/* $NetBSD: kern_synch.c,v 1.163 2006/07/08 00:23:29 matt Exp $ */ /*- * Copyright (c) 1999, 2000, 2004 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, * NASA Ames Research Center. * This code is derived from software contributed to The NetBSD Foundation * by Charles M. Hannum. * * 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 NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /*- * Copyright (c) 1982, 1986, 1990, 1991, 1993 * The Regents of the University of California. All rights reserved. * (c) UNIX System Laboratories, Inc. * All or some portions of this file are derived from material licensed * to the University of California by American Telephone and Telegraph * Co. or Unix System Laboratories, Inc. and are reproduced herein with * the permission of UNIX System Laboratories, Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 */ #include __KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.163 2006/07/08 00:23:29 matt Exp $"); #include "opt_ddb.h" #include "opt_ktrace.h" #include "opt_kstack.h" #include "opt_lockdebug.h" #include "opt_multiprocessor.h" #include "opt_perfctrs.h" #include #include #include #include #include #include #if defined(PERFCTRS) #include #endif #include #include #include #include #include #include #include #ifdef KTRACE #include #endif #include int lbolt; /* once a second sleep address */ int rrticks; /* number of hardclock ticks per roundrobin() */ /* * Sleep queues. * * 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 SLPQUE_TABLESIZE 128 #define SLPQUE_LOOKUP(x) (((u_long)(x) >> 8) & (SLPQUE_TABLESIZE - 1)) #define SLPQUE(ident) (&sched_slpque[SLPQUE_LOOKUP(ident)]) /* * The global scheduler state. */ struct prochd sched_qs[RUNQUE_NQS]; /* run queues */ volatile uint32_t sched_whichqs; /* bitmap of non-empty queues */ struct slpque sched_slpque[SLPQUE_TABLESIZE]; /* sleep queues */ struct simplelock sched_lock = SIMPLELOCK_INITIALIZER; void schedcpu(void *); void updatepri(struct lwp *); void endtsleep(void *); inline void sa_awaken(struct lwp *); inline void awaken(struct lwp *); struct callout schedcpu_ch = CALLOUT_INITIALIZER_SETFUNC(schedcpu, NULL); static unsigned int schedcpu_ticks; /* * Force switch among equal priority processes every 100ms. * Called from hardclock every hz/10 == rrticks hardclock ticks. */ /* ARGSUSED */ void roundrobin(struct cpu_info *ci) { struct schedstate_percpu *spc = &ci->ci_schedstate; spc->spc_rrticks = rrticks; if (curlwp != NULL) { if (spc->spc_flags & SPCF_SEENRR) { /* * The process has already been through a roundrobin * without switching and may be hogging the CPU. * Indicate that the process should yield. */ spc->spc_flags |= SPCF_SHOULDYIELD; } else spc->spc_flags |= SPCF_SEENRR; } need_resched(curcpu()); } #define PPQ (128 / RUNQUE_NQS) /* priorities per queue */ #define NICE_WEIGHT 2 /* priorities per nice level */ #define ESTCPU_SHIFT 11 #define ESTCPU_MAX ((NICE_WEIGHT * PRIO_MAX - PPQ) << ESTCPU_SHIFT) #define ESTCPULIM(e) min((e), ESTCPU_MAX) /* * 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 hardclock updates p_estcpu and p_cpticks independently. * * 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)) static fixpt_t decay_cpu(fixpt_t loadfac, fixpt_t estcpu) { if (estcpu == 0) { return 0; } #if !defined(_LP64) /* avoid 64bit arithmetics. */ #define FIXPT_MAX ((fixpt_t)((UINTMAX_C(1) << sizeof(fixpt_t) * CHAR_BIT) - 1)) if (__predict_true(loadfac <= FIXPT_MAX / ESTCPU_MAX)) { return estcpu * loadfac / (loadfac + FSCALE); } #endif /* !defined(_LP64) */ return (uint64_t)estcpu * loadfac / (loadfac + FSCALE); } /* * For all load averages >= 1 and max p_estcpu of (255 << ESTCPU_SHIFT), * sleeping for at least seven times the loadfactor will decay p_estcpu to * less than (1 << ESTCPU_SHIFT). * * note that our ESTCPU_MAX is actually much smaller than (255 << ESTCPU_SHIFT). */ static fixpt_t decay_cpu_batch(fixpt_t loadfac, fixpt_t estcpu, unsigned int n) { if ((n << FSHIFT) >= 7 * loadfac) { return 0; } while (estcpu != 0 && n > 1) { estcpu = decay_cpu(loadfac, estcpu); n--; } return estcpu; } /* 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, every hz ticks. */ /* ARGSUSED */ void schedcpu(void *arg) { fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); struct lwp *l; struct proc *p; int s, minslp; int clkhz; schedcpu_ticks++; proclist_lock_read(); PROCLIST_FOREACH(p, &allproc) { /* * 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. */ minslp = 2; LIST_FOREACH(l, &p->p_lwps, l_sibling) { l->l_swtime++; if (l->l_stat == LSSLEEP || l->l_stat == LSSTOP || l->l_stat == LSSUSPENDED) { l->l_slptime++; minslp = min(minslp, l->l_slptime); } else minslp = 0; } 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 (minslp > 1) continue; s = splstatclock(); /* prevent state changes */ /* * p_pctcpu is only for ps. */ clkhz = stathz != 0 ? stathz : hz; #if (FSHIFT >= CCPU_SHIFT) p->p_pctcpu += (clkhz == 100)? ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 100 * (((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT)) / clkhz; #else p->p_pctcpu += ((FSCALE - ccpu) * (p->p_cpticks * FSCALE / clkhz)) >> FSHIFT; #endif p->p_cpticks = 0; p->p_estcpu = decay_cpu(loadfac, p->p_estcpu); splx(s); /* Done with the process CPU ticks update */ SCHED_LOCK(s); LIST_FOREACH(l, &p->p_lwps, l_sibling) { if (l->l_slptime > 1) continue; resetpriority(l); if (l->l_priority >= PUSER) { if (l->l_stat == LSRUN && (l->l_flag & L_INMEM) && (l->l_priority / PPQ) != (l->l_usrpri / PPQ)) { remrunqueue(l); l->l_priority = l->l_usrpri; setrunqueue(l); } else l->l_priority = l->l_usrpri; } } SCHED_UNLOCK(s); } proclist_unlock_read(); uvm_meter(); wakeup((caddr_t)&lbolt); callout_schedule(&schedcpu_ch, hz); } /* * Recalculate the priority of a process after it has slept for a while. */ void updatepri(struct lwp *l) { struct proc *p = l->l_proc; fixpt_t loadfac; SCHED_ASSERT_LOCKED(); KASSERT(l->l_slptime > 1); loadfac = loadfactor(averunnable.ldavg[0]); l->l_slptime--; /* the first time was done in schedcpu */ /* XXX NJWLWP */ p->p_estcpu = decay_cpu_batch(loadfac, p->p_estcpu, l->l_slptime); resetpriority(l); } /* * 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 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). * * The interlock is held until the scheduler_slock is acquired. The * interlock will be locked before returning back to the caller * unless the PNORELOCK flag is specified, in which case the * interlock will always be unlocked upon return. */ int ltsleep(volatile const void *ident, int priority, const char *wmesg, int timo, volatile struct simplelock *interlock) { struct lwp *l = curlwp; struct