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

     /*-
      * Copyright (c) 1982, 1986, 1990, 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
      * the permission of UNIX System Laboratories, Inc.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)kern_synch.c        8.9 (Berkeley) 5/19/95
     * $FreeBSD: src/sys/kern/kern_synch.c,v 1.87.2.6 2002/10/13 07:29:53 kbyanc Exp $
     */
    
    #include "opt_ktrace.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    #include <sys/kernel.h>
    #include <sys/signalvar.h>
    #include <sys/resourcevar.h>
    #include <sys/vmmeter.h>
    #include <sys/sysctl.h>
    #include <sys/lock.h>
    #include <sys/uio.h>
    #ifdef KTRACE
    #include <sys/ktrace.h>
    #endif
    #include <sys/xwait.h>
    #include <sys/ktr.h>
    #include <sys/serialize.h>
    
    #include <sys/signal2.h>
    #include <sys/thread2.h>
    #include <sys/spinlock2.h>
    #include <sys/mutex2.h>
    
    #include <machine/cpu.h>
    #include <machine/smp.h>
    
    TAILQ_HEAD(tslpque, thread);
    
    static void sched_setup (void *dummy);
    SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
    
    int     hogticks;
    int     lbolt;
    void    *lbolt_syncer;
    int     sched_quantum;          /* Roundrobin scheduling quantum in ticks. */
    int     ncpus;
    int     ncpus2, ncpus2_shift, ncpus2_mask;      /* note: mask not cpumask_t */
    int     ncpus_fit, ncpus_fit_mask;              /* note: mask not cpumask_t */
    int     safepri;
    int     tsleep_now_works;
    int     tsleep_crypto_dump = 0;
    
    static struct callout loadav_callout;
    static struct callout schedcpu_callout;
    MALLOC_DEFINE(M_TSLEEP, "tslpque", "tsleep queues");
    
    #define __DEALL(ident)  __DEQUALIFY(void *, ident)
    
    #if !defined(KTR_TSLEEP)
    #define KTR_TSLEEP      KTR_ALL
    #endif
    KTR_INFO_MASTER(tsleep);
    KTR_INFO(KTR_TSLEEP, tsleep, tsleep_beg, 0, "tsleep enter %p", const volatile void *ident);
    KTR_INFO(KTR_TSLEEP, tsleep, tsleep_end, 1, "tsleep exit");
    KTR_INFO(KTR_TSLEEP, tsleep, wakeup_beg, 2, "wakeup enter %p", const volatile void *ident);
    KTR_INFO(KTR_TSLEEP, tsleep, wakeup_end, 3, "wakeup exit");
    KTR_INFO(KTR_TSLEEP, tsleep, ilockfail,  4, "interlock failed %p", const volatile void *ident);
    
    #define logtsleep1(name)        KTR_LOG(tsleep_ ## name)
    #define logtsleep2(name, val)   KTR_LOG(tsleep_ ## name, val)
    
   struct loadavg averunnable =
           { {0, 0, 0}, FSCALE };  /* load average, of runnable procs */
   /*
    * Constants for averages over 1, 5, and 15 minutes
    * when sampling at 5 second intervals.
    */
   static fixpt_t cexp[3] = {
           0.9200444146293232 * FSCALE,    /* exp(-1/12) */
           0.9834714538216174 * FSCALE,    /* exp(-1/60) */
           0.9944598480048967 * FSCALE,    /* exp(-1/180) */
   };
   
   static void     endtsleep (void *);
   static void     loadav (void *arg);
   static void     schedcpu (void *arg);
   
   /*
    * Adjust the scheduler quantum.  The quantum is specified in microseconds.
    * Note that 'tick' is in microseconds per tick.
    */
   static int
   sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
   {
           int error, new_val;
   
           new_val = sched_quantum * ustick;
           error = sysctl_handle_int(oidp, &new_val, 0, req);
           if (error != 0 || req->newptr == NULL)
                   return (error);
           if (new_val < ustick)
                   return (EINVAL);
           sched_quantum = new_val / ustick;
           hogticks = 2 * sched_quantum;
           return (0);
   }
   
   SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
           0, sizeof sched_quantum, sysctl_kern_quantum, "I", "");
   
   static int pctcpu_decay = 10;
   SYSCTL_INT(_kern, OID_AUTO, pctcpu_decay, CTLFLAG_RW, &pctcpu_decay, 0, "");
   
   /*
    * kernel uses `FSCALE', userland (SHOULD) use kern.fscale 
    */
   int     fscale __unused = FSCALE;       /* exported to systat */
   SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
   
   /*
    * Recompute process priorities, once a second.
    *
    * Since the userland schedulers are typically event oriented, if the
    * estcpu calculation at wakeup() time is not sufficient to make a
    * process runnable relative to other processes in the system we have
    * a 1-second recalc to help out.
    *
    * This code also allows us to store sysclock_t data in the process structure
    * without fear of an overrun, since sysclock_t are guarenteed to hold 
    * several seconds worth of count.
    *
    * WARNING!  callouts can preempt normal threads.  However, they will not
    * preempt a thread holding a spinlock so we *can* safely use spinlocks.
    */
   static int schedcpu_stats(struct proc *p, void *data __unused);
   static int schedcpu_resource(struct proc *p, void *data __unused);
   
   static void
   schedcpu(void *arg)
   {
           allproc_scan(schedcpu_stats, NULL);
           allproc_scan(schedcpu_resource, NULL);
           wakeup((caddr_t)&lbolt);
           wakeup(lbolt_syncer);
           callout_reset(&schedcpu_callout, hz, schedcpu, NULL);
   }
   
