+/*-
+ * Copyright (c) 1982, 1986, 1990 The Regents of the University of California.
+ * Copyright (c) 1991 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * 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 7.18 (Berkeley) 6/27/91
+ */
+
+#include "param.h"
+#include "systm.h"
+#include "proc.h"
+#include "kernel.h"
+#include "buf.h"
+#include "signalvar.h"
+#include "resourcevar.h"
+
+#include "machine/cpu.h"
+
+u_char curpri; /* usrpri of curproc */
+
+/*
+ * Force switch among equal priority processes every 100ms.
+ */
+roundrobin()
+{
+
+ need_resched();
+ timeout(roundrobin, (caddr_t)0, hz / 10);
+}
+
+/*
+ * constants for digital decay and forget
+ * 90% of (p_cpu) 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 hardclock updates p_cpu and p_cpticks independently.
+ *
+ * We wish to decay away 90% of p_cpu 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_cpu *= decay;
+ * will compute
+ * p_cpu *= 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 */
+fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
+
+/*
+ * 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 dont 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, once a second
+ */
+schedcpu()
+{
+ register fixpt_t loadfac = loadfactor(averunnable[0]);
+ register struct proc *p;
+ register int s;
+ register unsigned int newcpu;
+
+ wakeup((caddr_t)&lbolt);
+ for (p = allproc; p != NULL; p = p->p_nxt) {
+ /*
+ * 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_time++;
+ 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;
+ /*
+ * p_pctcpu is only for ps.
+ */
+#if (FSHIFT >= CCPU_SHIFT)
+ p->p_pctcpu += (hz == 100)?
+ ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT):
+ 100 * (((fixpt_t) p->p_cpticks)
+ << (FSHIFT - CCPU_SHIFT)) / hz;
+#else
+ p->p_pctcpu += ((FSCALE - ccpu) *
+ (p->p_cpticks * FSCALE / hz)) >> FSHIFT;
+#endif
+ p->p_cpticks = 0;
+ newcpu = (u_int) decay_cpu(loadfac, p->p_cpu) + p->p_nice;
+ p->p_cpu = min(newcpu, UCHAR_MAX);
+ setpri(p);
+ s = splhigh(); /* prevent state changes */
+ if (p->p_pri >= PUSER) {
+#define PPQ (128 / NQS) /* priorities per queue */
+ if ((p != curproc) &&
+ p->p_stat == SRUN &&
+ (p->p_flag & SLOAD) &&
+ (p->p_pri / PPQ) != (p->p_usrpri / PPQ)) {
+ remrq(p);
+ p->p_pri = p->p_usrpri;
+ setrq(p);
+ } else
+ p->p_pri = p->p_usrpri;
+ }
+ splx(s);
+ }
+ vmmeter();
+ if (bclnlist != NULL)
+ wakeup((caddr_t)pageproc);
+ timeout(schedcpu, (caddr_t)0, hz);
+}
+
+/*
+ * Recalculate the priority of a process after it has slept for a while.
+ * For all load averages >= 1 and max p_cpu of 255, sleeping for at least
+ * six times the loadfactor will decay p_cpu to zero.
+ */
+updatepri(p)
+ register struct proc *p;
+{
+ register unsigned int newcpu = p->p_cpu;
+ register fixpt_t loadfac = loadfactor(averunnable[0]);
+
+ if (p->p_slptime > 5 * loadfac)
+ p->p_cpu = 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_cpu = min(newcpu, UCHAR_MAX);
+ }
+ setpri(p);
+}
+
+#define SQSIZE 0100 /* Must be power of 2 */
+#define HASH(x) (( (int) x >> 5) & (SQSIZE-1))
+struct slpque {
+ struct proc *sq_head;
+ struct proc **sq_tailp;
+} slpque[SQSIZE];
+
+/*
+ * 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;
+
+/*
+ * General sleep call.
+ * Suspends current process until a wakeup is made on chan.
+ * The process will then be made runnable with priority pri.
+ * 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).