proc *p = l ? l->l_proc : NULL; struct slpque *qp; struct sadata_upcall *sau; int sig, s; int catch = priority & PCATCH; int relock = (priority & PNORELOCK) == 0; int exiterr = (priority & PNOEXITERR) == 0; /* * XXXSMP * This is probably bogus. Figure out what the right * thing to do here really is. * Note that not sleeping if ltsleep is called with curlwp == NULL * in the shutdown case is disgusting but partly necessary given * how shutdown (barely) works. */ if (cold || (doing_shutdown && (panicstr || (l == NULL)))) { /* * 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. */ s = splhigh(); splx(safepri); splx(s); if (interlock != NULL && relock == 0) simple_unlock(interlock); return (0); } KASSERT(p != NULL); LOCK_ASSERT(interlock == NULL || simple_lock_held(interlock)); #ifdef KTRACE if (KTRPOINT(p, KTR_CSW)) ktrcsw(l, 1, 0); #endif /* * XXX We need to allocate the sadata_upcall structure here, * XXX since we can't sleep while waiting for memory inside * XXX sa_upcall(). It would be nice if we could safely * XXX allocate the sadata_upcall structure on the stack, here. */ if (l->l_flag & L_SA) { sau = sadata_upcall_alloc(0); } else { sau = NULL; } SCHED_LOCK(s); #ifdef DIAGNOSTIC if (ident == NULL) panic("ltsleep: ident == NULL"); if (l->l_stat != LSONPROC) panic("ltsleep: l_stat %d != LSONPROC", l->l_stat); if (l->l_back != NULL) panic("ltsleep: p_back != NULL"); #endif l->l_wchan = ident; l->l_wmesg = wmesg; l->l_slptime = 0; l->l_priority = priority & PRIMASK; qp = SLPQUE(ident); if (qp->sq_head == 0) qp->sq_head = l; else { *qp->sq_tailp = l; } *(qp->sq_tailp = &l->l_forw) = 0; if (timo) callout_reset(&l->l_tsleep_ch, timo, endtsleep, l); /* * We can now release the interlock; the scheduler_slock * is held, so a thread can't get in to do wakeup() before * we do the switch. * * XXX We leave the code block here, after inserting ourselves * on the sleep queue, because we might want a more clever * data structure for the sleep queues at some point. */ if (interlock != NULL) simple_unlock(interlock); /* * 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) { l->l_flag |= L_SINTR; if (((sig = CURSIG(l)) != 0) || ((p->p_flag & P_WEXIT) && p->p_nlwps > 1)) { if (l->l_wchan != NULL) unsleep(l); l->l_stat = LSONPROC; SCHED_UNLOCK(s); goto resume; } if (l->l_wchan == NULL) { catch = 0; SCHED_UNLOCK(s); goto resume; } } else sig = 0; l->l_stat = LSSLEEP; p->p_nrlwps--; p->p_stats->p_ru.ru_nvcsw++; SCHED_ASSERT_LOCKED(); if (l->l_flag & L_SA) sa_switch(l, sau, SA_UPCALL_BLOCKED); else mi_switch(l, NULL); #if defined(DDB) && !defined(GPROF) && !defined(sun2) && !defined(__vax__) /* handy breakpoint location after process "wakes" */ __asm(".globl bpendtsleep\nbpendtsleep:"); #endif /* * p->p_nrlwps is incremented by whoever made us runnable again, * either setrunnable() or awaken(). */ SCHED_ASSERT_UNLOCKED(); splx(s); resume: KDASSERT(l->l_cpu != NULL); KDASSERT(l->l_cpu == curcpu()); l->l_cpu->ci_schedstate.spc_curpriority = l->l_usrpri; l->l_flag &= ~L_SINTR; if (l->l_flag & L_TIMEOUT) { l->l_flag &= ~(L_TIMEOUT|L_CANCELLED); if (sig == 0) { #ifdef KTRACE if (KTRPOINT(p, KTR_CSW)) ktrcsw(l, 0, 0); #endif if (relock && interlock != NULL) simple_lock(interlock); return (EWOULDBLOCK); } } else if (timo) callout_stop(&l->l_tsleep_ch); if (catch) { const