   /*
    * General process statistics once a second
    */
   static int
   schedcpu_stats(struct proc *p, void *data __unused)
   {
           struct lwp *lp;
   
           /*
            * Threads may not be completely set up if process in SIDL state.
            */
           if (p->p_stat == SIDL)
                   return(0);
   
           PHOLD(p);
           if (lwkt_trytoken(&p->p_token) == FALSE) {
                   PRELE(p);
                   return(0);
           }
   
           p->p_swtime++;
           FOREACH_LWP_IN_PROC(lp, p) {
                   if (lp->lwp_stat == LSSLEEP) {
                           ++lp->lwp_slptime;
                           if (lp->lwp_slptime == 1)
                                   p->p_usched->uload_update(lp);
                   }
   
                   /*
                    * Only recalculate processes that are active or have slept
                    * less then 2 seconds.  The schedulers understand this.
                    * Otherwise decay by 50% per second.
                    */
                   if (lp->lwp_slptime <= 1) {
                           p->p_usched->recalculate(lp);
                   } else {
                           int decay;
   
                           decay = pctcpu_decay;
                           cpu_ccfence();
                           if (decay <= 1)
                                   decay = 1;
                           if (decay > 100)
                                   decay = 100;
                           lp->lwp_pctcpu = (lp->lwp_pctcpu * (decay - 1)) / decay;
                   }
           }
           lwkt_reltoken(&p->p_token);
           lwkt_yield();
           PRELE(p);
           return(0);
   }
   
   /*
    * Resource checks.  XXX break out since ksignal/killproc can block,
    * limiting us to one process killed per second.  There is probably
    * a better way.
    */
   static int
   schedcpu_resource(struct proc *p, void *data __unused)
   {
           u_int64_t ttime;
           struct lwp *lp;
   
           if (p->p_stat == SIDL)
                   return(0);
   
           PHOLD(p);
           if (lwkt_trytoken(&p->p_token) == FALSE) {
                   PRELE(p);
                   return(0);
           }
   
           if (p->p_stat == SZOMB || p->p_limit == NULL) {
                   lwkt_reltoken(&p->p_token);
                   PRELE(p);
                   return(0);
           }
   
           ttime = 0;
           FOREACH_LWP_IN_PROC(lp, p) {
                   /*
                    * We may have caught an lp in the middle of being
                    * created, lwp_thread can be NULL.
                    */
                   if (lp->lwp_thread) {
                           ttime += lp->lwp_thread->td_sticks;
                           ttime += lp->lwp_thread->td_uticks;
                   }
           }
   
           switch(plimit_testcpulimit(p->p_limit, ttime)) {
           case PLIMIT_TESTCPU_KILL:
                   killproc(p, "exceeded maximum CPU limit");
                   break;
           case PLIMIT_TESTCPU_XCPU:
                   if ((p->p_flags & P_XCPU) == 0) {
                           p->p_flags |= P_XCPU;
                           ksignal(p, SIGXCPU);
                   }
                   break;
           default:
                   break;
           }
           lwkt_reltoken(&p->p_token);
           lwkt_yield();
           PRELE(p);
           return(0);
   }
   
   /*
    * This is only used by ps.  Generate a cpu percentage use over
    * a period of one second.
    */
   void
   updatepcpu(struct lwp *lp, int cpticks, int ttlticks)
   {
           fixpt_t acc;
           int remticks;
   
           acc = (cpticks << FSHIFT) / ttlticks;
           if (ttlticks >= ESTCPUFREQ) {
                   lp->lwp_pctcpu = acc;
           } else {
                   remticks = ESTCPUFREQ - ttlticks;
                   lp->lwp_pctcpu = (acc * ttlticks + lp->lwp_pctcpu * remticks) /
                                   ESTCPUFREQ;
           }
   }
   
   /*
    * tsleep/wakeup hash table parameters.  Try to find the sweet spot for
    * like addresses being slept on.
    */
   #define TABLESIZE       4001
   #define LOOKUP(x)       (((u_int)(uintptr_t)(x)) % TABLESIZE)
   
   static cpumask_t slpque_cpumasks[TABLESIZE];
   
   /*
    * General scheduler initialization.  We force a reschedule 25 times
    * a second by default.  Note that cpu0 is initialized in early boot and
    * cannot make any high level calls.
    *
    * Each cpu has its own sleep queue.
    */
   void
   sleep_gdinit(globaldata_t gd)
   {
           static struct tslpque slpque_cpu0[TABLESIZE];
           int i;
   
           if (gd->gd_cpuid == 0) {
                   sched_quantum = (hz + 24) / 25;
                   hogticks = 2 * sched_quantum;
   
                   gd->gd_tsleep_hash = slpque_cpu0;
           } else {
                   gd->gd_tsleep_hash = kmalloc(sizeof(slpque_cpu0), 
                                               M_TSLEEP, M_WAITOK | M_ZERO);
           }
           for (i = 0; i < TABLESIZE; ++i)
                   TAILQ_INIT(&gd->gd_tsleep_hash[i]);
   }
   
