1 #include "u.h" 2 #include "lib.h" 3 #include "dat.h" 4 #include "fns.h" 5 #include "error.h" 6 7 void 8 rlock(RWlock *l) 9 { 10 qlock(&l->x); /* wait here for writers and exclusion */ 11 lock(&l->lk); 12 l->readers++; 13 canqlock(&l->k); /* block writers if we are the first reader */ 14 unlock(&l->lk); 15 qunlock(&l->x); 16 } 17 18 void 19 runlock(RWlock *l) 20 { 21 lock(&l->lk); 22 if(--l->readers == 0) /* last reader out allows writers */ 23 qunlock(&l->k); 24 unlock(&l->lk); 25 } 26 27 void 28 wlock(RWlock *l) 29 { 30 qlock(&l->x); /* wait here for writers and exclusion */ 31 qlock(&l->k); /* wait here for last reader */ 32 } 33 34 void 35 wunlock(RWlock *l) 36 { 37 qunlock(&l->k); 38 qunlock(&l->x); 39 } 40