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


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

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

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    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  *      @(#)kern_synch.c        8.9 (Berkeley) 5/19/95
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: releng/10.0/sys/kern/kern_synch.c 255835 2013-09-24 07:03:16Z mav $");
   39 
   40 #include "opt_kdtrace.h"
   41 #include "opt_ktrace.h"
   42 #include "opt_sched.h"
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/condvar.h>
   47 #include <sys/kdb.h>
   48 #include <sys/kernel.h>
   49 #include <sys/ktr.h>
   50 #include <sys/lock.h>
   51 #include <sys/mutex.h>
   52 #include <sys/proc.h>
   53 #include <sys/resourcevar.h>
   54 #include <sys/sched.h>
   55 #include <sys/sdt.h>
   56 #include <sys/signalvar.h>
   57 #include <sys/sleepqueue.h>
   58 #include <sys/smp.h>
   59 #include <sys/sx.h>
   60 #include <sys/sysctl.h>
   61 #include <sys/sysproto.h>
   62 #include <sys/vmmeter.h>
   63 #ifdef KTRACE
   64 #include <sys/uio.h>
   65 #include <sys/ktrace.h>
   66 #endif
   67 
   68 #include <machine/cpu.h>
   69 
   70 #ifdef XEN
   71 #include <vm/vm.h>
   72 #include <vm/vm_param.h>
   73 #include <vm/pmap.h>
   74 #endif
   75 
   76 #define KTDSTATE(td)                                                    \
   77         (((td)->td_inhibitors & TDI_SLEEPING) != 0 ? "sleep"  :         \
   78         ((td)->td_inhibitors & TDI_SUSPENDED) != 0 ? "suspended" :      \
   79         ((td)->td_inhibitors & TDI_SWAPPED) != 0 ? "swapped" :          \
   80         ((td)->td_inhibitors & TDI_LOCK) != 0 ? "blocked" :             \
   81         ((td)->td_inhibitors & TDI_IWAIT) != 0 ? "iwait" : "yielding")
   82 
   83 static void synch_setup(void *dummy);
   84 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
   85     NULL);
   86 
   87 int     hogticks;
   88 static uint8_t pause_wchan[MAXCPU];
   89 
   90 static struct callout loadav_callout;
   91 
   92 struct loadavg averunnable =
   93         { {0, 0, 0}, FSCALE };  /* load average, of runnable procs */
   94 /*
   95  * Constants for averages over 1, 5, and 15 minutes
   96  * when sampling at 5 second intervals.
   97  */
   98 static fixpt_t cexp[3] = {
   99         0.9200444146293232 * FSCALE,    /* exp(-1/12) */
  100         0.9834714538216174 * FSCALE,    /* exp(-1/60) */
  101         0.9944598480048967 * FSCALE,    /* exp(-1/180) */
  102 };
  103 
  104 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
  105 static int      fscale __unused = FSCALE;
  106 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
  107 
  108 static void     loadav(void *arg);
  109 
  110 SDT_PROVIDER_DECLARE(sched);
  111 SDT_PROBE_DEFINE(sched, , , preempt, preempt);
  112 
  113 /*
  114  * These probes reference Solaris features that are not implemented in FreeBSD.
  115  * Create the probes anyway for compatibility with existing D scripts; they'll
  116  * just never fire.
  117  */
  118 SDT_PROBE_DEFINE(sched, , , cpucaps_sleep, cpucaps-sleep);
  119 SDT_PROBE_DEFINE(sched, , , cpucaps_wakeup, cpucaps-wakeup);
  120 SDT_PROBE_DEFINE(sched, , , schedctl_nopreempt, schedctl-nopreempt);
  121 SDT_PROBE_DEFINE(sched, , , schedctl_preempt, schedctl-preempt);
  122 SDT_PROBE_DEFINE(sched, , , schedctl_yield, schedctl-yield);
  123 
  124 static void
  125 sleepinit(void *unused)
  126 {
  127 
  128         hogticks = (hz / 10) * 2;       /* Default only. */
  129         init_sleepqueues();
  130 }
  131 
  132 /*
  133  * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure
  134  * it is available.
