ref: 15af8dd530c246b1f63ded61a592804d403033aa
dir: /kern/qlock.c/
#include "u.h" #include "lib.h" #include "dat.h" #include "fns.h" static void queue(Proc **first, Proc **last) { Proc *t; t = *last; if(t == 0) *first = up; else t->qnext = up; *last = up; up->qnext = 0; } static Proc* dequeue(Proc **first, Proc **last) { Proc *t; t = *first; if(t == 0) return 0; *first = t->qnext; if(*first == 0) *last = 0; return t; } void qlock(QLock *q) { lock(&q->lk); if(q->hold == 0) { q->hold = up; unlock(&q->lk); return; } /* * Can't assert this because of RWLock assert(q->hold != up); */ queue((Proc**)&q->first, (Proc**)&q->last); unlock(&q->lk); procsleep(); } int canqlock(QLock *q) { lock(&q->lk); if(q->hold == 0) { q->hold = up; unlock(&q->lk); return 1; } unlock(&q->lk); return 0; } void qunlock(QLock *q) { Proc *p; lock(&q->lk); /* * Can't assert this because of RWlock assert(q->hold == CT); */ p = dequeue((Proc**)&q->first, (Proc**)&q->last); if(p) { q->hold = p; unlock(&q->lk); procwakeup(p); } else { q->hold = 0; unlock(&q->lk); } } int holdqlock(QLock *q) { return q->hold == up; }