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  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1982, 1986, 1991, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  * (c) UNIX System Laboratories, Inc.
    7  * All or some portions of this file are derived from material licensed
    8  * to the University of California by American Telephone and Telegraph
    9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   10  * the permission of UNIX System Laboratories, Inc.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  *      @(#)kern_clock.c        8.5 (Berkeley) 1/21/94
   37  */
   38 
   39 #include <sys/cdefs.h>
   40 __FBSDID("$FreeBSD: stable/12/sys/kern/kern_clock.c 338487 2018-09-06 02:10:59Z markj $");
   41 
   42 #include "opt_kdb.h"
   43 #include "opt_device_polling.h"
   44 #include "opt_hwpmc_hooks.h"
   45 #include "opt_ntp.h"
   46 #include "opt_watchdog.h"
   47 
   48 #include <sys/param.h>
   49 #include <sys/systm.h>
   50 #include <sys/callout.h>
   51 #include <sys/epoch.h>
   52 #include <sys/gtaskqueue.h>
   53 #include <sys/kdb.h>
   54 #include <sys/kernel.h>
   55 #include <sys/kthread.h>
   56 #include <sys/ktr.h>
   57 #include <sys/lock.h>
   58 #include <sys/mutex.h>
   59 #include <sys/proc.h>
   60 #include <sys/resource.h>
   61 #include <sys/resourcevar.h>
   62 #include <sys/sched.h>
   63 #include <sys/sdt.h>
   64 #include <sys/signalvar.h>
   65 #include <sys/sleepqueue.h>
   66 #include <sys/smp.h>
   67 #include <vm/vm.h>
   68 #include <vm/pmap.h>
   69 #include <vm/vm_map.h>
   70 #include <sys/sysctl.h>
   71 #include <sys/bus.h>
   72 #include <sys/interrupt.h>
   73 #include <sys/limits.h>
   74 #include <sys/timetc.h>
   75 
   76 #ifdef GPROF
   77 #include <sys/gmon.h>
   78 #endif
   79 
   80 #ifdef HWPMC_HOOKS
   81 #include <sys/pmckern.h>
   82 PMC_SOFT_DEFINE( , , clock, hard);
   83 PMC_SOFT_DEFINE( , , clock, stat);
   84 PMC_SOFT_DEFINE_EX( , , clock, prof, \
   85     cpu_startprofclock, cpu_stopprofclock);
   86 #endif
   87 
   88 #ifdef DEVICE_POLLING
   89 extern void hardclock_device_poll(void);
   90 #endif /* DEVICE_POLLING */
   91 
   92 static void initclocks(void *dummy);
   93 SYSINIT(clocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, initclocks, NULL);
   94 
   95 /* Spin-lock protecting profiling statistics. */
   96 static struct mtx time_lock;
   97 
   98 SDT_PROVIDER_DECLARE(sched);
   99 SDT_PROBE_DEFINE2(sched, , , tick, "struct thread *", "struct proc *");
  100 
  101 static int
  102 sysctl_kern_cp_time(SYSCTL_HANDLER_ARGS)
  103 {
  104         int error;
  105         long cp_time[CPUSTATES];
  106 #ifdef SCTL_MASK32
  107         int i;
  108         unsigned int cp_time32[CPUSTATES];
  109 #endif
  110 
  111         read_cpu_time(cp_time);
  112 #ifdef SCTL_MASK32
  113         if (req->flags & SCTL_MASK32) {
  114                 if (!req->oldptr)
  115                         return SYSCTL_OUT(req, 0, sizeof(cp_time32));
  116                 for (i = 0; i < CPUSTATES; i++)
  117                         cp_time32[i] = (unsigned int)cp_time[i];
  118                 error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  119         } else
  120 #endif
  121         {
  122                 if (!req->oldptr)
  123                         return SYSCTL_OUT(req, 0, sizeof(cp_time));
  124                 error = SYSCTL_OUT(req, cp_time, sizeof(cp_time));
  125         }
  126         return error;
  127 }
  128 
  129 SYSCTL_PROC(_kern, OID_AUTO, cp_time, CTLTYPE_LONG|CTLFLAG_RD|CTLFLAG_MPSAFE,
  130     0,0, sysctl_kern_cp_time, "LU", "CPU time statistics");
  131 
  132 static long empty[CPUSTATES];
  133 
  134 static int
  135 sysctl_kern_cp_times(SYSCTL_HANDLER_ARGS)
  136 {
  137         struct pcpu *pcpu;
  138         int error;
