Aren
/
NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
NetBSD/sys/kern/kern_synch.c

1245 lines
32 KiB
C
Raw Blame History

/* $NetBSD: kern_synch.c,v 1.144 2004/05/18 11:59:11 yamt Exp $ */
/*-
* Copyright (c) 1999, 2000 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.
*
* 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 <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.144 2004/05/18 11:59:11 yamt 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/buf.h>
#if defined(PERFCTRS)
#include <sys/pmc.h>
#endif
#include <sys/signalvar.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sa.h>
#include <sys/savar.h>
#include <uvm/uvm_extern.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <machine/cpu.h>
int lbolt; /* once a second sleep address */
int rrticks; /* number of hardclock ticks per roundrobin() */
/*
* The global scheduler state.
*/
struct prochd sched_qs[RUNQUE_NQS]; /* run queues */
__volatile u_int32_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);
/*
* 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());
}
/*
* 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))
#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, every hz ticks.
*/
/* ARGSUSED */
void
schedcpu(void *arg)
{
fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
struct lwp *l;
struct proc *p;
int s, minslp;
unsigned int newcpu;
int clkhz;
proclist_lock_read();
LIST_FOREACH(p, &allproc, p_list) {
/*
* 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;
newcpu = (u_int)decay_cpu(loadfac, p->p_estcpu);
p->p_estcpu = newcpu;
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.
* For all load averages >= 1 and max p_estcpu of 255, sleeping for at
* least six times the loadfactor will decay p_estcpu to zero.
*/
void
updatepri(struct lwp *l)
{
struct proc *p = l->l_proc;
unsigned int newcpu;
fixpt_t loadfac;
SCHED_ASSERT_LOCKED();
newcpu = p->p_estcpu;
loadfac = loadfactor(averunnable.ldavg[0]);
if (l->l_slptime > 5 * loadfac)
p->p_estcpu = 0; /* XXX NJWLWP */
else {
l->l_slptime--; /* the first time was done in schedcpu */
while (newcpu && --l->l_slptime)
newcpu = (int) decay_cpu(loadfac, newcpu);
p->p_estcpu = newcpu;
}
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(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;
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(p, 1, 0);
#endif
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, SA_UPCALL_BLOCKED);
else
mi_switch(l, NULL);
#if defined(DDB) && !defined(GPROF)
/* 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(p, 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(p, 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(p, 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(const void *ident)
{
int s;
SCHED_ASSERT_UNLOCKED();
SCHED_LOCK(s);
sched_wakeup(ident);
SCHED_UNLOCK(s);
}
void
sched_wakeup(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(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. If a process is supplied,
* we switch to that process. Otherwise, we use the normal process selection
* criteria.
*/
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;
#if defined(LOCKDEBUG) || defined(DIAGNOSTIC)
spinlock_switchcheck();
#endif
#ifdef LOCKDEBUG
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 && p->p_ucred->cr_uid &&
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 +
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);
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();
}
/*
* 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.
*/
void
setrunqueue(struct lwp *l)
{
struct prochd *rq;
struct lwp *prev;
const int whichq = l->l_priority / 4;
#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;
}
void
remrunqueue(struct lwp *l)
{
struct lwp *prev, *next;
const int whichq = l->l_priority / 4;
#ifdef DIAGNOSTIC
if (((sched_whichqs & RQMASK(whichq)) == 0))
panic("remrunqueue");
#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);
}
#undef RQMASK
#endif /* !defined(__HAVE_MD_RUNQUEUE) */
Reference in New Issue View Git Blame Copy Permalink