  135  */
  136 SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, 0);
  137 
  138 /*
  139  * General sleep call.  Suspends the current thread until a wakeup is
  140  * performed on the specified identifier.  The thread will then be made
  141  * runnable with the specified priority.  Sleeps at most sbt units of time
  142  * (0 means no timeout).  If pri includes the PCATCH flag, let signals
  143  * interrupt the sleep, otherwise ignore them while sleeping.  Returns 0 if
  144  * awakened, EWOULDBLOCK if the timeout expires.  If PCATCH is set and a
  145  * signal becomes pending, ERESTART is returned if the current system
  146  * call should be restarted if possible, and EINTR is returned if the system
  147  * call should be interrupted by the signal (return EINTR).
  148  *
  149  * The lock argument is unlocked before the caller is suspended, and
  150  * re-locked before _sleep() returns.  If priority includes the PDROP
  151  * flag the lock is not re-locked before returning.
  152  */
  153 int
  154 _sleep(void *ident, struct lock_object *lock, int priority,
  155     const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
  156 {
  157         struct thread *td;
  158         struct proc *p;
  159         struct lock_class *class;
  160         uintptr_t lock_state;
  161         int catch, pri, rval, sleepq_flags;
  162         WITNESS_SAVE_DECL(lock_witness);
  163 
  164         td = curthread;
  165         p = td->td_proc;
  166 #ifdef KTRACE
  167         if (KTRPOINT(td, KTR_CSW))
  168                 ktrcsw(1, 0, wmesg);
  169 #endif
  170         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
  171             "Sleeping on \"%s\"", wmesg);
  172         KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL,
  173             ("sleeping without a lock"));
  174         KASSERT(p != NULL, ("msleep1"));
  175         KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
  176         if (priority & PDROP)
  177                 KASSERT(lock != NULL && lock != &Giant.lock_object,
  178                     ("PDROP requires a non-Giant lock"));
  179         if (lock != NULL)
  180                 class = LOCK_CLASS(lock);
  181         else
  182                 class = NULL;
  183 
  184         if (cold || SCHEDULER_STOPPED()) {
  185                 /*
  186                  * During autoconfiguration, just return;
  187                  * don't run any other threads or panic below,
  188                  * in case this is the idle thread and already asleep.
  189                  * XXX: this used to do "s = splhigh(); splx(safepri);
  190                  * splx(s);" to give interrupts a chance, but there is
  191                  * no way to give interrupts a chance now.
  192                  */
  193                 if (lock != NULL && priority & PDROP)
  194                         class->lc_unlock(lock);
  195                 return (0);
  196         }
  197         catch = priority & PCATCH;
  198         pri = priority & PRIMASK;
  199 
  200         /*
  201          * If we are already on a sleep queue, then remove us from that
  202          * sleep queue first.  We have to do this to handle recursive
  203          * sleeps.
  204          */
  205         if (TD_ON_SLEEPQ(td))
  206                 sleepq_remove(td, td->td_wchan);
  207 
  208         if ((uint8_t *)ident >= &pause_wchan[0] &&
  209             (uint8_t *)ident <= &pause_wchan[MAXCPU - 1])
  210                 sleepq_flags = SLEEPQ_PAUSE;
  211         else
  212                 sleepq_flags = SLEEPQ_SLEEP;
  213         if (catch)
  214                 sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
  215 
  216         sleepq_lock(ident);
  217         CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
  218             td->td_tid, p->p_pid, td->td_name, wmesg, ident);
  219 
  220         if (lock == &Giant.lock_object)
  221                 mtx_assert(&Giant, MA_OWNED);
  222         DROP_GIANT();
  223         if (lock != NULL && lock != &Giant.lock_object &&
  224             !(class->lc_flags & LC_SLEEPABLE)) {
  225                 WITNESS_SAVE(lock, lock_witness);
  226                 lock_state = class->lc_unlock(lock);
  227         } else
  228                 /* GCC needs to follow the Yellow Brick Road */
  229                 lock_state = -1;
  230 
  231         /*
  232          * We put ourselves on the sleep queue and start our timeout
  233          * before calling thread_suspend_check, as we could stop there,
  234          * and a wakeup or a SIGCONT (or both) could occur while we were
  235          * stopped without resuming us.  Thus, we must be ready for sleep
  236          * when cursig() is called.  If the wakeup happens while we're
  237          * stopped, then td will no longer be on a sleep queue upon
  238          * return from cursig().