   /*
    * This is a dandy function that allows us to interlock tsleep/wakeup
    * operations with unspecified upper level locks, such as lockmgr locks,
    * simply by holding a critical section.  The sequence is:
    *
    *      (acquire upper level lock)
    *      tsleep_interlock(blah)
    *      (release upper level lock)
    *      tsleep(blah, ...)
    *
    * Basically this functions queues us on the tsleep queue without actually
    * descheduling us.  When tsleep() is later called with PINTERLOCK it
    * assumes the thread was already queued, otherwise it queues it there.
    *
    * Thus it is possible to receive the wakeup prior to going to sleep and
    * the race conditions are covered.
    */
   static __inline void
   _tsleep_interlock(globaldata_t gd, const volatile void *ident, int flags)
   {
           thread_t td = gd->gd_curthread;
           int id;
   
           crit_enter_quick(td);
           if (td->td_flags & TDF_TSLEEPQ) {
                   id = LOOKUP(td->td_wchan);
                   TAILQ_REMOVE(&gd->gd_tsleep_hash[id], td, td_sleepq);
                   if (TAILQ_FIRST(&gd->gd_tsleep_hash[id]) == NULL) {
                           atomic_clear_cpumask(&slpque_cpumasks[id],
                                                gd->gd_cpumask);
                   }
           } else {
                   td->td_flags |= TDF_TSLEEPQ;
           }
           id = LOOKUP(ident);
           TAILQ_INSERT_TAIL(&gd->gd_tsleep_hash[id], td, td_sleepq);
           atomic_set_cpumask(&slpque_cpumasks[id], gd->gd_cpumask);
           td->td_wchan = ident;
           td->td_wdomain = flags & PDOMAIN_MASK;
           crit_exit_quick(td);
   }
   
   void
   tsleep_interlock(const volatile void *ident, int flags)
   {
           _tsleep_interlock(mycpu, ident, flags);
   }
   
   /*
    * Remove thread from sleepq.  Must be called with a critical section held.
    * The thread must not be migrating.
    */
   static __inline void
   _tsleep_remove(thread_t td)
   {
           globaldata_t gd = mycpu;
           int id;
   
           KKASSERT(td->td_gd == gd && IN_CRITICAL_SECT(td));
           KKASSERT((td->td_flags & TDF_MIGRATING) == 0);
           if (td->td_flags & TDF_TSLEEPQ) {
                   td->td_flags &= ~TDF_TSLEEPQ;
                   id = LOOKUP(td->td_wchan);
                   TAILQ_REMOVE(&gd->gd_tsleep_hash[id], td, td_sleepq);
                   if (TAILQ_FIRST(&gd->gd_tsleep_hash[id]) == NULL)
                           atomic_clear_cpumask(&slpque_cpumasks[id], gd->gd_cpumask);
                   td->td_wchan = NULL;
                   td->td_wdomain = 0;
           }
   }
   
   void
   tsleep_remove(thread_t td)
   {
           _tsleep_remove(td);
   }
   
   /*
    * General sleep call.  Suspends the current process until a wakeup is
    * performed on the specified identifier.  The process will then be made
    * runnable with the specified priority.  Sleeps at most timo/hz seconds
    * (0 means no timeout).  If flags includes PCATCH flag, signals are checked
    * before and after sleeping, else signals are not checked.  Returns 0 if
    * awakened, EWOULDBLOCK if the timeout expires.  If PCATCH is set and a
    * signal needs to be delivered, ERESTART is returned if the current system
    * call should be restarted if possible, and EINTR is returned if the system
    * call should be interrupted by the signal (return EINTR).
    *
    * Note that if we are a process, we release_curproc() before messing with
    * the LWKT scheduler.
    *
    * During autoconfiguration or after a panic, a sleep will simply
    * lower the priority briefly to allow interrupts, then return.
    *
    * WARNING!  This code can't block (short of switching away), or bad things
    *           will happen.  No getting tokens, no blocking locks, etc.
    */
   int
   tsleep(const volatile void *ident, int flags, const char *wmesg, int timo)
   {
           struct thread *td = curthread;
           struct lwp *lp = td->td_lwp;
           struct proc *p = td->td_proc;           /* may be NULL */
           globaldata_t gd;
           int sig;
           int catch;
           int error;
           int oldpri;
           struct callout thandle;
   
           /*
            * Currently a severe hack.  Make sure any delayed wakeups
            * are flushed before we sleep or we might deadlock on whatever
            * event we are sleeping on.
            */
           if (td->td_flags & TDF_DELAYED_WAKEUP)
                   wakeup_end_delayed();
   
