
  561                         hardclock_device_poll();
  562                         atomic_store_rel_int(&devpoll_run, 0);
  563                 }
  564 #endif /* DEVICE_POLLING */
  565                 if (watchdog_enabled > 0) {
  566                         i = atomic_fetchadd_int(&watchdog_ticks, -newticks);
  567                         if (i > 0 && i <= newticks)
  568                                 watchdog_fire();
  569                 }
  570         }
  571         if (curcpu == CPU_FIRST())
  572                 cpu_tick_calibration();
  573 }
  574 
  575 void
  576 hardclock_sync(int cpu)
  577 {
  578         int     *t = DPCPU_ID_PTR(cpu, pcputicks);
  579 
  580         *t = ticks;
  581 }
  582 
  583 /*
  584  * Compute number of ticks in the specified amount of time.
  585  */
  586 int
  587 tvtohz(struct timeval *tv)
  588 {
  589         unsigned long ticks;
  590         long sec, usec;
  591 
  592         /*
  593          * If the number of usecs in the whole seconds part of the time
  594          * difference fits in a long, then the total number of usecs will
  595          * fit in an unsigned long.  Compute the total and convert it to
  596          * ticks, rounding up and adding 1 to allow for the current tick
  597          * to expire.  Rounding also depends on unsigned long arithmetic
  598          * to avoid overflow.
  599          *
  600          * Otherwise, if the number of ticks in the whole seconds part of
  601          * the time difference fits in a long, then convert the parts to
  602          * ticks separately and add, using similar rounding methods and
  603          * overflow avoidance.  This method would work in the previous
  604          * case but it is slightly slower and assumes that hz is integral.
  605          *
  606          * Otherwise, round the time difference down to the maximum
  607          * representable value.
  608          *
  609          * If ints have 32 bits, then the maximum value for any timeout in
  610          * 10ms ticks is 248 days.
  611          */
  612         sec = tv->tv_sec;
  613         usec = tv->tv_usec;
  614         if (usec < 0) {
  615                 sec--;
  616                 usec += 1000000;
  617         }
  618         if (sec < 0) {
  619 #ifdef DIAGNOSTIC
  620                 if (usec > 0) {
  621                         sec++;
  622                         usec -= 1000000;
  623                 }
  624                 printf("tvotohz: negative time difference %ld sec %ld usec\n",
  625                        sec, usec);
  626 #endif
  627                 ticks = 1;
  628         } else if (sec <= LONG_MAX / 1000000)
  629                 ticks = howmany(sec * 1000000 + (unsigned long)usec, tick) + 1;
  630         else if (sec <= LONG_MAX / hz)
  631                 ticks = sec * hz
  632                         + howmany((unsigned long)usec, tick) + 1;
  633         else
  634                 ticks = LONG_MAX;
  635         if (ticks > INT_MAX)
  636                 ticks = INT_MAX;
  637         return ((int)ticks);
  638 }
  639 
  640 /*
  641  * Start profiling on a process.
  642  *
  643  * Kernel profiling passes proc0 which never exits and hence
  644  * keeps the profile clock running constantly.
  645  */
  646 void
  647 startprofclock(struct proc *p)
  648 {
  649 
  650         PROC_LOCK_ASSERT(p, MA_OWNED);
  651         if (p->p_flag & P_STOPPROF)
  652                 return;
  653         if ((p->p_flag & P_PROFIL) == 0) {
  654                 p->p_flag |= P_PROFIL;
  655                 mtx_lock(&time_lock);
  656                 if (++profprocs == 1)
  657                         cpu_startprofclock();
  658                 mtx_unlock(&time_lock);
  659         }
  660 }
  661 
  662 /*
  663  * Stop profiling on a process.
  664  */
  665 void
  666 stopprofclock(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                         while (p->p_profthreads != 0) {
  673                                 p->p_flag |= P_STOPPROF;
  674                                 msleep(&p->p_profthreads, &p->p_mtx, PPAUSE,
  675                                     "stopprof", 0);
  676                         }
  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 static void
  845 watchdog_config(void *unused __unused, u_int cmd, int *error)
  846 {
  847         u_int u;
  848 
  849         u = cmd & WD_INTERVAL;
  850         if (u >= WD_TO_1SEC) {
  851                 watchdog_ticks = (1 << (u - WD_TO_1SEC)) * hz;
  852                 watchdog_enabled = 1;
  853                 *error = 0;
  854         } else {
  855                 watchdog_enabled = 0;
  856         }
  857 }
  858 
  859 /*
  860  * Handle a watchdog timeout by dumping interrupt information and
  861  * then either dropping to DDB or panicking.
  862  */
  863 static void
  864 watchdog_fire(void)
  865 {
  866         int nintr;
  867         uint64_t inttotal;
  868         u_long *curintr;
  869         char *curname;
  870 
  871         curintr = intrcnt;
  872         curname = intrnames;
  873         inttotal = 0;
  874         nintr = sintrcnt / sizeof(u_long);
  875 
  876         printf("interrupt                   total\n");
  877         while (--nintr >= 0) {
  878                 if (*curintr)
  879                         printf("%-12s %20lu\n", curname, *curintr);
  880                 curname += strlen(curname) + 1;
  881                 inttotal += *curintr++;
  882         }
  883         printf("Total        %20ju\n", (uintmax_t)inttotal);
  884 
  885 #if defined(KDB) && !defined(KDB_UNATTENDED)
  886         kdb_backtrace();
  887         kdb_enter(KDB_WHY_WATCHDOG, "watchdog timeout");
  888 #else
  889         panic("watchdog timeout");
  890 #endif
  891 }

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