#include	"dat.h"#include	"fns.h"#include	"error.h" voidlock(Lock *l){	int i; 	if(_tas(&l->val) == 0)		return;	for(i=0; i<100; i++){		if(_tas(&l->val) == 0)			return;		osyield();	}	for(i=1;; i++){		if(_tas(&l->val) == 0)			return;		osmillisleep(i*10);		if(i > 100){			osyield();			i = 1;		}	}} intcanlock(Lock *l){	return _tas(&l->val) == 0;} voidunlock(Lock *l){	l->val = 0;} voidqlock(QLock *q){	Proc *p; 	lock(&q->use);	if(!q->locked) {		q->locked = 1;		unlock(&q->use);		return;	}	p = q->tail;	if(p == 0)		q->head = up;	else		p->qnext = up;	q->tail = up;	up->qnext = 0;	unlock(&q->use);	osblock();} intcanqlock(QLock *q){	if(!canlock(&q->use))		return 0;	if(q->locked){		unlock(&q->use);		return 0;	}	q->locked = 1;	unlock(&q->use);	return 1;} voidqunlock(QLock *q){	Proc *p; 	lock(&q->use);	p = q->head;	if(p) {		q->head = p->qnext;		if(q->head == 0)			q->tail = 0;		unlock(&q->use);		osready(p);		return;	}	q->locked = 0;	unlock(&q->use);} voidrlock(RWlock *l){	qlock(&l->x);		/* wait here for writers and exclusion */	lock(&l->l);	l->readers++;	canqlock(&l->k);	/* block writers if we are the first reader */	unlock(&l->l);	qunlock(&l->x);} /* same as rlock but punts if there are any writers waiting */intcanrlock(RWlock *l){	if (!canqlock(&l->x))		return 0;	lock(&l->l);	l->readers++;	canqlock(&l->k);	/* block writers if we are the first reader */	unlock(&l->l);	qunlock(&l->x);	return 1;} voidrunlock(RWlock *l){	lock(&l->l);	if(--l->readers == 0)	/* last reader out allows writers */		qunlock(&l->k);	unlock(&l->l);} voidwlock(RWlock *l){	qlock(&l->x);		/* wait here for writers and exclusion */	qlock(&l->k);		/* wait here for last reader */} voidwunlock(RWlock *l){	qunlock(&l->k);	qunlock(&l->x);}