           /*
            * NOTE: removed KTRPOINT, it could cause races due to blocking
            * even in stable.  Just scrap it for now.
            */
           if (!tsleep_crypto_dump && (tsleep_now_works == 0 || panicstr)) {
                   /*
                    * After a panic, or before we actually have an operational
                    * softclock, just give interrupts a chance, then just return;
                    *
                    * don't run any other procs or panic below,
                    * in case this is the idle process and already asleep.
                    */
                   splz();
                   oldpri = td->td_pri;
                   lwkt_setpri_self(safepri);
                   lwkt_switch();
                   lwkt_setpri_self(oldpri);
                   return (0);
           }
           logtsleep2(tsleep_beg, ident);
           gd = td->td_gd;
           KKASSERT(td != &gd->gd_idlethread);     /* you must be kidding! */
           td->td_wakefromcpu = -1;                /* overwritten by _wakeup */
   
           /*
            * NOTE: all of this occurs on the current cpu, including any
            * callout-based wakeups, so a critical section is a sufficient
            * interlock.
            *
            * The entire sequence through to where we actually sleep must
            * run without breaking the critical section.
            */
           catch = flags & PCATCH;
           error = 0;
           sig = 0;
   
           crit_enter_quick(td);
   
           KASSERT(ident != NULL, ("tsleep: no ident"));
           KASSERT(lp == NULL ||
                   lp->lwp_stat == LSRUN ||        /* Obvious */
                   lp->lwp_stat == LSSTOP,         /* Set in tstop */
                   ("tsleep %p %s %d",
                           ident, wmesg, lp->lwp_stat));
   
           /*
            * We interlock the sleep queue if the caller has not already done
            * it for us.  This must be done before we potentially acquire any
            * tokens or we can loose the wakeup.
            */
           if ((flags & PINTERLOCKED) == 0) {
                   _tsleep_interlock(gd, ident, flags);
           }
   
           /*
            * Setup for the current process (if this is a process).  We must
            * interlock with lwp_token to avoid remote wakeup races via
            * setrunnable()
            */
           if (lp) {
                   lwkt_gettoken(&lp->lwp_token);
                   if (catch) {
                           /*
                            * Early termination if PCATCH was set and a
                            * signal is pending, interlocked with the
                            * critical section.
                            *
                            * Early termination only occurs when tsleep() is
                            * entered while in a normal LSRUN state.
                            */
                           if ((sig = CURSIG(lp)) != 0)
                                   goto resume;
   
                           /*
                            * Causes ksignal to wake us up if a signal is
                            * received (interlocked with p->p_token).
                            */
                           lp->lwp_flags |= LWP_SINTR;
                   }
           } else {
                   KKASSERT(p == NULL);
           }
   
           /*
            * Make sure the current process has been untangled from
            * the userland scheduler and initialize slptime to start
            * counting.
            *
            * NOTE: td->td_wakefromcpu is pre-set by the release function
            *       for the dfly scheduler, and then adjusted by _wakeup()
            */
           if (lp) {
                   p->p_usched->release_curproc(lp);
                   lp->lwp_slptime = 0;
           }
   
           /*
            * If the interlocked flag is set but our cpu bit in the slpqueue
            * is no longer set, then a wakeup was processed inbetween the
            * tsleep_interlock() (ours or the callers), and here.  This can
            * occur under numerous circumstances including when we release the
            * current process.
            *
            * Extreme loads can cause the sending of an IPI (e.g. wakeup()'s)
            * to process incoming IPIs, thus draining incoming wakeups.
            */
           if ((td->td_flags & TDF_TSLEEPQ) == 0) {
                   logtsleep2(ilockfail, ident);
                   goto resume;
           }
   
           /*
            * scheduling is blocked while in a critical section.  Coincide
            * the descheduled-by-tsleep flag with the descheduling of the
            * lwkt.
            *
            * The timer callout is localized on our cpu and interlocked by
            * our critical section.
            */
           lwkt_deschedule_self(td);
           td->td_flags |= TDF_TSLEEP_DESCHEDULED;
           td->td_wmesg = wmesg;
   
           /*
            * Setup the timeout, if any.  The timeout is only operable while
            * the thread is flagged descheduled.
            */
           KKASSERT((td->td_flags & TDF_TIMEOUT) == 0);
           if (timo) {
                   callout_init_mp(&thandle);
                   callout_reset(&thandle, timo, endtsleep, td);
           }
   
           /*
            * Beddy bye bye.
            */
           if (lp) {
                   /*
                    * Ok, we are sleeping.  Place us in the SSLEEP state.
                    */
                   KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
   
                   /*
                    * tstop() sets LSSTOP, so don't fiddle with that.
                    */
                   if (lp->lwp_stat != LSSTOP)
                           lp->lwp_stat = LSSLEEP;
                   lp->lwp_ru.ru_nvcsw++;
                   p->p_usched->uload_update(lp);
                   lwkt_switch();
   
                   /*
                    * And when we are woken up, put us back in LSRUN.  If we
                    * slept for over a second, recalculate our estcpu.
                    */
                   lp->lwp_stat = LSRUN;
                   if (lp->lwp_slptime) {
                           p->p_usched->uload_update(lp);
                           p->p_usched->recalculate(lp);
                   }
                   lp->lwp_slptime = 0;
           } else {
                   lwkt_switch();
           }
   
