FreeBSD-5.3/sys/kern/kern_synch.c
/*-
* 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.
* 4. 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>
__FBSDID("$FreeBSD: src/sys/kern/kern_synch.c,v 1.257.2.3.2.1 2004/10/22 19:13:07 scottl Exp $");
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/condvar.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/sleepqueue.h>
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vmmeter.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#include <machine/cpu.h>
static void synch_setup(void *dummy);
SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, NULL)
int hogticks;
int lbolt;
static struct callout loadav_callout;
static struct callout lbolt_callout;
struct loadavg averunnable =
{ {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
/*
* Constants for averages over 1, 5, and 15 minutes
* when sampling at 5 second intervals.
*/
static fixpt_t cexp[3] = {
0.9200444146293232 * FSCALE, /* exp(-1/12) */
0.9834714538216174 * FSCALE, /* exp(-1/60) */
0.9944598480048967 * FSCALE, /* exp(-1/180) */
};
/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
static int fscale __unused = FSCALE;
SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
static void loadav(void *arg);
static void lboltcb(void *arg);
void
sleepinit(void)
{
hogticks = (hz / 10) * 2; /* Default only. */
init_sleepqueues();
}
/*
* 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 mutex argument is exited before the caller is suspended, and
* entered before msleep returns. If priority includes the PDROP
* flag the mutex is not entered before returning.
*/
int
msleep(ident, mtx, priority, wmesg, timo)
void *ident;
struct mtx *mtx;
int priority, timo;
const char *wmesg;
{
struct sleepqueue *sq;
struct thread *td;
struct proc *p;
int catch, rval, sig, flags;
WITNESS_SAVE_DECL(mtx);
td = curthread;
p = td->td_proc;
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(1, 0);
#endif
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, mtx == NULL ? NULL :
&mtx->mtx_object, "Sleeping on \"%s\"", wmesg);
KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL,
("sleeping without a mutex"));
KASSERT(p != NULL, ("msleep1"));
KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
if (cold) {
/*
* During autoconfiguration, just return;
* don't run any other threads or panic below,
* in case this is the idle thread and already asleep.
* XXX: this used to do "s = splhigh(); splx(safepri);
* splx(s);" to give interrupts a chance, but there is
* no way to give interrupts a chance now.
*/
if (mtx != NULL && priority & PDROP)
mtx_unlock(mtx);
return (0);
}
catch = priority & PCATCH;
rval = 0;
/*
* If we are already on a sleep queue, then remove us from that
* sleep queue first. We have to do this to handle recursive
* sleeps.
*/
if (TD_ON_SLEEPQ(td))
sleepq_remove(td, td->td_wchan);
sq = sleepq_lookup(ident);
if (catch) {
/*
* Don't bother sleeping if we are exiting and not the exiting
* thread or if our thread is marked as interrupted.
*/
mtx_lock_spin(&sched_lock);
rval = thread_sleep_check(td);
mtx_unlock_spin(&sched_lock);
if (rval != 0) {
sleepq_release(ident);
return (rval);
}
}
CTR5(KTR_PROC, "msleep: thread %p (pid %ld, %s) on %s (%p)",
(void *)td, (long)p->p_pid, p->p_comm, wmesg, ident);
DROP_GIANT();
if (mtx != NULL) {
mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
WITNESS_SAVE(&mtx->mtx_object, mtx);
mtx_unlock(mtx);
}
/*
* We put ourselves on the sleep queue and start our timeout
* before calling thread_suspend_check, as we could stop there,
* and a wakeup or a SIGCONT (or both) could occur while we were
* stopped without resuming us. Thus, we must be ready for sleep
* when cursig() is called. If the wakeup happens while we're
* stopped, then td will no longer be on a sleep queue upon
* return from cursig().
*/
flags = SLEEPQ_MSLEEP;
if (catch)
flags |= SLEEPQ_INTERRUPTIBLE;
sleepq_add(sq, ident, mtx, wmesg, flags);
if (timo)
sleepq_set_timeout(ident, timo);
if (catch) {
sig = sleepq_catch_signals(ident);
} else
sig = 0;
/*
* Adjust this thread's priority.
*
* XXX: do we need to save priority in td_base_pri?
*/
mtx_lock_spin(&sched_lock);
sched_prio(td, priority & PRIMASK);
mtx_unlock_spin(&sched_lock);
if (timo && catch)
rval = sleepq_timedwait_sig(ident, sig != 0);
else if (timo)
rval = sleepq_timedwait(ident);
else if (catch)
rval = sleepq_wait_sig(ident);
else {
sleepq_wait(ident);
rval = 0;
}
if (rval == 0 && catch)
rval = sleepq_calc_signal_retval(sig);
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(0, 0);
#endif
PICKUP_GIANT();
if (mtx != NULL && !(priority & PDROP)) {
mtx_lock(mtx);
WITNESS_RESTORE(&mtx->mtx_object, mtx);
}
return (rval);
}
/*
* Make all threads sleeping on the specified identifier runnable.
*/
void
wakeup(ident)
register void *ident;
{
sleepq_broadcast(ident, SLEEPQ_MSLEEP, -1);
}
/*
* Make a thread sleeping on the specified identifier runnable.
* May wake more than one thread if a target thread is currently
* swapped out.