  239          */
  240         sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
  241         if (sbt != 0)
  242                 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
  243         if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
  244                 sleepq_release(ident);
  245                 WITNESS_SAVE(lock, lock_witness);
  246                 lock_state = class->lc_unlock(lock);
  247                 sleepq_lock(ident);
  248         }
  249         if (sbt != 0 && catch)
  250                 rval = sleepq_timedwait_sig(ident, pri);
  251         else if (sbt != 0)
  252                 rval = sleepq_timedwait(ident, pri);
  253         else if (catch)
  254                 rval = sleepq_wait_sig(ident, pri);
  255         else {
  256                 sleepq_wait(ident, pri);
  257                 rval = 0;
  258         }
  259 #ifdef KTRACE
  260         if (KTRPOINT(td, KTR_CSW))
  261                 ktrcsw(0, 0, wmesg);
  262 #endif
  263         PICKUP_GIANT();
  264         if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
  265                 class->lc_lock(lock, lock_state);
  266                 WITNESS_RESTORE(lock, lock_witness);
  267         }
  268         return (rval);
  269 }
  270 
  271 int
  272 msleep_spin_sbt(void *ident, struct mtx *mtx, const char *wmesg,
  273     sbintime_t sbt, sbintime_t pr, int flags)
  274 {
  275         struct thread *td;
  276         struct proc *p;
  277         int rval;
  278         WITNESS_SAVE_DECL(mtx);
  279 
  280         td = curthread;
  281         p = td->td_proc;
  282         KASSERT(mtx != NULL, ("sleeping without a mutex"));
  283         KASSERT(p != NULL, ("msleep1"));
  284         KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
  285 
  286         if (cold || SCHEDULER_STOPPED()) {
  287                 /*
  288                  * During autoconfiguration, just return;
  289                  * don't run any other threads or panic below,
  290                  * in case this is the idle thread and already asleep.
  291                  * XXX: this used to do "s = splhigh(); splx(safepri);
  292                  * splx(s);" to give interrupts a chance, but there is
  293                  * no way to give interrupts a chance now.
  294                  */
  295                 return (0);
  296         }
  297 
  298         sleepq_lock(ident);
  299         CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
  300             td->td_tid, p->p_pid, td->td_name, wmesg, ident);
  301 
  302         DROP_GIANT();
  303         mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
  304         WITNESS_SAVE(&mtx->lock_object, mtx);
  305         mtx_unlock_spin(mtx);
  306 
  307         /*
  308          * We put ourselves on the sleep queue and start our timeout.
  309          */
  310         sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
  311         if (sbt != 0)
  312                 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
  313 
  314         /*
  315          * Can't call ktrace with any spin locks held so it can lock the
  316          * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
  317          * any spin lock.  Thus, we have to drop the sleepq spin lock while
  318          * we handle those requests.  This is safe since we have placed our
  319          * thread on the sleep queue already.
  320          */
  321 #ifdef KTRACE
  322         if (KTRPOINT(td, KTR_CSW)) {
  323                 sleepq_release(ident);
  324                 ktrcsw(1, 0, wmesg);
  325                 sleepq_lock(ident);
  326         }
  327 #endif
  328 #ifdef WITNESS
  329         sleepq_release(ident);
  330         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
  331             wmesg);
  332         sleepq_lock(ident);
  333 #endif
  334         if (sbt != 0)
  335                 rval = sleepq_timedwait(ident, 0);
  336         else {
  337                 sleepq_wait(ident, 0);
  338                 rval = 0;
  339         }
  340 #ifdef KTRACE
  341         if (KTRPOINT(td, KTR_CSW))
  342                 ktrcsw(0, 0, wmesg);
  343 #endif
  344         PICKUP_GIANT();
  345         mtx_lock_spin(mtx);
  346         WITNESS_RESTORE(&mtx->lock_object, mtx);
  347         return (rval);
  348 }
  349 
  350 /*
  351  * pause() delays the calling thread by the given number of system ticks.
  352  * During cold bootup, pause() uses the DELAY() function instead of
  353  * the tsleep() function to do the waiting. The "timo" argument must be
  354  * greater than or equal to zero. A "timo" value of zero is equivalent
  355  * to a "timo" value of one.
