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: releng/11.2/sys/kern/sched_4bsd.c 331722 2018-03-29 02:50:57Z eadler $");
   37 
   38 #include "opt_hwpmc_hooks.h"
   39 #include "opt_sched.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/cpuset.h>
   44 #include <sys/kernel.h>
   45 #include <sys/ktr.h>
   46 #include <sys/lock.h>
   47 #include <sys/kthread.h>
   48 #include <sys/mutex.h>
   49 #include <sys/proc.h>
   50 #include <sys/resourcevar.h>
   51 #include <sys/sched.h>
   52 #include <sys/sdt.h>
   53 #include <sys/smp.h>
   54 #include <sys/sysctl.h>
   55 #include <sys/sx.h>
   56 #include <sys/turnstile.h>
   57 #include <sys/umtx.h>
   58 #include <machine/pcb.h>
   59 #include <machine/smp.h>
   60 
   61 #ifdef HWPMC_HOOKS
   62 #include <sys/pmckern.h>
   63 #endif
   64 
   65 #ifdef KDTRACE_HOOKS
   66 #include <sys/dtrace_bsd.h>
   67 int                             dtrace_vtime_active;
   68 dtrace_vtime_switch_func_t      dtrace_vtime_switch_func;
   69 #endif
   70 
   71 /*
   72  * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in
   73  * the range 100-256 Hz (approximately).
   74  */
   75 #define ESTCPULIM(e) \
   76     min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \
   77     RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1)
   78 #ifdef SMP
   79 #define INVERSE_ESTCPU_WEIGHT   (8 * smp_cpus)
   80 #else
   81 #define INVERSE_ESTCPU_WEIGHT   8       /* 1 / (priorities per estcpu level). */
   82 #endif
   83 #define NICE_WEIGHT             1       /* Priorities per nice level. */
   84 
   85 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
   86 
   87 /*
   88  * The schedulable entity that runs a context.
   89  * This is  an extension to the thread structure and is tailored to
   90  * the requirements of this scheduler.
   91  * All fields are protected by the scheduler lock.
   92  */
   93 struct td_sched {
   94         fixpt_t         ts_pctcpu;      /* %cpu during p_swtime. */
   95         u_int           ts_estcpu;      /* Estimated cpu utilization. */
   96         int             ts_cpticks;     /* Ticks of cpu time. */
   97         int             ts_slptime;     /* Seconds !RUNNING. */
   98         int             ts_slice;       /* Remaining part of time slice. */
   99         int             ts_flags;
  100         struct runq     *ts_runq;       /* runq the thread is currently on */
  101 #ifdef KTR
  102         char            ts_name[TS_NAME_LEN];
  103 #endif
  104 };
  105 
  106 /* flags kept in td_flags */
  107 #define TDF_DIDRUN      TDF_SCHED0      /* thread actually ran. */
  108 #define TDF_BOUND       TDF_SCHED1      /* Bound to one CPU. */
  109 #define TDF_SLICEEND    TDF_SCHED2      /* Thread time slice is over. */
  110 
  111 /* flags kept in ts_flags */
  112 #define TSF_AFFINITY    0x0001          /* Has a non-"full" CPU set. */
  113 
  114 #define SKE_RUNQ_PCPU(ts)                                               \
  115     ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq)
  116 
  117 #define THREAD_CAN_SCHED(td, cpu)       \
  118     CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
  119 
  120 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <=
  121     sizeof(struct thread0_storage),
  122     "increase struct thread0_storage.t0st_sched size");
  123 
  124 static struct mtx sched_lock;
  125 
  126 static int      realstathz = 127; /* stathz is sometimes 0 and run off of hz. */
  127 static int      sched_tdcnt;    /* Total runnable threads in the system. */
  128 static int      sched_slice = 12; /* Thread run time before rescheduling. */
  129 
  130 static void     setup_runqs(void);
  131 static void     schedcpu(void);
  132 static void     schedcpu_thread(void);
  133 static void     sched_priority(struct thread *td, u_char prio);
  134 static void     sched_setup(void *dummy);
  135 static void     maybe_resched(struct thread *td);
  136 static void     updatepri(struct thread *td);
  137 static void     resetpriority(struct thread *td);
  138 static void     resetpriority_thread(struct thread *td);
  139 #ifdef SMP
  140 static int      sched_pickcpu(struct thread *td);
  141 static int      forward_wakeup(int cpunum);
  142 static void     kick_other_cpu(int pri, int cpuid);
  143 #endif
  144 
  145 static struct kproc_desc sched_kp = {
  146         "schedcpu",
  147         schedcpu_thread,
  148         NULL
  149 };
  150 SYSINIT(schedcpu, SI_SUB_LAST, SI_ORDER_FIRST, kproc_start,
  151     &sched_kp);
  152 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
  153 
  154 static void sched_initticks(void *dummy);
  155 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
  156     NULL);
  157 
  158 /*
  159  * Global run queue.
  160  */
  161 static struct runq runq;
  162 
  163 #ifdef SMP
  164 /*
  165  * Per-CPU run queues
  166  */
  167 static struct runq runq_pcpu[MAXCPU];
  168 long runq_length[MAXCPU];
  169 
  170 static cpuset_t idle_cpus_mask;
  171 #endif
  172 
  173 struct pcpuidlestat {
  174         u_int idlecalls;
  175         u_int oldidlecalls;
  176 };
  177 static DPCPU_DEFINE(struct pcpuidlestat, idlestat);
  178 
  179 static void
  180 setup_runqs(void)
  181 {
  182 #ifdef SMP
  183         int i;
  184 
  185         for (i = 0; i < MAXCPU; ++i)
  186                 runq_init(&runq_pcpu[i]);
  187 #endif
  188 
  189         runq_init(&runq);
  190 }
  191 
  192 static int
  193 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
  194 {
  195         int error, new_val, period;
  196 
  197         period = 1000000 / realstathz;
  198         new_val = period * sched_slice;
  199         error = sysctl_handle_int(oidp, &new_val, 0, req);
  200         if (error != 0 || req->newptr == NULL)
  201                 return (error);
  202         if (new_val <= 0)
  203                 return (EINVAL);
  204         sched_slice = imax(1, (new_val + period / 2) / period);
  205         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
  206             realstathz);
  207         return (0);
  208 }
  209 
  210 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD, 0, "Scheduler");
  211 
  212 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0,
  213     "Scheduler name");
  214 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
  215     NULL, 0, sysctl_kern_quantum, "I",
  216     "Quantum for timeshare threads in microseconds");
  217 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
  218     "Quantum for timeshare threads in stathz ticks");
  219 #ifdef SMP
  220 /* Enable forwarding of wakeups to all other cpus */
  221 static SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup, CTLFLAG_RD, NULL,
  222     "Kernel SMP");
  223 
  224 static int runq_fuzz = 1;
  225 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
  226 
  227 static int forward_wakeup_enabled = 1;
  228 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW,
  229            &forward_wakeup_enabled, 0,
  230            "Forwarding of wakeup to idle CPUs");
  231 
  232 static int forward_wakeups_requested = 0;
  233 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD,
  234            &forward_wakeups_requested, 0,
  235            "Requests for Forwarding of wakeup to idle CPUs");
  236 
  237 static int forward_wakeups_delivered = 0;
  238 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD,
  239            &forward_wakeups_delivered, 0,
  240            "Completed Forwarding of wakeup to idle CPUs");
  241 
  242 static int forward_wakeup_use_mask = 1;
  243 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW,
  244            &forward_wakeup_use_mask, 0,
  245            "Use the mask of idle cpus");
  246 
  247 static int forward_wakeup_use_loop = 0;
  248 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW,
  249            &forward_wakeup_use_loop, 0,
  250            "Use a loop to find idle cpus");
  251 
  252 #endif
  253 #if 0
  254 static int sched_followon = 0;
  255 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW,
  256            &sched_followon, 0,
  257            "allow threads to share a quantum");
  258 #endif
  259 
  260 SDT_PROVIDER_DEFINE(sched);
  261 
  262 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 
  263     "struct proc *", "uint8_t");
  264 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 
  265     "struct proc *", "void *");
  266 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 
  267     "struct proc *", "void *", "int");
  268 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 
  269     "struct proc *", "uint8_t", "struct thread *");
  270 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
  271 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
  272     "struct proc *");
  273 SDT_PROBE_DEFINE(sched, , , on__cpu);
  274 SDT_PROBE_DEFINE(sched, , , remain__cpu);
  275 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
  276     "struct proc *");
  277 
  278 static __inline void
  279 sched_load_add(void)
  280 {
  281 
  282         sched_tdcnt++;
  283         KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
  284         SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt);
  285 }
  286 
  287 static __inline void
  288 sched_load_rem(void)
  289 {
  290 
  291         sched_tdcnt--;
  292         KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt);
  293         SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt);
  294 }
  295 /*
  296  * Arrange to reschedule if necessary, taking the priorities and
  297  * schedulers into account.