*/
void
wakeup_one(ident)
register void *ident;
{
sleepq_signal(ident, SLEEPQ_MSLEEP, -1);
}
/*
* The machine independent parts of context switching.
*/
void
mi_switch(int flags, struct thread *newtd)
{
struct bintime new_switchtime;
struct thread *td;
struct proc *p;
mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
td = curthread; /* XXX */
p = td->td_proc; /* XXX */
KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
#ifdef INVARIANTS
if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
mtx_assert(&Giant, MA_NOTOWNED);
#endif
KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
(td->td_pflags & TDP_OWEPREEMPT) != 0 && (flags & SW_INVOL) != 0 &&
newtd == NULL),
("mi_switch: switch in a critical section"));
KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
("mi_switch: switch must be voluntary or involuntary"));
KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
if (flags & SW_VOL)
p->p_stats->p_ru.ru_nvcsw++;
else
p->p_stats->p_ru.ru_nivcsw++;
/*
* Compute the amount of time during which the current
* process was running, and add that to its total so far.
*/
binuptime(&new_switchtime);
bintime_add(&p->p_runtime, &new_switchtime);
bintime_sub(&p->p_runtime, PCPU_PTR(switchtime));
td->td_generation++; /* bump preempt-detect counter */
/*
* Don't perform context switches from the debugger.
*/
if (kdb_active) {
mtx_unlock_spin(&sched_lock);
kdb_backtrace();
kdb_reenter();
panic("%s: did not reenter debugger", __func__);
}
/*
* Check if the process exceeds its cpu resource allocation. If
* over max, arrange to kill the process in ast().
*/
if (p->p_cpulimit != RLIM_INFINITY &&
p->p_runtime.sec > p->p_cpulimit) {
p->p_sflag |= PS_XCPU;
td->td_flags |= TDF_ASTPENDING;
}
/*
* Finish up stats for outgoing thread.
*/
cnt.v_swtch++;
PCPU_SET(switchtime, new_switchtime);
PCPU_SET(switchticks, ticks);
CTR4(KTR_PROC, "mi_switch: old thread %p (kse %p, pid %ld, %s)",
(void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA))
newtd = thread_switchout(td, flags, newtd);
sched_switch(td, newtd, flags);
CTR4(KTR_PROC, "mi_switch: new thread %p (kse %p, pid %ld, %s)",
(void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
/*
* If the last thread was exiting, finish cleaning it up.
*/
if ((td = PCPU_GET(deadthread))) {
PCPU_SET(deadthread, NULL);
thread_stash(td);
}
}
/*
* 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 thread *td)
{
struct proc *p;
p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
switch (p->p_state) {
case PRS_ZOMBIE:
panic("setrunnable(1)");
default:
break;
}
switch (td->td_state) {
case TDS_RUNNING:
case TDS_RUNQ:
return;
case TDS_INHIBITED:
/*
* If we are only inhibited because we are swapped out
* then arange to swap in this process. Otherwise just return.
*/
if (td->td_inhibitors != TDI_SWAPPED)
return;
/* XXX: intentional fall-through ? */
case TDS_CAN_RUN:
break;
default:
printf("state is 0x%x", td->td_state);
panic("setrunnable(2)");
}
if ((p->p_sflag & PS_INMEM) == 0) {
if ((p->p_sflag & PS_SWAPPINGIN) == 0) {
p->p_sflag |= PS_SWAPINREQ;
/*
* due to a LOR between sched_lock and
* the sleepqueue chain locks, delay
* wakeup proc0 until thread leaves
* critical region.
*/
curthread->td_pflags |= TDP_WAKEPROC0;
}
} else
sched_wakeup(td);
}
/*
* Compute a tenex style load average of a quantity on
* 1, 5 and 15 minute intervals.
* XXXKSE Needs complete rewrite when correct info is available.
* Completely Bogus.. only works with 1:1 (but compiles ok now :-)
*/
static void
loadav(void *arg)
{
int i, nrun;
struct loadavg *avg;
nrun = sched_load();
avg = &averunnable;
for (i = 0; i < 3; i++)
avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
/*
* Schedule the next update to occur after 5 seconds, but add a
* random variation to avoid synchronisation with processes that
* run at regular intervals.
*/
callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
loadav, NULL);
}
static void
lboltcb(void *arg)
{
wakeup(&lbolt);
callout_reset(&lbolt_callout, hz, lboltcb, NULL);
}
/* ARGSUSED */
static void
synch_setup(dummy)
void *dummy;
{
callout_init(&loadav_callout, CALLOUT_MPSAFE);
callout_init(&lbolt_callout, CALLOUT_MPSAFE);
/* Kick off timeout driven events by calling first time. */
loadav(NULL);
lboltcb(NULL);
}
/*
* General purpose yield system call
*/
int
yield(struct thread *td, struct yield_args *uap)
{
struct ksegrp *kg;
kg = td->td_ksegrp;
mtx_assert(&Giant, MA_NOTOWNED);
mtx_lock_spin(&sched_lock);
sched_prio(td, PRI_MAX_TIMESHARE);
mi_switch(SW_VOL, NULL);
mtx_unlock_spin(&sched_lock);
td->td_retval[0] = 0;
return (0);
}