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/* $NetBSD: kern_synch.c,v 1.187 2007/03/11 21:36:49 ad Exp $ */
/*-
* Copyright (c) 1999, 2000, 2004, 2006, 2007 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, by Charles M. Hannum, and by Andrew Doran.
*
* 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 1.187 2007/03/11 21:36:49 ad Exp $");
#include "opt_ddb.h"
#include "opt_kstack.h"
#include "opt_lockdebug.h"
#include "opt_multiprocessor.h"
#include "opt_perfctrs.h"
#define __MUTEX_PRIVATE
#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/syscall_stats.h>
#include <sys/kauth.h>
#include <sys/sleepq.h>
#include <sys/lockdebug.h>
#include <uvm/uvm_extern.h>
#include <machine/cpu.h>
int lbolt; /* once a second sleep address */
int rrticks; /* number of hardclock ticks per roundrobin() */
/*
* The global scheduler state.
*/
kmutex_t sched_mutex; /* global sched state mutex */
struct prochd sched_qs[RUNQUE_NQS]; /* run queues */
volatile uint32_t sched_whichqs; /* bitmap of non-empty queues */
void schedcpu(void *);
void updatepri(struct lwp *);
void sched_unsleep(struct lwp *);
void sched_changepri(struct lwp *, pri_t);
void sched_lendpri(struct lwp *, pri_t);
struct callout schedcpu_ch = CALLOUT_INITIALIZER_SETFUNC(schedcpu, NULL);
static unsigned int schedcpu_ticks;
syncobj_t sleep_syncobj = {
SOBJ_SLEEPQ_SORTED,
sleepq_unsleep,
sleepq_changepri,
sleepq_lendpri,
syncobj_noowner,
};
syncobj_t sched_syncobj = {
SOBJ_SLEEPQ_SORTED,
sched_unsleep,
sched_changepri,
sched_lendpri,
syncobj_noowner,
};
/*
* 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;
}
cpu_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
/*
* schedcpu:
*
* Recompute process priorities, every hz ticks.
*
* XXXSMP This needs to be reorganised in order to reduce the locking
* burden.
*/
/* ARGSUSED */
void
schedcpu(void *arg)
{
fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
struct rlimit *rlim;
struct lwp *l;
struct proc *p;
int minslp, clkhz, sig;
long runtm;
schedcpu_ticks++;
mutex_enter(&proclist_mutex);
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;
mutex_enter(&p->p_smutex);
runtm = p->p_rtime.tv_sec;
LIST_FOREACH(l, &p->p_lwps, l_sibling) {
lwp_lock(l);
runtm += l->l_rtime.tv_sec;
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;
lwp_unlock(l);
}
p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT;
/*
* Check if the process exceeds its CPU resource allocation.
* If over max, kill it.
*/
rlim = &p->p_rlimit[RLIMIT_CPU];
sig = 0;
if (runtm >= rlim->rlim_cur) {
if (runtm >= rlim->rlim_max)
sig = SIGKILL;
else {
sig = SIGXCPU;
if (rlim->rlim_cur < rlim->rlim_max)
rlim->rlim_cur += 5;
}
}
/*
* If the process has run for more than autonicetime, reduce
* priority to give others a chance.
*/
if (autonicetime && runtm > autonicetime && p->p_nice == NZERO
&& kauth_cred_geteuid(p->p_cred)) {
mutex_spin_enter(&p->p_stmutex);
p->p_nice = autoniceval + NZERO;
resetprocpriority(p);
mutex_spin_exit(&p->p_stmutex);
}
/*
* If the process has slept the entire second,
* stop recalculating its priority until it wakes up.
*/
if (minslp <= 1) {
/*
* p_pctcpu is only for ps.