  298  */
  299 static void
  300 maybe_resched(struct thread *td)
  301 {
  302 
  303         THREAD_LOCK_ASSERT(td, MA_OWNED);
  304         if (td->td_priority < curthread->td_priority)
  305                 curthread->td_flags |= TDF_NEEDRESCHED;
  306 }
  307 
  308 /*
  309  * This function is called when a thread is about to be put on run queue
  310  * because it has been made runnable or its priority has been adjusted.  It
  311  * determines if the new thread should preempt the current thread.  If so,
  312  * it sets td_owepreempt to request a preemption.
  313  */
  314 int
  315 maybe_preempt(struct thread *td)
  316 {
  317 #ifdef PREEMPTION
  318         struct thread *ctd;
  319         int cpri, pri;
  320 
  321         /*
  322          * The new thread should not preempt the current thread if any of the
  323          * following conditions are true:
  324          *
  325          *  - The kernel is in the throes of crashing (panicstr).
  326          *  - The current thread has a higher (numerically lower) or
  327          *    equivalent priority.  Note that this prevents curthread from
  328          *    trying to preempt to itself.
  329          *  - The current thread has an inhibitor set or is in the process of
  330          *    exiting.  In this case, the current thread is about to switch
  331          *    out anyways, so there's no point in preempting.  If we did,
  332          *    the current thread would not be properly resumed as well, so
  333          *    just avoid that whole landmine.
  334          *  - If the new thread's priority is not a realtime priority and
  335          *    the current thread's priority is not an idle priority and
  336          *    FULL_PREEMPTION is disabled.
  337          *
  338          * If all of these conditions are false, but the current thread is in
  339          * a nested critical section, then we have to defer the preemption
  340          * until we exit the critical section.  Otherwise, switch immediately
  341          * to the new thread.
  342          */
  343         ctd = curthread;
  344         THREAD_LOCK_ASSERT(td, MA_OWNED);
  345         KASSERT((td->td_inhibitors == 0),
  346                         ("maybe_preempt: trying to run inhibited thread"));
  347         pri = td->td_priority;
  348         cpri = ctd->td_priority;
  349         if (panicstr != NULL || pri >= cpri /* || dumping */ ||
  350             TD_IS_INHIBITED(ctd))
  351                 return (0);
  352 #ifndef FULL_PREEMPTION
  353         if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE)
  354                 return (0);
  355 #endif
  356 
  357         CTR0(KTR_PROC, "maybe_preempt: scheduling preemption");
  358         ctd->td_owepreempt = 1;
  359         return (1);
  360 #else
  361         return (0);
  362 #endif
  363 }
  364 
  365 /*
  366  * Constants for digital decay and forget:
  367  *      90% of (ts_estcpu) usage in 5 * loadav time
  368  *      95% of (ts_pctcpu) usage in 60 seconds (load insensitive)
  369  *          Note that, as ps(1) mentions, this can let percentages
  370  *          total over 100% (I've seen 137.9% for 3 processes).
  371  *
  372  * Note that schedclock() updates ts_estcpu and p_cpticks asynchronously.
  373  *
  374  * We wish to decay away 90% of ts_estcpu in (5 * loadavg) seconds.
  375  * That is, the system wants to compute a value of decay such
  376  * that the following for loop:
  377  *      for (i = 0; i < (5 * loadavg); i++)
  378  *              ts_estcpu *= decay;
  379  * will compute
  380  *      ts_estcpu *= 0.1;
  381  * for all values of loadavg:
  382  *
  383  * Mathematically this loop can be expressed by saying:
  384  *      decay ** (5 * loadavg) ~= .1
  385  *
  386  * The system computes decay as:
  387  *      decay = (2 * loadavg) / (2 * loadavg + 1)
  388  *
  389  * We wish to prove that the system's computation of decay
  390  * will always fulfill the equation:
  391  *      decay ** (5 * loadavg) ~= .1
  392  *
  393  * If we compute b as:
  394  *      b = 2 * loadavg
  395  * then
  396  *      decay = b / (b + 1)
  397  *
  398  * We now need to prove two things:
  399  *      1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
  400  *      2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
  401  *
  402  * Facts:
  403  *         For x close to zero, exp(x) =~ 1 + x, since
  404  *              exp(x) = 0! + x**1/1! + x**2/2! + ... .
  405  *              therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
  406  *         For x close to zero, ln(1+x) =~ x, since
  407  *              ln(1+x) = x - x**2/2 + x**3/3 - ...     -1 < x < 1
  408  *              therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
  409  *         ln(.1) =~ -2.30
  410  *
  411  * Proof of (1):
  412  *    Solve (factor)**(power) =~ .1 given power (5*loadav):
  413  *      solving for factor,
  414  *      ln(factor) =~ (-2.30/5*loadav), or
  415  *      factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
  416  *          exp(-1/b) =~ (b-1)/b =~ b/(b+1).                    QED
  417  *
  418  * Proof of (2):
  419  *    Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
  420  *      solving for power,
  421  *      power*ln(b/(b+1)) =~ -2.30, or
  422  *      power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav.  QED
  423  *
  424  * Actual power values for the implemented algorithm are as follows:
  425  *      loadav: 1       2       3       4
  426  *      power:  5.68    10.32   14.94   19.55
  427  */
  428 
  429 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
  430 #define loadfactor(loadav)      (2 * (loadav))
  431 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
  432 
  433 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
  434 static fixpt_t  ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
  435 SYSCTL_UINT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
  436 
  437 /*
  438  * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
  439  * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
  440  * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
  441  *
  442  * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
  443  *      1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
  444  *
  445  * If you don't want to bother with the faster/more-accurate formula, you
  446  * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
  447  * (more general) method of calculating the %age of CPU used by a process.
  448  */
  449 #define CCPU_SHIFT      11
  450 
  451 /*
  452  * Recompute process priorities, every hz ticks.
  453  * MP-safe, called without the Giant mutex.
  454  */
  455 /* ARGSUSED */
  456 static void
  457 schedcpu(void)
  458 {
  459         fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
  460         struct thread *td;
  461         struct proc *p;
  462         struct td_sched *ts;
  463         int awake;
  464 
  465         sx_slock(&allproc_lock);
  466         FOREACH_PROC_IN_SYSTEM(p) {
  467                 PROC_LOCK(p);
  468                 if (p->p_state == PRS_NEW) {
  469                         PROC_UNLOCK(p);
  470                         continue;
  471                 }
  472                 FOREACH_THREAD_IN_PROC(p, td) {
  473                         awake = 0;
  474                         ts = td_get_sched(td);
  475                         thread_lock(td);
  476                         /*
  477                          * Increment sleep time (if sleeping).  We
  478                          * ignore overflow, as above.