int cancelled = l->l_flag & L_CANCELLED; l->l_flag &= ~L_CANCELLED; if (sig != 0 || (sig = CURSIG(l)) != 0 || cancelled) { #ifdef KTRACE if (KTRPOINT(p, KTR_CSW)) ktrcsw(l, 0, 0); #endif if (relock && interlock != NULL) simple_lock(interlock); /* * If this sleep was canceled, don't let the syscall * restart. */ if (cancelled || (SIGACTION(p, sig).sa_flags & SA_RESTART) == 0) return (EINTR); return (ERESTART); } } #ifdef KTRACE if (KTRPOINT(p, KTR_CSW)) ktrcsw(l, 0, 0); #endif if (relock && interlock != NULL) simple_lock(interlock); /* XXXNJW this is very much a kluge. * revisit. a better way of preventing looping/hanging syscalls like * wait4() and _lwp_wait() from wedging an exiting process * would be preferred. */ if (catch && ((p->p_flag & P_WEXIT) && p->p_nlwps > 1 && exiterr)) return (EINTR); 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. */ void endtsleep(void *arg) { struct lwp *l; int s; l = (struct lwp *)arg; SCHED_LOCK(s); if (l->l_wchan) { if (l->l_stat == LSSLEEP) setrunnable(l); else unsleep(l); l->l_flag |= L_TIMEOUT; } SCHED_UNLOCK(s); } /* * Remove a process from its wait queue */ void unsleep(struct lwp *l) { struct slpque *qp; struct lwp **hp; SCHED_ASSERT_LOCKED(); if (l->l_wchan) { hp = &(qp = SLPQUE(l->l_wchan))->sq_head; while (*hp != l) hp = &(*hp)->l_forw; *hp = l->l_forw; if (qp->sq_tailp == &l->l_forw) qp->sq_tailp = hp; l->l_wchan = 0; } } inline void sa_awaken(struct lwp *l) { SCHED_ASSERT_LOCKED(); if (l == l->l_savp->savp_lwp && l->l_flag & L_SA_YIELD) l->l_flag &= ~L_SA_IDLE; } /* * Optimized-for-wakeup() version of setrunnable(). */ inline void awaken(struct lwp *l) { SCHED_ASSERT_LOCKED(); if (l->l_proc->p_sa) sa_awaken(l); if (l->l_slptime > 1) updatepri(l); l->l_slptime = 0; l->l_stat = LSRUN; l->l_proc->p_nrlwps++; /* * Since curpriority is a user priority, p->p_priority * is always better than curpriority on the last CPU on * which it ran. * * XXXSMP See affinity comment in resched_proc(). */ if (l->l_flag & L_INMEM) { setrunqueue(l); KASSERT(l->l_cpu != NULL); need_resched(l->l_cpu); } else sched_wakeup(&proc0); } #if defined(MULTIPROCESSOR) || defined(LOCKDEBUG) void sched_unlock_idle(void) { simple_unlock(&sched_lock); } void sched_lock_idle(void) { simple_lock(&sched_lock); } #endif /* MULTIPROCESSOR || LOCKDEBUG */ /* * Make all processes sleeping on the specified identifier runnable. */ void wakeup(volatile const void *ident) { int s; SCHED_ASSERT_UNLOCKED(); SCHED_LOCK(s); sched_wakeup(ident); SCHED_UNLOCK(s); } void sched_wakeup(volatile const void *ident) { struct slpque *qp; struct lwp *l, **q; SCHED_ASSERT_LOCKED(); qp = SLPQUE(ident); restart: for (q = &qp->sq_head; (l = *q) != NULL; ) { #ifdef DIAGNOSTIC if (l->l_back || (l->l_stat != LSSLEEP && l->l_stat != LSSTOP && l->l_stat != LSSUSPENDED)) panic("wakeup"); #endif if (l->l_wchan == ident) { l->l_wchan = 0; *q = l->l_forw; if (qp->sq_tailp == &l->l_forw) qp->sq_tailp = q; if (l->l_stat == LSSLEEP) { awaken(l); goto restart; } } else q = &l->l_forw; } } /* * Make the highest priority process first in line on the specified * identifier runnable. */ void wakeup_one(volatile const void *ident) { struct slpque *qp; struct lwp *l, **q; struct lwp *best_sleepp, **best_sleepq; struct lwp *best_stopp, **best_stopq; int s; best_sleepp = best_stopp = NULL; best_sleepq = best_stopq = NULL; SCHED_LOCK(s); qp = SLPQUE(ident); for (q = &qp->sq_head; (l = *q) != NULL; q = &l->l_forw) { #ifdef DIAGNOSTIC if (l->l_back || (l->l_stat != LSSLEEP && l->l_stat != LSSTOP && l->l_stat != LSSUSPENDED)) panic("wakeup_one"); #endif if (l->l_wchan == ident) { if (l->l_stat == LSSLEEP) { if (best_sleepp == NULL || l->l_priority < best_sleepp->l_priority) { best_sleepp = l; best_sleepq = q; } } else { if (best_stopp == NULL || l->l_priority < best_stopp->l_priority) { best_stopp = l; best_stopq = q; } } } } /* * Consider any SSLEEP process higher than the highest priority SSTOP * process. */ if (best_sleepp != NULL) { l = best_sleepp; q = best_sleepq; } else { l = best_stopp; q = best_stopq; } if (l != NULL) { l->l_wchan = NULL; *q = l->l_forw; if (qp->sq_tailp == &l->l_forw) qp->sq_tailp = q; if (l->l_stat == LSSLEEP) awaken(l); } SCHED_UNLOCK(s); } /* * General yield call. Puts the current process back on its run queue and * performs a voluntary context switch. Should only be called when the * current process explicitly requests it (eg sched_yield(2) in compat code). */ void yield(void) { struct lwp *l = curlwp; int s; SCHED_LOCK(s); l->l_priority = l->l_usrpri; l->l_stat = LSRUN; setrunqueue(l); l->l_proc->p_stats->p_ru.ru_nvcsw++; mi_switch(l, NULL); SCHED_ASSERT_UNLOCKED(); splx(s); } /* * General preemption call. Puts the current process back on its run queue * and performs an involuntary context switch. * The 'more' ("more work to do") argument is boolean. Returning to userspace * preempt() calls pass 0. "Voluntary" preemptions in e.g. uiomove() pass 1. * This will be used to indicate to the SA subsystem that the LWP is * not yet finished in the kernel. */ void preempt(int more) { struct lwp *l = curlwp; int r, s; SCHED_LOCK(s); l->l_priority = l->l_usrpri; l->l_stat = LSRUN; setrunqueue(l); l->l_proc->p_stats->p_ru.ru_nivcsw++; r = mi_switch(l, NULL); SCHED_ASSERT_UNLOCKED(); splx(s); if ((l->l_flag & L_SA) != 0 && r != 0 && more == 0) sa_preempt(l); } /* * The machine independent parts of context switch. * Must be called at splsched() (no higher!) and with * the sched_lock held. * Switch to "new" if non-NULL, otherwise let cpu_switch choose * the next lwp. * * Returns 1 if another process was actually run. */ int mi_switch(struct lwp *l, struct lwp *newl) { struct schedstate_percpu *spc; struct rlimit *rlim; long s, u; struct timeval tv; int hold_count; struct proc *p = l->l_proc; int retval; SCHED_ASSERT_LOCKED(); /* * Release the kernel_lock, as we are about to yield the CPU. * The scheduler lock is still held until cpu_switch() * selects a new process and removes it from the run queue. */ hold_count = KERNEL_LOCK_RELEASE_ALL(); KDASSERT(l->l_cpu != NULL); KDASSERT(l->l_cpu == curcpu()); spc = &l->l_cpu->ci_schedstate; #ifdef LOCKDEBUG spinlock_switchcheck(); simple_lock_switchcheck(); #endif /* * Compute the amount of time during which the current * process was running. */ microtime(&tv); u = p->p_rtime.tv_usec + (tv.tv_usec - spc->spc_runtime.tv_usec); s = p->p_rtime.tv_sec + (tv.tv_sec - spc->spc_runtime.tv_sec); if (u < 0) { u += 1000000; s--; } else if (u >= 1000000) { u -= 1000000; s++; } p->p_rtime.tv_usec = u; p->p_rtime.tv_sec = s; /* * Check if the process exceeds its CPU resource allocation. * If over max, kill