  139         int c;
  140         long *cp_time;
  141 #ifdef SCTL_MASK32
  142         unsigned int cp_time32[CPUSTATES];
  143         int i;
  144 #endif
  145 
  146         if (!req->oldptr) {
  147 #ifdef SCTL_MASK32
  148                 if (req->flags & SCTL_MASK32)
  149                         return SYSCTL_OUT(req, 0, sizeof(cp_time32) * (mp_maxid + 1));
  150                 else
  151 #endif
  152                         return SYSCTL_OUT(req, 0, sizeof(long) * CPUSTATES * (mp_maxid + 1));
  153         }
  154         for (error = 0, c = 0; error == 0 && c <= mp_maxid; c++) {
  155                 if (!CPU_ABSENT(c)) {
  156                         pcpu = pcpu_find(c);
  157                         cp_time = pcpu->pc_cp_time;
  158                 } else {
  159                         cp_time = empty;
  160                 }
  161 #ifdef SCTL_MASK32
  162                 if (req->flags & SCTL_MASK32) {
  163                         for (i = 0; i < CPUSTATES; i++)
  164                                 cp_time32[i] = (unsigned int)cp_time[i];
  165                         error = SYSCTL_OUT(req, cp_time32, sizeof(cp_time32));
  166                 } else
  167 #endif
  168                         error = SYSCTL_OUT(req, cp_time, sizeof(long) * CPUSTATES);
  169         }
  170         return error;
  171 }
  172 
  173 SYSCTL_PROC(_kern, OID_AUTO, cp_times, CTLTYPE_LONG|CTLFLAG_RD|CTLFLAG_MPSAFE,
  174     0,0, sysctl_kern_cp_times, "LU", "per-CPU time statistics");
  175 
  176 #ifdef DEADLKRES
  177 static const char *blessed[] = {
  178         "getblk",
  179         "so_snd_sx",
  180         "so_rcv_sx",
  181         NULL
  182 };
  183 static int slptime_threshold = 1800;
  184 static int blktime_threshold = 900;
  185 static int sleepfreq = 3;
  186 
  187 static void
  188 deadlres_td_on_lock(struct proc *p, struct thread *td, int blkticks)
  189 {
  190         int tticks;
  191 
  192         sx_assert(&allproc_lock, SX_LOCKED);
  193         PROC_LOCK_ASSERT(p, MA_OWNED);
  194         THREAD_LOCK_ASSERT(td, MA_OWNED);
  195         /*
  196          * The thread should be blocked on a turnstile, simply check
  197          * if the turnstile channel is in good state.
  198          */
  199         MPASS(td->td_blocked != NULL);
  200 
  201         tticks = ticks - td->td_blktick;
  202         if (tticks > blkticks)
  203                 /*
  204                  * Accordingly with provided thresholds, this thread is stuck
  205                  * for too long on a turnstile.
  206                  */
  207                 panic("%s: possible deadlock detected for %p, "
  208                     "blocked for %d ticks\n", __func__, td, tticks);
  209 }
  210 
  211 static void
  212 deadlres_td_sleep_q(struct proc *p, struct thread *td, int slpticks)
  213 {
  214         void *wchan;
  215         int i, slptype, tticks;
  216 
  217         sx_assert(&allproc_lock, SX_LOCKED);
  218         PROC_LOCK_ASSERT(p, MA_OWNED);
  219         THREAD_LOCK_ASSERT(td, MA_OWNED);
  220         /*
  221          * Check if the thread is sleeping on a lock, otherwise skip the check.
  222          * Drop the thread lock in order to avoid a LOR with the sleepqueue
  223          * spinlock.
  224          */
  225         wchan = td->td_wchan;
  226         tticks = ticks - td->td_slptick;
  227         slptype = sleepq_type(wchan);
  228         if ((slptype == SLEEPQ_SX || slptype == SLEEPQ_LK) &&
  229             tticks > slpticks) {
  230 
  231                 /*
  232                  * Accordingly with provided thresholds, this thread is stuck
  233                  * for too long on a sleepqueue.
  234                  * However, being on a sleepqueue, we might still check for the
  235                  * blessed list.
