1990/05313/gnot/lock.c (diff list | history)

gnot/lock.c on 1990/03091
1990/03091		#include "u.h" #include "lib.h" #include "mem.h" #include "dat.h" #include "fns.h"
1990/0403		#define PCOFF -2 /* * N.B. Ken's compiler generates a TAS instruction for the sequence: * * if(l->key >= 0){ * l->key |= 0x80; * ... */
1990/03091		void lock(Lock *l) { int i; /* * Try the fast grab first */
1990/0403		if(l->key >= 0){ l->key |= 0x80; l->pc = ((ulong*)&i)[PCOFF];
1990/03091		return; } for(i=0; i<10000000; i++)
1990/0403		if(l->key >= 0){ l->key |= 0x80; l->pc = ((ulong*)&i)[PCOFF];
1990/03091		return; }
1990/0403		l->key = 0; panic("lock loop %lux pc %lux held by pc %lux\n", l, ((ulong*)&i)[PCOFF], l->pc);
1990/03091		} int canlock(Lock *l) {
1990/0403		int i; if(l->key >= 0){ l->key |= 0x80; l->pc = ((ulong*)&i)[PCOFF];
1990/03091		return 1; } return 0; } void unlock(Lock *l) { l->pc = 0;
1990/0403		l->key = 0;
1990/03091		} void qlock(QLock *q) { Proc *p; if(canlock(&q->use)) return; lock(&q->queue); if(canlock(&q->use)){ unlock(&q->queue); return; } p = q->tail; if(p == 0) q->head = u->p; else p->qnext = u->p; q->tail = u->p; u->p->qnext = 0; u->p->state = Queueing;
1990/05313		u->p->qlock = q; /* DEBUG */
1990/03091		unlock(&q->queue); sched(); }
1990/0312		int canqlock(QLock *q) { return canlock(&q->use); }
1990/03091		void qunlock(QLock *q) { Proc *p; lock(&q->queue); if(q->head){ p = q->head; q->head = p->qnext; if(q->head == 0) q->tail = 0; unlock(&q->queue); ready(p); }else{ unlock(&q->use); unlock(&q->queue); } }