*/
mutex_spin_enter(&p->p_stmutex);
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);
LIST_FOREACH(l, &p->p_lwps, l_sibling) {
lwp_lock(l);
if (l->l_slptime <= 1 &&
l->l_priority >= PUSER)
resetpriority(l);
lwp_unlock(l);
}
mutex_spin_exit(&p->p_stmutex);
}
mutex_exit(&p->p_smutex);
if (sig) {
psignal(p, sig);
}
}
mutex_exit(&proclist_mutex);
uvm_meter();
wakeup((void *)&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;
LOCK_ASSERT(lwp_locked(l, NULL));
KASSERT(l->l_slptime > 1);
loadfac = loadfactor(averunnable.ldavg[0]);
l->l_slptime--; /* the first time was done in schedcpu */
/* XXX NJWLWP */
/* XXXSMP occasionally unlocked, should be per-LWP */
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;
/*
* OBSOLETE INTERFACE
*
* 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 we are on a sleep queue. 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(wchan_t ident, pri_t priority, const char *wmesg, int timo,
volatile struct simplelock *interlock)
{
struct lwp *l = curlwp;
sleepq_t *sq;
int error, catch;
if (sleepq_dontsleep(l)) {
(void)sleepq_abort(NULL, 0);
if ((priority & PNORELOCK) != 0)
simple_unlock(interlock);
return 0;
}
sq = sleeptab_lookup(&sleeptab, ident);
sleepq_enter(sq, l);
if (interlock != NULL) {
LOCK_ASSERT(simple_lock_held(interlock));
simple_unlock(interlock);
}
catch = priority & PCATCH;
sleepq_block(sq, priority & PRIMASK, ident, wmesg, timo, catch,
&sleep_syncobj);
error = sleepq_unblock(timo, catch);
if (interlock != NULL && (priority & PNORELOCK) == 0)
simple_lock(interlock);
return error;
}
int
mtsleep(wchan_t ident, pri_t priority, const char *wmesg, int timo,
kmutex_t *mtx)
{
struct lwp *l = curlwp;
sleepq_t *sq;
int error, catch;
if (sleepq_dontsleep(l)) {
(void)sleepq_abort(mtx, (priority & PNORELOCK) != 0);
return 0;
}
sq = sleeptab_lookup(&sleeptab, ident);
sleepq_enter(sq, l);
mutex_exit(mtx);
catch = priority & PCATCH;
sleepq_block(sq, priority & PRIMASK, ident, wmesg, timo, catch,
&sleep_syncobj);
error = sleepq_unblock(timo, catch);
if ((priority & PNORELOCK) == 0)
mutex_enter(mtx);
return error;
}
/*
* General sleep call for situations where a wake-up is not expected.
*/
int
kpause(const char *wmesg, bool intr, int timo, kmutex_t *mtx)
{
struct lwp *l = curlwp;
sleepq_t *sq;
int error;
if (sleepq_dontsleep(l))
return sleepq_abort(NULL, 0);
if (mtx != NULL)
mutex_exit(mtx);
sq = sleeptab_lookup(&sleeptab, l);
sleepq_enter(sq, l);
sleepq_block(sq, sched_kpri(l), l, wmesg, timo, intr, &sleep_syncobj);
error = sleepq_unblock(timo, intr);
if (mtx != NULL)
mutex_enter(mtx);
return error;
}
/*
* OBSOLETE INTERFACE
*
* Make all processes sleeping on the specified identifier runnable.
*/
void
wakeup(wchan_t ident)
{
sleepq_t *sq;
if (cold)
return;
sq = sleeptab_lookup(&sleeptab, ident);
sleepq_wake(sq, ident, (u_int)-1);
}
/*
* OBSOLETE INTERFACE
*
* Make the highest priority process first in line on the specified
* identifier runnable.
*/
void
wakeup_one(wchan_t ident)
{
sleepq_t *sq;
if (cold)
return;
sq = sleeptab_lookup(&sleeptab, ident);
sleepq_wake(sq, ident, 1);
}
/*
* 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;
KERNEL_UNLOCK_ALL(l, &l->l_biglocks);
lwp_lock(l);
if (l->l_stat == LSONPROC) {
KASSERT(lwp_locked(l, &sched_mutex));
l->l_priority = l->l_usrpri;
}
l->l_nvcsw++;
mi_switch(l, NULL);
KERNEL_LOCK(l->l_biglocks, l);
}
/*
* General preemption call. Puts the current process back on its run queue
* and performs an involuntary context switch.
*/
void
preempt(void)
{
struct lwp *l = curlwp;
KERNEL_UNLOCK_ALL(l, &l->l_biglocks);
lwp_lock(l);
if (l->l_stat == LSONPROC) {
KASSERT(lwp_locked(l, &sched_mutex));
l->l_priority = l->l_usrpri;
}
l->l_nivcsw++;
(void)mi_switch(l, NULL);
KERNEL_LOCK(l->l_biglocks, l);
}
/*
* The machine independent parts of context switch. 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 timeval tv;
int retval, oldspl;
long s, u;
LOCK_ASSERT(lwp_locked(l, NULL));
#ifdef LOCKDEBUG
spinlock_switchcheck();
simple_lock_switchcheck();
#endif
#ifdef KSTACK_CHECK_MAGIC
kstack_check_magic(l);
#endif
/*
* It's safe to read the per CPU schedstate unlocked here, as all we
* are after is the run time and that's guarenteed to have been last
* updated by this CPU.
