Initial import from FreeBSD RELENG_4:
[dragonfly.git] / sys / kern / kern_synch.c
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1/*-
2 * Copyright (c) 1982, 1986, 1990, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
39 * $FreeBSD: src/sys/kern/kern_synch.c,v 1.87.2.6 2002/10/13 07:29:53 kbyanc Exp $
40 */
41
42#include "opt_ktrace.h"
43
44#include <sys/param.h>
45#include <sys/systm.h>
46#include <sys/proc.h>
47#include <sys/kernel.h>
48#include <sys/signalvar.h>
49#include <sys/resourcevar.h>
50#include <sys/vmmeter.h>
51#include <sys/sysctl.h>
52#ifdef KTRACE
53#include <sys/uio.h>
54#include <sys/ktrace.h>
55#endif
56
57#include <machine/cpu.h>
58#include <machine/ipl.h>
59#include <machine/smp.h>
60
61static void sched_setup __P((void *dummy));
62SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
63
64u_char curpriority;
65int hogticks;
66int lbolt;
67int sched_quantum; /* Roundrobin scheduling quantum in ticks. */
68
69static struct callout loadav_callout;
70
71struct loadavg averunnable =
72 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
73/*
74 * Constants for averages over 1, 5, and 15 minutes
75 * when sampling at 5 second intervals.
76 */
77static fixpt_t cexp[3] = {
78 0.9200444146293232 * FSCALE, /* exp(-1/12) */
79 0.9834714538216174 * FSCALE, /* exp(-1/60) */
80 0.9944598480048967 * FSCALE, /* exp(-1/180) */
81};
82
83static int curpriority_cmp __P((struct proc *p));
84static void endtsleep __P((void *));
85static void loadav __P((void *arg));
86static void maybe_resched __P((struct proc *chk));
87static void roundrobin __P((void *arg));
88static void schedcpu __P((void *arg));
89static void updatepri __P((struct proc *p));
90
91static int
92sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
93{
94 int error, new_val;
95
96 new_val = sched_quantum * tick;
97 error = sysctl_handle_int(oidp, &new_val, 0, req);
98 if (error != 0 || req->newptr == NULL)
99 return (error);
100 if (new_val < tick)
101 return (EINVAL);
102 sched_quantum = new_val / tick;
103 hogticks = 2 * sched_quantum;
104 return (0);
105}
106
107SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
108 0, sizeof sched_quantum, sysctl_kern_quantum, "I", "");
109
110/*-
111 * Compare priorities. Return:
112 * <0: priority of p < current priority
113 * 0: priority of p == current priority
114 * >0: priority of p > current priority
115 * The priorities are the normal priorities or the normal realtime priorities
116 * if p is on the same scheduler as curproc. Otherwise the process on the
117 * more realtimeish scheduler has lowest priority. As usual, a higher
118 * priority really means a lower priority.
119 */
120static int
121curpriority_cmp(p)
122 struct proc *p;
123{
124 int c_class, p_class;
125
126 c_class = RTP_PRIO_BASE(curproc->p_rtprio.type);
127 p_class = RTP_PRIO_BASE(p->p_rtprio.type);
128 if (p_class != c_class)
129 return (p_class - c_class);
130 if (p_class == RTP_PRIO_NORMAL)
131 return (((int)p->p_priority - (int)curpriority) / PPQ);
132 return ((int)p->p_rtprio.prio - (int)curproc->p_rtprio.prio);
133}
134
135/*
136 * Arrange to reschedule if necessary, taking the priorities and
137 * schedulers into account.
138 */
139static void
140maybe_resched(chk)
141 struct proc *chk;
142{
143 struct proc *p = curproc; /* XXX */
144
145 /*
146 * XXX idle scheduler still broken because proccess stays on idle
147 * scheduler during waits (such as when getting FS locks). If a
148 * standard process becomes runaway cpu-bound, the system can lockup
149 * due to idle-scheduler processes in wakeup never getting any cpu.