  236                  */
  237                 for (i = 0; blessed[i] != NULL; i++)
  238                         if (!strcmp(blessed[i], td->td_wmesg))
  239                                 return;
  240 
  241                 panic("%s: possible deadlock detected for %p, "
  242                     "blocked for %d ticks\n", __func__, td, tticks);
  243         }
  244 }
  245 
  246 static void
  247 deadlkres(void)
  248 {
  249         struct proc *p;
  250         struct thread *td;
  251         int blkticks, slpticks, tryl;
  252 
  253         tryl = 0;
  254         for (;;) {
  255                 blkticks = blktime_threshold * hz;
  256                 slpticks = slptime_threshold * hz;
  257 
  258                 /*
  259                  * Avoid to sleep on the sx_lock in order to avoid a
  260                  * possible priority inversion problem leading to
  261                  * starvation.
  262                  * If the lock can't be held after 100 tries, panic.
  263                  */
  264                 if (!sx_try_slock(&allproc_lock)) {
  265                         if (tryl > 100)
  266                                 panic("%s: possible deadlock detected "
  267                                     "on allproc_lock\n", __func__);
  268                         tryl++;
  269                         pause("allproc", sleepfreq * hz);
  270                         continue;
  271                 }
  272                 tryl = 0;
  273                 FOREACH_PROC_IN_SYSTEM(p) {
  274                         PROC_LOCK(p);
  275                         if (p->p_state == PRS_NEW) {
  276                                 PROC_UNLOCK(p);
  277                                 continue;
  278                         }
  279                         FOREACH_THREAD_IN_PROC(p, td) {
  280                                 thread_lock(td);
  281                                 if (TD_ON_LOCK(td))
  282                                         deadlres_td_on_lock(p, td,
  283                                             blkticks);
  284                                 else if (TD_IS_SLEEPING(td) &&
  285                                     TD_ON_SLEEPQ(td))
  286                                         deadlres_td_sleep_q(p, td,
  287                                             slpticks);
  288                                 thread_unlock(td);
  289                         }
  290                         PROC_UNLOCK(p);
  291                 }
  292                 sx_sunlock(&allproc_lock);
  293 
  294                 /* Sleep for sleepfreq seconds. */
  295                 pause("-", sleepfreq * hz);
  296         }
  297 }
  298 
  299 static struct kthread_desc deadlkres_kd = {
  300         "deadlkres",
  301         deadlkres,
  302         (struct thread **)NULL
  303 };
  304 
  305 SYSINIT(deadlkres, SI_SUB_CLOCKS, SI_ORDER_ANY, kthread_start, &deadlkres_kd);
  306 
  307 static SYSCTL_NODE(_debug, OID_AUTO, deadlkres, CTLFLAG_RW, 0,
  308     "Deadlock resolver");
  309 SYSCTL_INT(_debug_deadlkres, OID_AUTO, slptime_threshold, CTLFLAG_RW,
  310     &slptime_threshold, 0,
  311     "Number of seconds within is valid to sleep on a sleepqueue");
  312 SYSCTL_INT(_debug_deadlkres, OID_AUTO, blktime_threshold, CTLFLAG_RW,
  313     &blktime_threshold, 0,
  314     "Number of seconds within is valid to block on a turnstile");
  315 SYSCTL_INT(_debug_deadlkres, OID_AUTO, sleepfreq, CTLFLAG_RW, &sleepfreq, 0,
  316     "Number of seconds between any deadlock resolver thread run");
  317 #endif  /* DEADLKRES */
  318 
  319 void
  320 read_cpu_time(long *cp_time)
  321 {
  322         struct pcpu *pc;
  323         int i, j;
  324 
  325         /* Sum up global cp_time[]. */
  326         bzero(cp_time, sizeof(long) * CPUSTATES);
  327         CPU_FOREACH(i) {
  328                 pc = pcpu_find(i);
  329                 for (j = 0; j < CPUSTATES; j++)
  330                         cp_time[j] += pc->pc_cp_time[j];
  331         }
  332 }
  333 
  334 #include <sys/watchdog.h>
  335 
  336 static int watchdog_ticks;
  337 static int watchdog_enabled;
  338 static void watchdog_fire(void);
  339 static void watchdog_config(void *, u_int, int *);
  340 
  341 static void
  342 watchdog_attach(void)
  343 {
  344         EVENTHANDLER_REGISTER(watchdog_list, watchdog_config, NULL, 0);
  345 }
  346 
  347 /*
  348  * Clock handling routines.