           /* 
            * Make sure we haven't switched cpus while we were asleep.  It's
            * not supposed to happen.  Cleanup our temporary flags.
            */
           KKASSERT(gd == td->td_gd);
   
           /*
            * Cleanup the timeout.  If the timeout has already occured thandle
            * has already been stopped, otherwise stop thandle.  If the timeout
            * is running (the callout thread must be blocked trying to get
            * lwp_token) then wait for us to get scheduled.
            */
           if (timo) {
                   while (td->td_flags & TDF_TIMEOUT_RUNNING) {
                           lwkt_deschedule_self(td);
                           td->td_wmesg = "tsrace";
                           lwkt_switch();
                           kprintf("td %p %s: timeout race\n", td, td->td_comm);
                   }
                   if (td->td_flags & TDF_TIMEOUT) {
                           td->td_flags &= ~TDF_TIMEOUT;
                           error = EWOULDBLOCK;
                   } else {
                           /* does not block when on same cpu */
                           callout_stop(&thandle);
                   }
           }
           td->td_flags &= ~TDF_TSLEEP_DESCHEDULED;
   
           /*
            * Make sure we have been removed from the sleepq.  In most
            * cases this will have been done for us already but it is
            * possible for a scheduling IPI to be in-flight from a
            * previous tsleep/tsleep_interlock() or due to a straight-out
            * call to lwkt_schedule() (in the case of an interrupt thread),
            * causing a spurious wakeup.
            */
           _tsleep_remove(td);
           td->td_wmesg = NULL;
   
           /*
            * Figure out the correct error return.  If interrupted by a
            * signal we want to return EINTR or ERESTART.  
            */
   resume:
           if (lp) {
                   if (catch && error == 0) {
                           if (sig != 0 || (sig = CURSIG(lp))) {
                                   if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
                                           error = EINTR;
                                   else
                                           error = ERESTART;
                           }
                   }
                   lp->lwp_flags &= ~LWP_SINTR;
                   lwkt_reltoken(&lp->lwp_token);
           }
           logtsleep1(tsleep_end);
           crit_exit_quick(td);
           return (error);
   }
   
   /*
    * Interlocked spinlock sleep.  An exclusively held spinlock must
    * be passed to ssleep().  The function will atomically release the
    * spinlock and tsleep on the ident, then reacquire the spinlock and
    * return.
    *
    * This routine is fairly important along the critical path, so optimize it
    * heavily.
    */
   int
   ssleep(const volatile void *ident, struct spinlock *spin, int flags,
          const char *wmesg, int timo)
   {
           globaldata_t gd = mycpu;
           int error;
   
           _tsleep_interlock(gd, ident, flags);
           spin_unlock_quick(gd, spin);
           error = tsleep(ident, flags | PINTERLOCKED, wmesg, timo);
           _spin_lock_quick(gd, spin, wmesg);
   
           return (error);
   }
   
   int
   lksleep(const volatile void *ident, struct lock *lock, int flags,
           const char *wmesg, int timo)
   {
           globaldata_t gd = mycpu;
           int error;
   
           _tsleep_interlock(gd, ident, flags);
           lockmgr(lock, LK_RELEASE);
           error = tsleep(ident, flags | PINTERLOCKED, wmesg, timo);
           lockmgr(lock, LK_EXCLUSIVE);
   
           return (error);
   }
   
   /*
    * Interlocked mutex sleep.  An exclusively held mutex must be passed
    * to mtxsleep().  The function will atomically release the mutex
    * and tsleep on the ident, then reacquire the mutex and return.
    */
   int
   mtxsleep(const volatile void *ident, struct mtx *mtx, int flags,
            const char *wmesg, int timo)
   {
           globaldata_t gd = mycpu;
           int error;
   
           _tsleep_interlock(gd, ident, flags);
           mtx_unlock(mtx);
           error = tsleep(ident, flags | PINTERLOCKED, wmesg, timo);
           mtx_lock_ex_quick(mtx, wmesg);
   
           return (error);
   }
   
   /*
    * Interlocked serializer sleep.  An exclusively held serializer must
    * be passed to zsleep().  The function will atomically release
    * the serializer and tsleep on the ident, then reacquire the serializer
    * and return.
    */
   int
   zsleep(const volatile void *ident, struct lwkt_serialize *slz, int flags,
          const char *wmesg, int timo)
   {
           globaldata_t gd = mycpu;
           int ret;
   
           ASSERT_SERIALIZED(slz);
   
           _tsleep_interlock(gd, ident, flags);
           lwkt_serialize_exit(slz);
           ret = tsleep(ident, flags | PINTERLOCKED, wmesg, timo);
           lwkt_serialize_enter(slz);
   
           return ret;
   }
   
   /*
    * Directly block on the LWKT thread by descheduling it.  This
    * is much faster then tsleep(), but the only legal way to wake
    * us up is to directly schedule the thread.
    *
    * Setting TDF_SINTR will cause new signals to directly schedule us.
    *
    * This routine must be called while in a critical section.
    */
   int
   lwkt_sleep(const char *wmesg, int flags)
   {
           thread_t td = curthread;
           int sig;
   
           if ((flags & PCATCH) == 0 || td->td_lwp == NULL) {
                   td->td_flags |= TDF_BLOCKED;
                   td->td_wmesg = wmesg;
                   lwkt_deschedule_self(td);
                   lwkt_switch();
                   td->td_wmesg = NULL;
                   td->td_flags &= ~TDF_BLOCKED;
                   return(0);
           }
           if ((sig = CURSIG(td->td_lwp)) != 0) {
                   if (SIGISMEMBER(td->td_proc->p_sigacts->ps_sigintr, sig))
                           return(EINTR);
                   else
                           return(ERESTART);
                           