150 */
151 if (p == NULL) {
152#if 0
153 need_resched();
154#endif
155 } else if (chk == p) {
156 /* We may need to yield if our priority has been raised. */
157 if (curpriority_cmp(chk) > 0)
158 need_resched();
159 } else if (curpriority_cmp(chk) < 0)
160 need_resched();
161}
162
163int
164roundrobin_interval(void)
165{
166 return (sched_quantum);
167}
168
169/*
170 * Force switch among equal priority processes every 100ms.
171 */
172/* ARGSUSED */
173static void
174roundrobin(arg)
175 void *arg;
176{
177#ifndef SMP
178 struct proc *p = curproc; /* XXX */
179#endif
180
181#ifdef SMP
182 need_resched();
183 forward_roundrobin();
184#else
185 if (p == 0 || RTP_PRIO_NEED_RR(p->p_rtprio.type))
186 need_resched();
187#endif
188
189 timeout(roundrobin, NULL, sched_quantum);
190}
191
192/*
193 * Constants for digital decay and forget:
194 * 90% of (p_estcpu) usage in 5 * loadav time
195 * 95% of (p_pctcpu) usage in 60 seconds (load insensitive)
196 * Note that, as ps(1) mentions, this can let percentages
197 * total over 100% (I've seen 137.9% for 3 processes).
198 *
199 * Note that schedclock() updates p_estcpu and p_cpticks asynchronously.
200 *
201 * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds.
202 * That is, the system wants to compute a value of decay such
203 * that the following for loop:
204 * for (i = 0; i < (5 * loadavg); i++)
205 * p_estcpu *= decay;
206 * will compute
207 * p_estcpu *= 0.1;
208 * for all values of loadavg:
209 *
210 * Mathematically this loop can be expressed by saying:
211 * decay ** (5 * loadavg) ~= .1
212 *
213 * The system computes decay as:
214 * decay = (2 * loadavg) / (2 * loadavg + 1)
215 *
216 * We wish to prove that the system's computation of decay
217 * will always fulfill the equation:
218 * decay ** (5 * loadavg) ~= .1
219 *
220 * If we compute b as:
221 * b = 2 * loadavg
222 * then
223 * decay = b / (b + 1)
224 *
225 * We now need to prove two things:
226 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
227 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
228 *
229 * Facts:
230 * For x close to zero, exp(x) =~ 1 + x, since
231 * exp(x) = 0! + x**1/1! + x**2/2! + ... .
232 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
233 * For x close to zero, ln(1+x) =~ x, since
234 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
235 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
236 * ln(.1) =~ -2.30
237 *
238 * Proof of (1):
239 * Solve (factor)**(power) =~ .1 given power (5*loadav):
240 * solving for factor,
241 * ln(factor) =~ (-2.30/5*loadav), or
242 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
243 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
244 *
245 * Proof of (2):
246 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
247 * solving for power,
248 * power*ln(b/(b+1)) =~ -2.30, or
249 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
250 *
251 * Actual power values for the implemented algorithm are as follows:
252 * loadav: 1 2 3 4
253 * power: 5.68 10.32 14.94 19.55
254 */
255
256/* calculations for digital decay to forget 90% of usage in 5*loadav sec */
257#define loadfactor(loadav) (2 * (loadav))
258#define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
259
260/* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
261static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
262SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
263
264/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
265static int fscale __unused = FSCALE;
266SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
267
268/*
269 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
270 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
271 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
272 *
273 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
274 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
275 *
276 * If you don't want to bother with the faster/more-accurate formula, you
277 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
278 * (more general) method of calculating the %age of CPU used by a process.
279 */
280#define CCPU_SHIFT 11
281
282/*
283 * Recompute process priorities, every hz ticks.