*/
KDASSERT(l->l_cpu == curcpu());
spc = &l->l_cpu->ci_schedstate;
/*
* Compute the amount of time during which the current
* process was running.
*/
microtime(&tv);
u = l->l_rtime.tv_usec +
(tv.tv_usec - spc->spc_runtime.tv_usec);
s = l->l_rtime.tv_sec + (tv.tv_sec - spc->spc_runtime.tv_sec);
if (u < 0) {
u += 1000000;
s--;
} else if (u >= 1000000) {
u -= 1000000;
s++;
}
l->l_rtime.tv_usec = u;
l->l_rtime.tv_sec = s;
/* Count time spent in current system call */
SYSCALL_TIME_SLEEP(l);
/*
* XXXSMP If we are using h/w performance counters, save context.
*/
#if PERFCTRS
if (PMC_ENABLED(l->l_proc)) {
pmc_save_context(l->l_proc);
}
#endif
/*
* Acquire the sched_mutex if necessary. It will be released by
* cpu_switch once it has decided to idle, or picked another LWP
* to run.
*/
#if defined(MULTIPROCESSOR) || defined(LOCKDEBUG)
if (l->l_mutex != &sched_mutex) {
mutex_spin_enter(&sched_mutex);
lwp_unlock(l);
}
#endif
/*
* If on the CPU and we have gotten this far, then we must yield.
*/
KASSERT(l->l_stat != LSRUN);
if (l->l_stat == LSONPROC) {
KASSERT(lwp_locked(l, &sched_mutex));
l->l_stat = LSRUN;
setrunqueue(l);
}
uvmexp.swtch++;
/*
* Process is about to yield the CPU; clear the appropriate
* scheduling flags.
*/
spc->spc_flags &= ~SPCF_SWITCHCLEAR;
LOCKDEBUG_BARRIER(&sched_mutex, 1);
/*
* Switch to the new current LWP. When we run again, we'll
* return back here.
*/
oldspl = MUTEX_SPIN_OLDSPL(l->l_cpu);
if (newl == NULL || newl->l_back == NULL)
retval = cpu_switch(l, NULL);
else {
KASSERT(lwp_locked(newl, &sched_mutex));
remrunqueue(newl);
cpu_switchto(l, newl);
retval = 0;
}
/*
* XXXSMP If we are using h/w performance counters, restore context.
*/
#if PERFCTRS
if (PMC_ENABLED(l->l_proc)) {
pmc_restore_context(l->l_proc);
}
#endif
/*
* We're running again; record our new start time. We might
* be running on a new CPU now, so don't use the cached
* schedstate_percpu pointer.
*/
SYSCALL_TIME_WAKEUP(l);
KDASSERT(l->l_cpu == curcpu());
microtime(&l->l_cpu->ci_schedstate.spc_runtime);
splx(oldspl);
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];
mutex_init(&sched_mutex, MUTEX_SPIN, IPL_SCHED);
}
static inline void
resched_lwp(struct lwp *l)
{
struct cpu_info *ci;
const pri_t pri = lwp_eprio(l);
/*
* 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)
cpu_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.
*
* Call with the process and LWP locked. Will return with the LWP unlocked.
*/
void
setrunnable(struct lwp *l)
{
struct proc *p = l->l_proc;
sigset_t *ss;
KASSERT(mutex_owned(&p->p_smutex));
KASSERT(lwp_locked(l, NULL));
switch (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_slflag & PSL_TRACED) != 0 && p->p_xstat != 0) {
if ((sigprop[p->p_xstat] & SA_TOLWP) != 0)
ss = &l->l_sigpend.sp_set;
else
ss = &p->p_sigpend.sp_set;
sigaddset(ss, p->p_xstat);
signotify(l);
}
p->p_nrlwps++;
break;
case LSSUSPENDED:
l->l_flag &= ~LW_WSUSPEND;
p->p_nrlwps++;
break;
case LSSLEEP:
KASSERT(l->l_wchan != NULL);
break;
default:
panic("setrunnable: lwp %p state was %d", l, l->l_stat);
}
/*
* If the LWP was sleeping interruptably, then it's OK to start it
* again. If not, mark it as still sleeping.