+ */
+tsleep(chan, pri, wmesg, timo)
+ caddr_t chan;
+ int pri;
+ char *wmesg;
+ int timo;
+{
+ register struct proc *p = curproc;
+ register struct slpque *qp;
+ register s;
+ int sig, catch = pri & PCATCH;
+ extern int cold;
+ int endtsleep();
+
+ 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);
+ }
+#ifdef DIAGNOSTIC
+ if (chan == 0 || p->p_stat != SRUN || p->p_rlink)
+ panic("tsleep");
+#endif
+ p->p_wchan = chan;
+ p->p_wmesg = wmesg;
+ p->p_slptime = 0;
+ p->p_pri = pri & PRIMASK;
+ qp = &slpque[HASH(chan)];
+ if (qp->sq_head == 0)
+ qp->sq_head = p;
+ else
+ *qp->sq_tailp = p;
+ *(qp->sq_tailp = &p->p_link) = 0;
+ if (timo)
+ timeout(endtsleep, (caddr_t)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 |= SSINTR;
+ 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;
+ }
+ }
+ p->p_stat = SSLEEP;
+ p->p_stats->p_ru.ru_nvcsw++;
+ swtch();
+#include "ddb.h"
+#ifdef NDDB
+ /* handy breakpoint location after process "wakes" */
+ asm(".globl bpendtsleep ; bpendtsleep:");
+#endif
+resume:
+ curpri = p->p_usrpri;
+ splx(s);
+ p->p_flag &= ~SSINTR;
+ if (p->p_flag & STIMO) {
+ p->p_flag &= ~STIMO;
+ if (catch == 0 || sig == 0)
+ return (EWOULDBLOCK);
+ } else if (timo)
+ untimeout(endtsleep, (caddr_t)p);
+ if (catch && (sig != 0 || (sig = CURSIG(p)))) {
+ if (p->p_sigacts->ps_sigintr & sigmask(sig))
+ return (EINTR);
+ return (ERESTART);
+ }
+ return (0);
+}
+
+/*
+ * Implement timeout for tsleep.
+ * 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.
+ */
+endtsleep(p)
+ register struct proc *p;
+{
+ int s = splhigh();
+
+ if (p->p_wchan) {
+ if (p->p_stat == SSLEEP)
+ setrun(p);
+ else
+ unsleep(p);
+ p->p_flag |= STIMO;
+ }
+ splx(s);
+}
+
+/*
+ * Short-term, non-interruptable sleep.
+ */
+sleep(chan, pri)
+ caddr_t chan;
+ int pri;
+{
+ register struct proc *p = curproc;
+ register struct slpque *qp;
+ register s;
+ extern int cold;
+
+#ifdef DIAGNOSTIC
+ if (pri > PZERO) {
+ printf("sleep called with pri %d > PZERO, wchan: %x\n",
+ pri, chan);
+ panic("old sleep");
+ }
+#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;
+ }
+#ifdef DIAGNOSTIC
+ if (chan==0 || p->p_stat != SRUN || p->p_rlink)
+ panic("sleep");
+#endif
+ p->p_wchan = chan;
+ p->p_wmesg = NULL;
+ p->p_slptime = 0;
+ p->p_pri = pri;
+ qp = &slpque[HASH(chan)];
+ if (qp->sq_head == 0)
+ qp->sq_head = p;
+ else
+ *qp->sq_tailp = p;
+ *(qp->sq_tailp = &p->p_link) = 0;
+ p->p_stat = SSLEEP;
+ p->p_stats->p_ru.ru_nvcsw++;
+ swtch();
+#ifdef NDDB
+ /* handy breakpoint location after process "wakes" */
+ asm(".globl bpendsleep ; bpendsleep:");
+#endif
+ curpri = p->p_usrpri;
+ splx(s);
+}
+
+/*
+ * Remove a process from its wait queue
+ */
+unsleep(p)
+ register struct proc *p;
+{
+ register struct slpque *qp;
+ register struct proc **hp;
+ int s;
+
+ s = splhigh();
+ if (p->p_wchan) {
+ hp = &(qp = &slpque[HASH(p->p_wchan)])->sq_head;
+ while (*hp != p)
+ hp = &(*hp)->p_link;
+ *hp = p->p_link;
+ if (qp->sq_tailp == &p->p_link)
+ qp->sq_tailp = hp;
+ p->p_wchan = 0;
+ }
+ splx(s);
+}
+
+/*
+ * Wakeup on "chan"; set all processes
+ * sleeping on chan to run state.