284 */
285/* ARGSUSED */
286static void
287schedcpu(arg)
288 void *arg;
289{
290 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
291 register struct proc *p;
292 register int realstathz, s;
293
294 realstathz = stathz ? stathz : hz;
295 LIST_FOREACH(p, &allproc, p_list) {
296 /*
297 * Increment time in/out of memory and sleep time
298 * (if sleeping). We ignore overflow; with 16-bit int's
299 * (remember them?) overflow takes 45 days.
300 */
301 p->p_swtime++;
302 if (p->p_stat == SSLEEP || p->p_stat == SSTOP)
303 p->p_slptime++;
304 p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT;
305 /*
306 * If the process has slept the entire second,
307 * stop recalculating its priority until it wakes up.
308 */
309 if (p->p_slptime > 1)
310 continue;
311 s = splhigh(); /* prevent state changes and protect run queue */
312 /*
313 * p_pctcpu is only for ps.
314 */
315#if (FSHIFT >= CCPU_SHIFT)
316 p->p_pctcpu += (realstathz == 100)?
317 ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT):
318 100 * (((fixpt_t) p->p_cpticks)
319 << (FSHIFT - CCPU_SHIFT)) / realstathz;
320#else
321 p->p_pctcpu += ((FSCALE - ccpu) *
322 (p->p_cpticks * FSCALE / realstathz)) >> FSHIFT;
323#endif
324 p->p_cpticks = 0;
325 p->p_estcpu = decay_cpu(loadfac, p->p_estcpu);
326 resetpriority(p);
327 if (p->p_priority >= PUSER) {
328 if ((p != curproc) &&
329#ifdef SMP
330 p->p_oncpu == 0xff && /* idle */
331#endif
332 p->p_stat == SRUN &&
333 (p->p_flag & P_INMEM) &&
334 (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) {
335 remrunqueue(p);
336 p->p_priority = p->p_usrpri;
337 setrunqueue(p);
338 } else
339 p->p_priority = p->p_usrpri;
340 }
341 splx(s);
342 }
343 wakeup((caddr_t)&lbolt);
344 timeout(schedcpu, (void *)0, hz);
345}
346
347/*
348 * Recalculate the priority of a process after it has slept for a while.
349 * For all load averages >= 1 and max p_estcpu of 255, sleeping for at
350 * least six times the loadfactor will decay p_estcpu to zero.
351 */
352static void
353updatepri(p)
354 register struct proc *p;
355{
356 register unsigned int newcpu = p->p_estcpu;
357 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
358
359 if (p->p_slptime > 5 * loadfac)
360 p->p_estcpu = 0;
361 else {
362 p->p_slptime--; /* the first time was done in schedcpu */
363 while (newcpu && --p->p_slptime)
364 newcpu = decay_cpu(loadfac, newcpu);
365 p->p_estcpu = newcpu;
366 }
367 resetpriority(p);
368}
369
370/*
371 * We're only looking at 7 bits of the address; everything is
372 * aligned to 4, lots of things are aligned to greater powers
373 * of 2. Shift right by 8, i.e. drop the bottom 256 worth.
374 */
375#define TABLESIZE 128
376static TAILQ_HEAD(slpquehead, proc) slpque[TABLESIZE];
377#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1))
378
379/*
380 * During autoconfiguration or after a panic, a sleep will simply
381 * lower the priority briefly to allow interrupts, then return.
382 * The priority to be used (safepri) is machine-dependent, thus this
383 * value is initialized and maintained in the machine-dependent layers.
384 * This priority will typically be 0, or the lowest priority
385 * that is safe for use on the interrupt stack; it can be made
386 * higher to block network software interrupts after panics.