  479                          */
  480                         /*
  481                          * The td_sched slptimes are not touched in wakeup
  482                          * because the thread may not HAVE everything in
  483                          * memory? XXX I think this is out of date.
  484                          */
  485                         if (TD_ON_RUNQ(td)) {
  486                                 awake = 1;
  487                                 td->td_flags &= ~TDF_DIDRUN;
  488                         } else if (TD_IS_RUNNING(td)) {
  489                                 awake = 1;
  490                                 /* Do not clear TDF_DIDRUN */
  491                         } else if (td->td_flags & TDF_DIDRUN) {
  492                                 awake = 1;
  493                                 td->td_flags &= ~TDF_DIDRUN;
  494                         }
  495 
  496                         /*
  497                          * ts_pctcpu is only for ps and ttyinfo().
  498                          */
  499                         ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT;
  500                         /*
  501                          * If the td_sched has been idle the entire second,
  502                          * stop recalculating its priority until
  503                          * it wakes up.
  504                          */
  505                         if (ts->ts_cpticks != 0) {
  506 #if     (FSHIFT >= CCPU_SHIFT)
  507                                 ts->ts_pctcpu += (realstathz == 100)
  508                                     ? ((fixpt_t) ts->ts_cpticks) <<
  509                                     (FSHIFT - CCPU_SHIFT) :
  510                                     100 * (((fixpt_t) ts->ts_cpticks)
  511                                     << (FSHIFT - CCPU_SHIFT)) / realstathz;
  512 #else
  513                                 ts->ts_pctcpu += ((FSCALE - ccpu) *
  514                                     (ts->ts_cpticks *
  515                                     FSCALE / realstathz)) >> FSHIFT;
  516 #endif
  517                                 ts->ts_cpticks = 0;
  518                         }
  519                         /*
  520                          * If there are ANY running threads in this process,
  521                          * then don't count it as sleeping.
  522                          * XXX: this is broken.
  523                          */
  524                         if (awake) {
  525                                 if (ts->ts_slptime > 1) {
  526                                         /*
  527                                          * In an ideal world, this should not
  528                                          * happen, because whoever woke us
  529                                          * up from the long sleep should have
  530                                          * unwound the slptime and reset our
  531                                          * priority before we run at the stale
  532                                          * priority.  Should KASSERT at some
  533                                          * point when all the cases are fixed.
  534                                          */
  535                                         updatepri(td);
  536                                 }
  537                                 ts->ts_slptime = 0;
  538                         } else
  539                                 ts->ts_slptime++;
  540                         if (ts->ts_slptime > 1) {
  541                                 thread_unlock(td);
  542                                 continue;
  543                         }
  544                         ts->ts_estcpu = decay_cpu(loadfac, ts->ts_estcpu);
  545                         resetpriority(td);
  546                         resetpriority_thread(td);
  547                         thread_unlock(td);
  548                 }
  549                 PROC_UNLOCK(p);
  550         }
  551         sx_sunlock(&allproc_lock);
  552 }
  553 
  554 /*
  555  * Main loop for a kthread that executes schedcpu once a second.
  556  */
  557 static void
  558 schedcpu_thread(void)
  559 {
  560 
  561         for (;;) {
  562                 schedcpu();
  563                 pause("-", hz);
  564         }
  565 }
  566 
  567 /*
  568  * Recalculate the priority of a process after it has slept for a while.
  569  * For all load averages >= 1 and max ts_estcpu of 255, sleeping for at
  570  * least six times the loadfactor will decay ts_estcpu to zero.
  571  */
  572 static void
  573 updatepri(struct thread *td)
  574 {
  575         struct td_sched *ts;
  576         fixpt_t loadfac;
  577         unsigned int newcpu;
  578 
  579         ts = td_get_sched(td);
  580         loadfac = loadfactor(averunnable.ldavg[0]);
  581         if (ts->ts_slptime > 5 * loadfac)
  582                 ts->ts_estcpu = 0;
  583         else {
  584                 newcpu = ts->ts_estcpu;
  585                 ts->ts_slptime--;       /* was incremented in schedcpu() */
  586                 while (newcpu && --ts->ts_slptime)
  587                         newcpu = decay_cpu(loadfac, newcpu);
  588                 ts->ts_estcpu = newcpu;
  589         }
  590 }
  591 
  592 /*
  593  * Compute the priority of a process when running in user mode.
  594  * Arrange to reschedule if the resulting priority is better
  595  * than that of the current process.
  596  */
  597 static void
  598 resetpriority(struct thread *td)
  599 {
  600         u_int newpriority;
  601 
  602         if (td->td_pri_class != PRI_TIMESHARE)
  603                 return;
  604         newpriority = PUSER +
  605             td_get_sched(td)->ts_estcpu / INVERSE_ESTCPU_WEIGHT +
  606             NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN);
  607         newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
  608             PRI_MAX_TIMESHARE);
  609         sched_user_prio(td, newpriority);
  610 }
  611 
  612 /*
  613  * Update the thread's priority when the associated process's user
  614  * priority changes.
  615  */
  616 static void
  617 resetpriority_thread(struct thread *td)
  618 {
  619 
  620         /* Only change threads with a time sharing user priority. */
  621         if (td->td_priority < PRI_MIN_TIMESHARE ||
  622             td->td_priority > PRI_MAX_TIMESHARE)
  623                 return;
  624 
  625         /* XXX the whole needresched thing is broken, but not silly. */
  626         maybe_resched(td);
  627 
  628         sched_prio(td, td->td_user_pri);
  629 }
  630 
  631 /* ARGSUSED */
  632 static void
  633 sched_setup(void *dummy)
  634 {
  635 
  636         setup_runqs();
  637 
  638         /* Account for thread0. */
  639         sched_load_add();
  640 }
  641 
  642 /*
  643  * This routine determines time constants after stathz and hz are setup.
  644  */
  645 static void
  646 sched_initticks(void *dummy)
  647 {
  648 
  649         realstathz = stathz ? stathz : hz;
  650         sched_slice = realstathz / 10;  /* ~100ms */
  651         hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
  652             realstathz);
  653 }
  654 
  655 /* External interfaces start here */
  656 
  657 /*
  658  * Very early in the boot some setup of scheduler-specific
  659  * parts of proc0 and of some scheduler resources needs to be done.
  660  * Called from:
  661  *  proc0_init()
  662  */
  663 void
  664 schedinit(void)
  665 {
  666 
  667         /*
  668          * Set up the scheduler specific parts of thread0.
  669          */
  670         thread0.td_lock = &sched_lock;
  671         td_get_sched(&thread0)->ts_slice = sched_slice;
  672         mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE);
  673 }
  674 
  675 int
  676 sched_runnable(void)
  677 {
  678 #ifdef SMP
  679         return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]);
  680 #else
  681         return runq_check(&runq);
  682 #endif
  683 }
  684 
  685 int
  686 sched_rr_interval(void)
  687 {
  688 
  689         /* Convert sched_slice from stathz to hz. */
  690         return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
  691 }
  692 
  693 /*
  694  * We adjust the priority of the current process.  The priority of a
  695  * process gets worse as it accumulates CPU time.  The cpu usage
  696  * estimator (ts_estcpu) is increased here.  resetpriority() will
  697  * compute a different priority each time ts_estcpu increases by
  698  * INVERSE_ESTCPU_WEIGHT (until PRI_MAX_TIMESHARE is reached).  The
  699  * cpu usage estimator ramps up quite quickly when the process is
  700  * running (linearly), and decays away exponentially, at a rate which
  701  * is proportionally slower when the system is busy.  The basic
  702  * principle is that the system will 90% forget that the process used
  703  * a lot of CPU time in 5 * loadav seconds.  This causes the system to
  704  * favor processes which haven't run much recently, and to round-robin
  705  * among other processes.
