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


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FreeBSD/Linux Kernel Cross Reference
sys/kern/sched_4bsd.c

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1990, 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 
   35 #include <sys/cdefs.h>
   36 __FBSDID("$FreeBSD: stable/10/sys/kern/sched_4bsd.c 316841 2017-04-14 14:44:06Z avg $");
   37 
   38 #include "opt_hwpmc_hooks.h"
   39 #include "opt_sched.h"
   40 #include "opt_kdtrace.h"
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/cpuset.h>
   45 #include <sys/kernel.h>
   46 #include <sys/ktr.h>
   47 #include <sys/lock.h>
   48 #include <sys/kthread.h>
   49 #include <sys/mutex.h>
   50 #include <sys/proc.h>
   51 #include <sys/resourcevar.h>
   52 #include <sys/sched.h>
   53 #include <sys/sdt.h>
   54 #include <sys/smp.h>
   55 #include <sys/sysctl.h>
   56 #include <sys/sx.h>
   57 #include <sys/turnstile.h>
   58 #include <sys/umtx.h>
   59 #include <machine/pcb.h>
   60 #include <machine/smp.h>
   61 
   62 #ifdef HWPMC_HOOKS
   63 #include <sys/pmckern.h>
   64 #endif
   65 
   66 #ifdef KDTRACE_HOOKS
   67 #include <sys/dtrace_bsd.h>
   68 int                             dtrace_vtime_active;
   69 dtrace_vtime_switch_func_t      dtrace_vtime_switch_func;
   70 #endif
   71 
   72 /*
   73  * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in
   74  * the range 100-256 Hz (approximately).
   75  */
   76 #define ESTCPULIM(e) \
   77     min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \
   78     RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1)
   79 #ifdef SMP
   80 #define INVERSE_ESTCPU_WEIGHT   (8 * smp_cpus)
   81 #else
   82 #define INVERSE_ESTCPU_WEIGHT   8       /* 1 / (priorities per estcpu level). */
   83 #endif
   84 #define NICE_WEIGHT             1       /* Priorities per nice level. */
   85 
   86 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
   87 
   88 /*
   89  * The schedulable entity that runs a context.
   90  * This is  an extension to the thread structure and is tailored to
   91  * the requirements of this scheduler
   92  */
   93 struct td_sched {
   94         fixpt_t         ts_pctcpu;      /* (j) %cpu during p_swtime. */
   95         int             ts_cpticks;     /* (j) Ticks of cpu time. */
   96         int             ts_slptime;     /* (j) Seconds !RUNNING. */
   97         int             ts_slice;       /* Remaining part of time slice. */
   98         int             ts_flags;
   99         struct runq     *ts_runq;       /* runq the thread is currently on */
  100 #ifdef KTR
  101         char            ts_name[TS_NAME_LEN];
  102 #endif
  103 };
  104 
  105 /* flags kept in td_flags */
  106 #define TDF_DIDRUN      TDF_SCHED0      /* thread actually ran. */
  107 #define TDF_BOUND       TDF_SCHED1      /* Bound to one CPU. */
  108 #define TDF_SLICEEND    TDF_SCHED2      /* Thread time slice is over. */
  109 
  110 /* flags kept in ts_flags */
  111 #define TSF_AFFINITY    0x0001          /* Has a non-"full" CPU set. */
  112 
  113 #define SKE_RUNQ_PCPU(ts)                                               \
  114     ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq)
  115 
  116 #define THREAD_CAN_SCHED(td, cpu)       \
  117     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
  118 
  119 static struct td_sched td_sched0;
  120 struct mtx sched_lock;
  121 
  122 static int      realstathz = 127; /* stathz is sometimes 0 and run off of hz. */
  123 static int      sched_tdcnt;    /* Total runnable threads in the system. */
  124 static int      sched_slice = 12; /* Thread run time before rescheduling. */
  125 
  126 static void     setup_runqs(void);
  127 static void     schedcpu(void);
  128 static void     schedcpu_thread(void);
  129 static void     sched_priority(struct thread *td, u_char prio);
  130 static void     sched_setup(void *dummy);
  131 static void     maybe_resched(struct thread *td);
  132 static void     updatepri(struct thread *td);
  133 static void     resetpriority(struct thread *td);
  134 static void     resetpriority_thread(struct thread *td);
  135 #ifdef SMP
  136 static int      sched_pickcpu(struct thread *td);
  137 static int      forward_wakeup(int cpunum);
  138 static void     kick_other_cpu(int pri, int cpuid);
  139 #endif
  140 
  141 static struct kproc_desc sched_kp = {
  142         "schedcpu",
  143         schedcpu_thread,
  144         NULL
  145 };
  146 SYSINIT(schedcpu, SI_SUB_LAST, SI_ORDER_FIRST, kproc_start,
  147     &sched_kp);
  148 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  149 
  150 static void sched_initticks(void *dummy);
  151 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  152     NULL);
  153 
  154 /*
  155  * Global run queue.
  156  */
  157 static struct runq runq;
  158 
  159 #ifdef SMP
  160 /*
  161  * Per-CPU run queues
  162  */
  163 static struct runq runq_pcpu[MAXCPU];
  164 long runq_length[MAXCPU];
  165 
  166 static cpuset_t idle_cpus_mask;
  167 #endif
  168 
  169 struct pcpuidlestat {
  170         u_int idlecalls;
  171         u_int oldidlecalls;
  172 };
  173 static DPCPU_DEFINE(struct pcpuidlestat, idlestat);
  174 
  175 static void
  176 setup_runqs(void)
  177 {
  178 #ifdef SMP
  179         int i;
  180 
  181         for (i = 0; i < MAXCPU; ++i)
  182                 runq_init(&runq_pcpu[i]);
  183 #endif
  184 
  185         runq_init(&runq);
  186 }
  187 
  188 static int
  189 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
  190 {
  191         int error, new_val, period;
  192 
  193         period = 1000000 / realstathz;
  194         new_val = period * sched_slice;
  195         error = sysctl_handle_int(oidp, &new_val, 0, req);
  196         if (error != 0 || req->newptr == NULL)
  197                 return (error);
  198         if (new_val <= 0)
  199                 return (EINVAL);
  200         sched_slice = imax(1, (new_val + period / 2) / period);
  201         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
  202             realstathz);
  203         return (0);
  204 }
  205 
  206 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD, 0, "Scheduler");
  207 
  208 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0,
  209     "Scheduler name");
  210 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
  211     NULL, 0, sysctl_kern_quantum, "I",
  212     "Quantum for timeshare threads in microseconds");
  213 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
  214     "Quantum for timeshare threads in stathz ticks");
  215 #ifdef SMP
  216 /* Enable forwarding of wakeups to all other cpus */
  217 static SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup, CTLFLAG_RD, NULL,
  218     "Kernel SMP");
  219 
  220 static int runq_fuzz = 1;
  221 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
  222 
  223 static int forward_wakeup_enabled = 1;
  224 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW,
  225            &forward_wakeup_enabled, 0,
  226            "Forwarding of wakeup to idle CPUs");
  227 
  228 static int forward_wakeups_requested = 0;
  229 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD,
  230            &forward_wakeups_requested, 0,
  231            "Requests for Forwarding of wakeup to idle CPUs");
  232 
  233 static int forward_wakeups_delivered = 0;
  234 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD,
  235            &forward_wakeups_delivered, 0,
  236            "Completed Forwarding of wakeup to idle CPUs");
  237 
  238 static int forward_wakeup_use_mask = 1;
  239 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW,
  240            &forward_wakeup_use_mask, 0,
  241            "Use the mask of idle cpus");
  242 
  243 static int forward_wakeup_use_loop = 0;
  244 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW,
  245            &forward_wakeup_use_loop, 0,
  246            "Use a loop to find idle cpus");
  247 
  248 #endif
  249 #if 0
  250 static int sched_followon = 0;
  251 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW,
  252            &sched_followon, 0,
  253            "allow threads to share a quantum");
  254 #endif
  255 
  256 SDT_PROVIDER_DEFINE(sched);
  257 
  258 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 
  259     "struct proc *", "uint8_t");
  260 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 
  261     "struct proc *", "void *");
  262 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 
  263     "struct proc *", "void *", "int");
  264 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 
  265     "struct proc *", "uint8_t", "struct thread *");
  266 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
  267 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
  268     "struct proc *");
  269 SDT_PROBE_DEFINE(sched, , , on__cpu);
  270 SDT_PROBE_DEFINE(sched, , , remain__cpu);
  271 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
  272     "struct proc *");
  273 
  274 static __inline void
  275 sched_load_add(void)
  276 {
  277 
  278         sched_tdcnt++;
  279         KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
  280         SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt);
  281 }
  282 
  283 static __inline void
  284 sched_load_rem(void)
  285 {
  286 
  287         sched_tdcnt--;
  288         KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
  289         SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt);
  290 }
  291 /*
  292  * Arrange to reschedule if necessary, taking the priorities and
  293  * schedulers into account.
