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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 * $DragonFly: src/sys/kern/kern_synch.c,v 1.57 2005/12/10 18:27:24 dillon Exp $
43 #include "opt_ktrace.h"
45 #include <sys/param.h>
46 #include <sys/systm.h>
48 #include <sys/kernel.h>
49 #include <sys/signalvar.h>
50 #include <sys/resourcevar.h>
51 #include <sys/vmmeter.h>
52 #include <sys/sysctl.h>
53 #include <sys/thread2.h>
57 #include <sys/ktrace.h>
59 #include <sys/xwait.h>
62 #include <machine/cpu.h>
63 #include <machine/ipl.h>
64 #include <machine/smp.h>
66 TAILQ_HEAD(tslpque, thread);
68 static void sched_setup (void *dummy);
69 SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
74 int sched_quantum; /* Roundrobin scheduling quantum in ticks. */
76 int ncpus2, ncpus2_shift, ncpus2_mask;
79 static struct callout loadav_callout;
80 static struct callout schedcpu_callout;
81 MALLOC_DEFINE(M_TSLEEP, "tslpque", "tsleep queues");
83 #if !defined(KTR_TSLEEP)
84 #define KTR_TSLEEP KTR_ALL
86 KTR_INFO_MASTER(tsleep);
87 KTR_INFO(KTR_TSLEEP, tsleep, tsleep_beg, 0, "tsleep enter", 0);
88 KTR_INFO(KTR_TSLEEP, tsleep, tsleep_end, 0, "tsleep exit", 0);
89 KTR_INFO(KTR_TSLEEP, tsleep, wakeup_beg, 0, "wakeup enter", 0);
90 KTR_INFO(KTR_TSLEEP, tsleep, wakeup_end, 0, "wakeup exit", 0);
91 #define logtsleep(name) KTR_LOG(tsleep_ ## name)
93 struct loadavg averunnable =
94 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
96 * Constants for averages over 1, 5, and 15 minutes
97 * when sampling at 5 second intervals.
99 static fixpt_t cexp[3] = {
100 0.9200444146293232 * FSCALE, /* exp(-1/12) */
101 0.9834714538216174 * FSCALE, /* exp(-1/60) */
102 0.9944598480048967 * FSCALE, /* exp(-1/180) */
105 static void endtsleep (void *);
106 static void unsleep_and_wakeup_thread(struct thread *td);
107 static void loadav (void *arg);
108 static void schedcpu (void *arg);
111 * Adjust the scheduler quantum. The quantum is specified in microseconds.
112 * Note that 'tick' is in microseconds per tick.
115 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
119 new_val = sched_quantum * tick;
120 error = sysctl_handle_int(oidp, &new_val, 0, req);
121 if (error != 0 || req->newptr == NULL)
125 sched_quantum = new_val / tick;
126 hogticks = 2 * sched_quantum;
130 SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
131 0, sizeof sched_quantum, sysctl_kern_quantum, "I", "");
134 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
135 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
136 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
138 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
139 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
141 * If you don't want to bother with the faster/more-accurate formula, you
142 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
143 * (more general) method of calculating the %age of CPU used by a process.
145 * decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing
147 #define CCPU_SHIFT 11
149 static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
150 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
153 * kernel uses `FSCALE', userland (SHOULD) use kern.fscale
155 static int fscale __unused = FSCALE;
156 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
159 * Recompute process priorities, once a second.
161 * Since the userland schedulers are typically event oriented, if the
162 * estcpu calculation at wakeup() time is not sufficient to make a
163 * process runnable relative to other processes in the system we have
164 * a 1-second recalc to help out.
166 * This code also allows us to store sysclock_t data in the process structure
167 * without fear of an overrun, since sysclock_t are guarenteed to hold
168 * several seconds worth of count.
179 * General process statistics once a second
181 FOREACH_PROC_IN_SYSTEM(p) {
184 if (p->p_stat == SSLEEP)
188 * Only recalculate processes that are active or have slept
189 * less then 2 seconds. The schedulers understand this.
