#include	"u.h"#include	"../port/lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"io.h" #include	"ureg.h" typedef struct Clock0link Clock0link;typedef struct Clock0link {	void		(*clock)(void);	Clock0link*	link;} Clock0link; static Clock0link *clock0link;static Lock clock0lock; voidmicrodelay(int ms){	int i; 	ms *= 13334;		/* experimentally indetermined */	for(i=0; i<ms; i++)		;} typedef struct Ctr Ctr;struct Ctr{	ulong	lim;	ulong	ctr;	ulong	limnr;	/* non-resetting */	ulong	ctl;};Ctr	*ctr; voidclockinit(void){	KMap *k; 	putphys(TIMECONFIG, 0);	/* it's a processor counter */	k = kmappa(CLOCK, PTENOCACHE|PTEIO);	ctr = (Ctr*)VA(k);	ctr->lim = (CLOCKFREQ/HZ)<<10;} voidclock(Ureg *ur){	Clock0link *lp;	ulong i; 	USED(ur); 	i = ctr->lim;	/* clear interrupt */	USED(i);	 /* is this needed? page 6-43 801-3137-10 suggests so */	ctr->lim = (CLOCKFREQ/HZ)<<10; 	m->ticks++; 	if(up)		up->pc = ur->pc; 	checkalarms(); 	lock(&clock0lock);	for(lp = clock0link; lp; lp = lp->link)		lp->clock();	unlock(&clock0lock); 	if(up && up->state == Running) {		if(anyready())			sched();	}} Timer*addclock0link(void (*clockfunc)(void), int){	Clock0link *lp; 	if((lp = malloc(sizeof(Clock0link))) == 0){		print("addclock0link: too many links\n");		return nil;	}	ilock(&clock0lock);	lp->clock = clockfunc;	lp->link = clock0link;	clock0link = lp;	iunlock(&clock0lock);	return nil;} uvlongfastticks(uvlong *hz){	if(hz)		*hz = HZ;	return m->ticks;}