  294  */
  295 static void
  296 maybe_resched(struct thread *td)
  297 {
  298 
  299         THREAD_LOCK_ASSERT(td, MA_OWNED);
  300         if (td->td_priority < curthread->td_priority)
  301                 curthread->td_flags |= TDF_NEEDRESCHED;
  302 }
  303 
  304 /*
  305  * This function is called when a thread is about to be put on run queue
  306  * because it has been made runnable or its priority has been adjusted.  It
  307  * determines if the new thread should preempt the current thread.  If so,
  308  * it sets td_owepreempt to request a preemption.
  309  */
  310 int
  311 maybe_preempt(struct thread *td)
  312 {
  313 #ifdef PREEMPTION
  314         struct thread *ctd;
  315         int cpri, pri;
  316 
  317         /*
  318          * The new thread should not preempt the current thread if any of the
  319          * following conditions are true:
  320          *
  321          *  - The kernel is in the throes of crashing (panicstr).
  322          *  - The current thread has a higher (numerically lower) or
  323          *    equivalent priority.  Note that this prevents curthread from
  324          *    trying to preempt to itself.
  325          *  - It is too early in the boot for context switches (cold is set).
  326          *  - The current thread has an inhibitor set or is in the process of
  327          *    exiting.  In this case, the current thread is about to switch
  328          *    out anyways, so there's no point in preempting.  If we did,
  329          *    the current thread would not be properly resumed as well, so
  330          *    just avoid that whole landmine.
  331          *  - If the new thread's priority is not a realtime priority and
  332          *    the current thread's priority is not an idle priority and
  333          *    FULL_PREEMPTION is disabled.
  334          *
  335          * If all of these conditions are false, but the current thread is in
  336          * a nested critical section, then we have to defer the preemption
  337          * until we exit the critical section.  Otherwise, switch immediately
  338          * to the new thread.
  339          */
  340         ctd = curthread;
  341         THREAD_LOCK_ASSERT(td, MA_OWNED);
  342         KASSERT((td->td_inhibitors == 0),
  343                         ("maybe_preempt: trying to run inhibited thread"));
  344         pri = td->td_priority;
  345         cpri = ctd->td_priority;
  346         if (panicstr != NULL || pri >= cpri || cold /* || dumping */ ||
  347             TD_IS_INHIBITED(ctd))
  348                 return (0);
  349 #ifndef FULL_PREEMPTION
  350         if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE)
  351                 return (0);
  352 #endif
  353 
  354         CTR0(KTR_PROC, "maybe_preempt: scheduling preemption");
  355         ctd->td_owepreempt = 1;
  356         return (1);
  357 #else
  358         return (0);
  359 #endif
  360 }
  361 
  362 /*
  363  * Constants for digital decay and forget:
  364  *      90% of (td_estcpu) usage in 5 * loadav time
  365  *      95% of (ts_pctcpu) usage in 60 seconds (load insensitive)
  366  *          Note that, as ps(1) mentions, this can let percentages
  367  *          total over 100% (I've seen 137.9% for 3 processes).
  368  *
  369  * Note that schedclock() updates td_estcpu and p_cpticks asynchronously.
  370  *
  371  * We wish to decay away 90% of td_estcpu in (5 * loadavg) seconds.
  372  * That is, the system wants to compute a value of decay such
  373  * that the following for loop:
  374  *      for (i = 0; i < (5 * loadavg); i++)
  375  *              td_estcpu *= decay;
  376  * will compute
  377  *      td_estcpu *= 0.1;
  378  * for all values of loadavg:
  379  *
  380  * Mathematically this loop can be expressed by saying:
  381  *      decay ** (5 * loadavg) ~= .1
  382  *
  383  * The system computes decay as:
  384  *      decay = (2 * loadavg) / (2 * loadavg + 1)
  385  *
  386  * We wish to prove that the system's computation of decay
  387  * will always fulfill the equation:
  388  *      decay ** (5 * loadavg) ~= .1
  389  *
  390  * If we compute b as:
  391  *      b = 2 * loadavg
  392  * then
  393  *      decay = b / (b + 1)
  394  *
  395  * We now need to prove two things:
  396  *      1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
  397  *      2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
  398  *
  399  * Facts:
  400  *         For x close to zero, exp(x) =~ 1 + x, since
  401  *              exp(x) = 0! + x**1/1! + x**2/2! + ... .
  402  *              therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
  403  *         For x close to zero, ln(1+x) =~ x, since
  404  *              ln(1+x) = x - x**2/2 + x**3/3 - ...     -1 < x < 1
  405  *              therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
  406  *         ln(.1) =~ -2.30
  407  *
  408  * Proof of (1):
  409  *    Solve (factor)**(power) =~ .1 given power (5*loadav):
  410  *      solving for factor,
  411  *      ln(factor) =~ (-2.30/5*loadav), or
  412  *      factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
  413  *          exp(-1/b) =~ (b-1)/b =~ b/(b+1).                    QED
  414  *
  415  * Proof of (2):
  416  *    Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
  417  *      solving for power,
  418  *      power*ln(b/(b+1)) =~ -2.30, or
  419  *      power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav.  QED
  420  *
  421  * Actual power values for the implemented algorithm are as follows:
  422  *      loadav: 1       2       3       4
  423  *      power:  5.68    10.32   14.94   19.55
  424  */
  425 
  426 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
  427 #define loadfactor(loadav)      (2 * (loadav))
  428 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
  429 
  430 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
  431 static fixpt_t  ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
  432 SYSCTL_UINT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
  433 
  434 /*
  435  * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
  436  * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
  437  * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
  438  *
  439  * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
  440  *      1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
  441  *
  442  * If you don't want to bother with the faster/more-accurate formula, you
  443  * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
  444  * (more general) method of calculating the %age of CPU used by a process.
  445  */
  446 #define CCPU_SHIFT      11
  447 
  448 /*
  449  * Recompute process priorities, every hz ticks.
  450  * MP-safe, called without the Giant mutex.