191 if (p->p_slptime <= 1) {
192 p->p_usched->recalculate(&p->p_lwp);
194 p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT;
200 * Resource checks. XXX break out since psignal/killproc can block,
201 * limiting us to one process killed per second. There is probably
204 FOREACH_PROC_IN_SYSTEM(p) {
206 if (p->p_stat == SIDL ||
207 (p->p_flag & P_ZOMBIE) ||
208 p->p_limit == NULL ||
214 ttime = p->p_thread->td_sticks + p->p_thread->td_uticks;
215 if (p->p_limit->p_cpulimit != RLIM_INFINITY &&
216 ttime > p->p_limit->p_cpulimit
218 rlim = &p->p_rlimit[RLIMIT_CPU];
219 if (ttime / (rlim_t)1000000 >= rlim->rlim_max) {
220 killproc(p, "exceeded maximum CPU limit");
223 if (rlim->rlim_cur < rlim->rlim_max) {
224 /* XXX: we should make a private copy */
234 wakeup((caddr_t)&lbolt);
235 wakeup((caddr_t)&lbolt_syncer);
236 callout_reset(&schedcpu_callout, hz, schedcpu, NULL);
240 * This is only used by ps. Generate a cpu percentage use over
241 * a period of one second.
244 updatepcpu(struct lwp *lp, int cpticks, int ttlticks)
249 acc = (cpticks << FSHIFT) / ttlticks;
250 if (ttlticks >= ESTCPUFREQ) {
251 lp->lwp_pctcpu = acc;
253 remticks = ESTCPUFREQ - ttlticks;
254 lp->lwp_pctcpu = (acc * ttlticks + lp->lwp_pctcpu * remticks) /
260 * We're only looking at 7 bits of the address; everything is
261 * aligned to 4, lots of things are aligned to greater powers
262 * of 2. Shift right by 8, i.e. drop the bottom 256 worth.
264 #define TABLESIZE 128
265 #define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1))
267 static cpumask_t slpque_cpumasks[TABLESIZE];
270 * General scheduler initialization. We force a reschedule 25 times
271 * a second by default. Note that cpu0 is initialized in early boot and
272 * cannot make any high level calls.
274 * Each cpu has its own sleep queue.
277 sleep_gdinit(globaldata_t gd)
279 static struct tslpque slpque_cpu0[TABLESIZE];
282 if (gd->gd_cpuid == 0) {
283 sched_quantum = (hz + 24) / 25;
284 hogticks = 2 * sched_quantum;
286 gd->gd_tsleep_hash = slpque_cpu0;
288 gd->gd_tsleep_hash = malloc(sizeof(slpque_cpu0),
289 M_TSLEEP, M_WAITOK | M_ZERO);
291 for (i = 0; i < TABLESIZE; ++i)
292 TAILQ_INIT(&gd->gd_tsleep_hash[i]);
296 * General sleep call. Suspends the current process until a wakeup is
297 * performed on the specified identifier. The process will then be made
298 * runnable with the specified priority. Sleeps at most timo/hz seconds
299 * (0 means no timeout). If flags includes PCATCH flag, signals are checked
300 * before and after sleeping, else signals are not checked. Returns 0 if
301 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
302 * signal needs to be delivered, ERESTART is returned if the current system
303 * call should be restarted if possible, and EINTR is returned if the system
304 * call should be interrupted by the signal (return EINTR).
306 * Note that if we are a process, we release_curproc() before messing with
307 * the LWKT scheduler.
309 * During autoconfiguration or after a panic, a sleep will simply
310 * lower the priority briefly to allow interrupts, then return.
313 tsleep(void *ident, int flags, const char *wmesg, int timo)
315 struct thread *td = curthread;
316 struct proc *p = td->td_proc; /* may be NULL */
323 struct callout thandle;
326 * NOTE: removed KTRPOINT, it could cause races due to blocking
327 * even in stable. Just scrap it for now.
329 if (cold || panicstr) {
331 * After a panic, or during autoconfiguration,
332 * just give interrupts a chance, then just return;
333 * don't run any other procs or panic below,
334 * in case this is the idle process and already asleep.
337 oldpri = td->td_pri & TDPRI_MASK;
338 lwkt_setpri_self(safepri);
340 lwkt_setpri_self(oldpri);
343 logtsleep(tsleep_beg);
345 KKASSERT(td != &gd->gd_idlethread); /* you must be kidding! */
348 * NOTE: all of this occurs on the current cpu, including any
349 * callout-based wakeups, so a critical section is a sufficient
352 * The entire sequence through to where we actually sleep must
353 * run without breaking the critical section.