  706  */
  707 void
  708 sched_clock(struct thread *td)
  709 {
  710         struct pcpuidlestat *stat;
  711         struct td_sched *ts;
  712 
  713         THREAD_LOCK_ASSERT(td, MA_OWNED);
  714         ts = td_get_sched(td);
  715 
  716         ts->ts_cpticks++;
  717         ts->ts_estcpu = ESTCPULIM(ts->ts_estcpu + 1);
  718         if ((ts->ts_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
  719                 resetpriority(td);
  720                 resetpriority_thread(td);
  721         }
  722 
  723         /*
  724          * Force a context switch if the current thread has used up a full
  725          * time slice (default is 100ms).
  726          */
  727         if (!TD_IS_IDLETHREAD(td) && --ts->ts_slice <= 0) {
  728                 ts->ts_slice = sched_slice;
  729                 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
  730         }
  731 
  732         stat = DPCPU_PTR(idlestat);
  733         stat->oldidlecalls = stat->idlecalls;
  734         stat->idlecalls = 0;
  735 }
  736 
  737 /*
  738  * Charge child's scheduling CPU usage to parent.
  739  */
  740 void
  741 sched_exit(struct proc *p, struct thread *td)
  742 {
  743 
  744         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit",
  745             "prio:%d", td->td_priority);
  746 
  747         PROC_LOCK_ASSERT(p, MA_OWNED);
  748         sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
  749 }
  750 
  751 void
  752 sched_exit_thread(struct thread *td, struct thread *child)
  753 {
  754 
  755         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit",
  756             "prio:%d", child->td_priority);
  757         thread_lock(td);
  758         td_get_sched(td)->ts_estcpu = ESTCPULIM(td_get_sched(td)->ts_estcpu +
  759             td_get_sched(child)->ts_estcpu);
  760         thread_unlock(td);
  761         thread_lock(child);
  762         if ((child->td_flags & TDF_NOLOAD) == 0)
  763                 sched_load_rem();
  764         thread_unlock(child);
  765 }
  766 
  767 void
  768 sched_fork(struct thread *td, struct thread *childtd)
  769 {
  770         sched_fork_thread(td, childtd);
  771 }
  772 
  773 void
  774 sched_fork_thread(struct thread *td, struct thread *childtd)
  775 {
  776         struct td_sched *ts, *tsc;
  777 
  778         childtd->td_oncpu = NOCPU;
  779         childtd->td_lastcpu = NOCPU;
  780         childtd->td_lock = &sched_lock;
  781         childtd->td_cpuset = cpuset_ref(td->td_cpuset);
  782         childtd->td_priority = childtd->td_base_pri;
  783         ts = td_get_sched(childtd);
  784         bzero(ts, sizeof(*ts));
  785         tsc = td_get_sched(td);
  786         ts->ts_estcpu = tsc->ts_estcpu;
  787         ts->ts_flags |= (tsc->ts_flags & TSF_AFFINITY);
  788         ts->ts_slice = 1;
  789 }
  790 
  791 void
  792 sched_nice(struct proc *p, int nice)
  793 {
  794         struct thread *td;
  795 
  796         PROC_LOCK_ASSERT(p, MA_OWNED);
  797         p->p_nice = nice;
  798         FOREACH_THREAD_IN_PROC(p, td) {
  799                 thread_lock(td);
  800                 resetpriority(td);
  801                 resetpriority_thread(td);
  802                 thread_unlock(td);
  803         }
  804 }
  805 
  806 void
  807 sched_class(struct thread *td, int class)
  808 {
  809         THREAD_LOCK_ASSERT(td, MA_OWNED);
  810         td->td_pri_class = class;
  811 }
  812 
  813 /*
  814  * Adjust the priority of a thread.
  815  */
  816 static void
  817 sched_priority(struct thread *td, u_char prio)
  818 {
  819 
  820 
  821         KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change",
  822             "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED,
  823             sched_tdname(curthread));
  824         SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
  825         if (td != curthread && prio > td->td_priority) {
  826                 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
  827                     "lend prio", "prio:%d", td->td_priority, "new prio:%d",
  828                     prio, KTR_ATTR_LINKED, sched_tdname(td));
  829                 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 
  830                     curthread);
  831         }
  832         THREAD_LOCK_ASSERT(td, MA_OWNED);
  833         if (td->td_priority == prio)
  834                 return;
  835         td->td_priority = prio;
  836         if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) {
  837                 sched_rem(td);
  838                 sched_add(td, SRQ_BORING);
  839         }
  840 }
  841 
  842 /*
  843  * Update a thread's priority when it is lent another thread's
  844  * priority.
  845  */
  846 void
  847 sched_lend_prio(struct thread *td, u_char prio)
  848 {
  849 
  850         td->td_flags |= TDF_BORROWING;
  851         sched_priority(td, prio);
  852 }
  853 
  854 /*
  855  * Restore a thread's priority when priority propagation is
  856  * over.  The prio argument is the minimum priority the thread
  857  * needs to have to satisfy other possible priority lending
  858  * requests.  If the thread's regulary priority is less
  859  * important than prio the thread will keep a priority boost
  860  * of prio.
  861  */
  862 void
  863 sched_unlend_prio(struct thread *td, u_char prio)
  864 {
  865         u_char base_pri;
  866 
  867         if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
  868             td->td_base_pri <= PRI_MAX_TIMESHARE)
  869                 base_pri = td->td_user_pri;
  870         else
  871                 base_pri = td->td_base_pri;
  872         if (prio >= base_pri) {
  873                 td->td_flags &= ~TDF_BORROWING;
  874                 sched_prio(td, base_pri);
  875         } else
  876                 sched_lend_prio(td, prio);
  877 }
  878 
  879 void
  880 sched_prio(struct thread *td, u_char prio)
  881 {
  882         u_char oldprio;
  883 
  884         /* First, update the base priority. */
  885         td->td_base_pri = prio;
  886 
  887         /*
  888          * If the thread is borrowing another thread's priority, don't ever
  889          * lower the priority.
  890          */
  891         if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
  892                 return;
  893 
  894         /* Change the real priority. */
  895         oldprio = td->td_priority;
  896         sched_priority(td, prio);
  897 
  898         /*
  899          * If the thread is on a turnstile, then let the turnstile update
  900          * its state.
  901          */
  902         if (TD_ON_LOCK(td) && oldprio != prio)
  903                 turnstile_adjust(td, oldprio);
  904 }
  905 
  906 void
  907 sched_user_prio(struct thread *td, u_char prio)
  908 {
  909 
  910         THREAD_LOCK_ASSERT(td, MA_OWNED);
  911         td->td_base_user_pri = prio;
  912         if (td->td_lend_user_pri <= prio)
  913                 return;
  914         td->td_user_pri = prio;
  915 }
  916 
  917 void
  918 sched_lend_user_prio(struct thread *td, u_char prio)
  919 {
  920 
  921         THREAD_LOCK_ASSERT(td, MA_OWNED);
  922         td->td_lend_user_pri = prio;
  923         td->td_user_pri = min(prio, td->td_base_user_pri);
  924         if (td->td_priority > td->td_user_pri)
  925                 sched_prio(td, td->td_user_pri);
  926         else if (td->td_priority != td->td_user_pri)
  927                 td->td_flags |= TDF_NEEDRESCHED;
  928 }
  929 
  930 void
  931 sched_sleep(struct thread *td, int pri)
  932 {
  933 
  934         THREAD_LOCK_ASSERT(td, MA_OWNED);
  935         td->td_slptick = ticks;
  936         td_get_sched(td)->ts_slptime = 0;
  937         if (pri != 0 && PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
  938                 sched_prio(td, pri);
  939         if (TD_IS_SUSPENDED(td) || pri >= PSOCK)
  940                 td->td_flags |= TDF_CANSWAP;
  941 }
  942 
  943 void
  944 sched_switch(struct thread *td, struct thread *newtd, int flags)
  945 {
  946         struct mtx *tmtx;
  947         struct td_sched *ts;
  948         struct proc *p;
  949         int preempted;
  950 
  951         tmtx = NULL;
  952         ts = td_get_sched(td);
  953         p = td->td_proc;
  954 
  955         THREAD_LOCK_ASSERT(td, MA_OWNED);
  956 
  957         /* 
  958          * Switch to the sched lock to fix things up and pick
  959          * a new thread.