  451  */
  452 /* ARGSUSED */
  453 static void
  454 schedcpu(void)
  455 {
  456         register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
  457         struct thread *td;
  458         struct proc *p;
  459         struct td_sched *ts;
  460         int awake;
  461 
  462         sx_slock(&allproc_lock);
  463         FOREACH_PROC_IN_SYSTEM(p) {
  464                 PROC_LOCK(p);
  465                 if (p->p_state == PRS_NEW) {
  466                         PROC_UNLOCK(p);
  467                         continue;
  468                 }
  469                 FOREACH_THREAD_IN_PROC(p, td) {
  470                         awake = 0;
  471                         thread_lock(td);
  472                         ts = td->td_sched;
  473                         /*
  474                          * Increment sleep time (if sleeping).  We
  475                          * ignore overflow, as above.
  476                          */
  477                         /*
  478                          * The td_sched slptimes are not touched in wakeup
  479                          * because the thread may not HAVE everything in
  480                          * memory? XXX I think this is out of date.
  481                          */
  482                         if (TD_ON_RUNQ(td)) {
  483                                 awake = 1;
  484                                 td->td_flags &= ~TDF_DIDRUN;
  485                         } else if (TD_IS_RUNNING(td)) {
  486                                 awake = 1;
  487                                 /* Do not clear TDF_DIDRUN */
  488                         } else if (td->td_flags & TDF_DIDRUN) {
  489                                 awake = 1;
  490                                 td->td_flags &= ~TDF_DIDRUN;
  491                         }
  492 
  493                         /*
  494                          * ts_pctcpu is only for ps and ttyinfo().
  495                          */
  496                         ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT;
  497                         /*
  498                          * If the td_sched has been idle the entire second,
  499                          * stop recalculating its priority until
  500                          * it wakes up.
  501                          */
  502                         if (ts->ts_cpticks != 0) {
  503 #if     (FSHIFT >= CCPU_SHIFT)
  504                                 ts->ts_pctcpu += (realstathz == 100)
  505                                     ? ((fixpt_t) ts->ts_cpticks) <<
  506                                     (FSHIFT - CCPU_SHIFT) :
  507                                     100 * (((fixpt_t) ts->ts_cpticks)
  508                                     << (FSHIFT - CCPU_SHIFT)) / realstathz;
  509 #else
  510                                 ts->ts_pctcpu += ((FSCALE - ccpu) *
  511                                     (ts->ts_cpticks *
  512                                     FSCALE / realstathz)) >> FSHIFT;
  513 #endif
  514                                 ts->ts_cpticks = 0;
  515                         }
  516                         /*
  517                          * If there are ANY running threads in this process,
  518                          * then don't count it as sleeping.
  519                          * XXX: this is broken.
  520                          */
  521                         if (awake) {
  522                                 if (ts->ts_slptime > 1) {
  523                                         /*
  524                                          * In an ideal world, this should not
  525                                          * happen, because whoever woke us
  526                                          * up from the long sleep should have
  527                                          * unwound the slptime and reset our
  528                                          * priority before we run at the stale
  529                                          * priority.  Should KASSERT at some
  530                                          * point when all the cases are fixed.
  531                                          */
  532                                         updatepri(td);
  533                                 }
  534                                 ts->ts_slptime = 0;
  535                         } else
  536                                 ts->ts_slptime++;
  537                         if (ts->ts_slptime > 1) {
  538                                 thread_unlock(td);
  539                                 continue;
  540                         }
  541                         td->td_estcpu = decay_cpu(loadfac, td->td_estcpu);
  542                         resetpriority(td);
  543                         resetpriority_thread(td);
  544                         thread_unlock(td);
  545                 }
  546                 PROC_UNLOCK(p);
  547         }
  548         sx_sunlock(&allproc_lock);
  549 }
  550 
  551 /*
  552  * Main loop for a kthread that executes schedcpu once a second.
  553  */
  554 static void
  555 schedcpu_thread(void)
  556 {
  557 
  558         for (;;) {
  559                 schedcpu();
  560                 pause("-", hz);
  561         }
  562 }
  563 
  564 /*
  565  * Recalculate the priority of a process after it has slept for a while.
  566  * For all load averages >= 1 and max td_estcpu of 255, sleeping for at
  567  * least six times the loadfactor will decay td_estcpu to zero.
  568  */
  569 static void
  570 updatepri(struct thread *td)
  571 {
  572         struct td_sched *ts;
  573         fixpt_t loadfac;
  574         unsigned int newcpu;
  575 
  576         ts = td->td_sched;
  577         loadfac = loadfactor(averunnable.ldavg[0]);
  578         if (ts->ts_slptime > 5 * loadfac)
  579                 td->td_estcpu = 0;
  580         else {
  581                 newcpu = td->td_estcpu;
  582                 ts->ts_slptime--;       /* was incremented in schedcpu() */
  583                 while (newcpu && --ts->ts_slptime)
  584                         newcpu = decay_cpu(loadfac, newcpu);
  585                 td->td_estcpu = newcpu;
  586         }
  587 }
  588 
  589 /*
  590  * Compute the priority of a process when running in user mode.
  591  * Arrange to reschedule if the resulting priority is better
  592  * than that of the current process.
  593  */
  594 static void
  595 resetpriority(struct thread *td)
  596 {
  597         register unsigned int newpriority;
  598 
  599         if (td->td_pri_class == PRI_TIMESHARE) {
  600                 newpriority = PUSER + td->td_estcpu / INVERSE_ESTCPU_WEIGHT +
  601                     NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN);
  602                 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
  603                     PRI_MAX_TIMESHARE);
  604                 sched_user_prio(td, newpriority);
  605         }
  606 }
  607 
  608 /*
  609  * Update the thread's priority when the associated process's user
  610  * priority changes.
  611  */
  612 static void
  613 resetpriority_thread(struct thread *td)
  614 {
  615 
  616         /* Only change threads with a time sharing user priority. */
  617         if (td->td_priority < PRI_MIN_TIMESHARE ||
  618             td->td_priority > PRI_MAX_TIMESHARE)
  619                 return;
  620 
  621         /* XXX the whole needresched thing is broken, but not silly. */
  622         maybe_resched(td);
  623 
  624         sched_prio(td, td->td_user_pri);
  625 }
  626 
  627 /* ARGSUSED */
  628 static void
  629 sched_setup(void *dummy)
  630 {
  631 
  632         setup_runqs();
  633 
  634         /* Account for thread0. */
  635         sched_load_add();
  636 }
  637 
  638 /*
  639  * This routine determines time constants after stathz and hz are setup.
  640  */
  641 static void
  642 sched_initticks(void *dummy)
  643 {
  644 
  645         realstathz = stathz ? stathz : hz;
  646         sched_slice = realstathz / 10;  /* ~100ms */
  647         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
  648             realstathz);
  649 }
  650 
  651 /* External interfaces start here */
  652 
  653 /*
  654  * Very early in the boot some setup of scheduler-specific
  655  * parts of proc0 and of some scheduler resources needs to be done.
  656  * Called from:
  657  *  proc0_init()
  658  */
  659 void
  660 schedinit(void)
  661 {
  662         /*
  663          * Set up the scheduler specific parts of proc0.
  664          */
  665         proc0.p_sched = NULL; /* XXX */
  666         thread0.td_sched = &td_sched0;
  667         thread0.td_lock = &sched_lock;
  668         td_sched0.ts_slice = sched_slice;
  669         mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE);
  670 }
  671 
  672 int
  673 sched_runnable(void)
  674 {
  675 #ifdef SMP
  676         return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]);
  677 #else
  678         return runq_check(&runq);
  679 #endif
  680 }
  681 
  682 int
  683 sched_rr_interval(void)
  684 {
  685 
  686         /* Convert sched_slice from stathz to hz. */
  687         return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
  688 }
  689 
  690 /*
  691  * We adjust the priority of the current process.  The priority of
  692  * a process gets worse as it accumulates CPU time.  The cpu usage
  693  * estimator (td_estcpu) is increased here.  resetpriority() will
  694  * compute a different priority each time td_estcpu increases by
  695  * INVERSE_ESTCPU_WEIGHT
  696  * (until MAXPRI is reached).  The cpu usage estimator ramps up
  697  * quite quickly when the process is running (linearly), and decays
  698  * away exponentially, at a rate which is proportionally slower when
  699  * the system is busy.  The basic principle is that the system will
  700  * 90% forget that the process used a lot of CPU time in 5 * loadav
  701  * seconds.  This causes the system to favor processes which haven't
  702  * run much recently, and to round-robin among other processes.