356 catch = flags & PCATCH;
360 crit_enter_quick(td);
362 KASSERT(ident != NULL, ("tsleep: no ident"));
363 KASSERT(p == NULL || p->p_stat == SRUN, ("tsleep %p %s %d",
364 ident, wmesg, p->p_stat));
367 * Setup for the current process (if this is a process).
372 * Early termination if PCATCH was set and a
373 * signal is pending, interlocked with the
376 * Early termination only occurs when tsleep() is
377 * entered while in a normal SRUN state.
379 if ((sig = CURSIG(p)) != 0)
383 * Causes psignal to wake us up when.
385 p->p_flag |= P_SINTR;
389 * Make sure the current process has been untangled from
390 * the userland scheduler and initialize slptime to start
393 if (flags & PNORESCHED)
394 td->td_flags |= TDF_NORESCHED;
395 p->p_usched->release_curproc(&p->p_lwp);
400 * Move our thread to the correct queue and setup our wchan, etc.
402 lwkt_deschedule_self(td);
403 td->td_flags |= TDF_TSLEEPQ;
404 TAILQ_INSERT_TAIL(&gd->gd_tsleep_hash[id], td, td_threadq);
405 atomic_set_int(&slpque_cpumasks[id], gd->gd_cpumask);
407 td->td_wchan = ident;
408 td->td_wmesg = wmesg;
409 td->td_wdomain = flags & PDOMAIN_MASK;
412 * Setup the timeout, if any
415 callout_init(&thandle);
416 callout_reset(&thandle, timo, endtsleep, td);
424 * Ok, we are sleeping. Remove us from the userland runq
425 * and place us in the SSLEEP state.
427 if (p->p_flag & P_ONRUNQ)
428 p->p_usched->remrunqueue(&p->p_lwp);
430 p->p_stats->p_ru.ru_nvcsw++;
438 * Make sure we haven't switched cpus while we were asleep. It's
439 * not supposed to happen. Cleanup our temporary flags.
441 KKASSERT(gd == td->td_gd);
442 td->td_flags &= ~TDF_NORESCHED;
445 * Cleanup the timeout.
448 if (td->td_flags & TDF_TIMEOUT) {
449 td->td_flags &= ~TDF_TIMEOUT;
453 callout_stop(&thandle);
458 * Since td_threadq is used both for our run queue AND for the
459 * tsleep hash queue, we can't still be on it at this point because
460 * we've gotten cpu back.
462 KASSERT((td->td_flags & TDF_TSLEEPQ) == 0, ("tsleep: impossible thread flags %08x", td->td_flags));
468 * Figure out the correct error return
472 p->p_flag &= ~(P_BREAKTSLEEP | P_SINTR);
473 if (catch && error == 0 && (sig != 0 || (sig = CURSIG(p)))) {
474 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
480 logtsleep(tsleep_end);
486 * This is a dandy function that allows us to interlock tsleep/wakeup
487 * operations with unspecified upper level locks, such as lockmgr locks,
488 * simply by holding a critical section. The sequence is:
490 * (enter critical section)
491 * (acquire upper level lock)
492 * tsleep_interlock(blah)
493 * (release upper level lock)
495 * (exit critical section)
497 * Basically this function sets our cpumask for the ident which informs
498 * other cpus that our cpu 'might' be waiting (or about to wait on) the
499 * hash index related to the ident. The critical section prevents another
500 * cpu's wakeup() from being processed on our cpu until we are actually
501 * able to enter the tsleep(). Thus, no race occurs between our attempt
502 * to release a resource and sleep, and another cpu's attempt to acquire
503 * a resource and call wakeup.
505 * There isn't much of a point to this function unless you call it while
506 * holding a critical section.
509 tsleep_interlock(void *ident)
511 int id = LOOKUP(ident);
513 atomic_set_int(&slpque_cpumasks[id], mycpu->gd_cpumask);
517 * Implement the timeout for tsleep.
519 * We set P_BREAKTSLEEP to indicate that an event has occured, but
520 * we only call setrunnable if the process is not stopped.
522 * This type of callout timeout is scheduled on the same cpu the process
523 * is sleeping on. Also, at the moment, the MP lock is held.
531 ASSERT_MP_LOCK_HELD(curthread);
535 * cpu interlock. Thread flags are only manipulated on
536 * the cpu owning the thread. proc flags are only manipulated
537 * by the older of the MP lock. We have both.