  356  */
  357 int
  358 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
  359 {
  360         KASSERT(sbt >= 0, ("pause: timeout must be >= 0"));
  361 
  362         /* silently convert invalid timeouts */
  363         if (sbt == 0)
  364                 sbt = tick_sbt;
  365 
  366         if (cold) {
  367                 /*
  368                  * We delay one second at a time to avoid overflowing the
  369                  * system specific DELAY() function(s):
  370                  */
  371                 while (sbt >= SBT_1S) {
  372                         DELAY(1000000);
  373                         sbt -= SBT_1S;
  374                 }
  375                 /* Do the delay remainder, if any */
  376                 sbt = (sbt + SBT_1US - 1) / SBT_1US;
  377                 if (sbt > 0)
  378                         DELAY(sbt);
  379                 return (0);
  380         }
  381         return (_sleep(&pause_wchan[curcpu], NULL, 0, wmesg, sbt, pr, flags));
  382 }
  383 
  384 /*
  385  * Make all threads sleeping on the specified identifier runnable.
  386  */
  387 void
  388 wakeup(void *ident)
  389 {
  390         int wakeup_swapper;
  391 
  392         sleepq_lock(ident);
  393         wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
  394         sleepq_release(ident);
  395         if (wakeup_swapper) {
  396                 KASSERT(ident != &proc0,
  397                     ("wakeup and wakeup_swapper and proc0"));
  398                 kick_proc0();
  399         }
  400 }
  401 
  402 /*
  403  * Make a thread sleeping on the specified identifier runnable.
  404  * May wake more than one thread if a target thread is currently
  405  * swapped out.
  406  */
  407 void
  408 wakeup_one(void *ident)
  409 {
  410         int wakeup_swapper;
  411 
  412         sleepq_lock(ident);
  413         wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
  414         sleepq_release(ident);
  415         if (wakeup_swapper)
  416                 kick_proc0();
  417 }
  418 
  419 static void
  420 kdb_switch(void)
  421 {
  422         thread_unlock(curthread);
  423         kdb_backtrace();
  424         kdb_reenter();
  425         panic("%s: did not reenter debugger", __func__);
  426 }
  427 
  428 /*
  429  * The machine independent parts of context switching.
  430  */
  431 void
  432 mi_switch(int flags, struct thread *newtd)
  433 {
  434         uint64_t runtime, new_switchtime;
  435         struct thread *td;
  436         struct proc *p;
  437 
  438         td = curthread;                 /* XXX */
  439         THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
  440         p = td->td_proc;                /* XXX */
  441         KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
  442 #ifdef INVARIANTS
  443         if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
  444                 mtx_assert(&Giant, MA_NOTOWNED);
  445 #endif
  446         KASSERT(td->td_critnest == 1 || panicstr,
  447             ("mi_switch: switch in a critical section"));
  448         KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
  449             ("mi_switch: switch must be voluntary or involuntary"));
  450         KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
  451 
  452         /*
  453          * Don't perform context switches from the debugger.
  454          */
  455         if (kdb_active)
  456                 kdb_switch();
  457         if (SCHEDULER_STOPPED())
  458                 return;
  459         if (flags & SW_VOL) {
  460                 td->td_ru.ru_nvcsw++;
  461                 td->td_swvoltick = ticks;
  462         } else
  463                 td->td_ru.ru_nivcsw++;
  464 #ifdef SCHED_STATS
  465         SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
  466 #endif
  467         /*
  468          * Compute the amount of time during which the current
  469          * thread was running, and add that to its total so far.
  470          */
  471         new_switchtime = cpu_ticks();
  472         runtime = new_switchtime - PCPU_GET(switchtime);
  473         td->td_runtime += runtime;
  474         td->td_incruntime += runtime;
  475         PCPU_SET(switchtime, new_switchtime);
  476         td->td_generation++;    /* bump preempt-detect counter */
  477         PCPU_INC(cnt.v_swtch);
  478         PCPU_SET(switchticks, ticks);
  479         CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
  480             td->td_tid, td->td_sched, p->p_pid, td->td_name);
  481 #if (KTR_COMPILE & KTR_SCHED) != 0
  482         if (TD_IS_IDLETHREAD(td))
  483                 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
  484                     "prio:%d", td->td_priority);
  485         else
  486                 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
  487                     "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
  488                     "lockname:\"%s\"", td->td_lockname);
  489 #endif
  490         SDT_PROBE0(sched, , , preempt);
  491 #ifdef XEN
  492         PT_UPDATES_FLUSH();
  493 #endif
  494         sched_switch(td, newtd, flags);
  495         KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
  496             "prio:%d", td->td_priority);
  497 
  498         CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
  499             td->td_tid, td->td_sched, p->p_pid, td->td_name);
  500 
  501         /* 
  502          * If the last thread was exiting, finish cleaning it up.