it. In any case, if it has run for more * than 10 minutes, reduce priority to give others a chance. */ rlim = &p->p_rlimit[RLIMIT_CPU]; if (s >= rlim->rlim_cur) { /* * XXXSMP: we're inside the scheduler lock perimeter; * use sched_psignal. */ if (s >= rlim->rlim_max) sched_psignal(p, SIGKILL); else { sched_psignal(p, SIGXCPU); if (rlim->rlim_cur < rlim->rlim_max) rlim->rlim_cur += 5; } } if (autonicetime && s > autonicetime && kauth_cred_geteuid(p->p_cred) && p->p_nice == NZERO) { p->p_nice = autoniceval + NZERO; resetpriority(l); } /* * Process is about to yield the CPU; clear the appropriate * scheduling flags. */ spc->spc_flags &= ~SPCF_SWITCHCLEAR; #ifdef KSTACK_CHECK_MAGIC kstack_check_magic(l); #endif /* * If we are using h/w performance counters, save context. */ #if PERFCTRS if (PMC_ENABLED(p)) pmc_save_context(p); #endif /* * Switch to the new current process. When we * run again, we'll return back here. */ uvmexp.swtch++; if (newl == NULL) { retval = cpu_switch(l, NULL); } else { remrunqueue(newl); cpu_switchto(l, newl); retval = 0; } /* * If we are using h/w performance counters, restore context. */ #if PERFCTRS if (PMC_ENABLED(p)) pmc_restore_context(p); #endif /* * Make sure that MD code released the scheduler lock before * resuming us. */ SCHED_ASSERT_UNLOCKED(); /* * We're running again; record our new start time. We might * be running on a new CPU now, so don't use the cache'd * schedstate_percpu pointer. */ KDASSERT(l->l_cpu != NULL); KDASSERT(l->l_cpu == curcpu()); microtime(&l->l_cpu->ci_schedstate.spc_runtime); /* * Reacquire the kernel_lock now. We do this after we've * released the scheduler lock to avoid deadlock, and before * we reacquire the interlock. */ KERNEL_LOCK_ACQUIRE_COUNT(hold_count); return retval; } /* * Initialize the (doubly-linked) run queues * to be empty. */ void rqinit() { int i; for (i = 0; i < RUNQUE_NQS; i++) sched_qs[i].ph_link = sched_qs[i].ph_rlink = (struct lwp *)&sched_qs[i]; } static inline void resched_proc(struct lwp *l, u_char pri) { struct cpu_info *ci; /* * XXXSMP * Since l->l_cpu persists across a context switch, * this gives us *very weak* processor affinity, in * that we notify the CPU on which the process last * ran that it should try to switch. * * This does not guarantee that the process will run on * that processor next, because another processor might * grab it the next time it performs a context switch. * * This also does not handle the case where its last * CPU is running a higher-priority process, but every * other CPU is running a lower-priority process. There * are ways to handle this situation, but they're not * currently very pretty, and we also need to weigh the * cost of moving a process from one CPU to another. * * XXXSMP * There is also the issue of locking the other CPU's * sched state, which we currently do not do. */ ci = (l->l_cpu != NULL) ? l->l_cpu : curcpu(); if (pri < ci->ci_schedstate.spc_curpriority) need_resched(ci); } /* * 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(struct lwp *l) { struct proc *p = l->l_proc; SCHED_ASSERT_LOCKED(); switch (l->l_stat) { case 0: case LSRUN: case LSONPROC: case LSZOMB: case LSDEAD: default: panic("setrunnable: lwp %p state was %d", l, l->l_stat); case LSSTOP: /* * If we're being traced (possibly because someone attached us * while