  703  */
  704 void
  705 sched_clock(struct thread *td)
  706 {
  707         struct pcpuidlestat *stat;
  708         struct td_sched *ts;
  709 
  710         THREAD_LOCK_ASSERT(td, MA_OWNED);
  711         ts = td->td_sched;
  712 
  713         ts->ts_cpticks++;
  714         td->td_estcpu = ESTCPULIM(td->td_estcpu + 1);
  715         if ((td->td_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
  716                 resetpriority(td);
  717                 resetpriority_thread(td);
  718         }
  719 
  720         /*
  721          * Force a context switch if the current thread has used up a full
  722          * time slice (default is 100ms).
  723          */
  724         if (!TD_IS_IDLETHREAD(td) && --ts->ts_slice <= 0) {
  725                 ts->ts_slice = sched_slice;
  726                 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
  727         }
  728 
  729         stat = DPCPU_PTR(idlestat);
  730         stat->oldidlecalls = stat->idlecalls;
  731         stat->idlecalls = 0;
  732 }
  733 
  734 /*
  735  * Charge child's scheduling CPU usage to parent.
  736  */
  737 void
  738 sched_exit(struct proc *p, struct thread *td)
  739 {
  740 
  741         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit",
  742             "prio:%d", td->td_priority);
  743 
  744         PROC_LOCK_ASSERT(p, MA_OWNED);
  745         sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
  746 }
  747 
  748 void
  749 sched_exit_thread(struct thread *td, struct thread *child)
  750 {
  751 
  752         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit",
  753             "prio:%d", child->td_priority);
  754         thread_lock(td);
  755         td->td_estcpu = ESTCPULIM(td->td_estcpu + child->td_estcpu);
  756         thread_unlock(td);
  757         thread_lock(child);
  758         if ((child->td_flags & TDF_NOLOAD) == 0)
  759                 sched_load_rem();
  760         thread_unlock(child);
  761 }
  762 
  763 void
  764 sched_fork(struct thread *td, struct thread *childtd)
  765 {
  766         sched_fork_thread(td, childtd);
  767 }
  768 
  769 void
  770 sched_fork_thread(struct thread *td, struct thread *childtd)
  771 {
  772         struct td_sched *ts;
  773 
  774         childtd->td_oncpu = NOCPU;
  775         childtd->td_lastcpu = NOCPU;
  776         childtd->td_estcpu = td->td_estcpu;
  777         childtd->td_lock = &sched_lock;
  778         childtd->td_cpuset = cpuset_ref(td->td_cpuset);
  779         childtd->td_priority = childtd->td_base_pri;
  780         ts = childtd->td_sched;
  781         bzero(ts, sizeof(*ts));
  782         ts->ts_flags |= (td->td_sched->ts_flags & TSF_AFFINITY);
  783         ts->ts_slice = 1;
  784 }
  785 
  786 void
  787 sched_nice(struct proc *p, int nice)
  788 {
  789         struct thread *td;
  790 
  791         PROC_LOCK_ASSERT(p, MA_OWNED);
  792         p->p_nice = nice;
  793         FOREACH_THREAD_IN_PROC(p, td) {
  794                 thread_lock(td);
  795                 resetpriority(td);
  796                 resetpriority_thread(td);
  797                 thread_unlock(td);
  798         }
  799 }
  800 
  801 void
  802 sched_class(struct thread *td, int class)
  803 {
  804         THREAD_LOCK_ASSERT(td, MA_OWNED);
  805         td->td_pri_class = class;
  806 }
  807 
  808 /*
  809  * Adjust the priority of a thread.
  810  */
  811 static void
  812 sched_priority(struct thread *td, u_char prio)
  813 {
  814 
  815 
  816         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change",
  817             "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED,
  818             sched_tdname(curthread));
  819         SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
  820         if (td != curthread && prio > td->td_priority) {
  821                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
  822                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
  823                     prio, KTR_ATTR_LINKED, sched_tdname(td));
  824                 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 
  825                     curthread);
  826         }
  827         THREAD_LOCK_ASSERT(td, MA_OWNED);
  828         if (td->td_priority == prio)
  829                 return;
  830         td->td_priority = prio;
  831         if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) {
  832                 sched_rem(td);
  833                 sched_add(td, SRQ_BORING);
  834         }
  835 }
  836 
  837 /*
  838  * Update a thread's priority when it is lent another thread's
  839  * priority.
  840  */
  841 void
  842 sched_lend_prio(struct thread *td, u_char prio)
  843 {
  844 
  845         td->td_flags |= TDF_BORROWING;
  846         sched_priority(td, prio);
  847 }
  848 
  849 /*
  850  * Restore a thread's priority when priority propagation is
  851  * over.  The prio argument is the minimum priority the thread
  852  * needs to have to satisfy other possible priority lending
  853  * requests.  If the thread's regulary priority is less
  854  * important than prio the thread will keep a priority boost
  855  * of prio.
  856  */
  857 void
  858 sched_unlend_prio(struct thread *td, u_char prio)
  859 {
  860         u_char base_pri;
  861 
  862         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
  863             td->td_base_pri <= PRI_MAX_TIMESHARE)
  864                 base_pri = td->td_user_pri;
  865         else
  866                 base_pri = td->td_base_pri;
  867         if (prio >= base_pri) {
  868                 td->td_flags &= ~TDF_BORROWING;
  869                 sched_prio(td, base_pri);
  870         } else
  871                 sched_lend_prio(td, prio);
  872 }
  873 
  874 void
  875 sched_prio(struct thread *td, u_char prio)
  876 {
  877         u_char oldprio;
  878 
  879         /* First, update the base priority. */
  880         td->td_base_pri = prio;
  881 
  882         /*
  883          * If the thread is borrowing another thread's priority, don't ever
  884          * lower the priority.
  885          */
  886         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
  887                 return;
  888 
  889         /* Change the real priority. */
  890         oldprio = td->td_priority;
  891         sched_priority(td, prio);
  892 
  893         /*
  894          * If the thread is on a turnstile, then let the turnstile update
  895          * its state.
