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. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. 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
     * $FreeBSD$
     */
    
    #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 <vm/vm.h>
    #include <vm/vm_extern.h>
    #ifdef KTRACE
    #include <sys/uio.h>
    #include <sys/ktrace.h>
    #endif
    
    #include <machine/cpu.h>
    #ifdef SMP
    #include <machine/smp.h>
    #endif
    #include <machine/limits.h>     /* for UCHAR_MAX = typeof(p_priority)_MAX */
    
    static void rqinit __P((void *));
    SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL)
    static void sched_setup __P((void *dummy));
    SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
    
    u_char  curpriority;
    int     hogticks;
    int     lbolt;
    int     sched_quantum;          /* Roundrobin scheduling quantum in ticks. */
    
    static void     endtsleep __P((void *));
    static void     roundrobin __P((void *arg));
    static void     schedcpu __P((void *arg));
    static void     updatepri __P((struct proc *p));
    
    static int
    sysctl_kern_quantum SYSCTL_HANDLER_ARGS
    {
            int error, new_val;
    
            new_val = sched_quantum * tick;
            error = sysctl_handle_int(oidp, &new_val, 0, req);
            if (error != 0 || req->newptr == NULL)
                    return (error);
            if (new_val < tick)
                    return (EINVAL);
            sched_quantum = new_val / tick;
            hogticks = 2 * sched_quantum;
            return (0);
    }
    
    SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
            0, sizeof sched_quantum, sysctl_kern_quantum, "I", "");
    
    /* maybe_resched: Decide if you need to reschedule or not
    * taking the priorities and schedulers into account.
    */
   static void maybe_resched(struct proc *chk)
   {
           struct proc *p = curproc; /* XXX */
   
           /*
            * Compare priorities if the new process is on the same scheduler,
            * otherwise the one on the more realtimeish scheduler wins.
            *
            * XXX idle scheduler still broken because proccess stays on idle
            * scheduler during waits (such as when getting FS locks).  If a
            * standard process becomes runaway cpu-bound, the system can lockup
            * due to idle-scheduler processes in wakeup never getting any cpu.
            */
           if (p == 0 ||
                   (chk->p_priority < curpriority && RTP_PRIO_BASE(p->p_rtprio.type) == RTP_PRIO_BASE(chk->p_rtprio.type)) ||
                   RTP_PRIO_BASE(chk->p_rtprio.type) < RTP_PRIO_BASE(p->p_rtprio.type)
           ) {
                   need_resched();
           }
   }
   
   int 
   roundrobin_interval(void)
   {
           return (sched_quantum);
   }
   
   /*
    * Force switch among equal priority processes every 100ms.
    */
   /* ARGSUSED */
   static void
   roundrobin(arg)
           void *arg;
   {
   #ifndef SMP
           struct proc *p = curproc; /* XXX */
   #endif
    
   #ifdef SMP
           need_resched();
           forward_roundrobin();
   #else 
           if (p == 0 || RTP_PRIO_NEED_RR(p->p_rtprio.type))
                   need_resched();
   #endif
   
           timeout(roundrobin, NULL, sched_quantum);
   }
   
   /*
    * Constants for digital decay and forget:
    *      90% of (p_estcpu) usage in 5 * loadav time
    *      95% of (p_pctcpu) usage in 60 seconds (load insensitive)
    *          Note that, as ps(1) mentions, this can let percentages
    *          total over 100% (I've seen 137.9% for 3 processes).
    *
    * Note that statclock() updates p_estcpu and p_cpticks asynchronously.
    *
    * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds.
    * That is, the system wants to compute a value of decay such
    * that the following for loop:
    *      for (i = 0; i < (5 * loadavg); i++)
    *              p_estcpu *= decay;
    * will compute
    *      p_estcpu *= 0.1;
    * for all values of loadavg:
    *
    * Mathematically this loop can be expressed by saying:
    *      decay ** (5 * loadavg) ~= .1
    *
    * The system computes decay as:
    *      decay = (2 * loadavg) / (2 * loadavg + 1)
    *
    * We wish to prove that the system's computation of decay
    * will always fulfill the equation:
    *      decay ** (5 * loadavg) ~= .1
    *
    * If we compute b as:
    *      b = 2 * loadavg
    * then
    *      decay = b / (b + 1)
    *
    * We now need to prove two things:
    *      1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
    *      2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
    *
    * Facts:
    *         For x close to zero, exp(x) =~ 1 + x, since
    *              exp(x) = 0! + x**1/1! + x**2/2! + ... .
    *              therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
    *         For x close to zero, ln(1+x) =~ x, since
    *              ln(1+x) = x - x**2/2 + x**3/3 - ...     -1 < x < 1
    *              therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
    *         ln(.1) =~ -2.30
    *
    * Proof of (1):
    *    Solve (factor)**(power) =~ .1 given power (5*loadav):
    *      solving for factor,
    *      ln(factor) =~ (-2.30/5*loadav), or
    *      factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
    *          exp(-1/b) =~ (b-1)/b =~ b/(b+1).                    QED
    *
    * Proof of (2):
    *    Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
    *      solving for power,
    *      power*ln(b/(b+1)) =~ -2.30, or
    *      power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav.  QED
    *
    * Actual power values for the implemented algorithm are as follows:
    *      loadav: 1       2       3       4
    *      power:  5.68    10.32   14.94   19.55
    */
   