387 */
388int safepri;
389
390void
391sleepinit(void)
392{
393 int i;
394
395 sched_quantum = hz/10;
396 hogticks = 2 * sched_quantum;
397 for (i = 0; i < TABLESIZE; i++)
398 TAILQ_INIT(&slpque[i]);
399}
400
401/*
402 * General sleep call. Suspends the current process until a wakeup is
403 * performed on the specified identifier. The process will then be made
404 * runnable with the specified priority. Sleeps at most timo/hz seconds
405 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
406 * before and after sleeping, else signals are not checked. Returns 0 if
407 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
408 * signal needs to be delivered, ERESTART is returned if the current system
409 * call should be restarted if possible, and EINTR is returned if the system
410 * call should be interrupted by the signal (return EINTR).
411 */
412int
413tsleep(ident, priority, wmesg, timo)
414 void *ident;
415 int priority, timo;
416 const char *wmesg;
417{
418 struct proc *p = curproc;
419 int s, sig, catch = priority & PCATCH;
420 struct callout_handle thandle;
421
422#ifdef KTRACE
423 if (p && KTRPOINT(p, KTR_CSW))
424 ktrcsw(p->p_tracep, 1, 0);
425#endif
426 s = splhigh();
427 if (cold || panicstr) {
428 /*
429 * After a panic, or during autoconfiguration,
430 * just give interrupts a chance, then just return;
431 * don't run any other procs or panic below,
432 * in case this is the idle process and already asleep.
433 */
434 splx(safepri);
435 splx(s);
436 return (0);
437 }
438 KASSERT(p != NULL, ("tsleep1"));
439 KASSERT(ident != NULL && p->p_stat == SRUN, ("tsleep"));
440 /*
441 * Process may be sitting on a slpque if asleep() was called, remove
442 * it before re-adding.
443 */
444 if (p->p_wchan != NULL)
445 unsleep(p);
446
447 p->p_wchan = ident;
448 p->p_wmesg = wmesg;
449 p->p_slptime = 0;
450 p->p_priority = priority & PRIMASK;
451 TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_procq);
452 if (timo)
453 thandle = timeout(endtsleep, (void *)p, timo);
454 /*
455 * We put ourselves on the sleep queue and start our timeout
456 * before calling CURSIG, as we could stop there, and a wakeup
457 * or a SIGCONT (or both) could occur while we were stopped.
458 * A SIGCONT would cause us to be marked as SSLEEP
459 * without resuming us, thus we must be ready for sleep
460 * when CURSIG is called. If the wakeup happens while we're
461 * stopped, p->p_wchan will be 0 upon return from CURSIG.
462 */
463 if (catch) {
464 p->p_flag |= P_SINTR;
465 if ((sig = CURSIG(p))) {
466 if (p->p_wchan)
467 unsleep(p);
468 p->p_stat = SRUN;
469 goto resume;
470 }
471 if (p->p_wchan == 0) {
472 catch = 0;
473 goto resume;
474 }
475 } else
476 sig = 0;
477 p->p_stat = SSLEEP;
478 p->p_stats->p_ru.ru_nvcsw++;
479 mi_switch();
480resume:
481 curpriority = p->p_usrpri;
482 splx(s);
483 p->p_flag &= ~P_SINTR;
484 if (p->p_flag & P_TIMEOUT) {
485 p->p_flag &= ~P_TIMEOUT;
486 if (sig == 0) {
487#ifdef KTRACE
488 if (KTRPOINT(p, KTR_CSW))
489 ktrcsw(p->p_tracep, 0, 0);
490#endif
491 return (EWOULDBLOCK);
492 }
493 } else if (timo)
494 untimeout(endtsleep, (void *)p, thandle);
495 if (catch && (sig != 0 || (sig = CURSIG(p)))) {
496#ifdef KTRACE
497 if (KTRPOINT(p, KTR_CSW))
498 ktrcsw(p->p_tracep, 0, 0);
499#endif
500 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
501 return (EINTR);
502 return (ERESTART);
503 }
504#ifdef KTRACE
505 if (KTRPOINT(p, KTR_CSW))
506 ktrcsw(p->p_tracep, 0, 0);
507#endif
508 return (0);
509}
510
511/*
512 * asleep() - async sleep call. Place process on wait queue and return
513 * immediately without blocking. The process stays runnable until await()
514 * is called. If ident is NULL, remove process from wait queue if it is still
515 * on one.
