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freebsd/sys/kern/kern_synch.c
Justin T. Gibbs ab36c06737 init_main.c subr_autoconf.c: 
Add support for "interrupt driven configuration hooks".
	A component of the kernel can register a hook, most likely
	during auto-configuration, and receive a callback once
	interrupt services are available.  This callback will occur before
	the root and dump devices are configured, so the configuration
	task can affect the selection of those two devices or complete
	any tasks that need to be performed prior to launching init.
	System boot is posponed so long as a hook is registered.  The
	hook owner is responsible for removing the hook once their task
	is complete or the system boot can continue.

kern_acct.c kern_clock.c kern_exit.c kern_synch.c kern_time.c:
	Change the interface and implementation for the kernel callout
	service.  The new implemntaion is based on the work of
	Adam M. Costello and George Varghese, published in a technical
	report entitled "Redesigning the BSD Callout and Timer Facilities".
	The interface used in FreeBSD is a little different than the one
	outlined in the paper.  The new function prototypes are:

	struct callout_handle timeout(void (*func)(void *),
				      void *arg, int ticks);

	void untimeout(void (*func)(void *), void *arg,
		       struct callout_handle handle);

	If a client wishes to remove a timeout, it must store the
	callout_handle returned by timeout and pass it to untimeout.

	The new implementation gives 0(1) insert and removal of callouts
	making this interface scale well even for applications that
	keep 100s of callouts outstanding.