  960          * Block the td_lock in order to avoid breaking the critical path.
  961          */
  962         if (td->td_lock != &sched_lock) {
  963                 mtx_lock_spin(&sched_lock);
  964                 tmtx = thread_lock_block(td);
  965         }
  966 
  967         if ((td->td_flags & TDF_NOLOAD) == 0)
  968                 sched_load_rem();
  969 
  970         td->td_lastcpu = td->td_oncpu;
  971         preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
  972             (flags & SW_PREEMPT) != 0;
  973         td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
  974         td->td_owepreempt = 0;
  975         td->td_oncpu = NOCPU;
  976 
  977         /*
  978          * At the last moment, if this thread is still marked RUNNING,
  979          * then put it back on the run queue as it has not been suspended
  980          * or stopped or any thing else similar.  We never put the idle
  981          * threads on the run queue, however.
  982          */
  983         if (td->td_flags & TDF_IDLETD) {
  984                 TD_SET_CAN_RUN(td);
  985 #ifdef SMP
  986                 CPU_CLR(PCPU_GET(cpuid), &idle_cpus_mask);
  987 #endif
  988         } else {
  989                 if (TD_IS_RUNNING(td)) {
  990                         /* Put us back on the run queue. */
  991                         sched_add(td, preempted ?
  992                             SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
  993                             SRQ_OURSELF|SRQ_YIELDING);
  994                 }
  995         }
  996         if (newtd) {
  997                 /*
  998                  * The thread we are about to run needs to be counted
  999                  * as if it had been added to the run queue and selected.
 1000                  * It came from:
 1001                  * * A preemption
 1002                  * * An upcall
 1003                  * * A followon
 1004                  */
 1005                 KASSERT((newtd->td_inhibitors == 0),
 1006                         ("trying to run inhibited thread"));
 1007                 newtd->td_flags |= TDF_DIDRUN;
 1008                 TD_SET_RUNNING(newtd);
 1009                 if ((newtd->td_flags & TDF_NOLOAD) == 0)
 1010                         sched_load_add();
 1011         } else {
 1012                 newtd = choosethread();
 1013                 MPASS(newtd->td_lock == &sched_lock);
 1014         }
 1015 
 1016 #if (KTR_COMPILE & KTR_SCHED) != 0
 1017         if (TD_IS_IDLETHREAD(td))
 1018                 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
 1019                     "prio:%d", td->td_priority);
 1020         else
 1021                 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
 1022                     "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
 1023                     "lockname:\"%s\"", td->td_lockname);
 1024 #endif
 1025 
 1026         if (td != newtd) {
 1027 #ifdef  HWPMC_HOOKS
 1028                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1029                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 1030 #endif
 1031 
 1032                 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
 1033 
 1034                 /* I feel sleepy */
 1035                 lock_profile_release_lock(&sched_lock.lock_object);
 1036 #ifdef KDTRACE_HOOKS
 1037                 /*
 1038                  * If DTrace has set the active vtime enum to anything
 1039                  * other than INACTIVE (0), then it should have set the
 1040                  * function to call.
 1041                  */
 1042                 if (dtrace_vtime_active)
 1043                         (*dtrace_vtime_switch_func)(newtd);
 1044 #endif
 1045 
 1046                 cpu_switch(td, newtd, tmtx != NULL ? tmtx : td->td_lock);
 1047                 lock_profile_obtain_lock_success(&sched_lock.lock_object,
 1048                     0, 0, __FILE__, __LINE__);
 1049                 /*
 1050                  * Where am I?  What year is it?
 1051                  * We are in the same thread that went to sleep above,
 1052                  * but any amount of time may have passed. All our context
 1053                  * will still be available as will local variables.
 1054                  * PCPU values however may have changed as we may have
 1055                  * changed CPU so don't trust cached values of them.
 1056                  * New threads will go to fork_exit() instead of here
 1057                  * so if you change things here you may need to change
 1058                  * things there too.
 1059                  *
 1060                  * If the thread above was exiting it will never wake
 1061                  * up again here, so either it has saved everything it
 1062                  * needed to, or the thread_wait() or wait() will
 1063                  * need to reap it.
 1064                  */
 1065 
 1066                 SDT_PROBE0(sched, , , on__cpu);
 1067 #ifdef  HWPMC_HOOKS
 1068                 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 1069                         PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
 1070 #endif
 1071         } else
 1072                 SDT_PROBE0(sched, , , remain__cpu);
 1073 
 1074         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
 1075             "prio:%d", td->td_priority);
 1076 
 1077 #ifdef SMP
 1078         if (td->td_flags & TDF_IDLETD)
 1079                 CPU_SET(PCPU_GET(cpuid), &idle_cpus_mask);
 1080 #endif
 1081         sched_lock.mtx_lock = (uintptr_t)td;
 1082         td->td_oncpu = PCPU_GET(cpuid);
 1083         MPASS(td->td_lock == &sched_lock);
 1084 }
 1085 
 1086 void
 1087 sched_wakeup(struct thread *td)
 1088 {
 1089         struct td_sched *ts;
 1090 
 1091         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1092         ts = td_get_sched(td);
 1093         td->td_flags &= ~TDF_CANSWAP;
 1094         if (ts->ts_slptime > 1) {
 1095                 updatepri(td);
 1096                 resetpriority(td);
 1097         }
 1098         td->td_slptick = 0;
 1099         ts->ts_slptime = 0;
 1100         ts->ts_slice = sched_slice;
 1101         sched_add(td, SRQ_BORING);
 1102 }
 1103 
 1104 #ifdef SMP
 1105 static int
 1106 forward_wakeup(int cpunum)
 1107 {
 1108         struct pcpu *pc;
 1109         cpuset_t dontuse, map, map2;
 1110         u_int id, me;
 1111         int iscpuset;
 1112 
 1113         mtx_assert(&sched_lock, MA_OWNED);
 1114 
 1115         CTR0(KTR_RUNQ, "forward_wakeup()");
 1116 
 1117         if ((!forward_wakeup_enabled) ||
 1118              (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0))
 1119                 return (0);
 1120         if (!smp_started || panicstr)
 1121                 return (0);
 1122 
 1123         forward_wakeups_requested++;
 1124 
 1125         /*
 1126          * Check the idle mask we received against what we calculated
 1127          * before in the old version.