516 *
517 * Only the most recent sleep condition is effective when making successive
518 * calls to asleep() or when calling tsleep().
519 *
520 * The timeout, if any, is not initiated until await() is called. The sleep
521 * priority, signal, and timeout is specified in the asleep() call but may be
522 * overriden in the await() call.
523 *
524 * <<<<<<<< EXPERIMENTAL, UNTESTED >>>>>>>>>>
525 */
526
527int
528asleep(void *ident, int priority, const char *wmesg, int timo)
529{
530 struct proc *p = curproc;
531 int s;
532
533 /*
534 * splhigh() while manipulating sleep structures and slpque.
535 *
536 * Remove preexisting wait condition (if any) and place process
537 * on appropriate slpque, but do not put process to sleep.
538 */
539
540 s = splhigh();
541
542 if (p->p_wchan != NULL)
543 unsleep(p);
544
545 if (ident) {
546 p->p_wchan = ident;
547 p->p_wmesg = wmesg;
548 p->p_slptime = 0;
549 p->p_asleep.as_priority = priority;
550 p->p_asleep.as_timo = timo;
551 TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_procq);
552 }
553
554 splx(s);
555
556 return(0);
557}
558
559/*
560 * await() - wait for async condition to occur. The process blocks until
561 * wakeup() is called on the most recent asleep() address. If wakeup is called
562 * priority to await(), await() winds up being a NOP.
563 *
564 * If await() is called more then once (without an intervening asleep() call),
565 * await() is still effectively a NOP but it calls mi_switch() to give other
566 * processes some cpu before returning. The process is left runnable.
567 *
568 * <<<<<<<< EXPERIMENTAL, UNTESTED >>>>>>>>>>
569 */
570
571int
572await(int priority, int timo)
573{
574 struct proc *p = curproc;
575 int s;
576
577 s = splhigh();
578
579 if (p->p_wchan != NULL) {
580 struct callout_handle thandle;
581 int sig;
582 int catch;
583
584 /*
585 * The call to await() can override defaults specified in
586 * the original asleep().
587 */
588 if (priority < 0)
589 priority = p->p_asleep.as_priority;
590 if (timo < 0)
591 timo = p->p_asleep.as_timo;
592
593 /*
594 * Install timeout
595 */
596
597 if (timo)
598 thandle = timeout(endtsleep, (void *)p, timo);
599
600 sig = 0;
601 catch = priority & PCATCH;
602
603 if (catch) {
604 p->p_flag |= P_SINTR;
605 if ((sig = CURSIG(p))) {
606 if (p->p_wchan)
607 unsleep(p);
608 p->p_stat = SRUN;
609 goto resume;
610 }
611 if (p->p_wchan == NULL) {
612 catch = 0;
613 goto resume;
614 }
615 }
616 p->p_stat = SSLEEP;
617 p->p_stats->p_ru.ru_nvcsw++;
618 mi_switch();
619resume:
620 curpriority = p->p_usrpri;
621
622 splx(s);
623 p->p_flag &= ~P_SINTR;
624 if (p->p_flag & P_TIMEOUT) {
625 p->p_flag &= ~P_TIMEOUT;
626 if (sig == 0) {
627#ifdef KTRACE
628 if (KTRPOINT(p, KTR_CSW))
629 ktrcsw(p->p_tracep, 0, 0);
630#endif
631 return (EWOULDBLOCK);
632 }
633 } else if (timo)
634 untimeout(endtsleep, (void *)p, thandle);
635 if (catch && (sig != 0 || (sig = CURSIG(p)))) {
636#ifdef KTRACE
637 if (KTRPOINT(p, KTR_CSW))
638 ktrcsw(p->p_tracep, 0, 0);
639#endif
640 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
641 return (EINTR);
642 return (ERESTART);
643 }
644#ifdef KTRACE
645 if (KTRPOINT(p, KTR_CSW))
646 ktrcsw(p->p_tracep, 0, 0);
647#endif
648 } else {
649 /*
650 * If as_priority is 0, await() has been called without an
651 * intervening asleep(). We are still effectively a NOP,
652 * but we call mi_switch() for safety.