	See the updated timeout.9 man page for more details.
1997-09-21 22:00:25 +00:00

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/*-
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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
* $Id: kern_synch.c,v 1.38 1997/09/02 20:05:43 bde Exp $
*/
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/signalvar.h>
#include <sys/resourcevar.h>
#include <sys/vmmeter.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <machine/cpu.h>
#include <machine/limits.h> /* for UCHAR_MAX = typeof(p_priority)_MAX */
static void rqinit __P((void *));
SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL)
u_char curpriority; /* usrpri of curproc */
int lbolt; /* once a second sleep address */
extern void endtsleep __P((void *));
extern void updatepri __P((struct proc *p));
#define MAXIMUM_SCHEDULE_QUANTUM (1000000) /* arbitrary limit */
#ifndef DEFAULT_SCHEDULE_QUANTUM
#define DEFAULT_SCHEDULE_QUANTUM 10
#endif
static int quantum = DEFAULT_SCHEDULE_QUANTUM; /* default value */
static int
sysctl_kern_quantum SYSCTL_HANDLER_ARGS
{
int error;
int new_val = quantum;
new_val = quantum;
error = sysctl_handle_int(oidp, &new_val, 0, req);
if (error == 0) {
if ((new_val > 0) && (new_val < MAXIMUM_SCHEDULE_QUANTUM)) {
quantum = new_val;
} else {
error = EINVAL;
}
}
return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
0, sizeof quantum, sysctl_kern_quantum, "I", "");
/*
* Force switch among equal priority processes every 100ms.
*/
/* ARGSUSED */
void
roundrobin(arg)
void *arg;
{
need_resched();
timeout(roundrobin, NULL, hz / quantum);
}
/*
* 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 statclock 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(arg)
void *arg;
{
register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
register struct proc *p;
register int s;
register unsigned int newcpu;
wakeup((caddr_t)&lbolt);
for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
/*
* 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.
*/
p->p_swtime++;
if (p->p_stat == SSLEEP || p->p_stat == SSTOP)
p->p_slptime++;
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 (p->p_slptime > 1)
continue;
s = splhigh(); /* prevent state changes and protect run queue */
/*
* p_pctcpu is only for ps.
*/
#if (FSHIFT >= CCPU_SHIFT)
p->p_pctcpu += (hz == 100)?
((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT):
100 * (((fixpt_t) p->p_cpticks)
<< (FSHIFT - CCPU_SHIFT)) / hz;
#else
p->p_pctcpu += ((FSCALE - ccpu) *
(p->p_cpticks * FSCALE / hz)) >> FSHIFT;
#endif
p->p_cpticks = 0;
newcpu = (u_int) decay_cpu(loadfac, p->p_estcpu) + p->p_nice;
p->p_estcpu = min(newcpu, UCHAR_MAX);
resetpriority(p);
if (p->p_priority >= PUSER) {
#define PPQ (128 / NQS) /* priorities per queue */
if ((p != curproc) &&
#ifdef SMP
(u_char)p->p_oncpu == 0xff && /* idle */
#endif
p->p_stat == SRUN &&
(p->p_flag & P_INMEM) &&
(p->p_priority / PPQ) != (p->p_usrpri / PPQ)) {
remrq(p);
p->p_priority = p->p_usrpri;
setrunqueue(p);
} else
p->p_priority = p->p_usrpri;
}
splx(s);
}
vmmeter();
timeout(schedcpu, (void *)0, 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(p)
register struct proc *p;
{
register unsigned int newcpu = p->p_estcpu;
register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
if (p->p_slptime > 5 * loadfac)
p->p_estcpu = 0;
else {
p->p_slptime--; /* the first time was done in schedcpu */
while (newcpu && --p->p_slptime)
newcpu = (int) decay_cpu(loadfac, newcpu);
p->p_estcpu = min(newcpu, UCHAR_MAX);
}
resetpriority(p);
}
/*
* 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 TABLESIZE 128
TAILQ_HEAD(slpquehead, proc) slpque[TABLESIZE];
#define LOOKUP(x) (((long)(x) >> 8) & (TABLESIZE - 1))
/*
* 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;
void
sleepinit()
{
int i;
for (i = 0; i < TABLESIZE; i++)
TAILQ_INIT(&slpque[i]);
}
/*
* 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).
*/
int
tsleep(ident, priority, wmesg, timo)
void *ident;
int priority, timo;
char *wmesg;
{
struct proc *p = curproc;
int s, sig, catch = priority & PCATCH;
struct callout_handle thandle;
#ifdef KTRACE
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 1, 0);
#endif
s = splhigh();
if (cold || panicstr) {
/*
* 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.
*/
splx(safepri);
splx(s);
return (0);
}
#ifdef DIAGNOSTIC
if(p == NULL)
panic("tsleep1");
if (ident == NULL || p->p_stat != SRUN)
panic("tsleep");
/* XXX This is not exhaustive, just the most common case */
if ((p->p_procq.tqe_prev != NULL) && (*p->p_procq.tqe_prev == p))
panic("sleeping process already on another queue");
#endif
p->p_wchan = ident;
p->p_wmesg = wmesg;
p->p_slptime = 0;
p->p_priority = priority & PRIMASK;
TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_procq);
if (timo)
thandle = timeout(endtsleep, (void *)p, timo);
/*
* 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) {
p->p_flag |= P_SINTR;
if ((sig = CURSIG(p))) {
if (p->p_wchan)
unsleep(p);
p->p_stat = SRUN;
goto resume;
}
if (p->p_wchan == 0) {
catch = 0;
goto resume;
}
} else
sig = 0;
p->p_stat = SSLEEP;
p->p_stats->p_ru.ru_nvcsw++;
mi_switch();
resume:
curpriority = p->p_usrpri;
splx(s);
p->p_flag &= ~P_SINTR;
if (p->p_flag & P_TIMEOUT) {
p->p_flag &= ~P_TIMEOUT;
if (sig == 0) {
#ifdef KTRACE
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
#endif
return (EWOULDBLOCK);
}
} else if (timo)
untimeout(endtsleep, (void *)p, thandle);
if (catch && (sig != 0 || (sig = CURSIG(p)))) {
#ifdef KTRACE
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
#endif
if (p->p_sigacts->ps_sigintr & sigmask(sig))
