Query about HSH_EXPBUSY & HSH_EXP in HSH_Lookup

[Arvind Narayanan]

Hi,

I was trying to understand the function

 enum lookup_e
HSH_Lookup(struct req *req, struct objcore **ocp, struct objcore **bocp,
    int always_insert)

located in bin/varnishd/cache/cache_hash.c

My understanding is, if the lookedup-object in the cache is expired, the
code seems to look if the object is busy or not and accordingly returns
HSH_EXPBUSY or HSH_BUSY.

lines 474 to 501 in cache_hash.c
    if (exp_oc != NULL && exp_oc->flags & OC_F_PASS) {
        wrk->stats->cache_hitmiss++;
        VSLb(req->vsl, SLT_HitMiss, "%u %.6f", ObjGetXID(wrk, exp_oc),
            EXP_Dttl(req, exp_oc));
        exp_oc = NULL;
        busy_found = 0;
    }

    if (exp_oc != NULL) {
        assert(oh->refcnt > 1);
        assert(exp_oc->objhead == oh);
        exp_oc->refcnt++;

        if (!busy_found) {
            *bocp = hsh_insert_busyobj(wrk, oh);
            retval = HSH_EXPBUSY;
        } else {
            AZ(req->hash_ignore_busy);
            retval = HSH_EXP;
        }
        if (exp_oc->hits < LONG_MAX)
            exp_oc->hits++;
        Lck_Unlock(&oh->mtx);
        if (retval == HSH_EXP)
            assert(HSH_DerefObjHead(wrk, &oh));
        *ocp = exp_oc;
        return (retval);
    }

    if (!busy_found) {
        /* Insert objcore in objecthead and release mutex */
        *bocp = hsh_insert_busyobj(wrk, oh);
        /* NB: no deref of objhead, new object inherits reference */
        Lck_Unlock(&oh->mtx);
        return (HSH_MISS);
    }


If busy, is the variable busy_found set to 0 or 1? For expired objects, it
looks like if it is not busy, then you set the return value to HSH_EXPBUSY,
shouldn't it be HSH_EXP? Can anyone help me understand this piece of code?
Because below, the code returns HSH_MISS

​Thanks,
Arvind
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