 1128          */
 1129         me = PCPU_GET(cpuid);
 1130 
 1131         /* Don't bother if we should be doing it ourself. */
 1132         if (CPU_ISSET(me, &idle_cpus_mask) &&
 1133             (cpunum == NOCPU || me == cpunum))
 1134                 return (0);
 1135 
 1136         CPU_SETOF(me, &dontuse);
 1137         CPU_OR(&dontuse, &stopped_cpus);
 1138         CPU_OR(&dontuse, &hlt_cpus_mask);
 1139         CPU_ZERO(&map2);
 1140         if (forward_wakeup_use_loop) {
 1141                 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
 1142                         id = pc->pc_cpuid;
 1143                         if (!CPU_ISSET(id, &dontuse) &&
 1144                             pc->pc_curthread == pc->pc_idlethread) {
 1145                                 CPU_SET(id, &map2);
 1146                         }
 1147                 }
 1148         }
 1149 
 1150         if (forward_wakeup_use_mask) {
 1151                 map = idle_cpus_mask;
 1152                 CPU_NAND(&map, &dontuse);
 1153 
 1154                 /* If they are both on, compare and use loop if different. */
 1155                 if (forward_wakeup_use_loop) {
 1156                         if (CPU_CMP(&map, &map2)) {
 1157                                 printf("map != map2, loop method preferred\n");
 1158                                 map = map2;
 1159                         }
 1160                 }
 1161         } else {
 1162                 map = map2;
 1163         }
 1164 
 1165         /* If we only allow a specific CPU, then mask off all the others. */
 1166         if (cpunum != NOCPU) {
 1167                 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum."));
 1168                 iscpuset = CPU_ISSET(cpunum, &map);
 1169                 if (iscpuset == 0)
 1170                         CPU_ZERO(&map);
 1171                 else
 1172                         CPU_SETOF(cpunum, &map);
 1173         }
 1174         if (!CPU_EMPTY(&map)) {
 1175                 forward_wakeups_delivered++;
 1176                 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
 1177                         id = pc->pc_cpuid;
 1178                         if (!CPU_ISSET(id, &map))
 1179                                 continue;
 1180                         if (cpu_idle_wakeup(pc->pc_cpuid))
 1181                                 CPU_CLR(id, &map);
 1182                 }
 1183                 if (!CPU_EMPTY(&map))
 1184                         ipi_selected(map, IPI_AST);
 1185                 return (1);
 1186         }
 1187         if (cpunum == NOCPU)
 1188                 printf("forward_wakeup: Idle processor not found\n");
 1189         return (0);
 1190 }
 1191 
 1192 static void
 1193 kick_other_cpu(int pri, int cpuid)
 1194 {
 1195         struct pcpu *pcpu;
 1196         int cpri;
 1197 
 1198         pcpu = pcpu_find(cpuid);
 1199         if (CPU_ISSET(cpuid, &idle_cpus_mask)) {
 1200                 forward_wakeups_delivered++;
 1201                 if (!cpu_idle_wakeup(cpuid))
 1202                         ipi_cpu(cpuid, IPI_AST);
 1203                 return;
 1204         }
 1205 
 1206         cpri = pcpu->pc_curthread->td_priority;
 1207         if (pri >= cpri)
 1208                 return;
 1209 
 1210 #if defined(IPI_PREEMPTION) && defined(PREEMPTION)
 1211 #if !defined(FULL_PREEMPTION)
 1212         if (pri <= PRI_MAX_ITHD)
 1213 #endif /* ! FULL_PREEMPTION */
 1214         {
 1215                 ipi_cpu(cpuid, IPI_PREEMPT);
 1216                 return;
 1217         }
 1218 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */
 1219 
 1220         pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED;
 1221         ipi_cpu(cpuid, IPI_AST);
 1222         return;
 1223 }
 1224 #endif /* SMP */
 1225 
 1226 #ifdef SMP
 1227 static int
 1228 sched_pickcpu(struct thread *td)
 1229 {
 1230         int best, cpu;
 1231 
 1232         mtx_assert(&sched_lock, MA_OWNED);
 1233 
 1234         if (td->td_lastcpu != NOCPU && THREAD_CAN_SCHED(td, td->td_lastcpu))
 1235                 best = td->td_lastcpu;
 1236         else
 1237                 best = NOCPU;
 1238         CPU_FOREACH(cpu) {
 1239                 if (!THREAD_CAN_SCHED(td, cpu))
 1240                         continue;
 1241         
 1242                 if (best == NOCPU)
 1243                         best = cpu;
 1244                 else if (runq_length[cpu] < runq_length[best])
 1245                         best = cpu;
 1246         }
 1247         KASSERT(best != NOCPU, ("no valid CPUs"));
 1248 
 1249         return (best);
 1250 }
 1251 #endif
 1252 
 1253 void
 1254 sched_add(struct thread *td, int flags)
 1255 #ifdef SMP
 1256 {
 1257         cpuset_t tidlemsk;
 1258         struct td_sched *ts;
 1259         u_int cpu, cpuid;
 1260         int forwarded = 0;
 1261         int single_cpu = 0;
 1262 
 1263         ts = td_get_sched(td);
 1264         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1265         KASSERT((td->td_inhibitors == 0),
 1266             ("sched_add: trying to run inhibited thread"));
 1267         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 1268             ("sched_add: bad thread state"));
 1269         KASSERT(td->td_flags & TDF_INMEM,
 1270             ("sched_add: thread swapped out"));
 1271 
 1272         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 1273             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 1274             sched_tdname(curthread));
 1275         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 1276             KTR_ATTR_LINKED, sched_tdname(td));
 1277         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 1278             flags & SRQ_PREEMPTED);
 1279 
 1280 
 1281         /*
 1282          * Now that the thread is moving to the run-queue, set the lock
 1283          * to the scheduler's lock.
 1284          */
 1285         if (td->td_lock != &sched_lock) {
 1286                 mtx_lock_spin(&sched_lock);
 1287                 thread_lock_set(td, &sched_lock);
 1288         }
 1289         TD_SET_RUNQ(td);
 1290 
 1291         /*
 1292          * If SMP is started and the thread is pinned or otherwise limited to
 1293          * a specific set of CPUs, queue the thread to a per-CPU run queue.
 1294          * Otherwise, queue the thread to the global run queue.
 1295          *
 1296          * If SMP has not yet been started we must use the global run queue
 1297          * as per-CPU state may not be initialized yet and we may crash if we
 1298          * try to access the per-CPU run queues.
 1299          */
 1300         if (smp_started && (td->td_pinned != 0 || td->td_flags & TDF_BOUND ||
 1301             ts->ts_flags & TSF_AFFINITY)) {
 1302                 if (td->td_pinned != 0)
 1303                         cpu = td->td_lastcpu;
 1304                 else if (td->td_flags & TDF_BOUND) {
 1305                         /* Find CPU from bound runq. */
 1306                         KASSERT(SKE_RUNQ_PCPU(ts),
 1307                             ("sched_add: bound td_sched not on cpu runq"));
 1308                         cpu = ts->ts_runq - &runq_pcpu[0];
 1309                 } else
 1310                         /* Find a valid CPU for our cpuset */
 1311                         cpu = sched_pickcpu(td);
 1312                 ts->ts_runq = &runq_pcpu[cpu];
 1313                 single_cpu = 1;
 1314                 CTR3(KTR_RUNQ,
 1315                     "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td,
 1316                     cpu);
 1317         } else {
 1318                 CTR2(KTR_RUNQ,
 1319                     "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts,
 1320                     td);
 1321                 cpu = NOCPU;
 1322                 ts->ts_runq = &runq;
 1323         }
 1324 
 1325         if ((td->td_flags & TDF_NOLOAD) == 0)
 1326                 sched_load_add();
 1327         runq_add(ts->ts_runq, td, flags);
 1328         if (cpu != NOCPU)
 1329                 runq_length[cpu]++;
 1330 
 1331         cpuid = PCPU_GET(cpuid);
 1332         if (single_cpu && cpu != cpuid) {
 1333                 kick_other_cpu(td->td_priority, cpu);
 1334         } else {
 1335                 if (!single_cpu) {
 1336                         tidlemsk = idle_cpus_mask;
 1337                         CPU_NAND(&tidlemsk, &hlt_cpus_mask);
 1338                         CPU_CLR(cpuid, &tidlemsk);
 1339 
 1340                         if (!CPU_ISSET(cpuid, &idle_cpus_mask) &&
 1341                             ((flags & SRQ_INTR) == 0) &&
 1342                             !CPU_EMPTY(&tidlemsk))
 1343                                 forwarded = forward_wakeup(cpu);
 1344                 }
 1345 
 1346                 if (!forwarded) {
 1347                         if (!maybe_preempt(td))
 1348                                 maybe_resched(td);
 1349                 }
 1350         }
 1351 }
 1352 #else /* SMP */
 1353 {
 1354         struct td_sched *ts;
 1355 
 1356         ts = td_get_sched(td);
 1357         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1358         KASSERT((td->td_inhibitors == 0),
 1359             ("sched_add: trying to run inhibited thread"));
 1360         KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
 1361             ("sched_add: bad thread state"));
 1362         KASSERT(td->td_flags & TDF_INMEM,
 1363             ("sched_add: thread swapped out"));
 1364         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
 1365             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 1366             sched_tdname(curthread));
 1367         KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
 1368             KTR_ATTR_LINKED, sched_tdname(td));
 1369         SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 
 1370             flags & SRQ_PREEMPTED);
 1371 
 1372         /*
 1373          * Now that the thread is moving to the run-queue, set the lock
 1374          * to the scheduler's lock.