+ */
+wakeup(chan)
+ register caddr_t chan;
+{
+ register struct slpque *qp;
+ register struct proc *p, **q;
+ int s;
+
+ s = splhigh();
+ qp = &slpque[HASH(chan)];
+restart:
+ for (q = &qp->sq_head; p = *q; ) {
+#ifdef DIAGNOSTIC
+ if (p->p_rlink || p->p_stat != SSLEEP && p->p_stat != SSTOP)
+ panic("wakeup");
+#endif
+ if (p->p_wchan == chan) {
+ p->p_wchan = 0;
+ *q = p->p_link;
+ if (qp->sq_tailp == &p->p_link)
+ qp->sq_tailp = q;
+ if (p->p_stat == SSLEEP) {
+ /* OPTIMIZED INLINE EXPANSION OF setrun(p) */
+ if (p->p_slptime > 1)
+ updatepri(p);
+ p->p_slptime = 0;
+ p->p_stat = SRUN;
+ if (p->p_flag & SLOAD)
+ setrq(p);
+ /*
+ * Since curpri is a usrpri,
+ * p->p_pri is always better than curpri.
+ */
+ if ((p->p_flag&SLOAD) == 0)
+ wakeup((caddr_t)&proc0);
+ else
+ need_resched();
+ /* END INLINE EXPANSION */
+ goto restart;
+ }
+ } else
+ q = &p->p_link;
+ }
+ splx(s);
+}
+
+/*
+ * Initialize the (doubly-linked) run queues
+ * to be empty.
+ */
+rqinit()
+{
+ register int i;
+
+ for (i = 0; i < NQS; i++)
+ qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[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.
+ */
+setrun(p)
+ register struct proc *p;
+{
+ register int s;
+
+ s = splhigh();
+ switch (p->p_stat) {
+
+ case 0:
+ case SWAIT:
+ case SRUN:
+ case SZOMB:
+ default:
+ panic("setrun");
+
+ case SSTOP:
+ case SSLEEP:
+ unsleep(p); /* e.g. when sending signals */
+ break;
+
+ case SIDL:
+ break;
+ }
+ p->p_stat = SRUN;
+ if (p->p_flag & SLOAD)
+ setrq(p);
+ splx(s);
+ if (p->p_slptime > 1)
+ updatepri(p);
+ p->p_slptime = 0;
+ if ((p->p_flag&SLOAD) == 0)
+ wakeup((caddr_t)&proc0);
+ else if (p->p_pri < curpri)
+ need_resched();
+}
+
+/*
+ * Compute priority of process when running in user mode.
+ * Arrange to reschedule if the resulting priority
+ * is better than that of the current process.
+ */
+setpri(p)
+ register struct proc *p;
+{
+ register unsigned int newpri;
+
+ newpri = PUSER + p->p_cpu / 4 + 2 * p->p_nice;
+ newpri = min(newpri, MAXPRI);
+ p->p_usrpri = newpri;
+ if (newpri < curpri)
+ need_resched();
+}
+
+#ifdef NDDB
+#define DDBFUNC(s) ddb_##s
+DDBFUNC(ps) () {
+ int np;
+ struct proc *ap, *p, *pp;
+ np = nprocs;
+ p = ap = allproc;
+ printf(" pid proc addr uid ppid pgrp flag stat comm wchan\n");
+ while (--np >= 0) {
+ pp = p->p_pptr;
+ if (pp == 0)
+ pp = p;
+ if (p->p_stat) {
+ printf("%5d %06x %06x %3d %5d %5d %06x %d %s ",
+ p->p_pid, ap, p->p_addr, p->p_cred->p_ruid, pp->p_pid,
+ p->p_pgrp->pg_id, p->p_flag, p->p_stat,
+ p->p_comm);
+ if (p->p_wchan) {
+ if (p->p_wmesg)
+ printf("%s ", p->p_wmesg);
+ printf("%x", p->p_wchan);
+ }
+ printf("\n");
+ }
+ ap = p->p_nxt;
+ if (ap == 0 && np > 0)
+ ap = zombproc;
+ p = ap;
+ }
+}
+#endif
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