   /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
   #define loadfactor(loadav)      (2 * (loadav))
   #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
   
   /* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
   static fixpt_t  ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
   SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
   
   /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
   static int      fscale __unused = FSCALE;
   SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
   
   /*
    * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
    * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
    * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
    *
    * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
    *      1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
    *
    * If you don't want to bother with the faster/more-accurate formula, you
    * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
    * (more general) method of calculating the %age of CPU used by a process.
    */
   #define CCPU_SHIFT      11
   
   /*
    * Recompute process priorities, every hz ticks.
    */
   /* ARGSUSED */
   static void
   schedcpu(arg)
           void *arg;
   {
           register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
           register struct proc *p;
           register int realstathz, s;
           register unsigned int newcpu;
   
           realstathz = stathz ? stathz : hz;
           for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
                   /*
                    * Increment time in/out of memory and sleep time
                    * (if sleeping).  We ignore overflow; with 16-bit int's
                    * (remember them?) overflow takes 45 days.
                    */
                   p->p_swtime++;
                   if (p->p_stat == SSLEEP || p->p_stat == SSTOP)
                           p->p_slptime++;
                   p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT;
                   /*
                    * If the process has slept the entire second,
                    * stop recalculating its priority until it wakes up.
                    */
                   if (p->p_slptime > 1)
                           continue;
                   s = splhigh();  /* prevent state changes and protect run queue */
                   /*
                    * p_pctcpu is only for ps.
                    */
   #if     (FSHIFT >= CCPU_SHIFT)
                   p->p_pctcpu += (realstathz == 100)?
                           ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT):
                           100 * (((fixpt_t) p->p_cpticks)
                                   << (FSHIFT - CCPU_SHIFT)) / realstathz;
   #else
                   p->p_pctcpu += ((FSCALE - ccpu) *
                           (p->p_cpticks * FSCALE / realstathz)) >> FSHIFT;
   #endif
                   p->p_cpticks = 0;
                   newcpu = (u_int) decay_cpu(loadfac, p->p_estcpu) + p->p_nice;
                   p->p_estcpu = min(newcpu, UCHAR_MAX);
                   resetpriority(p);
                   if (p->p_priority >= PUSER) {
   #define PPQ     (128 / NQS)             /* priorities per queue */
                           if ((p != curproc) &&
   #ifdef SMP
                               (u_char)p->p_oncpu == 0xff &&       /* idle */
   #endif
                               p->p_stat == SRUN &&
                               (p->p_flag & P_INMEM) &&
                               (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) {
                                   remrq(p);
                                   p->p_priority = p->p_usrpri;
                                   setrunqueue(p);
                           } else
                                   p->p_priority = p->p_usrpri;
                   }
                   splx(s);
           }
           vmmeter();
           wakeup((caddr_t)&lbolt);
           timeout(schedcpu, (void *)0, hz);
   }
   
   /*
    * Recalculate the priority of a process after it has slept for a while.
    * For all load averages >= 1 and max p_estcpu of 255, sleeping for at
    * least six times the loadfactor will decay p_estcpu to zero.
    */
   static void
   updatepri(p)
           register struct proc *p;
   {
           register unsigned int newcpu = p->p_estcpu;
           register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
   
           if (p->p_slptime > 5 * loadfac)
                   p->p_estcpu = 0;
           else {
                   p->p_slptime--; /* the first time was done in schedcpu */
                   while (newcpu && --p->p_slptime)
                           newcpu = (int) decay_cpu(loadfac, newcpu);
                   p->p_estcpu = min(newcpu, UCHAR_MAX);
           }
           resetpriority(p);
   }
   