653 */
654
655 if (p->p_asleep.as_priority == 0) {
656 p->p_stats->p_ru.ru_nvcsw++;
657 mi_switch();
658 }
659 splx(s);
660 }
661
662 /*
663 * clear p_asleep.as_priority as an indication that await() has been
664 * called. If await() is called again without an intervening asleep(),
665 * await() is still effectively a NOP but the above mi_switch() code
666 * is triggered as a safety.
667 */
668 p->p_asleep.as_priority = 0;
669
670 return (0);
671}
672
673/*
674 * Implement timeout for tsleep or asleep()/await()
675 *
676 * If process hasn't been awakened (wchan non-zero),
677 * set timeout flag and undo the sleep. If proc
678 * is stopped, just unsleep so it will remain stopped.
679 */
680static void
681endtsleep(arg)
682 void *arg;
683{
684 register struct proc *p;
685 int s;
686
687 p = (struct proc *)arg;
688 s = splhigh();
689 if (p->p_wchan) {
690 if (p->p_stat == SSLEEP)
691 setrunnable(p);
692 else
693 unsleep(p);
694 p->p_flag |= P_TIMEOUT;
695 }
696 splx(s);
697}
698
699/*
700 * Remove a process from its wait queue
701 */
702void
703unsleep(p)
704 register struct proc *p;
705{
706 int s;
707
708 s = splhigh();
709 if (p->p_wchan) {
710 TAILQ_REMOVE(&slpque[LOOKUP(p->p_wchan)], p, p_procq);
711 p->p_wchan = 0;
712 }
713 splx(s);
714}
715
716/*
717 * Make all processes sleeping on the specified identifier runnable.
718 */
719void
720wakeup(ident)
721 register void *ident;
722{
723 register struct slpquehead *qp;
724 register struct proc *p;
725 struct proc *np;
726 int s;
727
728 s = splhigh();
729 qp = &slpque[LOOKUP(ident)];
730restart:
731 for (p = TAILQ_FIRST(qp); p != NULL; p = np) {
732 np = TAILQ_NEXT(p, p_procq);
733 if (p->p_wchan == ident) {
734 TAILQ_REMOVE(qp, p, p_procq);
735 p->p_wchan = 0;
736 if (p->p_stat == SSLEEP) {
737 /* OPTIMIZED EXPANSION OF setrunnable(p); */
738 if (p->p_slptime > 1)
739 updatepri(p);
740 p->p_slptime = 0;
741 p->p_stat = SRUN;
742 if (p->p_flag & P_INMEM) {
743 setrunqueue(p);
744 maybe_resched(p);
745 } else {
746 p->p_flag |= P_SWAPINREQ;
747 wakeup((caddr_t)&proc0);
748 }
749 /* END INLINE EXPANSION */
750 goto restart;
751 }
752 }
753 }
754 splx(s);
755}
756
757/*
758 * Make a process sleeping on the specified identifier runnable.
759 * May wake more than one process if a target process is currently
760 * swapped out.