  349  *
  350  * This code is written to operate with two timers that run independently of
  351  * each other.
  352  *
  353  * The main timer, running hz times per second, is used to trigger interval
  354  * timers, timeouts and rescheduling as needed.
  355  *
  356  * The second timer handles kernel and user profiling,
  357  * and does resource use estimation.  If the second timer is programmable,
  358  * it is randomized to avoid aliasing between the two clocks.  For example,
  359  * the randomization prevents an adversary from always giving up the cpu
  360  * just before its quantum expires.  Otherwise, it would never accumulate
  361  * cpu ticks.  The mean frequency of the second timer is stathz.
  362  *
  363  * If no second timer exists, stathz will be zero; in this case we drive
  364  * profiling and statistics off the main clock.  This WILL NOT be accurate;
  365  * do not do it unless absolutely necessary.
  366  *
  367  * The statistics clock may (or may not) be run at a higher rate while
  368  * profiling.  This profile clock runs at profhz.  We require that profhz
  369  * be an integral multiple of stathz.
  370  *
  371  * If the statistics clock is running fast, it must be divided by the ratio
  372  * profhz/stathz for statistics.  (For profiling, every tick counts.)
  373  *
  374  * Time-of-day is maintained using a "timecounter", which may or may
  375  * not be related to the hardware generating the above mentioned
  376  * interrupts.
  377  */
  378 
  379 int     stathz;
  380 int     profhz;
  381 int     profprocs;
  382 volatile int    ticks;
  383 int     psratio;
  384 
  385 DPCPU_DEFINE_STATIC(int, pcputicks);    /* Per-CPU version of ticks. */
  386 #ifdef DEVICE_POLLING
  387 static int devpoll_run = 0;
  388 #endif
  389 
  390 /*
  391  * Initialize clock frequencies and start both clocks running.
  392  */
  393 /* ARGSUSED*/
  394 static void
  395 initclocks(void *dummy)
  396 {
  397         int i;
  398 
  399         /*
  400          * Set divisors to 1 (normal case) and let the machine-specific
  401          * code do its bit.
  402          */
  403         mtx_init(&time_lock, "time lock", NULL, MTX_DEF);
  404         cpu_initclocks();
  405 
  406         /*
  407          * Compute profhz/stathz, and fix profhz if needed.
  408          */
  409         i = stathz ? stathz : hz;
  410         if (profhz == 0)
  411                 profhz = i;
  412         psratio = profhz / i;
  413 
  414 #ifdef SW_WATCHDOG
  415         /* Enable hardclock watchdog now, even if a hardware watchdog exists. */
  416         watchdog_attach();
  417 #else
  418         /* Volunteer to run a software watchdog. */
  419         if (wdog_software_attach == NULL)
  420                 wdog_software_attach = watchdog_attach;
  421 #endif
  422 }
  423 
  424 void
  425 hardclock(int cnt, int usermode)
  426 {
  427         struct pstats *pstats;
  428         struct thread *td = curthread;
  429         struct proc *p = td->td_proc;
  430         int *t = DPCPU_PTR(pcputicks);
  431         int flags, global, newticks;
  432         int i;
  433 
  434         /*
  435          * Update per-CPU and possibly global ticks values.
  436          */
  437         *t += cnt;
  438         do {
  439                 global = ticks;
  440                 newticks = *t - global;
  441                 if (newticks <= 0) {
  442                         if (newticks < -1)
  443                                 *t = global - 1;
  444                         newticks = 0;
  445                         break;
  446                 }
  447         } while (!atomic_cmpset_int(&ticks, global, *t));
  448 
  449         /*
  450          * Run current process's virtual and profile time, as needed.