           }
           td->td_flags |= TDF_BLOCKED | TDF_SINTR;
           td->td_wmesg = wmesg;
           lwkt_deschedule_self(td);
           lwkt_switch();
           td->td_flags &= ~(TDF_BLOCKED | TDF_SINTR);
           td->td_wmesg = NULL;
           return(0);
   }
   
   /*
    * Implement the timeout for tsleep.
    *
    * This type of callout timeout is scheduled on the same cpu the process
    * is sleeping on.  Also, at the moment, the MP lock is held.
    */
   static void
   endtsleep(void *arg)
   {
           thread_t td = arg;
           struct lwp *lp;
   
           /*
            * We are going to have to get the lwp_token, which means we might
            * block.  This can race a tsleep getting woken up by other means
            * so set TDF_TIMEOUT_RUNNING to force the tsleep to wait for our
            * processing to complete (sorry tsleep!).
            *
            * We can safely set td_flags because td MUST be on the same cpu
            * as we are.
            */
           KKASSERT(td->td_gd == mycpu);
           crit_enter();
           td->td_flags |= TDF_TIMEOUT_RUNNING | TDF_TIMEOUT;
   
           /*
            * This can block but TDF_TIMEOUT_RUNNING will prevent the thread
            * from exiting the tsleep on us.  The flag is interlocked by virtue
            * of lp being on the same cpu as we are.
            */
           if ((lp = td->td_lwp) != NULL)
                   lwkt_gettoken(&lp->lwp_token);
   
           KKASSERT(td->td_flags & TDF_TSLEEP_DESCHEDULED);
   
           if (lp) {
                   /*
                    * callout timer should never be set in tstop() because
                    * it passes a timeout of 0.
                    */
                   KKASSERT(lp->lwp_stat != LSSTOP);
                   setrunnable(lp);
                   lwkt_reltoken(&lp->lwp_token);
           } else {
                   _tsleep_remove(td);
                   lwkt_schedule(td);
           }
           KKASSERT(td->td_gd == mycpu);
           td->td_flags &= ~TDF_TIMEOUT_RUNNING;
           crit_exit();
   }
   
   /*
    * Make all processes sleeping on the specified identifier runnable.
    * count may be zero or one only.
    *
    * The domain encodes the sleep/wakeup domain, flags, plus the originating
    * cpu.
    *
    * This call may run without the MP lock held.  We can only manipulate thread
    * state on the cpu owning the thread.  We CANNOT manipulate process state
    * at all.
    *
    * _wakeup() can be passed to an IPI so we can't use (const volatile
    * void *ident).
    */
   static void
   _wakeup(void *ident, int domain)
   {
           struct tslpque *qp;
           struct thread *td;
           struct thread *ntd;
           globaldata_t gd;
           cpumask_t mask;
           int id;
   
           crit_enter();
           logtsleep2(wakeup_beg, ident);
           gd = mycpu;
           id = LOOKUP(ident);
           qp = &gd->gd_tsleep_hash[id];
   restart:
           for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) {
                   ntd = TAILQ_NEXT(td, td_sleepq);
                   if (td->td_wchan == ident && 
                       td->td_wdomain == (domain & PDOMAIN_MASK)
                   ) {
                           KKASSERT(td->td_gd == gd);
                           _tsleep_remove(td);
                           td->td_wakefromcpu = PWAKEUP_DECODE(domain);
                           if (td->td_flags & TDF_TSLEEP_DESCHEDULED) {
                                   lwkt_schedule(td);
                                   if (domain & PWAKEUP_ONE)
                                           goto done;
                           }
                           goto restart;
                   }
           }
   
           /*
            * We finished checking the current cpu but there still may be
            * more work to do.  Either wakeup_one was requested and no matching
            * thread was found, or a normal wakeup was requested and we have
            * to continue checking cpus.
            *
            * It should be noted that this scheme is actually less expensive then
            * the old scheme when waking up multiple threads, since we send 
            * only one IPI message per target candidate which may then schedule
            * multiple threads.  Before we could have wound up sending an IPI
            * message for each thread on the target cpu (!= current cpu) that
            * needed to be woken up.
            *
            * NOTE: Wakeups occuring on remote cpus are asynchronous.  This
            * should be ok since we are passing idents in the IPI rather then
            * thread pointers.
            */
           if ((domain & PWAKEUP_MYCPU) == 0 &&
               (mask = slpque_cpumasks[id] & gd->gd_other_cpus) != 0) {
                   lwkt_send_ipiq2_mask(mask, _wakeup, ident,
                                        domain | PWAKEUP_MYCPU);
           }
   done:
           logtsleep1(wakeup_end);
           crit_exit();
   }
   