 1375          */
 1376         if (td->td_lock != &sched_lock) {
 1377                 mtx_lock_spin(&sched_lock);
 1378                 thread_lock_set(td, &sched_lock);
 1379         }
 1380         TD_SET_RUNQ(td);
 1381         CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td);
 1382         ts->ts_runq = &runq;
 1383 
 1384         if ((td->td_flags & TDF_NOLOAD) == 0)
 1385                 sched_load_add();
 1386         runq_add(ts->ts_runq, td, flags);
 1387         if (!maybe_preempt(td))
 1388                 maybe_resched(td);
 1389 }
 1390 #endif /* SMP */
 1391 
 1392 void
 1393 sched_rem(struct thread *td)
 1394 {
 1395         struct td_sched *ts;
 1396 
 1397         ts = td_get_sched(td);
 1398         KASSERT(td->td_flags & TDF_INMEM,
 1399             ("sched_rem: thread swapped out"));
 1400         KASSERT(TD_ON_RUNQ(td),
 1401             ("sched_rem: thread not on run queue"));
 1402         mtx_assert(&sched_lock, MA_OWNED);
 1403         KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
 1404             "prio:%d", td->td_priority, KTR_ATTR_LINKED,
 1405             sched_tdname(curthread));
 1406         SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
 1407 
 1408         if ((td->td_flags & TDF_NOLOAD) == 0)
 1409                 sched_load_rem();
 1410 #ifdef SMP
 1411         if (ts->ts_runq != &runq)
 1412                 runq_length[ts->ts_runq - runq_pcpu]--;
 1413 #endif
 1414         runq_remove(ts->ts_runq, td);
 1415         TD_SET_CAN_RUN(td);
 1416 }
 1417 
 1418 /*
 1419  * Select threads to run.  Note that running threads still consume a
 1420  * slot.
 1421  */
 1422 struct thread *
 1423 sched_choose(void)
 1424 {
 1425         struct thread *td;
 1426         struct runq *rq;
 1427 
 1428         mtx_assert(&sched_lock,  MA_OWNED);
 1429 #ifdef SMP
 1430         struct thread *tdcpu;
 1431 
 1432         rq = &runq;
 1433         td = runq_choose_fuzz(&runq, runq_fuzz);
 1434         tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]);
 1435 
 1436         if (td == NULL ||
 1437             (tdcpu != NULL &&
 1438              tdcpu->td_priority < td->td_priority)) {
 1439                 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu,
 1440                      PCPU_GET(cpuid));
 1441                 td = tdcpu;
 1442                 rq = &runq_pcpu[PCPU_GET(cpuid)];
 1443         } else {
 1444                 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td);
 1445         }
 1446 
 1447 #else
 1448         rq = &runq;
 1449         td = runq_choose(&runq);
 1450 #endif
 1451 
 1452         if (td) {
 1453 #ifdef SMP
 1454                 if (td == tdcpu)
 1455                         runq_length[PCPU_GET(cpuid)]--;
 1456 #endif
 1457                 runq_remove(rq, td);
 1458                 td->td_flags |= TDF_DIDRUN;
 1459 
 1460                 KASSERT(td->td_flags & TDF_INMEM,
 1461                     ("sched_choose: thread swapped out"));
 1462                 return (td);
 1463         }
 1464         return (PCPU_GET(idlethread));
 1465 }
 1466 
 1467 void
 1468 sched_preempt(struct thread *td)
 1469 {
 1470 
 1471         SDT_PROBE2(sched, , , surrender, td, td->td_proc);
 1472         thread_lock(td);
 1473         if (td->td_critnest > 1)
 1474                 td->td_owepreempt = 1;
 1475         else
 1476                 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, NULL);
 1477         thread_unlock(td);
 1478 }
 1479 
 1480 void
 1481 sched_userret(struct thread *td)
 1482 {
 1483         /*
 1484          * XXX we cheat slightly on the locking here to avoid locking in
 1485          * the usual case.  Setting td_priority here is essentially an
 1486          * incomplete workaround for not setting it properly elsewhere.
 1487          * Now that some interrupt handlers are threads, not setting it
 1488          * properly elsewhere can clobber it in the window between setting
 1489          * it here and returning to user mode, so don't waste time setting
 1490          * it perfectly here.
 1491          */
 1492         KASSERT((td->td_flags & TDF_BORROWING) == 0,
 1493             ("thread with borrowed priority returning to userland"));
 1494         if (td->td_priority != td->td_user_pri) {
 1495                 thread_lock(td);
 1496                 td->td_priority = td->td_user_pri;
 1497                 td->td_base_pri = td->td_user_pri;
 1498                 thread_unlock(td);
 1499         }
 1500 }
 1501 
 1502 void
 1503 sched_bind(struct thread *td, int cpu)
 1504 {
 1505         struct td_sched *ts;
 1506 
 1507         THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
 1508         KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
 1509 
 1510         ts = td_get_sched(td);
 1511 
 1512         td->td_flags |= TDF_BOUND;
 1513 #ifdef SMP
 1514         ts->ts_runq = &runq_pcpu[cpu];
 1515         if (PCPU_GET(cpuid) == cpu)
 1516                 return;
 1517 
 1518         mi_switch(SW_VOL, NULL);
 1519 #endif
 1520 }
 1521 
 1522 void
 1523 sched_unbind(struct thread* td)
 1524 {
 1525         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1526         KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
 1527         td->td_flags &= ~TDF_BOUND;
 1528 }
 1529 
 1530 int
 1531 sched_is_bound(struct thread *td)
 1532 {
 1533         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1534         return (td->td_flags & TDF_BOUND);
 1535 }
 1536 
 1537 void
 1538 sched_relinquish(struct thread *td)
 1539 {
 1540         thread_lock(td);
 1541         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 1542         thread_unlock(td);
 1543 }
 1544 
 1545 int
 1546 sched_load(void)
 1547 {
 1548         return (sched_tdcnt);
 1549 }
 1550 
 1551 int
 1552 sched_sizeof_proc(void)
 1553 {
 1554         return (sizeof(struct proc));
 1555 }
 1556 
 1557 int
 1558 sched_sizeof_thread(void)
 1559 {
 1560         return (sizeof(struct thread) + sizeof(struct td_sched));
 1561 }
 1562 
 1563 fixpt_t
 1564 sched_pctcpu(struct thread *td)
 1565 {
 1566         struct td_sched *ts;
 1567 
 1568         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1569         ts = td_get_sched(td);
 1570         return (ts->ts_pctcpu);
 1571 }
 1572 
 1573 #ifdef RACCT
 1574 /*
 1575  * Calculates the contribution to the thread cpu usage for the latest
 1576  * (unfinished) second.