return (EINTR);
return (ERESTART);
}
#ifdef KTRACE
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
#endif
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(arg)
void *arg;
{
register struct proc *p;
int s;
p = (struct proc *)arg;
s = splhigh();
if (p->p_wchan) {
if (p->p_stat == SSLEEP)
setrunnable(p);
else
unsleep(p);
p->p_flag |= P_TIMEOUT;
}
splx(s);
}
/*
* Remove a process from its wait queue
*/
void
unsleep(p)
register struct proc *p;
{
int s;
s = splhigh();
if (p->p_wchan) {
TAILQ_REMOVE(&slpque[LOOKUP(p->p_wchan)], p, p_procq);
p->p_wchan = 0;
}
splx(s);
}
/*
* Make all processes sleeping on the specified identifier runnable.
*/
void
wakeup(ident)
register void *ident;
{
register struct slpquehead *qp;
register struct proc *p;
int s;
s = splhigh();
qp = &slpque[LOOKUP(ident)];
restart:
for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) {
#ifdef DIAGNOSTIC
if (p->p_stat != SSLEEP && p->p_stat != SSTOP)
panic("wakeup");
#endif
if (p->p_wchan == ident) {
TAILQ_REMOVE(qp, p, p_procq);
p->p_wchan = 0;
if (p->p_stat == SSLEEP) {
/* OPTIMIZED EXPANSION OF setrunnable(p); */
if (p->p_slptime > 1)
updatepri(p);
p->p_slptime = 0;
p->p_stat = SRUN;
if (p->p_flag & P_INMEM) {
setrunqueue(p);
need_resched();
} else {
p->p_flag |= P_SWAPINREQ;
wakeup((caddr_t)&proc0);
}
/* END INLINE EXPANSION */
goto restart;
}
}
}
splx(s);
}
/*
* Make a process sleeping on the specified identifier runnable.
* May wake more than one process if a target prcoess is currently
* swapped out.
*/
void
wakeup_one(ident)
register void *ident;
{
register struct slpquehead *qp;
register struct proc *p;
int s;
s = splhigh();
qp = &slpque[LOOKUP(ident)];
for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) {
#ifdef DIAGNOSTIC
if (p->p_stat != SSLEEP && p->p_stat != SSTOP)
panic("wakeup_one");
#endif
if (p->p_wchan == ident) {
TAILQ_REMOVE(qp, p, p_procq);
p->p_wchan = 0;
if (p->p_stat == SSLEEP) {
/* OPTIMIZED EXPANSION OF setrunnable(p); */
if (p->p_slptime > 1)
updatepri(p);
p->p_slptime = 0;
p->p_stat = SRUN;
if (p->p_flag & P_INMEM) {
setrunqueue(p);
need_resched();
break;
} else {
p->p_flag |= P_SWAPINREQ;
wakeup((caddr_t)&proc0);
}
/* END INLINE EXPANSION */
}
}
}
splx(s);
}
/*
* The machine independent parts of mi_switch().
* Must be called at splstatclock() or higher.
*/
void
mi_switch()
{
register struct proc *p = curproc; /* XXX */
register struct rlimit *rlim;
register long s, u;
int x;
struct timeval tv;
/*
* XXX this spl is almost unnecessary. It is partly to allow for
* sloppy callers that don't do it (issignal() via CURSIG() is the
* main offender). It is partly to work around a bug in the i386
* cpu_switch() (the ipl is not preserved). We ran for years
* without it. I think there was only a interrupt latency problem.
* The main caller, tsleep(), does an splx() a couple of instructions
* after calling here. The buggy caller, issignal(), usually calls
* here at spl0() and sometimes returns at splhigh(). The process
* then runs for a little too long at splhigh(). The ipl gets fixed
* when the process returns to user mode (or earlier).
*
* It would probably be better to always call here at spl0(). Callers
* are prepared to give up control to another process, so they must
* be prepared to be interrupted. The clock stuff here may not
* actually need splstatclock().
*/
x = splstatclock();
#ifdef SIMPLELOCK_DEBUG
if (p->p_simple_locks)
printf("sleep: holding simple lock");
#endif
/*
* Compute the amount of time during which the current
* process was running, and add that to its total so far.
*/
microtime(&tv);
u = p->p_rtime.tv_usec + (tv.tv_usec - runtime.tv_usec);
s = p->p_rtime.tv_sec + (tv.tv_sec - runtime.tv_sec);
if (u < 0) {
u += 1000000;
s--;
} else if (u >= 1000000) {
u -= 1000000;
s++;
}
#ifdef SMP
if (s < 0)
s = u = 0;
#endif
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.
*/
if (p->p_stat != SZOMB) {
rlim = &p->p_rlimit[RLIMIT_CPU];
if (s >= rlim->rlim_cur) {
if (s >= rlim->rlim_max)
killproc(p, "exceeded maximum CPU limit");
else {
psignal(p, SIGXCPU);
if (rlim->rlim_cur < rlim->rlim_max)
rlim->rlim_cur += 5;
}
}
}
/*
* Pick a new current process and record its start time.
*/
cnt.v_swtch++;
cpu_switch(p);
microtime(&runtime);
splx(x);
}
/*
* Initialize the (doubly-linked) run queues
* to be empty.
*/
/* ARGSUSED*/
static void
rqinit(dummy)
void *dummy;
{
register int i;
for (i = 0; i < NQS; i++) {
qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i];
rtqs[i].ph_link = rtqs[i].ph_rlink = (struct proc *)&rtqs[i];
idqs[i].ph_link = idqs[i].ph_rlink = (struct proc *)&idqs[i];
}
}
/*
* 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(p)
register struct proc *p;
{
register int s;
s = splhigh();
switch (p->p_stat) {
case 0:
case SRUN:
case SZOMB:
default:
panic("setrunnable");
case SSTOP:
case SSLEEP:
unsleep(p); /* e.g. when sending signals */
break;
case SIDL:
break;
}
p->p_stat = SRUN;
if (p->p_flag & P_INMEM)
setrunqueue(p);
splx(s);
if (p->p_slptime > 1)
updatepri(p);
p->p_slptime = 0;
if ((p->p_flag & P_INMEM) == 0) {
p->p_flag |= P_SWAPINREQ;
wakeup((caddr_t)&proc0);
}
else if (p->p_priority < curpriority)
need_resched();
}
/*
* 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(p)
register struct proc *p;
{
register unsigned int newpriority;
if (p->p_rtprio.type == RTP_PRIO_NORMAL) {
newpriority = PUSER + p->p_estcpu / 4 + 2 * p->p_nice;
newpriority = min(newpriority, MAXPRI);
p->p_usrpri = newpriority;
if (newpriority < curpriority)
need_resched();
} else {
need_resched();
}
}
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