  896          */
  897         if (TD_ON_LOCK(td) && oldprio != prio)
  898                 turnstile_adjust(td, oldprio);
  899 }
  900 
  901 void
  902 sched_user_prio(struct thread *td, u_char prio)
  903 {
  904 
  905         THREAD_LOCK_ASSERT(td, MA_OWNED);
  906         td->td_base_user_pri = prio;
  907         if (td->td_lend_user_pri <= prio)
  908                 return;
  909         td->td_user_pri = prio;
  910 }
  911 
  912 void
  913 sched_lend_user_prio(struct thread *td, u_char prio)
  914 {
  915 
  916         THREAD_LOCK_ASSERT(td, MA_OWNED);
  917         td->td_lend_user_pri = prio;
  918         td->td_user_pri = min(prio, td->td_base_user_pri);
  919         if (td->td_priority > td->td_user_pri)
  920                 sched_prio(td, td->td_user_pri);
  921         else if (td->td_priority != td->td_user_pri)
  922                 td->td_flags |= TDF_NEEDRESCHED;
  923 }
  924 
  925 void
  926 sched_sleep(struct thread *td, int pri)
  927 {
  928 
  929         THREAD_LOCK_ASSERT(td, MA_OWNED);
  930         td->td_slptick = ticks;
  931         td->td_sched->ts_slptime = 0;
  932         if (pri != 0 && PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
  933                 sched_prio(td, pri);
  934         if (TD_IS_SUSPENDED(td) || pri >= PSOCK)
  935                 td->td_flags |= TDF_CANSWAP;
  936 }
  937 
  938 void
  939 sched_switch(struct thread *td, struct thread *newtd, int flags)
  940 {
  941         struct mtx *tmtx;
  942         struct td_sched *ts;
  943         struct proc *p;
  944         int preempted;
  945 
  946         tmtx = NULL;
  947         ts = td->td_sched;
  948         p = td->td_proc;
  949 
  950         THREAD_LOCK_ASSERT(td, MA_OWNED);
  951 
  952         /* 
  953          * Switch to the sched lock to fix things up and pick
  954          * a new thread.
  955          * Block the td_lock in order to avoid breaking the critical path.
  956          */
  957         if (td->td_lock != &sched_lock) {
  958                 mtx_lock_spin(&sched_lock);
  959                 tmtx = thread_lock_block(td);
  960         }
  961 
  962         if ((td->td_flags & TDF_NOLOAD) == 0)
  963                 sched_load_rem();
  964 
  965         td->td_lastcpu = td->td_oncpu;
  966         preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
  967             (flags & SW_PREEMPT) != 0;
  968         td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
  969         td->td_owepreempt = 0;
  970         td->td_oncpu = NOCPU;
  971 
  972         /*
  973          * At the last moment, if this thread is still marked RUNNING,
  974          * then put it back on the run queue as it has not been suspended
  975          * or stopped or any thing else similar.  We never put the idle
  976          * threads on the run queue, however.
  977          */
  978         if (td->td_flags & TDF_IDLETD) {
  979                 TD_SET_CAN_RUN(td);
  980 #ifdef SMP
  981                 CPU_CLR(PCPU_GET(cpuid), &idle_cpus_mask);
  982 #endif
  983         } else {
  984                 if (TD_IS_RUNNING(td)) {
  985                         /* Put us back on the run queue. */
  986                         sched_add(td, preempted ?
  987                             SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
  988                             SRQ_OURSELF|SRQ_YIELDING);
  989                 }
  990         }
  991         if (newtd) {
  992                 /*
  993                  * The thread we are about to run needs to be counted
  994                  * as if it had been added to the run queue and selected.
  995                  * It came from:
  996                  * * A preemption
  997                  * * An upcall
  998                  * * A followon
  999                  */
 1000                 KASSERT((newtd->td_inhibitors == 0),
 1001                         ("trying to run inhibited thread"));
 1002                 newtd->td_flags |= TDF_DIDRUN;
 1003                 TD_SET_RUNNING(newtd);
 1004                 if ((newtd->td_flags & TDF_NOLOAD) == 0)
 1005                         sched_load_add();
 1006         } else {
 1007                 newtd = choosethread();
 1008                 MPASS(newtd->td_lock == &sched_lock);
 1009         }
 1010 
 1011 #if (KTR_COMPILE & KTR_SCHED) != 0
 1012         if (TD_IS_IDLETHREAD(td))
 1013                 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
 1014                     "prio:%d", td->td_priority);
 1015         else
 1016                 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
 1017                     "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
 1018                     "lockname:\"%s\"", td->td_lockname);
 1019 #endif
 1020 
 1021         if (td != newtd) {
 1022 #ifdef  HWPMC_HOOKS
 1023                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1024                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1025 #endif
 1026 
 1027                 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
 1028 
 1029                 /* I feel sleepy */
 1030                 lock_profile_release_lock(&sched_lock.lock_object);
 1031 #ifdef KDTRACE_HOOKS
 1032                 /*
 1033                  * If DTrace has set the active vtime enum to anything
 1034                  * other than INACTIVE (0), then it should have set the
 1035                  * function to call.
 1036                  */
 1037                 if (dtrace_vtime_active)
 1038                         (*dtrace_vtime_switch_func)(newtd);
 1039 #endif
 1040 
 1041                 cpu_switch(td, newtd, tmtx != NULL ? tmtx : td->td_lock);
 1042                 lock_profile_obtain_lock_success(&sched_lock.lock_object,
 1043                     0, 0, __FILE__, __LINE__);
 1044                 /*
 1045                  * Where am I?  What year is it?
 1046                  * We are in the same thread that went to sleep above,
 1047                  * but any amount of time may have passed. All our context
 1048                  * will still be available as will local variables.
 1049                  * PCPU values however may have changed as we may have
 1050                  * changed CPU so don't trust cached values of them.
 1051                  * New threads will go to fork_exit() instead of here
 1052                  * so if you change things here you may need to change
 1053                  * things there too.
 1054                  *
 1055                  * If the thread above was exiting it will never wake
 1056                  * up again here, so either it has saved everything it
 1057                  * needed to, or the thread_wait() or wait() will
 1058                  * need to reap it.
 1059                  */
 1060 
 1061                 SDT_PROBE0(sched, , , on__cpu);
 1062 #ifdef  HWPMC_HOOKS
 1063                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1064                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1065 #endif
 1066         } else
 1067                 SDT_PROBE0(sched, , , remain__cpu);
 1068 
 1069         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
 1070             "prio:%d", td->td_priority);
 1071 
 1072 #ifdef SMP
 1073         if (td->td_flags & TDF_IDLETD)
 1074                 CPU_SET(PCPU_GET(cpuid), &idle_cpus_mask);
 1075 #endif
 1076         sched_lock.mtx_lock = (uintptr_t)td;
 1077         td->td_oncpu = PCPU_GET(cpuid);
 1078         MPASS(td->td_lock == &sched_lock);
 1079 }
 1080 
 1081 void
 1082 sched_wakeup(struct thread *td)
 1083 {
 1084         struct td_sched *ts;
 1085 
 1086         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1087         ts = td->td_sched;
 1088         td->td_flags &= ~TDF_CANSWAP;
 1089         if (ts->ts_slptime > 1) {
 1090                 updatepri(td);
 1091                 resetpriority(td);
 1092         }
 1093         td->td_slptick = 0;
 1094         ts->ts_slptime = 0;
 1095         ts->ts_slice = sched_slice;
 1096         sched_add(td, SRQ_BORING);
 1097 }
 1098 
 1099 #ifdef SMP
 1100 static int
 1101 forward_wakeup(int cpunum)
 1102 {
 1103         struct pcpu *pc;
 1104         cpuset_t dontuse, map, map2;
 1105         u_int id, me;
 1106         int iscpuset;
 1107 
 1108         mtx_assert(&sched_lock, MA_OWNED);
 1109 
 1110         CTR0(KTR_RUNQ, "forward_wakeup()");
 1111 
 1112         if ((!forward_wakeup_enabled) ||
 1113              (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0))
 1114                 return (0);
 1115         if (!smp_started || cold || panicstr)
 1116                 return (0);
 1117 
 1118         forward_wakeups_requested++;
 1119 
 1120         /*
 1121          * Check the idle mask we received against what we calculated
 1122          * before in the old version.