761 */
762void
763wakeup_one(ident)
764 register void *ident;
765{
766 register struct slpquehead *qp;
767 register struct proc *p;
768 struct proc *np;
769 int s;
770
771 s = splhigh();
772 qp = &slpque[LOOKUP(ident)];
773
774restart:
775 for (p = TAILQ_FIRST(qp); p != NULL; p = np) {
776 np = TAILQ_NEXT(p, p_procq);
777 if (p->p_wchan == ident) {
778 TAILQ_REMOVE(qp, p, p_procq);
779 p->p_wchan = 0;
780 if (p->p_stat == SSLEEP) {
781 /* OPTIMIZED EXPANSION OF setrunnable(p); */
782 if (p->p_slptime > 1)
783 updatepri(p);
784 p->p_slptime = 0;
785 p->p_stat = SRUN;
786 if (p->p_flag & P_INMEM) {
787 setrunqueue(p);
788 maybe_resched(p);
789 break;
790 } else {
791 p->p_flag |= P_SWAPINREQ;
792 wakeup((caddr_t)&proc0);
793 }
794 /* END INLINE EXPANSION */
795 goto restart;
796 }
797 }
798 }
799 splx(s);
800}
801
802/*
803 * The machine independent parts of mi_switch().
804 * Must be called at splstatclock() or higher.
805 */
806void
807mi_switch()
808{
809 struct timeval new_switchtime;
810 register struct proc *p = curproc; /* XXX */
811 register struct rlimit *rlim;
812 int x;
813
814 /*
815 * XXX this spl is almost unnecessary. It is partly to allow for
816 * sloppy callers that don't do it (issignal() via CURSIG() is the
817 * main offender). It is partly to work around a bug in the i386
818 * cpu_switch() (the ipl is not preserved). We ran for years
819 * without it. I think there was only a interrupt latency problem.
820 * The main caller, tsleep(), does an splx() a couple of instructions
821 * after calling here. The buggy caller, issignal(), usually calls
822 * here at spl0() and sometimes returns at splhigh(). The process
823 * then runs for a little too long at splhigh(). The ipl gets fixed
824 * when the process returns to user mode (or earlier).
825 *
826 * It would probably be better to always call here at spl0(). Callers
827 * are prepared to give up control to another process, so they must
828 * be prepared to be interrupted. The clock stuff here may not
829 * actually need splstatclock().
830 */
831 x = splstatclock();
832
833#ifdef SIMPLELOCK_DEBUG
834 if (p->p_simple_locks)
835 printf("sleep: holding simple lock\n");
836#endif
837 /*
838 * Compute the amount of time during which the current
839 * process was running, and add that to its total so far.
840 */
841 microuptime(&new_switchtime);
842 if (timevalcmp(&new_switchtime, &switchtime, <)) {
843 printf("microuptime() went backwards (%ld.%06ld -> %ld.%06ld)\n",
844 switchtime.tv_sec, switchtime.tv_usec,
845 new_switchtime.tv_sec, new_switchtime.tv_usec);
846 new_switchtime = switchtime;
847 } else {
848 p->p_runtime += (new_switchtime.tv_usec - switchtime.tv_usec) +
849 (new_switchtime.tv_sec - switchtime.tv_sec) * (int64_t)1000000;
850 }
851
852 /*
853 * Check if the process exceeds its cpu resource allocation.
854 * If over max, kill it.
855 */
856 if (p->p_stat != SZOMB && p->p_limit->p_cpulimit != RLIM_INFINITY &&
857 p->p_runtime > p->p_limit->p_cpulimit) {
858 rlim = &p->p_rlimit[RLIMIT_CPU];
859 if (p->p_runtime / (rlim_t)1000000 >= rlim->rlim_max) {
860 killproc(p, "exceeded maximum CPU limit");
861 } else {
862 psignal(p, SIGXCPU);
863 if (rlim->rlim_cur < rlim->rlim_max) {
864 /* XXX: we should make a private copy */
865 rlim->rlim_cur += 5;
866 }
867 }
868 }
869
870 /*
871 * Pick a new current process and record its start time.
872 */
873 cnt.v_swtch++;
874 switchtime = new_switchtime;
875 cpu_switch(p);
876 if (switchtime.tv_sec == 0)
877 microuptime(&switchtime);
878 switchticks = ticks;
879
880 splx(x);
881}
882
883/*
884 * Change process state to be runnable,
885 * placing it on the run queue if it is in memory,
886 * and awakening the swapper if it isn't in memory.