   /*
    * Wakeup all threads tsleep()ing on the specified ident, on all cpus
    */
   void
   wakeup(const volatile void *ident)
   {
       globaldata_t gd = mycpu;
       thread_t td = gd->gd_curthread;
   
       if (td && (td->td_flags & TDF_DELAYED_WAKEUP)) {
           /*
            * If we are in a delayed wakeup section, record up to two wakeups in
            * a per-CPU queue and issue them when we block or exit the delayed
            * wakeup section.
            */
           if (atomic_cmpset_ptr(&gd->gd_delayed_wakeup[0], NULL, ident))
                   return;
           if (atomic_cmpset_ptr(&gd->gd_delayed_wakeup[1], NULL, ident))
                   return;
   
           ident = atomic_swap_ptr(__DEQUALIFY(volatile void **, &gd->gd_delayed_wakeup[1]),
                                   __DEALL(ident));
           ident = atomic_swap_ptr(__DEQUALIFY(volatile void **, &gd->gd_delayed_wakeup[0]),
                                   __DEALL(ident));
       }
   
       _wakeup(__DEALL(ident), PWAKEUP_ENCODE(0, gd->gd_cpuid));
   }
   
   /*
    * Wakeup one thread tsleep()ing on the specified ident, on any cpu.
    */
   void
   wakeup_one(const volatile void *ident)
   {
       /* XXX potentially round-robin the first responding cpu */
       _wakeup(__DEALL(ident), PWAKEUP_ENCODE(0, mycpu->gd_cpuid) |
                               PWAKEUP_ONE);
   }
   
   /*
    * Wakeup threads tsleep()ing on the specified ident on the current cpu
    * only.
    */
   void
   wakeup_mycpu(const volatile void *ident)
   {
       _wakeup(__DEALL(ident), PWAKEUP_ENCODE(0, mycpu->gd_cpuid) |
                               PWAKEUP_MYCPU);
   }
   
   /*
    * Wakeup one thread tsleep()ing on the specified ident on the current cpu
    * only.
    */
   void
   wakeup_mycpu_one(const volatile void *ident)
   {
       /* XXX potentially round-robin the first responding cpu */
       _wakeup(__DEALL(ident), PWAKEUP_ENCODE(0, mycpu->gd_cpuid) |
                               PWAKEUP_MYCPU | PWAKEUP_ONE);
   }
   
   /*
    * Wakeup all thread tsleep()ing on the specified ident on the specified cpu
    * only.
   */
  void
  wakeup_oncpu(globaldata_t gd, const volatile void *ident)
  {
      globaldata_t mygd = mycpu;
      if (gd == mycpu) {
          _wakeup(__DEALL(ident), PWAKEUP_ENCODE(0, mygd->gd_cpuid) |
                                  PWAKEUP_MYCPU);
      } else {
          lwkt_send_ipiq2(gd, _wakeup, __DEALL(ident),
                          PWAKEUP_ENCODE(0, mygd->gd_cpuid) |
                          PWAKEUP_MYCPU);
      }
  }
  
  /*
   * Wakeup one thread tsleep()ing on the specified ident on the specified cpu
   * only.
   */
  void
  wakeup_oncpu_one(globaldata_t gd, const volatile void *ident)
  {
      globaldata_t mygd = mycpu;
      if (gd == mygd) {
          _wakeup(__DEALL(ident), PWAKEUP_ENCODE(0, mygd->gd_cpuid) |
                                  PWAKEUP_MYCPU | PWAKEUP_ONE);
      } else {
          lwkt_send_ipiq2(gd, _wakeup, __DEALL(ident),
                          PWAKEUP_ENCODE(0, mygd->gd_cpuid) |
                          PWAKEUP_MYCPU | PWAKEUP_ONE);
      }
  }
  
  /*
   * Wakeup all threads waiting on the specified ident that slept using
   * the specified domain, on all cpus.
   */
  void
  wakeup_domain(const volatile void *ident, int domain)
  {
      _wakeup(__DEALL(ident), PWAKEUP_ENCODE(domain, mycpu->gd_cpuid));
  }
  
  /*
   * Wakeup one thread waiting on the specified ident that slept using
   * the specified  domain, on any cpu.
   */
  void
  wakeup_domain_one(const volatile void *ident, int domain)
  {
      /* XXX potentially round-robin the first responding cpu */
      _wakeup(__DEALL(ident),
              PWAKEUP_ENCODE(domain, mycpu->gd_cpuid) | PWAKEUP_ONE);
  }
  
  void
  wakeup_start_delayed(void)
  {
      globaldata_t gd = mycpu;
  
      crit_enter();
      gd->gd_curthread->td_flags |= TDF_DELAYED_WAKEUP;
      crit_exit();
  }
  
  void
  wakeup_end_delayed(void)
  {
      globaldata_t gd = mycpu;
  
      if (gd->gd_curthread->td_flags & TDF_DELAYED_WAKEUP) {
          crit_enter();
          gd->gd_curthread->td_flags &= ~TDF_DELAYED_WAKEUP;
          if (gd->gd_delayed_wakeup[0] || gd->gd_delayed_wakeup[1]) {
              if (gd->gd_delayed_wakeup[0]) {
                      wakeup(gd->gd_delayed_wakeup[0]);
                      gd->gd_delayed_wakeup[0] = NULL;
              }
              if (gd->gd_delayed_wakeup[1]) {
                      wakeup(gd->gd_delayed_wakeup[1]);
                      gd->gd_delayed_wakeup[1] = NULL;
              }
          }
          crit_exit();
      }
  }
  