 1577  */
 1578 fixpt_t
 1579 sched_pctcpu_delta(struct thread *td)
 1580 {
 1581         struct td_sched *ts;
 1582         fixpt_t delta;
 1583         int realstathz;
 1584 
 1585         THREAD_LOCK_ASSERT(td, MA_OWNED);
 1586         ts = td_get_sched(td);
 1587         delta = 0;
 1588         realstathz = stathz ? stathz : hz;
 1589         if (ts->ts_cpticks != 0) {
 1590 #if     (FSHIFT >= CCPU_SHIFT)
 1591                 delta = (realstathz == 100)
 1592                     ? ((fixpt_t) ts->ts_cpticks) <<
 1593                     (FSHIFT - CCPU_SHIFT) :
 1594                     100 * (((fixpt_t) ts->ts_cpticks)
 1595                     << (FSHIFT - CCPU_SHIFT)) / realstathz;
 1596 #else
 1597                 delta = ((FSCALE - ccpu) *
 1598                     (ts->ts_cpticks *
 1599                     FSCALE / realstathz)) >> FSHIFT;
 1600 #endif
 1601         }
 1602 
 1603         return (delta);
 1604 }
 1605 #endif
 1606 
 1607 u_int
 1608 sched_estcpu(struct thread *td)
 1609 {
 1610         
 1611         return (td_get_sched(td)->ts_estcpu);
 1612 }
 1613 
 1614 /*
 1615  * The actual idle process.
 1616  */
 1617 void
 1618 sched_idletd(void *dummy)
 1619 {
 1620         struct pcpuidlestat *stat;
 1621 
 1622         THREAD_NO_SLEEPING();
 1623         stat = DPCPU_PTR(idlestat);
 1624         for (;;) {
 1625                 mtx_assert(&Giant, MA_NOTOWNED);
 1626 
 1627                 while (sched_runnable() == 0) {
 1628                         cpu_idle(stat->idlecalls + stat->oldidlecalls > 64);
 1629                         stat->idlecalls++;
 1630                 }
 1631 
 1632                 mtx_lock_spin(&sched_lock);
 1633                 mi_switch(SW_VOL | SWT_IDLE, NULL);
 1634                 mtx_unlock_spin(&sched_lock);
 1635         }
 1636 }
 1637 
 1638 /*
 1639  * A CPU is entering for the first time or a thread is exiting.
 1640  */
 1641 void
 1642 sched_throw(struct thread *td)
 1643 {
 1644         /*
 1645          * Correct spinlock nesting.  The idle thread context that we are
 1646          * borrowing was created so that it would start out with a single
 1647          * spin lock (sched_lock) held in fork_trampoline().  Since we've
 1648          * explicitly acquired locks in this function, the nesting count
 1649          * is now 2 rather than 1.  Since we are nested, calling
 1650          * spinlock_exit() will simply adjust the counts without allowing
 1651          * spin lock using code to interrupt us.
 1652          */
 1653         if (td == NULL) {
 1654                 mtx_lock_spin(&sched_lock);
 1655                 spinlock_exit();
 1656                 PCPU_SET(switchtime, cpu_ticks());
 1657                 PCPU_SET(switchticks, ticks);
 1658         } else {
 1659                 lock_profile_release_lock(&sched_lock.lock_object);
 1660                 MPASS(td->td_lock == &sched_lock);
 1661                 td->td_lastcpu = td->td_oncpu;
 1662                 td->td_oncpu = NOCPU;
 1663         }
 1664         mtx_assert(&sched_lock, MA_OWNED);
 1665         KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 1666         cpu_throw(td, choosethread());  /* doesn't return */
 1667 }
 1668 
 1669 void
 1670 sched_fork_exit(struct thread *td)
 1671 {
 1672 
 1673         /*
 1674          * Finish setting up thread glue so that it begins execution in a
 1675          * non-nested critical section with sched_lock held but not recursed.
 1676          */
 1677         td->td_oncpu = PCPU_GET(cpuid);
 1678         sched_lock.mtx_lock = (uintptr_t)td;
 1679         lock_profile_obtain_lock_success(&sched_lock.lock_object,
 1680             0, 0, __FILE__, __LINE__);
 1681         THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
 1682 
 1683         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
 1684             "prio:%d", td->td_priority);
 1685         SDT_PROBE0(sched, , , on__cpu);
 1686 }
 1687 
 1688 char *
 1689 sched_tdname(struct thread *td)
 1690 {
 1691 #ifdef KTR
 1692         struct td_sched *ts;
 1693 
 1694         ts = td_get_sched(td);
 1695         if (ts->ts_name[0] == '\0')
 1696                 snprintf(ts->ts_name, sizeof(ts->ts_name),
 1697                     "%s tid %d", td->td_name, td->td_tid);
 1698         return (ts->ts_name);
 1699 #else   
 1700         return (td->td_name);
 1701 #endif
 1702 }
 1703 
 1704 #ifdef KTR
 1705 void
 1706 sched_clear_tdname(struct thread *td)
 1707 {
 1708         struct td_sched *ts;
 1709 
 1710         ts = td_get_sched(td);
 1711         ts->ts_name[0] = '\0';
 1712 }
 1713 #endif
 1714 
 1715 void
 1716 sched_affinity(struct thread *td)
 1717 {
 1718 #ifdef SMP
 1719         struct td_sched *ts;
 1720         int cpu;
 1721 
 1722         THREAD_LOCK_ASSERT(td, MA_OWNED);       
 1723 
 1724         /*
 1725          * Set the TSF_AFFINITY flag if there is at least one CPU this
 1726          * thread can't run on.
 1727          */
 1728         ts = td_get_sched(td);
 1729         ts->ts_flags &= ~TSF_AFFINITY;
 1730         CPU_FOREACH(cpu) {
 1731                 if (!THREAD_CAN_SCHED(td, cpu)) {
 1732                         ts->ts_flags |= TSF_AFFINITY;
 1733                         break;
 1734                 }
 1735         }
 1736 
 1737         /*
 1738          * If this thread can run on all CPUs, nothing else to do.
 1739          */
 1740         if (!(ts->ts_flags & TSF_AFFINITY))
 1741                 return;
 1742 
 1743         /* Pinned threads and bound threads should be left alone. */
 1744         if (td->td_pinned != 0 || td->td_flags & TDF_BOUND)
 1745                 return;
 1746 
 1747         switch (td->td_state) {
 1748         case TDS_RUNQ:
 1749                 /*
 1750                  * If we are on a per-CPU runqueue that is in the set,
 1751                  * then nothing needs to be done.
 1752                  */
 1753                 if (ts->ts_runq != &runq &&
 1754                     THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu))
 1755                         return;
 1756 
 1757                 /* Put this thread on a valid per-CPU runqueue. */
 1758                 sched_rem(td);
 1759                 sched_add(td, SRQ_BORING);
 1760                 break;
 1761         case TDS_RUNNING:
 1762                 /*
 1763                  * See if our current CPU is in the set.  If not, force a
 1764                  * context switch.
 1765                  */
 1766                 if (THREAD_CAN_SCHED(td, td->td_oncpu))
 1767                         return;
 1768 
 1769                 td->td_flags |= TDF_NEEDRESCHED;
 1770                 if (td != curthread)
 1771                         ipi_cpu(cpu, IPI_AST);
 1772                 break;
 1773         default:
 1774                 break;
 1775         }
 1776 #endif
 1777 }

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