  451          */
  452         pstats = p->p_stats;
  453         flags = 0;
  454         if (usermode &&
  455             timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value)) {
  456                 PROC_ITIMLOCK(p);
  457                 if (itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL],
  458                     tick * cnt) == 0)
  459                         flags |= TDF_ALRMPEND | TDF_ASTPENDING;
  460                 PROC_ITIMUNLOCK(p);
  461         }
  462         if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value)) {
  463                 PROC_ITIMLOCK(p);
  464                 if (itimerdecr(&pstats->p_timer[ITIMER_PROF],
  465                     tick * cnt) == 0)
  466                         flags |= TDF_PROFPEND | TDF_ASTPENDING;
  467                 PROC_ITIMUNLOCK(p);
  468         }
  469         if (flags != 0) {
  470                 thread_lock(td);
  471                 td->td_flags |= flags;
  472                 thread_unlock(td);
  473         }
  474 
  475 #ifdef  HWPMC_HOOKS
  476         if (PMC_CPU_HAS_SAMPLES(PCPU_GET(cpuid)))
  477                 PMC_CALL_HOOK_UNLOCKED(curthread, PMC_FN_DO_SAMPLES, NULL);
  478         if (td->td_intr_frame != NULL)
  479                 PMC_SOFT_CALL_TF( , , clock, hard, td->td_intr_frame);
  480 #endif
  481         /* We are in charge to handle this tick duty. */
  482         if (newticks > 0) {
  483                 tc_ticktock(newticks);
  484 #ifdef DEVICE_POLLING
  485                 /* Dangerous and no need to call these things concurrently. */
  486                 if (atomic_cmpset_acq_int(&devpoll_run, 0, 1)) {
  487                         /* This is very short and quick. */
  488                         hardclock_device_poll();
  489                         atomic_store_rel_int(&devpoll_run, 0);
  490                 }
  491 #endif /* DEVICE_POLLING */
  492                 if (watchdog_enabled > 0) {
  493                         i = atomic_fetchadd_int(&watchdog_ticks, -newticks);
  494                         if (i > 0 && i <= newticks)
  495                                 watchdog_fire();
  496                 }
  497         }
  498         if (curcpu == CPU_FIRST())
  499                 cpu_tick_calibration();
  500         if (__predict_false(DPCPU_GET(epoch_cb_count)))
  501                 GROUPTASK_ENQUEUE(DPCPU_PTR(epoch_cb_task));
  502 }
  503 
  504 void
  505 hardclock_sync(int cpu)
  506 {
  507         int *t;
  508         KASSERT(!CPU_ABSENT(cpu), ("Absent CPU %d", cpu));
  509         t = DPCPU_ID_PTR(cpu, pcputicks);
  510 
  511         *t = ticks;
  512 }
  513 
  514 /*
  515  * Compute number of ticks in the specified amount of time.
  516  */
  517 int
  518 tvtohz(struct timeval *tv)
  519 {
  520         unsigned long ticks;
  521         long sec, usec;
  522 
  523         /*
  524          * If the number of usecs in the whole seconds part of the time
  525          * difference fits in a long, then the total number of usecs will
  526          * fit in an unsigned long.  Compute the total and convert it to
  527          * ticks, rounding up and adding 1 to allow for the current tick
  528          * to expire.  Rounding also depends on unsigned long arithmetic
  529          * to avoid overflow.
  530          *
  531          * Otherwise, if the number of ticks in the whole seconds part of
  532          * the time difference fits in a long, then convert the parts to
  533          * ticks separately and add, using similar rounding methods and
  534          * overflow avoidance.  This method would work in the previous
  535          * case but it is slightly slower and assumes that hz is integral.
  536          *
  537          * Otherwise, round the time difference down to the maximum
  538          * representable value.
  539          *
  540          * If ints have 32 bits, then the maximum value for any timeout in
  541          * 10ms ticks is 248 days.
  542          */
  543         sec = tv->tv_sec;
  544         usec = tv->tv_usec;
  545         if (usec < 0) {
  546                 sec--;
  547                 usec += 1000000;
  548         }
  549         if (sec < 0) {
  550 #ifdef DIAGNOSTIC
  551                 if (usec > 0) {
  552                         sec++;
  553                         usec -= 1000000;
  554                 }
  555                 printf("tvotohz: negative time difference %ld sec %ld usec\n",
  556                        sec, usec);
  557 #endif
  558                 ticks = 1;
  559         } else if (sec <= LONG_MAX / 1000000)
  560                 ticks = howmany(sec * 1000000 + (unsigned long)usec, tick) + 1;
  561         else if (sec <= LONG_MAX / hz)
  562                 ticks = sec * hz
  563                         + howmany((unsigned long)usec, tick) + 1;
  564         else
  565                 ticks = LONG_MAX;
  566         if (ticks > INT_MAX)
  567                 ticks = INT_MAX;
  568         return ((int)ticks);
  569 }
  570 
  571 /*
  572  * Start profiling on a process.
  573  *
  574  * Kernel profiling passes proc0 which never exits and hence
  575  * keeps the profile clock running constantly.