   /*
    * We're only looking at 7 bits of the address; everything is
    * aligned to 4, lots of things are aligned to greater powers
    * of 2.  Shift right by 8, i.e. drop the bottom 256 worth.
    */
   #define TABLESIZE       128
   static TAILQ_HEAD(slpquehead, proc) slpque[TABLESIZE];
   #define LOOKUP(x)       (((intptr_t)(x) >> 8) & (TABLESIZE - 1))
   
   /*
    * During autoconfiguration or after a panic, a sleep will simply
    * lower the priority briefly to allow interrupts, then return.
    * The priority to be used (safepri) is machine-dependent, thus this
    * value is initialized and maintained in the machine-dependent layers.
    * This priority will typically be 0, or the lowest priority
    * that is safe for use on the interrupt stack; it can be made
    * higher to block network software interrupts after panics.
    */
   int safepri;
   
   void
   sleepinit(void)
   {
           int i;
   
           sched_quantum = hz/10;
           hogticks = 2 * sched_quantum;
           for (i = 0; i < TABLESIZE; i++)
                   TAILQ_INIT(&slpque[i]);
   }
   
   /*
    * 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 pri 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).
    */
   int
   tsleep(ident, priority, wmesg, timo)
           void *ident;
           int priority, timo;
           const char *wmesg;
   {
           struct proc *p = curproc;
           int s, sig, catch = priority & PCATCH;
           struct callout_handle thandle;
   
   #ifdef KTRACE
           if (p && KTRPOINT(p, KTR_CSW))
                   ktrcsw(p->p_tracep, 1, 0);
   #endif
           s = splhigh();
           if (cold || panicstr) {
                   /*
                    * After a panic, or during autoconfiguration,
                    * 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.
                    */
                   splx(safepri);
                   splx(s);
                   return (0);
           }
           KASSERT(p != NULL, ("tsleep1"));
           KASSERT(ident != NULL && p->p_stat == SRUN, ("tsleep"));
           /*
            * Process may be sitting on a slpque if asleep() was called, remove
            * it before re-adding.
            */
           if (p->p_wchan != NULL)
                   unsleep(p);
   
           p->p_wchan = ident;
           p->p_wmesg = wmesg;
           p->p_slptime = 0;
           p->p_priority = priority & PRIMASK;
           TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_procq);
           if (timo)
                   thandle = timeout(endtsleep, (void *)p, timo);
           /*
            * We put ourselves on the sleep queue and start our timeout
            * before calling CURSIG, as we could stop there, and a wakeup
            * or a SIGCONT (or both) could occur while we were stopped.
            * A SIGCONT would cause us to be marked as SSLEEP
            * without resuming us, thus we must be ready for sleep
            * when CURSIG is called.  If the wakeup happens while we're
            * stopped, p->p_wchan will be 0 upon return from CURSIG.
            */
           if (catch) {
                   p->p_flag |= P_SINTR;
                   if ((sig = CURSIG(p))) {
                           if (p->p_wchan)
                                   unsleep(p);
                           p->p_stat = SRUN;
                           goto resume;
                   }
                   if (p->p_wchan == 0) {
                           catch = 0;
                           goto resume;
                   }
           } else
                   sig = 0;
           p->p_stat = SSLEEP;
           p->p_stats->p_ru.ru_nvcsw++;
           mi_switch();
   resume:
           curpriority = p->p_usrpri;
           splx(s);
           p->p_flag &= ~P_SINTR;
           if (p->p_flag & P_TIMEOUT) {
                   p->p_flag &= ~P_TIMEOUT;
                   if (sig == 0) {
   #ifdef KTRACE
                           if (KTRPOINT(p, KTR_CSW))
                                   ktrcsw(p->p_tracep, 0, 0);
   #endif
                           return (EWOULDBLOCK);
                   }
           } else if (timo)
                   untimeout(endtsleep, (void *)p, thandle);
           if (catch && (sig != 0 || (sig = CURSIG(p)))) {
   #ifdef KTRACE
                   if (KTRPOINT(p, KTR_CSW))
                           ktrcsw(p->p_tracep, 0, 0);
   #endif
                   if (p->p_sigacts->ps_sigintr & sigmask(sig))
                           return (EINTR);
                   return (ERESTART);
           }
   #ifdef KTRACE
           if (KTRPOINT(p, KTR_CSW))
                   ktrcsw(p->p_tracep, 0, 0);
   #endif
           return (0);
   }
   