*/
if (l->l_wchan != NULL) {
l->l_stat = LSSLEEP;
/* lwp_unsleep() will release the lock. */
lwp_unsleep(l);
return;
}
LOCK_ASSERT(lwp_locked(l, &sched_mutex));
/*
* If the LWP is still on the CPU, mark it as LSONPROC. It may be
* about to call mi_switch(), in which case it will yield.
*
* XXXSMP Will need to change for preemption.
*/
#ifdef MULTIPROCESSOR
if (l->l_cpu->ci_curlwp == l) {
#else
if (l == curlwp) {
#endif
l->l_stat = LSONPROC;
l->l_slptime = 0;
lwp_unlock(l);
return;
}
/*
* Set the LWP runnable. If it's swapped out, we need to wake the swapper
* to bring it back in. Otherwise, enter it into a run queue.
*/
if (l->l_slptime > 1)
updatepri(l);
l->l_stat = LSRUN;
l->l_slptime = 0;
if (l->l_flag & LW_INMEM) {
setrunqueue(l);
resched_lwp(l);
lwp_unlock(l);
} else {
lwp_unlock(l);
uvm_kick_scheduler();
}
}
/*
* 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)
{
pri_t newpriority;
struct proc *p = l->l_proc;
/* XXXSMP LOCK_ASSERT(mutex_owned(&p->p_stmutex)); */
LOCK_ASSERT(lwp_locked(l, NULL));
if ((l->l_flag & LW_SYSTEM) != 0)
return;
newpriority = PUSER + (p->p_estcpu >> ESTCPU_SHIFT) +
NICE_WEIGHT * (p->p_nice - NZERO);
newpriority = min(newpriority, MAXPRI);
lwp_changepri(l, newpriority);
}
/*
* Recompute priority for all LWPs in a process.
*/
void
resetprocpriority(struct proc *p)
{
struct lwp *l;
LOCK_ASSERT(mutex_owned(&p->p_stmutex));
LIST_FOREACH(l, &p->p_lwps, l_sibling) {
lwp_lock(l);
resetpriority(l);
lwp_unlock(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;
mutex_spin_enter(&p->p_stmutex);
p->p_estcpu = ESTCPULIM(p->p_estcpu + (1 << ESTCPU_SHIFT));
lwp_lock(l);
resetpriority(l);
mutex_spin_exit(&p->p_stmutex);
if ((l->l_flag & LW_SYSTEM) == 0 && l->l_priority >= PUSER)
l->l_priority = l->l_usrpri;
lwp_unlock(l);
}
/*
* suspendsched:
*
* Convert all non-L_SYSTEM LSSLEEP or LSRUN LWPs to LSSUSPENDED.
*/
void
suspendsched(void)
{
#ifdef MULTIPROCESSOR
CPU_INFO_ITERATOR cii;
struct cpu_info *ci;
#endif
struct lwp *l;
struct proc *p;
/*
* We do this by process in order not to violate the locking rules.
*/
mutex_enter(&proclist_mutex);
PROCLIST_FOREACH(p, &allproc) {
mutex_enter(&p->p_smutex);
if ((p->p_flag & PK_SYSTEM) != 0) {
mutex_exit(&p->p_smutex);
continue;
}
p->p_stat = SSTOP;
LIST_FOREACH(l, &p->p_lwps, l_sibling) {
if (l == curlwp)
continue;
lwp_lock(l);
/*
* Set L_WREBOOT so that the LWP will suspend itself
* when it tries to return to user mode. We want to
* try and get to get as many LWPs as possible to
* the user / kernel boundary, so that they will
* release any locks that they hold.
*/
l->l_flag |= (LW_WREBOOT | LW_WSUSPEND);
if (l->l_stat == LSSLEEP &&
(l->l_flag & LW_SINTR) != 0) {
/* setrunnable() will release the lock. */
setrunnable(l);
continue;
}
lwp_unlock(l);
}
mutex_exit(&p->p_smutex);
}
mutex_exit(&proclist_mutex);
/*
* Kick all CPUs to make them preempt any LWPs running in user mode.
* They'll trap into the kernel and suspend themselves in userret().