  576  */
  577 void
  578 startprofclock(struct proc *p)
  579 {
  580 
  581         PROC_LOCK_ASSERT(p, MA_OWNED);
  582         if (p->p_flag & P_STOPPROF)
  583                 return;
  584         if ((p->p_flag & P_PROFIL) == 0) {
  585                 p->p_flag |= P_PROFIL;
  586                 mtx_lock(&time_lock);
  587                 if (++profprocs == 1)
  588                         cpu_startprofclock();
  589                 mtx_unlock(&time_lock);
  590         }
  591 }
  592 
  593 /*
  594  * Stop profiling on a process.
  595  */
  596 void
  597 stopprofclock(struct proc *p)
  598 {
  599 
  600         PROC_LOCK_ASSERT(p, MA_OWNED);
  601         if (p->p_flag & P_PROFIL) {
  602                 if (p->p_profthreads != 0) {
  603                         while (p->p_profthreads != 0) {
  604                                 p->p_flag |= P_STOPPROF;
  605                                 msleep(&p->p_profthreads, &p->p_mtx, PPAUSE,
  606                                     "stopprof", 0);
  607                         }
  608                 }
  609                 if ((p->p_flag & P_PROFIL) == 0)
  610                         return;
  611                 p->p_flag &= ~P_PROFIL;
  612                 mtx_lock(&time_lock);
  613                 if (--profprocs == 0)
  614                         cpu_stopprofclock();
  615                 mtx_unlock(&time_lock);
  616         }
  617 }
  618 
  619 /*
  620  * Statistics clock.  Updates rusage information and calls the scheduler
  621  * to adjust priorities of the active thread.
  622  *
  623  * This should be called by all active processors.
  624  */
  625 void
  626 statclock(int cnt, int usermode)
  627 {
  628         struct rusage *ru;
  629         struct vmspace *vm;
  630         struct thread *td;
  631         struct proc *p;
  632         long rss;
  633         long *cp_time;
  634 
  635         td = curthread;
  636         p = td->td_proc;
  637 
  638         cp_time = (long *)PCPU_PTR(cp_time);
  639         if (usermode) {
  640                 /*
  641                  * Charge the time as appropriate.
  642                  */
  643                 td->td_uticks += cnt;
  644                 if (p->p_nice > NZERO)
  645                         cp_time[CP_NICE] += cnt;
  646                 else
  647                         cp_time[CP_USER] += cnt;
  648         } else {
  649                 /*
  650                  * Came from kernel mode, so we were:
  651                  * - handling an interrupt,
  652                  * - doing syscall or trap work on behalf of the current
  653                  *   user process, or
  654                  * - spinning in the idle loop.
  655                  * Whichever it is, charge the time as appropriate.
  656                  * Note that we charge interrupts to the current process,
  657                  * regardless of whether they are ``for'' that process,
  658                  * so that we know how much of its real time was spent
  659                  * in ``non-process'' (i.e., interrupt) work.
  660                  */
  661                 if ((td->td_pflags & TDP_ITHREAD) ||
  662                     td->td_intr_nesting_level >= 2) {
  663                         td->td_iticks += cnt;
  664                         cp_time[CP_INTR] += cnt;
  665                 } else {
  666                         td->td_pticks += cnt;
  667                         td->td_sticks += cnt;
  668                         if (!TD_IS_IDLETHREAD(td))
  669                                 cp_time[CP_SYS] += cnt;
  670                         else
  671                                 cp_time[CP_IDLE] += cnt;
  672                 }
  673         }
  674 
  675         /* Update resource usage integrals and maximums. */
  676         MPASS(p->p_vmspace != NULL);
  677         vm = p->p_vmspace;
  678         ru = &td->td_ru;
  679         ru->ru_ixrss += pgtok(vm->vm_tsize) * cnt;
  680         ru->ru_idrss += pgtok(vm->vm_dsize) * cnt;
  681         ru->ru_isrss += pgtok(vm->vm_ssize) * cnt;
  682         rss = pgtok(vmspace_resident_count(vm));
  683         if (ru->ru_maxrss < rss)
  684                 ru->ru_maxrss = rss;
  685         KTR_POINT2(KTR_SCHED, "thread", sched_tdname(td), "statclock",
  686             "prio:%d", td->td_priority, "stathz:%d", (stathz)?stathz:hz);
  687         SDT_PROBE2(sched, , , tick, td, td->td_proc);
  688         thread_lock_flags(td, MTX_QUIET);
  689         for ( ; cnt > 0; cnt--)
  690                 sched_clock(td);
  691         thread_unlock(td);
  692 #ifdef HWPMC_HOOKS
  693         if (td->td_intr_frame != NULL)
  694                 PMC_SOFT_CALL_TF( , , clock, stat, td->td_intr_frame);
  695 #endif
  696 }
  697 
  698 void
  699 profclock(int cnt, int usermode, uintfptr_t pc)
  700 {
  701         struct thread *td;
  702 #ifdef GPROF
  703         struct gmonparam *g;
  704         uintfptr_t i;
  705 #endif
  706 
  707         td = curthread;
  708         if (usermode) {
  709                 /*
  710                  * Came from user mode; CPU was in user state.