   /*
    * asleep() - async sleep call.  Place process on wait queue and return 
    * immediately without blocking.  The process stays runnable until await() 
    * is called.  If ident is NULL, remove process from wait queue if it is still
    * on one.
    *
    * Only the most recent sleep condition is effective when making successive
    * calls to asleep() or when calling tsleep().
    *
    * The timeout, if any, is not initiated until await() is called.  The sleep
    * priority, signal, and timeout is specified in the asleep() call but may be
    * overriden in the await() call.
    *
    * <<<<<<<< EXPERIMENTAL, UNTESTED >>>>>>>>>>
    */
   
   int
   asleep(void *ident, int priority, const char *wmesg, int timo)
   {
           struct proc *p = curproc;
           int s;
   
           /*
            * splhigh() while manipulating sleep structures and slpque.
            *
            * Remove preexisting wait condition (if any) and place process
            * on appropriate slpque, but do not put process to sleep.
            */
   
           s = splhigh();
   
           if (p->p_wchan != NULL)
                   unsleep(p);
   
           if (ident) {
                   p->p_wchan = ident;
                   p->p_wmesg = wmesg;
                   p->p_slptime = 0;
                   p->p_asleep.as_priority = priority;
                   p->p_asleep.as_timo = timo;
                   TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_procq);
           }
   
           splx(s);
   
           return(0);
   }
   
   /*
    * await() - wait for async condition to occur.   The process blocks until
    * wakeup() is called on the most recent asleep() address.  If wakeup is called
    * priority to await(), await() winds up being a NOP.
    *
    * If await() is called more then once (without an intervening asleep() call),
    * await() is still effectively a NOP but it calls mi_switch() to give other
    * processes some cpu before returning.  The process is left runnable.
    *
    * <<<<<<<< EXPERIMENTAL, UNTESTED >>>>>>>>>>
    */
   
   int
   await(int priority, int timo)
   {
           struct proc *p = curproc;
           int s;
   
           s = splhigh();
   
           if (p->p_wchan != NULL) {
                   struct callout_handle thandle;
                   int sig;
                   int catch;
   
                   /*
                    * The call to await() can override defaults specified in
                    * the original asleep().
                    */
                   if (priority < 0)
                           priority = p->p_asleep.as_priority;
                   if (timo < 0)
                           timo = p->p_asleep.as_timo;
   
                   /*
                    * Install timeout
                    */
   
                   if (timo)
                           thandle = timeout(endtsleep, (void *)p, timo);
   
                   sig = 0;
                   catch = priority & PCATCH;
   
                   if (catch) {
                           p->p_flag |= P_SINTR;
                           if ((sig = CURSIG(p))) {
                                   if (p->p_wchan)
                                           unsleep(p);
                                   p->p_stat = SRUN;
                                   goto resume;
                           }
                           if (p->p_wchan == NULL) {
                                   catch = 0;
                                   goto resume;
                           }
                   }
                   p->p_stat = SSLEEP;
                   p->p_stats->p_ru.ru_nvcsw++;
                   mi_switch();
   resume:
                   curpriority = p->p_usrpri;
   
                   splx(s);
                   p->p_flag &= ~P_SINTR;
                   if (p->p_flag & P_TIMEOUT) {
                           p->p_flag &= ~P_TIMEOUT;
                           if (sig == 0) {
   #ifdef KTRACE
                                   if (KTRPOINT(p, KTR_CSW))
                                           ktrcsw(p->p_tracep, 0, 0);
   #endif
                                   return (EWOULDBLOCK);
                           }
                   } else if (timo)
                           untimeout(endtsleep, (void *)p, thandle);
                   if (catch && (sig != 0 || (sig = CURSIG(p)))) {
   #ifdef KTRACE
                           if (KTRPOINT(p, KTR_CSW))
                                   ktrcsw(p->p_tracep, 0, 0);
   #endif
                           if (p->p_sigacts->ps_sigintr & sigmask(sig))
                                   return (EINTR);
                           return (ERESTART);
                   }
   #ifdef KTRACE
                   if (KTRPOINT(p, KTR_CSW))
                           ktrcsw(p->p_tracep, 0, 0);
   #endif
           } else {
                   /*
                    * If as_priority is 0, await() has been called without an 
                    * intervening asleep().  We are still effectively a NOP, 
                    * but we call mi_switch() for safety.
                    */
   
                   if (p->p_asleep.as_priority == 0) {
                           p->p_stats->p_ru.ru_nvcsw++;
                           mi_switch();
                   }
                   splx(s);
           }
   