*/
sched_lock(0);
#ifdef MULTIPROCESSOR
for (CPU_INFO_FOREACH(cii, ci))
cpu_need_resched(ci);
#else
cpu_need_resched(curcpu());
#endif
sched_unlock(0);
}
/*
* scheduler_fork_hook:
*
* Inherit the parent's scheduler history.
*/
void
scheduler_fork_hook(struct proc *parent, struct proc *child)
{
LOCK_ASSERT(mutex_owned(&parent->p_smutex));
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?? */
mutex_spin_enter(&parent->p_stmutex);
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);
mutex_spin_exit(&parent->p_stmutex);
}
/*
* sched_kpri:
*
* Scale a priority level to a kernel priority level, usually
* for an LWP that is about to sleep.
*/
pri_t
sched_kpri(struct lwp *l)
{
/*
* Scale user priorities (127 -> 50) up to kernel priorities
* in the range (49 -> 8). Reserve the top 8 kernel priorities
* for high priority kthreads. Kernel priorities passed in
* are left "as is". XXX This is somewhat arbitrary.
*/
static const uint8_t kpri_tab[] = {
0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31,
32, 33, 34, 35, 36, 37, 38, 39,
40, 41, 42, 43, 44, 45, 46, 47,
48, 49, 8, 8, 9, 9, 10, 10,
11, 11, 12, 12, 13, 14, 14, 15,
15, 16, 16, 17, 17, 18, 18, 19,
20, 20, 21, 21, 22, 22, 23, 23,
24, 24, 25, 26, 26, 27, 27, 28,
28, 29, 29, 30, 30, 31, 32, 32,
33, 33, 34, 34, 35, 35, 36, 36,
37, 38, 38, 39, 39, 40, 40, 41,
41, 42, 42, 43, 44, 44, 45, 45,
46, 46, 47, 47, 48, 48, 49, 49,
};
return (pri_t)kpri_tab[l->l_usrpri];
}
/*
* sched_unsleep:
*
* The is called when the LWP has not been awoken normally but instead
* interrupted: for example, if the sleep timed out. Because of this,
* it's not a valid action for running or idle LWPs.
*/
void
sched_unsleep(struct lwp *l)
{
lwp_unlock(l);
panic("sched_unsleep");
}
/*
* sched_changepri:
*
* Adjust the priority of an LWP.
*/
void
sched_changepri(struct lwp *l, pri_t pri)
{
LOCK_ASSERT(lwp_locked(l, &sched_mutex));
l->l_usrpri = pri;
if (l->l_priority < PUSER)
return;
if (l->l_stat != LSRUN || (l->l_flag & LW_INMEM) == 0) {
l->l_priority = pri;
return;
}
remrunqueue(l);
l->l_priority = pri;
setrunqueue(l);
resched_lwp(l);
}
void
sched_lendpri(struct lwp *l, pri_t pri)
{
LOCK_ASSERT(lwp_locked(l, &sched_mutex));
if (l->l_stat != LSRUN || (l->l_flag & LW_INMEM) == 0) {
l->l_inheritedprio = pri;
return;
}
remrunqueue(l);
l->l_inheritedprio = pri;
setrunqueue(l);
resched_lwp(l);
}
struct lwp *
syncobj_noowner(wchan_t wchan)
{
return NULL;
}
/*
* 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 != (const 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 = lwp_eprio(l) / PPQ;
LOCK_ASSERT(lwp_locked(l, &sched_mutex));
#ifdef RQDEBUG
checkrunqueue(whichq, NULL);
#endif
#ifdef DIAGNOSTIC
if (l->l_back != 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
}
/*
* XXXSMP When LWP dispatch (cpu_switch()) is changed to use remrunqueue(),
* drop of the effective priority level from kernel to user needs to be
* moved here from userret(). The assignment in userret() is currently
* done unlocked.
*/
void
remrunqueue(struct lwp *l)
{
struct lwp *prev, *next;
const int whichq = lwp_eprio(l) / PPQ;
LOCK_ASSERT(lwp_locked(l, &sched_mutex));
#ifdef RQDEBUG
checkrunqueue(whichq, l);
#endif
#if defined(DIAGNOSTIC)
if (((sched_whichqs & RQMASK(whichq)) == 0) || l->l_back == NULL) {
/* Shouldn't happen - interrupts disabled. */
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) */
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