539 if (td->td_flags & TDF_TSLEEPQ) {
540 td->td_flags |= TDF_TIMEOUT;
542 if ((p = td->td_proc) != NULL) {
543 p->p_flag |= P_BREAKTSLEEP;
544 if ((p->p_flag & P_STOPPED) == 0)
547 unsleep_and_wakeup_thread(td);
554 * Unsleep and wakeup a thread. This function runs without the MP lock
555 * which means that it can only manipulate thread state on the owning cpu,
556 * and cannot touch the process state at all.
560 unsleep_and_wakeup_thread(struct thread *td)
562 globaldata_t gd = mycpu;
566 if (td->td_gd != gd) {
567 lwkt_send_ipiq(td->td_gd, (ipifunc1_t)unsleep_and_wakeup_thread, td);
572 if (td->td_flags & TDF_TSLEEPQ) {
573 td->td_flags &= ~TDF_TSLEEPQ;
574 id = LOOKUP(td->td_wchan);
575 TAILQ_REMOVE(&gd->gd_tsleep_hash[id], td, td_threadq);
576 if (TAILQ_FIRST(&gd->gd_tsleep_hash[id]) == NULL)
577 atomic_clear_int(&slpque_cpumasks[id], gd->gd_cpumask);
584 * Make all processes sleeping on the specified identifier runnable.
585 * count may be zero or one only.
587 * The domain encodes the sleep/wakeup domain AND the first cpu to check
588 * (which is always the current cpu). As we iterate across cpus
590 * This call may run without the MP lock held. We can only manipulate thread
591 * state on the cpu owning the thread. We CANNOT manipulate process state
595 _wakeup(void *ident, int domain)
610 logtsleep(wakeup_beg);
613 qp = &gd->gd_tsleep_hash[id];
615 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) {
616 ntd = TAILQ_NEXT(td, td_threadq);
617 if (td->td_wchan == ident &&
618 td->td_wdomain == (domain & PDOMAIN_MASK)
620 KKASSERT(td->td_flags & TDF_TSLEEPQ);
621 td->td_flags &= ~TDF_TSLEEPQ;
622 TAILQ_REMOVE(qp, td, td_threadq);
623 if (TAILQ_FIRST(qp) == NULL) {
624 atomic_clear_int(&slpque_cpumasks[id],
628 if (domain & PWAKEUP_ONE)
636 * We finished checking the current cpu but there still may be
637 * more work to do. Either wakeup_one was requested and no matching
638 * thread was found, or a normal wakeup was requested and we have
639 * to continue checking cpus.
641 * The cpu that started the wakeup sequence is encoded in the domain.
642 * We use this information to determine which cpus still need to be
643 * checked, locate a candidate cpu, and chain the wakeup
644 * asynchronously with an IPI message.
646 * It should be noted that this scheme is actually less expensive then
647 * the old scheme when waking up multiple threads, since we send
648 * only one IPI message per target candidate which may then schedule
649 * multiple threads. Before we could have wound up sending an IPI
650 * message for each thread on the target cpu (!= current cpu) that
651 * needed to be woken up.
653 * NOTE: Wakeups occuring on remote cpus are asynchronous. This
654 * should be ok since we are passing idents in the IPI rather then
657 if ((mask = slpque_cpumasks[id]) != 0) {
659 * Look for a cpu that might have work to do. Mask out cpus
660 * which have already been processed.
662 * 31xxxxxxxxxxxxxxxxxxxxxxxxxxxxx0
664 * start currentcpu start
667 * 11111111111111110000000000000111 case1
668 * 00000000111111110000000000000000 case2
670 * case1: We started at start_case1 and processed through
671 * to the current cpu. We have to check any bits
672 * after the current cpu, then check bits before
675 * case2: We have already checked all the bits from
676 * start_case2 to the end, and from 0 to the current
677 * cpu. We just have the bits from the current cpu
678 * to start_case2 left to check.