           /*
            * clear p_asleep.as_priority as an indication that await() has been
            * called.  If await() is called again without an intervening asleep(),
            * await() is still effectively a NOP but the above mi_switch() code
            * is triggered as a safety.
            */
           p->p_asleep.as_priority = 0;
   
           return (0);
   }
   
   /*
    * Implement timeout for tsleep or asleep()/await()
    *
    * If process hasn't been awakened (wchan non-zero),
    * set timeout flag and undo the sleep.  If proc
    * is stopped, just unsleep so it will remain stopped.
    */
   static void
   endtsleep(arg)
           void *arg;
   {
           register struct proc *p;
           int s;
   
           p = (struct proc *)arg;
           s = splhigh();
           if (p->p_wchan) {
                   if (p->p_stat == SSLEEP)
                           setrunnable(p);
                   else
                           unsleep(p);
                   p->p_flag |= P_TIMEOUT;
           }
           splx(s);
   }
   
   /*
    * Remove a process from its wait queue
    */
   void
   unsleep(p)
           register struct proc *p;
   {
           int s;
   
           s = splhigh();
           if (p->p_wchan) {
                   TAILQ_REMOVE(&slpque[LOOKUP(p->p_wchan)], p, p_procq);
                   p->p_wchan = 0;
           }
           splx(s);
   }
   
   /*
    * Make all processes sleeping on the specified identifier runnable.
    */
   void
   wakeup(ident)
           register void *ident;
   {
           register struct slpquehead *qp;
           register struct proc *p;
           int s;
   
           s = splhigh();
           qp = &slpque[LOOKUP(ident)];
   restart:
           for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) {
                   if (p->p_wchan == ident) {
                           TAILQ_REMOVE(qp, p, p_procq);
                           p->p_wchan = 0;
                           if (p->p_stat == SSLEEP) {
                                   /* OPTIMIZED EXPANSION OF setrunnable(p); */
                                   if (p->p_slptime > 1)
                                           updatepri(p);
                                   p->p_slptime = 0;
                                   p->p_stat = SRUN;
                                   if (p->p_flag & P_INMEM) {
                                           setrunqueue(p);
                                           maybe_resched(p);
                                   } else {
                                           p->p_flag |= P_SWAPINREQ;
                                           wakeup((caddr_t)&proc0);
                                   }
                                   /* END INLINE EXPANSION */
                                   goto restart;
                           }
                   }
           }
           splx(s);
   }
   
   /*
    * Make a process sleeping on the specified identifier runnable.
    * May wake more than one process if a target prcoess is currently
    * swapped out.
    */
   void
   wakeup_one(ident)
           register void *ident;
   {
           register struct slpquehead *qp;
           register struct proc *p;
           int s;
   
           s = splhigh();
           qp = &slpque[LOOKUP(ident)];
   
           for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) {
                   if (p->p_wchan == ident) {
                           TAILQ_REMOVE(qp, p, p_procq);
                           p->p_wchan = 0;
                           if (p->p_stat == SSLEEP) {
                                   /* OPTIMIZED EXPANSION OF setrunnable(p); */
                                   if (p->p_slptime > 1)
                                           updatepri(p);
                                   p->p_slptime = 0;
                                   p->p_stat = SRUN;
                                   if (p->p_flag & P_INMEM) {
                                           setrunqueue(p);
                                           maybe_resched(p);
                                           break;
                                   } else {
                                           p->p_flag |= P_SWAPINREQ;
                                           wakeup((caddr_t)&proc0);
                                   }
                                   /* END INLINE EXPANSION */
                           }
                   }
           }
           splx(s);
   }
   
   /*
    * The machine independent parts of mi_switch().
    * Must be called at splstatclock() or higher.
    */
   void
   mi_switch()
   {
           register struct proc *p = curproc;      /* XXX */
           register struct rlimit *rlim;
           int x;
   