887 */
888void
889setrunnable(p)
890 register struct proc *p;
891{
892 register int s;
893
894 s = splhigh();
895 switch (p->p_stat) {
896 case 0:
897 case SRUN:
898 case SZOMB:
899 default:
900 panic("setrunnable");
901 case SSTOP:
902 case SSLEEP:
903 unsleep(p); /* e.g. when sending signals */
904 break;
905
906 case SIDL:
907 break;
908 }
909 p->p_stat = SRUN;
910 if (p->p_flag & P_INMEM)
911 setrunqueue(p);
912 splx(s);
913 if (p->p_slptime > 1)
914 updatepri(p);
915 p->p_slptime = 0;
916 if ((p->p_flag & P_INMEM) == 0) {
917 p->p_flag |= P_SWAPINREQ;
918 wakeup((caddr_t)&proc0);
919 }
920 else
921 maybe_resched(p);
922}
923
924/*
925 * Compute the priority of a process when running in user mode.
926 * Arrange to reschedule if the resulting priority is better
927 * than that of the current process.
928 */
929void
930resetpriority(p)
931 register struct proc *p;
932{
933 register unsigned int newpriority;
934
935 if (p->p_rtprio.type == RTP_PRIO_NORMAL) {
936 newpriority = PUSER + p->p_estcpu / INVERSE_ESTCPU_WEIGHT +
937 NICE_WEIGHT * p->p_nice;
938 newpriority = min(newpriority, MAXPRI);
939 p->p_usrpri = newpriority;
940 }
941 maybe_resched(p);
942}
943
944/*
945 * Compute a tenex style load average of a quantity on
946 * 1, 5 and 15 minute intervals.
947 */
948static void
949loadav(void *arg)
950{
951 int i, nrun;
952 struct loadavg *avg;
953 struct proc *p;
954
955 avg = &averunnable;
956 nrun = 0;
957 LIST_FOREACH(p, &allproc, p_list) {
958 switch (p->p_stat) {
959 case SRUN:
960 case SIDL:
961 nrun++;
962 }
963 }
964 for (i = 0; i < 3; i++)
965 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
966 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
967
968 /*
969 * Schedule the next update to occur after 5 seconds, but add a
970 * random variation to avoid synchronisation with processes that
971 * run at regular intervals.
972 */
973 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
974 loadav, NULL);
975}
976
977/* ARGSUSED */
978static void
979sched_setup(dummy)
980 void *dummy;
981{
982
983 callout_init(&loadav_callout);
984
985 /* Kick off timeout driven events by calling first time. */
986 roundrobin(NULL);
987 schedcpu(NULL);
988 loadav(NULL);
989}
990
991/*
992 * We adjust the priority of the current process. The priority of
993 * a process gets worse as it accumulates CPU time. The cpu usage
994 * estimator (p_estcpu) is increased here. resetpriority() will
995 * compute a different priority each time p_estcpu increases by
996 * INVERSE_ESTCPU_WEIGHT
997 * (until MAXPRI is reached). The cpu usage estimator ramps up
998 * quite quickly when the process is running (linearly), and decays
999 * away exponentially, at a rate which is proportionally slower when
1000 * the system is busy. The basic principle is that the system will
1001 * 90% forget that the process used a lot of CPU time in 5 * loadav
1002 * seconds. This causes the system to favor processes which haven't
1003 * run much recently, and to round-robin among other processes.
1004 */
1005void
1006schedclock(p)
1007 struct proc *p;
1008{
1009
1010 p->p_cpticks++;
1011 p->p_estcpu = ESTCPULIM(p->p_estcpu + 1);
1012 if ((p->p_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
1013 resetpriority(p);
1014 if (p->p_priority >= PUSER)
1015 p->p_priority = p->p_usrpri;
1016 }
1017}