ref: c8b187f9db503465460d8bafa2d7a758bbcf59ca
dir: /lib9/lock.c/
#include "dat.h" #include "fns.h" #include "error.h" void lock(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; } } } int canlock(Lock *l) { return _tas(&l->val) == 0; } void unlock(Lock *l) { l->val = 0; } void qlock(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(); } int canqlock(QLock *q) { if(!canlock(&q->use)) return 0; if(q->locked){ unlock(&q->use); return 0; } q->locked = 1; unlock(&q->use); return 1; } void qunlock(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); } void rlock(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 */ int canrlock(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; } void runlock(RWlock *l) { lock(&l->l); if(--l->readers == 0) /* last reader out allows writers */ qunlock(&l->k); unlock(&l->l); } void wlock(RWlock *l) { qlock(&l->x); /* wait here for writers and exclusion */ qlock(&l->k); /* wait here for last reader */ } void wunlock(RWlock *l) { qunlock(&l->k); qunlock(&l->x); }