  711                  * If this process is being profiled, record the tick.
  712                  * if there is no related user location yet, don't
  713                  * bother trying to count it.
  714                  */
  715                 if (td->td_proc->p_flag & P_PROFIL)
  716                         addupc_intr(td, pc, cnt);
  717         }
  718 #ifdef GPROF
  719         else {
  720                 /*
  721                  * Kernel statistics are just like addupc_intr, only easier.
  722                  */
  723                 g = &_gmonparam;
  724                 if (g->state == GMON_PROF_ON && pc >= g->lowpc) {
  725                         i = PC_TO_I(g, pc);
  726                         if (i < g->textsize) {
  727                                 KCOUNT(g, i) += cnt;
  728                         }
  729                 }
  730         }
  731 #endif
  732 #ifdef HWPMC_HOOKS
  733         if (td->td_intr_frame != NULL)
  734                 PMC_SOFT_CALL_TF( , , clock, prof, td->td_intr_frame);
  735 #endif
  736 }
  737 
  738 /*
  739  * Return information about system clocks.
  740  */
  741 static int
  742 sysctl_kern_clockrate(SYSCTL_HANDLER_ARGS)
  743 {
  744         struct clockinfo clkinfo;
  745         /*
  746          * Construct clockinfo structure.
  747          */
  748         bzero(&clkinfo, sizeof(clkinfo));
  749         clkinfo.hz = hz;
  750         clkinfo.tick = tick;
  751         clkinfo.profhz = profhz;
  752         clkinfo.stathz = stathz ? stathz : hz;
  753         return (sysctl_handle_opaque(oidp, &clkinfo, sizeof clkinfo, req));
  754 }
  755 
  756 SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate,
  757         CTLTYPE_STRUCT|CTLFLAG_RD|CTLFLAG_MPSAFE,
  758         0, 0, sysctl_kern_clockrate, "S,clockinfo",
  759         "Rate and period of various kernel clocks");
  760 
  761 static void
  762 watchdog_config(void *unused __unused, u_int cmd, int *error)
  763 {
  764         u_int u;
  765 
  766         u = cmd & WD_INTERVAL;
  767         if (u >= WD_TO_1SEC) {
  768                 watchdog_ticks = (1 << (u - WD_TO_1SEC)) * hz;
  769                 watchdog_enabled = 1;
  770                 *error = 0;
  771         } else {
  772                 watchdog_enabled = 0;
  773         }
  774 }
  775 
  776 /*
  777  * Handle a watchdog timeout by dumping interrupt information and
  778  * then either dropping to DDB or panicking.
  779  */
  780 static void
  781 watchdog_fire(void)
  782 {
  783         int nintr;
  784         uint64_t inttotal;
  785         u_long *curintr;
  786         char *curname;
  787 
  788         curintr = intrcnt;
  789         curname = intrnames;
  790         inttotal = 0;
  791         nintr = sintrcnt / sizeof(u_long);
  792 
  793         printf("interrupt                   total\n");
  794         while (--nintr >= 0) {
  795                 if (*curintr)
  796                         printf("%-12s %20lu\n", curname, *curintr);
  797                 curname += strlen(curname) + 1;
  798                 inttotal += *curintr++;
  799         }
  800         printf("Total        %20ju\n", (uintmax_t)inttotal);
  801 
  802 #if defined(KDB) && !defined(KDB_UNATTENDED)
  803         kdb_backtrace();
  804         kdb_enter(KDB_WHY_WATCHDOG, "watchdog timeout");
  805 #else
  806         panic("watchdog timeout");
  807 #endif
  808 }

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