1990/03091/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" void lock(Lock *l) { int i; /* * Try the fast grab first */ if(tas(l->key) == 0){ l->pc = ((ulong*)&l)[-1]; return; } for(i=0; i<10000000; i++) if(tas(l->key) == 0){ l->pc = ((ulong*)&l)[-1]; return; } l->key[0] = 0; panic("lock loop %lux pc %lux held by pc %lux\n", l, ((ulong*)&l)[-1], l->pc); } int canlock(Lock *l) { if(tas(l->key) == 0){ l->pc = ((ulong*)&l)[-1]; return 1; } return 0; } void unlock(Lock *l) { l->pc = 0; l->key[0] = 0; } 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; unlock(&q->queue); sched(); } 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); } }