           /*
            * XXX this spl is almost unnecessary.  It is partly to allow for
            * sloppy callers that don't do it (issignal() via CURSIG() is the
            * main offender).  It is partly to work around a bug in the i386
            * cpu_switch() (the ipl is not preserved).  We ran for years
            * without it.  I think there was only a interrupt latency problem.
            * The main caller, tsleep(), does an splx() a couple of instructions
            * after calling here.  The buggy caller, issignal(), usually calls
            * here at spl0() and sometimes returns at splhigh().  The process
            * then runs for a little too long at splhigh().  The ipl gets fixed
            * when the process returns to user mode (or earlier).
            *
            * It would probably be better to always call here at spl0(). Callers
            * are prepared to give up control to another process, so they must
            * be prepared to be interrupted.  The clock stuff here may not
            * actually need splstatclock().
            */
           x = splstatclock();
   
   #ifdef SIMPLELOCK_DEBUG
           if (p->p_simple_locks)
                   printf("sleep: holding simple lock\n");
   #endif
           /*
            * Compute the amount of time during which the current
            * process was running, and add that to its total so far.
            */
           microuptime(&switchtime);
           p->p_runtime += (switchtime.tv_usec - p->p_switchtime.tv_usec) +
               (switchtime.tv_sec - p->p_switchtime.tv_sec) * (int64_t)1000000;
   
           /*
            * Check if the process exceeds its cpu resource allocation.
            * If over max, kill it.
            */
           if (p->p_stat != SZOMB && p->p_limit->p_cpulimit != RLIM_INFINITY &&
               p->p_runtime > p->p_limit->p_cpulimit) {
                   rlim = &p->p_rlimit[RLIMIT_CPU];
                   if (p->p_runtime / (rlim_t)1000000 >= rlim->rlim_max) {
                           killproc(p, "exceeded maximum CPU limit");
                   } else {
                           psignal(p, SIGXCPU);
                           if (rlim->rlim_cur < rlim->rlim_max) {
                                   /* XXX: we should make a private copy */
                                   rlim->rlim_cur += 5;
                           }
                   }
           }
   
           /*
            * Pick a new current process and record its start time.
            */
           cnt.v_swtch++;
           cpu_switch(p);
           if (switchtime.tv_sec)
                   p->p_switchtime = switchtime;
           else
                   microuptime(&p->p_switchtime);
           switchticks = ticks;
   
           splx(x);
   }
   
   /*
    * Initialize the (doubly-linked) run queues
    * to be empty.
    */
   /* ARGSUSED*/
   static void
   rqinit(dummy)
           void *dummy;
   {
           register int i;
   
           for (i = 0; i < NQS; i++) {
                   qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i];
                   rtqs[i].ph_link = rtqs[i].ph_rlink = (struct proc *)&rtqs[i];
                   idqs[i].ph_link = idqs[i].ph_rlink = (struct proc *)&idqs[i];
           }
   }
   
   /*
    * Change process state to be runnable,
    * placing it on the run queue if it is in memory,
    * and awakening the swapper if it isn't in memory.
    */
   void
   setrunnable(p)
           register struct proc *p;
   {
           register int s;
   
           s = splhigh();
           switch (p->p_stat) {
           case 0:
           case SRUN:
           case SZOMB:
           default:
                   panic("setrunnable");
           case SSTOP:
           case SSLEEP:
                   unsleep(p);             /* e.g. when sending signals */
                   break;
   
           case SIDL:
                   break;
           }
           p->p_stat = SRUN;
           if (p->p_flag & P_INMEM)
                   setrunqueue(p);
           splx(s);
           if (p->p_slptime > 1)
                   updatepri(p);
           p->p_slptime = 0;
           if ((p->p_flag & P_INMEM) == 0) {
                   p->p_flag |= P_SWAPINREQ;
                   wakeup((caddr_t)&proc0);
           }
           else
                   maybe_resched(p);
   }
   
   /*
    * Compute the priority of a process when running in user mode.
    * Arrange to reschedule if the resulting priority is better
    * than that of the current process.
    */
   void
   resetpriority(p)
           register struct proc *p;
   {
           register unsigned int newpriority;
   
           if (p->p_rtprio.type == RTP_PRIO_NORMAL) {
                   newpriority = PUSER + p->p_estcpu / 4 + 2 * p->p_nice;
                   newpriority = min(newpriority, MAXPRI);
                   p->p_usrpri = newpriority;
           }
           maybe_resched(p);
   }
   
   /* ARGSUSED */
   static void
   sched_setup(dummy)
           void *dummy;
   {
           /* Kick off timeout driven events by calling first time. */
           roundrobin(NULL);
           schedcpu(NULL);
   }
   

Cache object: 229c508552e938b50e62784cfc36172b