  /*
   * setrunnable()
   *
   * Make a process runnable.  lp->lwp_token must be held on call and this
   * function must be called from the cpu owning lp.
   *
   * This only has an effect if we are in LSSTOP or LSSLEEP.
   */
  void
  setrunnable(struct lwp *lp)
  {
          thread_t td = lp->lwp_thread;
  
          ASSERT_LWKT_TOKEN_HELD(&lp->lwp_token);
          KKASSERT(td->td_gd == mycpu);
          crit_enter();
          if (lp->lwp_stat == LSSTOP)
                  lp->lwp_stat = LSSLEEP;
          if (lp->lwp_stat == LSSLEEP) {
                  _tsleep_remove(td);
                  lwkt_schedule(td);
          } else if (td->td_flags & TDF_SINTR) {
                  lwkt_schedule(td);
          }
          crit_exit();
  }
  
  /*
   * The process is stopped due to some condition, usually because p_stat is
   * set to SSTOP, but also possibly due to being traced.  
   *
   * Caller must hold p->p_token
   *
   * NOTE!  If the caller sets SSTOP, the caller must also clear P_WAITED
   * because the parent may check the child's status before the child actually
   * gets to this routine.
   *
   * This routine is called with the current lwp only, typically just
   * before returning to userland if the process state is detected as
   * possibly being in a stopped state.
   */
  void
  tstop(void)
  {
          struct lwp *lp = curthread->td_lwp;
          struct proc *p = lp->lwp_proc;
          struct proc *q;
  
          lwkt_gettoken(&lp->lwp_token);
          crit_enter();
  
          /*
           * If LWP_MP_WSTOP is set, we were sleeping
           * while our process was stopped.  At this point
           * we were already counted as stopped.
           */
          if ((lp->lwp_mpflags & LWP_MP_WSTOP) == 0) {
                  /*
                   * If we're the last thread to stop, signal
                   * our parent.
                   */
                  p->p_nstopped++;
                  atomic_set_int(&lp->lwp_mpflags, LWP_MP_WSTOP);
                  wakeup(&p->p_nstopped);
                  if (p->p_nstopped == p->p_nthreads) {
                          /*
                           * Token required to interlock kern_wait()
                           */
                          q = p->p_pptr;
                          PHOLD(q);
                          lwkt_gettoken(&q->p_token);
                          p->p_flags &= ~P_WAITED;
                          wakeup(p->p_pptr);
                          if ((q->p_sigacts->ps_flag & PS_NOCLDSTOP) == 0)
                                  ksignal(q, SIGCHLD);
                          lwkt_reltoken(&q->p_token);
                          PRELE(q);
                  }
          }
          while (p->p_stat == SSTOP) {
                  lp->lwp_stat = LSSTOP;
                  tsleep(p, 0, "stop", 0);
          }
          p->p_nstopped--;
          atomic_clear_int(&lp->lwp_mpflags, LWP_MP_WSTOP);
          crit_exit();
          lwkt_reltoken(&lp->lwp_token);
  }
  
  /*
   * Compute a tenex style load average of a quantity on
   * 1, 5 and 15 minute intervals.
   */
  static int loadav_count_runnable(struct lwp *p, void *data);
  
  static void
  loadav(void *arg)
  {
          struct loadavg *avg;
          int i, nrun;
  
          nrun = 0;
          alllwp_scan(loadav_count_runnable, &nrun);
          avg = &averunnable;
          for (i = 0; i < 3; i++) {
                  avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
                      nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
          }
  
          /*
           * Schedule the next update to occur after 5 seconds, but add a
           * random variation to avoid synchronisation with processes that
           * run at regular intervals.
           */
          callout_reset(&loadav_callout, hz * 4 + (int)(krandom() % (hz * 2 + 1)),
                        loadav, NULL);
  }
  
  static int
  loadav_count_runnable(struct lwp *lp, void *data)
  {
          int *nrunp = data;
          thread_t td;
  
          switch (lp->lwp_stat) {
          case LSRUN:
                  if ((td = lp->lwp_thread) == NULL)
                          break;
                  if (td->td_flags & TDF_BLOCKED)
                          break;
                  ++*nrunp;
                  break;
          default:
                  break;
          }
          lwkt_yield();
          return(0);
  }
  
  /* ARGSUSED */
  static void
  sched_setup(void *dummy)
  {
          callout_init_mp(&loadav_callout);
          callout_init_mp(&schedcpu_callout);
  
          /* Kick off timeout driven events by calling first time. */
          schedcpu(NULL);
          loadav(NULL);
  }
  

Cache object: 84a8bc130d4b4f9187097327a034e059