680 startcpu = PWAKEUP_DECODE(domain);
681 if (gd->gd_cpuid >= startcpu) {
685 tmask = mask & ~((gd->gd_cpumask << 1) - 1);
687 nextcpu = bsfl(mask & tmask);
688 lwkt_send_ipiq2(globaldata_find(nextcpu),
689 _wakeup, ident, domain);
691 tmask = (1 << startcpu) - 1;
693 nextcpu = bsfl(mask & tmask);
695 globaldata_find(nextcpu),
696 _wakeup, ident, domain);
703 tmask = ~((gd->gd_cpumask << 1) - 1) &
704 ((1 << startcpu) - 1);
706 nextcpu = bsfl(mask & tmask);
707 lwkt_send_ipiq2(globaldata_find(nextcpu),
708 _wakeup, ident, domain);
714 logtsleep(wakeup_end);
721 _wakeup(ident, PWAKEUP_ENCODE(0, mycpu->gd_cpuid));
725 wakeup_one(void *ident)
727 /* XXX potentially round-robin the first responding cpu */
728 _wakeup(ident, PWAKEUP_ENCODE(0, mycpu->gd_cpuid) | PWAKEUP_ONE);
732 wakeup_domain(void *ident, int domain)
734 _wakeup(ident, PWAKEUP_ENCODE(domain, mycpu->gd_cpuid));
738 wakeup_domain_one(void *ident, int domain)
740 /* XXX potentially round-robin the first responding cpu */
741 _wakeup(ident, PWAKEUP_ENCODE(domain, mycpu->gd_cpuid) | PWAKEUP_ONE);
747 * Make a process runnable. The MP lock must be held on call. This only
748 * has an effect if we are in SSLEEP. We only break out of the
749 * tsleep if P_BREAKTSLEEP is set, otherwise we just fix-up the state.
751 * NOTE: With the MP lock held we can only safely manipulate the process
752 * structure. We cannot safely manipulate the thread structure.
755 setrunnable(struct proc *p)
758 ASSERT_MP_LOCK_HELD(curthread);
759 p->p_flag &= ~P_STOPPED;
760 if (p->p_stat == SSLEEP && (p->p_flag & P_BREAKTSLEEP)) {
761 unsleep_and_wakeup_thread(p->p_thread);
767 * The process is stopped due to some condition, usually because P_STOPPED
768 * is set but also possibly due to being traced.
770 * NOTE! If the caller sets P_STOPPED, the caller must also clear P_WAITED
771 * because the parent may check the child's status before the child actually
772 * gets to this routine.
774 * This routine is called with the current process only, typically just
775 * before returning to userland.
777 * Setting P_BREAKTSLEEP before entering the tsleep will cause a passive
778 * SIGCONT to break out of the tsleep.
781 tstop(struct proc *p)
783 wakeup((caddr_t)p->p_pptr);
784 p->p_flag |= P_BREAKTSLEEP;
785 tsleep(p, 0, "stop", 0);
789 * Yield / synchronous reschedule. This is a bit tricky because the trap
790 * code might have set a lazy release on the switch function. Setting
791 * P_PASSIVE_ACQ will ensure that the lazy release executes when we call
792 * switch, and that we are given a greater chance of affinity with our
795 * We call lwkt_setpri_self() to rotate our thread to the end of the lwkt
796 * run queue. lwkt_switch() will also execute any assigned passive release
797 * (which usually calls release_curproc()), allowing a same/higher priority
798 * process to be designated as the current process.
800 * While it is possible for a lower priority process to be designated,
801 * it's call to lwkt_maybe_switch() in acquire_curproc() will likely
802 * round-robin back to us and we will be able to re-acquire the current
803 * process designation.
808 struct thread *td = curthread;
809 struct proc *p = td->td_proc;
811 lwkt_setpri_self(td->td_pri & TDPRI_MASK);
813 p->p_flag |= P_PASSIVE_ACQ;
815 p->p_flag &= ~P_PASSIVE_ACQ;
822 * Compute a tenex style load average of a quantity on
823 * 1, 5 and 15 minute intervals.
835 FOREACH_PROC_IN_SYSTEM(p) {
838 if ((td = p->p_thread) == NULL)
840 if (td->td_flags & TDF_BLOCKED)
850 for (i = 0; i < 3; i++)
851 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
852 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
855 * Schedule the next update to occur after 5 seconds, but add a
856 * random variation to avoid synchronisation with processes that
857 * run at regular intervals.
859 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
865 sched_setup(void *dummy)
867 callout_init(&loadav_callout);
868 callout_init(&schedcpu_callout);
870 /* Kick off timeout driven events by calling first time. */