  503          */
  504         if ((td = PCPU_GET(deadthread))) {
  505                 PCPU_SET(deadthread, NULL);
  506                 thread_stash(td);
  507         }
  508 }
  509 
  510 /*
  511  * Change thread state to be runnable, placing it on the run queue if
  512  * it is in memory.  If it is swapped out, return true so our caller
  513  * will know to awaken the swapper.
  514  */
  515 int
  516 setrunnable(struct thread *td)
  517 {
  518 
  519         THREAD_LOCK_ASSERT(td, MA_OWNED);
  520         KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
  521             ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
  522         switch (td->td_state) {
  523         case TDS_RUNNING:
  524         case TDS_RUNQ:
  525                 return (0);
  526         case TDS_INHIBITED:
  527                 /*
  528                  * If we are only inhibited because we are swapped out
  529                  * then arange to swap in this process. Otherwise just return.
  530                  */
  531                 if (td->td_inhibitors != TDI_SWAPPED)
  532                         return (0);
  533                 /* FALLTHROUGH */
  534         case TDS_CAN_RUN:
  535                 break;
  536         default:
  537                 printf("state is 0x%x", td->td_state);
  538                 panic("setrunnable(2)");
  539         }
  540         if ((td->td_flags & TDF_INMEM) == 0) {
  541                 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
  542                         td->td_flags |= TDF_SWAPINREQ;
  543                         return (1);
  544                 }
  545         } else
  546                 sched_wakeup(td);
  547         return (0);
  548 }
  549 
  550 /*
  551  * Compute a tenex style load average of a quantity on
  552  * 1, 5 and 15 minute intervals.
  553  */
  554 static void
  555 loadav(void *arg)
  556 {
  557         int i, nrun;
  558         struct loadavg *avg;
  559 
  560         nrun = sched_load();
  561         avg = &averunnable;
  562 
  563         for (i = 0; i < 3; i++)
  564                 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
  565                     nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
  566 
  567         /*
  568          * Schedule the next update to occur after 5 seconds, but add a
  569          * random variation to avoid synchronisation with processes that
  570          * run at regular intervals.
  571          */
  572         callout_reset_sbt(&loadav_callout,
  573             SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
  574             loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
  575 }
  576 
  577 /* ARGSUSED */
  578 static void
  579 synch_setup(void *dummy)
  580 {
  581         callout_init(&loadav_callout, CALLOUT_MPSAFE);
  582 
  583         /* Kick off timeout driven events by calling first time. */
  584         loadav(NULL);
  585 }
  586 
  587 int
  588 should_yield(void)
  589 {
  590 
  591         return ((unsigned int)(ticks - curthread->td_swvoltick) >= hogticks);
  592 }
  593 
  594 void
  595 maybe_yield(void)
  596 {
  597 
  598         if (should_yield())
  599                 kern_yield(PRI_USER);
  600 }
  601 
  602 void
  603 kern_yield(int prio)
  604 {
  605         struct thread *td;
  606 
  607         td = curthread;
  608         DROP_GIANT();
  609         thread_lock(td);
  610         if (prio == PRI_USER)
  611                 prio = td->td_user_pri;
  612         if (prio >= 0)
  613                 sched_prio(td, prio);
  614         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
  615         thread_unlock(td);
  616         PICKUP_GIANT();
  617 }
  618 
  619 /*
  620  * General purpose yield system call.
  621  */
  622 int
  623 sys_yield(struct thread *td, struct yield_args *uap)
  624 {
  625 
  626         thread_lock(td);
  627         if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
  628                 sched_prio(td, PRI_MAX_TIMESHARE);
  629         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
  630         thread_unlock(td);
  631         td->td_retval[0] = 0;
  632         return (0);
  633 }

Cache object: 89dcbd3b856d41e5b5e5cc3005667dc6


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.