 1123          */
 1124         me = PCPU_GET(cpuid);
 1125 
 1126         /* Don't bother if we should be doing it ourself. */
 1127         if (CPU_ISSET(me, &idle_cpus_mask) &&
 1128             (cpunum == NOCPU || me == cpunum))
 1129                 return (0);
 1130 
 1131         CPU_SETOF(me, &dontuse);
 1132         CPU_OR(&dontuse, &stopped_cpus);
 1133         CPU_OR(&dontuse, &hlt_cpus_mask);
 1134         CPU_ZERO(&map2);
 1135         if (forward_wakeup_use_loop) {
 1136                 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
 1137                         id = pc->pc_cpuid;
 1138                         if (!CPU_ISSET(id, &dontuse) &&
 1139                             pc->pc_curthread == pc->pc_idlethread) {
 1140                                 CPU_SET(id, &map2);
 1141                         }
 1142                 }
 1143         }
 1144 
 1145         if (forward_wakeup_use_mask) {
 1146                 map = idle_cpus_mask;
 1147                 CPU_NAND(&map, &dontuse);
 1148 
 1149                 /* If they are both on, compare and use loop if different. */
 1150                 if (forward_wakeup_use_loop) {
 1151                         if (CPU_CMP(&map, &map2)) {
 1152                                 printf("map != map2, loop method preferred\n");
 1153                                 map = map2;
 1154                         }
 1155                 }
 1156         } else {
 1157                 map = map2;
 1158         }
 1159 
 1160         /* If we only allow a specific CPU, then mask off all the others. */
 1161         if (cpunum != NOCPU) {
 1162                 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum."));
 1163                 iscpuset = CPU_ISSET(cpunum, &map);
 1164                 if (iscpuset == 0)
 1165                         CPU_ZERO(&map);
 1166                 else
 1167                         CPU_SETOF(cpunum, &map);
 1168         }
 1169         if (!CPU_EMPTY(&map)) {
 1170                 forward_wakeups_delivered++;
 1171                 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
 1172                         id = pc->pc_cpuid;
 1173                         if (!CPU_ISSET(id, &map))
 1174                                 continue;
 1175                         if (cpu_idle_wakeup(pc->pc_cpuid))
 1176                                 CPU_CLR(id, &map);
 1177                 }
 1178                 if (!CPU_EMPTY(&map))
 1179                         ipi_selected(map, IPI_AST);
 1180                 return (1);
 1181         }
 1182         if (cpunum == NOCPU)
 1183                 printf("forward_wakeup: Idle processor not found\n");
 1184         return (0);
 1185 }
 1186 
 1187 static void
 1188 kick_other_cpu(int pri, int cpuid)
 1189 {
 1190         struct pcpu *pcpu;
 1191         int cpri;
 1192 
 1193         pcpu = pcpu_find(cpuid);
 1194         if (CPU_ISSET(cpuid, &idle_cpus_mask)) {
 1195                 forward_wakeups_delivered++;
 1196                 if (!cpu_idle_wakeup(cpuid))
 1197                         ipi_cpu(cpuid, IPI_AST);
 1198                 return;
 1199         }
 1200 
 1201         cpri = pcpu->pc_curthread->td_priority;
 1202         if (pri >= cpri)
 1203                 return;
 1204 
 1205 #if defined(IPI_PREEMPTION) && defined(PREEMPTION)
 1206 #if !defined(FULL_PREEMPTION)
 1207         if (pri <= PRI_MAX_ITHD)
 1208 #endif /* ! FULL_PREEMPTION */
 1209         {
 1210                 ipi_cpu(cpuid, IPI_PREEMPT);
 1211                 return;
 1212         }
 1213 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */
 1214 
 1215         pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED;
 1216         ipi_cpu(cpuid, IPI_AST);
 1217         return;
 1218 }
 1219 #endif /* SMP */
 1220 
 1221 #ifdef SMP
 1222 static int
 1223 sched_pickcpu(struct thread *td)
 1224 {
 1225         int best, cpu;
 1226 
 1227         mtx_assert(&sched_lock, MA_OWNED);
 1228 
 1229         if (td->td_lastcpu != NOCPU && THREAD_CAN_SCHED(td, td->td_lastcpu))
 1230                 best = td->td_lastcpu;
 1231         else
 1232                 best = NOCPU;
 1233         CPU_FOREACH(cpu) {
 1234                 if (!THREAD_CAN_SCHED(td, cpu))
 1235                         continue;
 1236         
 1237                 if (best == NOCPU)
 1238                         best = cpu;
 1239                 else if (runq_length[cpu] < runq_length[best])
 1240                         best = cpu;
 1241         }
 1242         KASSERT(best != NOCPU, ("no valid CPUs"));
 1243 
 1244         return (best);
 1245 }
 1246 #endif
 1247 
 1248 void
 1249 sched_add(struct thread *td, int flags)
 1250 #ifdef SMP
 1251 {
 1252         cpuset_t tidlemsk;
 1253         struct td_sched *ts;
 1254         u_int cpu, cpuid;
 1255         int forwarded = 0;
 1256         int single_cpu = 0;
 1257 
 1258         ts = td->td_sched;
 1259         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1260         KASSERT((td->td_inhibitors == 0),
 1261             ("sched_add: trying to run inhibited thread"));
 1262         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 1263             ("sched_add: bad thread state"));
 1264         KASSERT(td->td_flags & TDF_INMEM,
 1265             ("sched_add: thread swapped out"));
 1266 
 1267         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 1268             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 1269             sched_tdname(curthread));
 1270         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 1271             KTR_ATTR_LINKED, sched_tdname(td));
 1272         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 1273             flags & SRQ_PREEMPTED);
 1274 
 1275 
 1276         /*
 1277          * Now that the thread is moving to the run-queue, set the lock
 1278          * to the scheduler's lock.
 1279          */
 1280         if (td->td_lock != &sched_lock) {
 1281                 mtx_lock_spin(&sched_lock);
 1282                 thread_lock_set(td, &sched_lock);
 1283         }
 1284         TD_SET_RUNQ(td);
 1285 
 1286         /*
 1287          * If SMP is started and the thread is pinned or otherwise limited to
 1288          * a specific set of CPUs, queue the thread to a per-CPU run queue.
 1289          * Otherwise, queue the thread to the global run queue.
 1290          *
 1291          * If SMP has not yet been started we must use the global run queue
 1292          * as per-CPU state may not be initialized yet and we may crash if we
 1293          * try to access the per-CPU run queues.