we were stopped), check for a signal from the debugger. */ if ((p->p_flag & P_TRACED) != 0 && p->p_xstat != 0) { sigaddset(&p->p_sigctx.ps_siglist, p->p_xstat); CHECKSIGS(p); } case LSSLEEP: unsleep(l); /* e.g. when sending signals */ break; case LSIDL: break; case LSSUSPENDED: break; } if (l->l_proc->p_sa) sa_awaken(l); l->l_stat = LSRUN; p->p_nrlwps++; if (l->l_flag & L_INMEM) setrunqueue(l); if (l->l_slptime > 1) updatepri(l); l->l_slptime = 0; if ((l->l_flag & L_INMEM) == 0) sched_wakeup((caddr_t)&proc0); else resched_proc(l, l->l_priority); } /* * 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(struct lwp *l) { unsigned int newpriority; struct proc *p = l->l_proc; SCHED_ASSERT_LOCKED(); newpriority = PUSER + (p->p_estcpu >> ESTCPU_SHIFT) + NICE_WEIGHT * (p->p_nice - NZERO); newpriority = min(newpriority, MAXPRI); l->l_usrpri = newpriority; resched_proc(l, l->l_usrpri); } /* * Recompute priority for all LWPs in a process. */ void resetprocpriority(struct proc *p) { struct lwp *l; LIST_FOREACH(l, &p->p_lwps, l_sibling) resetpriority(l); } /* * We adjust the priority of the current process. The priority of a process * gets worse as it accumulates CPU time. The CPU usage estimator (p_estcpu) * is increased here. The formula for computing priorities (in kern_synch.c) * will compute a different value each time p_estcpu increases. This can * cause a switch, but unless the priority crosses a PPQ boundary the actual * queue will not change. The CPU usage estimator ramps up quite quickly * when the process is running (linearly), and decays away exponentially, at * a rate which is proportionally slower when the system is busy. The basic * principle is that the system will 90% forget that the process used a lot * of CPU time in 5 * loadav seconds. This causes the system to favor * processes which haven't run much recently, and to round-robin among other * processes. */ void schedclock(struct lwp *l) { struct proc *p = l->l_proc; int s; p->p_estcpu = ESTCPULIM(p->p_estcpu + (1 << ESTCPU_SHIFT)); SCHED_LOCK(s); resetpriority(l); SCHED_UNLOCK(s); if (l->l_priority >= PUSER) l->l_priority = l->l_usrpri; } void suspendsched() { struct lwp *l; int s; /* * Convert all non-P_SYSTEM LSSLEEP or LSRUN processes to * LSSUSPENDED. */ proclist_lock_read(); SCHED_LOCK(s); LIST_FOREACH(l, &alllwp, l_list) { if ((l->l_proc->p_flag & P_SYSTEM) != 0) continue; switch (l->l_stat) { case LSRUN: l->l_proc->p_nrlwps--; if ((l->l_flag & L_INMEM) != 0) remrunqueue(l); /* FALLTHROUGH */ case LSSLEEP: l->l_stat = LSSUSPENDED; break; case LSONPROC: /* * XXX SMP: we need to deal with processes on * others CPU ! */ break; default: break; } } SCHED_UNLOCK(s); proclist_unlock_read(); } /* * scheduler_fork_hook: * * Inherit the parent's scheduler history. */ void scheduler_fork_hook(struct proc *parent, struct proc *child) { child->p_estcpu = child->p_estcpu_inherited = parent->p_estcpu; child->p_forktime = schedcpu_ticks; } /* * scheduler_wait_hook: * * Chargeback parents for the sins of their children. */ void scheduler_wait_hook(struct proc *parent, struct proc *child) { fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); fixpt_t estcpu; /* XXX Only if parent != init?? */ estcpu = decay_cpu_batch(loadfac, child->p_estcpu_inherited, schedcpu_ticks - child->p_forktime); if (child->p_estcpu > estcpu) { parent->p_estcpu = ESTCPULIM(parent->p_estcpu + child->p_estcpu - estcpu); } } /* * Low-level routines to access the run queue. Optimised assembler * routines can override these. */ #ifndef __HAVE_MD_RUNQUEUE /* * On some architectures, it's faster to use a MSB ordering for the priorites * than the traditional LSB ordering. */ #ifdef __HAVE_BIGENDIAN_BITOPS #define RQMASK(n) (0x80000000 >> (n)) #else #define RQMASK(n) (0x00000001 << (n)) #endif /* * The primitives that manipulate the run queues. whichqs tells which * of the 32 queues qs have processes in them. Setrunqueue puts processes * into queues, remrunqueue removes them from queues. The running process is * on no queue, other processes are on a queue related to p->p_priority, * divided by 4 actually to shrink the 0-127 range of priorities into the 32 * available queues. */ #ifdef RQDEBUG static void checkrunqueue(int whichq, struct lwp *l) { const struct prochd * const rq = &sched_qs[whichq]; struct lwp *l2; int found = 0; int die = 0; int empty = 1; for (l2 = rq->ph_link; l2 != (void*) rq; l2 = l2->l_forw) { if (l2->l_stat != LSRUN) { printf("checkrunqueue[%d]: lwp %p state (%d) " " != LSRUN\n", whichq, l2, l2->l_stat); } if (l2->l_back->l_forw != l2) { printf("checkrunqueue[%d]: lwp %p back-qptr (%p) " "corrupt %p\n", whichq, l2, l2->l_back, l2->l_back->l_forw); die = 1; } if (l2->l_forw->l_back != l2) { printf("checkrunqueue[%d]: lwp %p forw-qptr (%p) " "corrupt %p\n", whichq, l2, l2->l_forw, l2->l_forw->l_back); die = 1; } if (l2 == l) found = 1; empty = 0; } if (empty && (sched_whichqs & RQMASK(whichq)) != 0) { printf("checkrunqueue[%d]: bit set for empty run-queue %p\n", whichq, rq); die = 1; } else if (!empty && (sched_whichqs & RQMASK(whichq)) == 0) { printf("checkrunqueue[%d]: bit clear for non-empty " "run-queue %p\n", whichq, rq); die = 1; } if (l != NULL && (sched_whichqs & RQMASK(whichq)) == 0) { printf("checkrunqueue[%d]: bit clear for active lwp %p\n", whichq, l); die = 1; } if (l != NULL && empty) { printf("checkrunqueue[%d]: empty run-queue %p with " "active lwp %p\n", whichq, rq, l); die = 1; } if (l != NULL && !found) { printf("checkrunqueue[%d]: lwp %p not in runqueue %p!", whichq, l, rq); die = 1; } if (die) panic("checkrunqueue: inconsistency found"); } #endif /* RQDEBUG */ void setrunqueue(struct lwp *l) { struct prochd *rq; struct lwp *prev; const int whichq = l->l_priority / PPQ; #ifdef RQDEBUG checkrunqueue(whichq, NULL); #endif #ifdef DIAGNOSTIC if (l->l_back != NULL || l->l_wchan != NULL || l->l_stat != LSRUN) panic("setrunqueue"); #endif sched_whichqs |= RQMASK(whichq); rq = &sched_qs[whichq]; prev = rq->ph_rlink; l->l_forw = (struct lwp *)rq; rq->ph_rlink = l; prev->l_forw = l; l->l_back = prev; #ifdef RQDEBUG checkrunqueue(whichq, l); #endif } void remrunqueue(struct lwp *l) { struct lwp *prev, *next; const int whichq = l->l_priority / PPQ; #ifdef RQDEBUG checkrunqueue(whichq, l); #endif #ifdef DIAGNOSTIC if (((sched_whichqs & RQMASK(whichq)) == 0)) panic("remrunqueue: bit %d not set", whichq); #endif prev = l->l_back; l->l_back = NULL; next = l->l_forw; prev->l_forw = next; next->l_back = prev; if (prev == next) sched_whichqs &= ~RQMASK(whichq); #ifdef RQDEBUG checkrunqueue(whichq, NULL); #endif } #undef RQMASK #endif /* !defined(__HAVE_MD_RUNQUEUE) */