 1294          */
 1295         if (smp_started && (td->td_pinned != 0 || td->td_flags & TDF_BOUND ||
 1296             ts->ts_flags & TSF_AFFINITY)) {
 1297                 if (td->td_pinned != 0)
 1298                         cpu = td->td_lastcpu;
 1299                 else if (td->td_flags & TDF_BOUND) {
 1300                         /* Find CPU from bound runq. */
 1301                         KASSERT(SKE_RUNQ_PCPU(ts),
 1302                             ("sched_add: bound td_sched not on cpu runq"));
 1303                         cpu = ts->ts_runq - &runq_pcpu[0];
 1304                 } else
 1305                         /* Find a valid CPU for our cpuset */
 1306                         cpu = sched_pickcpu(td);
 1307                 ts->ts_runq = &runq_pcpu[cpu];
 1308                 single_cpu = 1;
 1309                 CTR3(KTR_RUNQ,
 1310                     "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
 1311                     cpu);
 1312         } else {
 1313                 CTR2(KTR_RUNQ,
 1314                     "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts,
 1315                     td);
 1316                 cpu = NOCPU;
 1317                 ts->ts_runq = &runq;
 1318         }
 1319 
 1320         if ((td->td_flags & TDF_NOLOAD) == 0)
 1321                 sched_load_add();
 1322         runq_add(ts->ts_runq, td, flags);
 1323         if (cpu != NOCPU)
 1324                 runq_length[cpu]++;
 1325 
 1326         cpuid = PCPU_GET(cpuid);
 1327         if (single_cpu && cpu != cpuid) {
 1328                 kick_other_cpu(td->td_priority, cpu);
 1329         } else {
 1330                 if (!single_cpu) {
 1331                         tidlemsk = idle_cpus_mask;
 1332                         CPU_NAND(&tidlemsk, &hlt_cpus_mask);
 1333                         CPU_CLR(cpuid, &tidlemsk);
 1334 
 1335                         if (!CPU_ISSET(cpuid, &idle_cpus_mask) &&
 1336                             ((flags & SRQ_INTR) == 0) &&
 1337                             !CPU_EMPTY(&tidlemsk))
 1338                                 forwarded = forward_wakeup(cpu);
 1339                 }
 1340 
 1341                 if (!forwarded) {
 1342                         if (!maybe_preempt(td))
 1343                                 maybe_resched(td);
 1344                 }
 1345         }
 1346 }
 1347 #else /* SMP */
 1348 {
 1349         struct td_sched *ts;
 1350 
 1351         ts = td->td_sched;
 1352         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1353         KASSERT((td->td_inhibitors == 0),
 1354             ("sched_add: trying to run inhibited thread"));
 1355         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 1356             ("sched_add: bad thread state"));
 1357         KASSERT(td->td_flags & TDF_INMEM,
 1358             ("sched_add: thread swapped out"));
 1359         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 1360             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 1361             sched_tdname(curthread));
 1362         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 1363             KTR_ATTR_LINKED, sched_tdname(td));
 1364         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 1365             flags & SRQ_PREEMPTED);
 1366 
 1367         /*
 1368          * Now that the thread is moving to the run-queue, set the lock
 1369          * to the scheduler's lock.
 1370          */
 1371         if (td->td_lock != &sched_lock) {
 1372                 mtx_lock_spin(&sched_lock);
 1373                 thread_lock_set(td, &sched_lock);
 1374         }
 1375         TD_SET_RUNQ(td);
 1376         CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td);
 1377         ts->ts_runq = &runq;
 1378 
 1379         if ((td->td_flags & TDF_NOLOAD) == 0)
 1380                 sched_load_add();
 1381         runq_add(ts->ts_runq, td, flags);
 1382         if (!maybe_preempt(td))
 1383                 maybe_resched(td);
 1384 }
 1385 #endif /* SMP */
 1386 
 1387 void
 1388 sched_rem(struct thread *td)
 1389 {
 1390         struct td_sched *ts;
 1391 
 1392         ts = td->td_sched;
 1393         KASSERT(td->td_flags & TDF_INMEM,
 1394             ("sched_rem: thread swapped out"));
 1395         KASSERT(TD_ON_RUNQ(td),
 1396             ("sched_rem: thread not on run queue"));
 1397         mtx_assert(&sched_lock, MA_OWNED);
 1398         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 1399             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 1400             sched_tdname(curthread));
 1401         SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
 1402 
 1403         if ((td->td_flags & TDF_NOLOAD) == 0)
 1404                 sched_load_rem();
 1405 #ifdef SMP
 1406         if (ts->ts_runq != &runq)
 1407                 runq_length[ts->ts_runq - runq_pcpu]--;
 1408 #endif
 1409         runq_remove(ts->ts_runq, td);
 1410         TD_SET_CAN_RUN(td);
 1411 }
 1412 
 1413 /*
 1414  * Select threads to run.  Note that running threads still consume a
 1415  * slot.
 1416  */
 1417 struct thread *
 1418 sched_choose(void)
 1419 {
 1420         struct thread *td;
 1421         struct runq *rq;
 1422 
 1423         mtx_assert(&sched_lock,  MA_OWNED);
 1424 #ifdef SMP
 1425         struct thread *tdcpu;
 1426 
 1427         rq = &runq;
 1428         td = runq_choose_fuzz(&runq, runq_fuzz);
 1429         tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]);
 1430 
 1431         if (td == NULL ||
 1432             (tdcpu != NULL &&
 1433              tdcpu->td_priority < td->td_priority)) {
 1434                 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu,
 1435                      PCPU_GET(cpuid));
 1436                 td = tdcpu;
 1437                 rq = &runq_pcpu[PCPU_GET(cpuid)];
 1438         } else {
 1439                 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td);
 1440         }
 1441 
 1442 #else
 1443         rq = &runq;
 1444         td = runq_choose(&runq);
 1445 #endif
 1446 
 1447         if (td) {
 1448 #ifdef SMP
 1449                 if (td == tdcpu)
 1450                         runq_length[PCPU_GET(cpuid)]--;
 1451 #endif
 1452                 runq_remove(rq, td);
 1453                 td->td_flags |= TDF_DIDRUN;
 1454 
 1455                 KASSERT(td->td_flags & TDF_INMEM,
 1456                     ("sched_choose: thread swapped out"));
 1457                 return (td);
 1458         }
 1459         return (PCPU_GET(idlethread));
 1460 }
 1461 
 1462 void
 1463 sched_preempt(struct thread *td)
 1464 {
 1465 
 1466         SDT_PROBE2(sched, , , surrender, td, td->td_proc);
 1467         thread_lock(td);
 1468         if (td->td_critnest > 1)
 1469                 td->td_owepreempt = 1;
 1470         else
 1471                 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, NULL);
 1472         thread_unlock(td);
 1473 }
 1474 
 1475 void
 1476 sched_userret(struct thread *td)
 1477 {
 1478         /*
 1479          * XXX we cheat slightly on the locking here to avoid locking in
 1480          * the usual case.  Setting td_priority here is essentially an
 1481          * incomplete workaround for not setting it properly elsewhere.
 1482          * Now that some interrupt handlers are threads, not setting it
 1483          * properly elsewhere can clobber it in the window between setting
 1484          * it here and returning to user mode, so don't waste time setting
 1485          * it perfectly here.
 1486          */
 1487         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 1488             ("thread with borrowed priority returning to userland"));
 1489         if (td->td_priority != td->td_user_pri) {
 1490                 thread_lock(td);
 1491                 td->td_priority = td->td_user_pri;
 1492                 td->td_base_pri = td->td_user_pri;
 1493                 thread_unlock(td);
 1494         }
 1495 }
 1496 
 1497 void
 1498 sched_bind(struct thread *td, int cpu)
 1499 {
 1500         struct td_sched *ts;
 1501 
 1502         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 1503         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 1504 
 1505         ts = td->td_sched;
 1506 
 1507         td->td_flags |= TDF_BOUND;
 1508 #ifdef SMP
 1509         ts->ts_runq = &runq_pcpu[cpu];
 1510         if (PCPU_GET(cpuid) == cpu)
 1511                 return;
 1512 
 1513         mi_switch(SW_VOL, NULL);
 1514 #endif
 1515 }
 1516 
 1517 void
 1518 sched_unbind(struct thread* td)
 1519 {
 1520         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1521         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 1522         td->td_flags &= ~TDF_BOUND;
 1523 }
 1524 
 1525 int
 1526 sched_is_bound(struct thread *td)
 1527 {
 1528         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1529         return (td->td_flags & TDF_BOUND);
 1530 }
 1531 
 1532 void
 1533 sched_relinquish(struct thread *td)
 1534 {
 1535         thread_lock(td);
 1536         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 1537         thread_unlock(td);
 1538 }
 1539 
 1540 int
 1541 sched_load(void)
 1542 {
 1543         return (sched_tdcnt);
 1544 }
 1545 
 1546 int
 1547 sched_sizeof_proc(void)
 1548 {
 1549         return (sizeof(struct proc));
 1550 }
 1551 
 1552 int
 1553 sched_sizeof_thread(void)
 1554 {
 1555         return (sizeof(struct thread) + sizeof(struct td_sched));
 1556 }
 1557 
 1558 fixpt_t
 1559 sched_pctcpu(struct thread *td)
 1560 {
 1561         struct td_sched *ts;
 1562 
 1563         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1564         ts = td->td_sched;
 1565         return (ts->ts_pctcpu);
 1566 }
 1567 
 1568 #ifdef RACCT
 1569 /*
 1570  * Calculates the contribution to the thread cpu usage for the latest
 1571  * (unfinished) second.
 1572  */
 1573 fixpt_t
 1574 sched_pctcpu_delta(struct thread *td)
 1575 {
 1576         struct td_sched *ts;
 1577         fixpt_t delta;
 1578         int realstathz;
 1579 
 1580         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1581         ts = td->td_sched;
 1582         delta = 0;
 1583         realstathz = stathz ? stathz : hz;
 1584         if (ts->ts_cpticks != 0) {
 1585 #if     (FSHIFT >= CCPU_SHIFT)
 1586                 delta = (realstathz == 100)
 1587                     ? ((fixpt_t) ts->ts_cpticks) <<
 1588                     (FSHIFT - CCPU_SHIFT) :
 1589                     100 * (((fixpt_t) ts->ts_cpticks)
 1590                     << (FSHIFT - CCPU_SHIFT)) / realstathz;
 1591 #else
 1592                 delta = ((FSCALE - ccpu) *
 1593                     (ts->ts_cpticks *
 1594                     FSCALE / realstathz)) >> FSHIFT;
 1595 #endif
 1596         }
 1597 
 1598         return (delta);
 1599 }
 1600 #endif
 1601 
 1602 void
 1603 sched_tick(int cnt)
 1604 {
 1605 }
 1606 
 1607 /*
 1608  * The actual idle process.
 1609  */
 1610 void
 1611 sched_idletd(void *dummy)
 1612 {
 1613         struct pcpuidlestat *stat;
 1614 
 1615         THREAD_NO_SLEEPING();
 1616         stat = DPCPU_PTR(idlestat);
 1617         for (;;) {
 1618                 mtx_assert(&Giant, MA_NOTOWNED);
 1619 
 1620                 while (sched_runnable() == 0) {
 1621                         cpu_idle(stat->idlecalls + stat->oldidlecalls > 64);
 1622                         stat->idlecalls++;
 1623                 }
 1624 
 1625                 mtx_lock_spin(&sched_lock);
 1626                 mi_switch(SW_VOL | SWT_IDLE, NULL);
 1627                 mtx_unlock_spin(&sched_lock);
 1628         }
 1629 }
 1630 
 1631 /*
 1632  * A CPU is entering for the first time or a thread is exiting.
 1633  */
 1634 void
 1635 sched_throw(struct thread *td)
 1636 {
 1637         /*
 1638          * Correct spinlock nesting.  The idle thread context that we are
 1639          * borrowing was created so that it would start out with a single
 1640          * spin lock (sched_lock) held in fork_trampoline().  Since we've
 1641          * explicitly acquired locks in this function, the nesting count
 1642          * is now 2 rather than 1.  Since we are nested, calling
 1643          * spinlock_exit() will simply adjust the counts without allowing
 1644          * spin lock using code to interrupt us.
 1645          */
 1646         if (td == NULL) {
 1647                 mtx_lock_spin(&sched_lock);
 1648                 spinlock_exit();
 1649                 PCPU_SET(switchtime, cpu_ticks());
 1650                 PCPU_SET(switchticks, ticks);
 1651         } else {
 1652                 lock_profile_release_lock(&sched_lock.lock_object);
 1653                 MPASS(td->td_lock == &sched_lock);
 1654                 td->td_lastcpu = td->td_oncpu;
 1655                 td->td_oncpu = NOCPU;
 1656         }
 1657         mtx_assert(&sched_lock, MA_OWNED);
 1658         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 1659         cpu_throw(td, choosethread());  /* doesn't return */
 1660 }
 1661 
 1662 void
 1663 sched_fork_exit(struct thread *td)
 1664 {
 1665 
 1666         /*
 1667          * Finish setting up thread glue so that it begins execution in a
 1668          * non-nested critical section with sched_lock held but not recursed.
 1669          */
 1670         td->td_oncpu = PCPU_GET(cpuid);
 1671         sched_lock.mtx_lock = (uintptr_t)td;
 1672         lock_profile_obtain_lock_success(&sched_lock.lock_object,
 1673             0, 0, __FILE__, __LINE__);
 1674         THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
 1675 
 1676         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
 1677             "prio:%d", td->td_priority);
 1678         SDT_PROBE0(sched, , , on__cpu);
 1679 }
 1680 
 1681 char *
 1682 sched_tdname(struct thread *td)
 1683 {
 1684 #ifdef KTR
 1685         struct td_sched *ts;
 1686 
 1687         ts = td->td_sched;
 1688         if (ts->ts_name[0] == '\0')
 1689                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 1690                     "%s tid %d", td->td_name, td->td_tid);
 1691         return (ts->ts_name);
 1692 #else   
 1693         return (td->td_name);
 1694 #endif
 1695 }
 1696 
 1697 #ifdef KTR
 1698 void
 1699 sched_clear_tdname(struct thread *td)
 1700 {
 1701         struct td_sched *ts;
 1702 
 1703         ts = td->td_sched;
 1704         ts->ts_name[0] = '\0';
 1705 }
 1706 #endif
 1707 
 1708 void
 1709 sched_affinity(struct thread *td)
 1710 {
 1711 #ifdef SMP
 1712         struct td_sched *ts;
 1713         int cpu;
 1714 
 1715         THREAD_LOCK_ASSERT(td, MA_OWNED);       
 1716 
 1717         /*
 1718          * Set the TSF_AFFINITY flag if there is at least one CPU this
 1719          * thread can't run on.
 1720          */
 1721         ts = td->td_sched;
 1722         ts->ts_flags &= ~TSF_AFFINITY;
 1723         CPU_FOREACH(cpu) {
 1724                 if (!THREAD_CAN_SCHED(td, cpu)) {
 1725                         ts->ts_flags |= TSF_AFFINITY;
 1726                         break;
 1727                 }
 1728         }
 1729 
 1730         /*
 1731          * If this thread can run on all CPUs, nothing else to do.
 1732          */
 1733         if (!(ts->ts_flags & TSF_AFFINITY))
 1734                 return;
 1735 
 1736         /* Pinned threads and bound threads should be left alone. */
 1737         if (td->td_pinned != 0 || td->td_flags & TDF_BOUND)
 1738                 return;
 1739 
 1740         switch (td->td_state) {
 1741         case TDS_RUNQ:
 1742                 /*
 1743                  * If we are on a per-CPU runqueue that is in the set,
 1744                  * then nothing needs to be done.
 1745                  */
 1746                 if (ts->ts_runq != &runq &&
 1747                     THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu))
 1748                         return;
 1749 
 1750                 /* Put this thread on a valid per-CPU runqueue. */
 1751                 sched_rem(td);
 1752                 sched_add(td, SRQ_BORING);
 1753                 break;
 1754         case TDS_RUNNING:
 1755                 /*
 1756                  * See if our current CPU is in the set.  If not, force a
 1757                  * context switch.
 1758                  */
 1759                 if (THREAD_CAN_SCHED(td, td->td_oncpu))
 1760                         return;
 1761 
 1762                 td->td_flags |= TDF_NEEDRESCHED;
 1763                 if (td != curthread)
 1764                         ipi_cpu(cpu, IPI_AST);
 1765                 break;
 1766         default:
 1767                 break;
 1768         }
 1769 #endif
 1770 }

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