hash: New HSH_Replace() function

bin/varnishd/cache/cache_fetch.c

@@ -756,7 +756,7 @@ vbf_stp_fetchend(struct worker *wrk, struct busyobj *bo)
 		VSL(SLT_ExpKill, NO_VXID, "VBF_Superseded x=%ju n=%ju",
 		    VXID(ObjGetXID(wrk, bo->stale_oc)),
 		    VXID(ObjGetXID(wrk, bo->fetch_objcore)));
-		HSH_Kill(bo->stale_oc);
+		HSH_Replace(bo->stale_oc, bo->fetch_objcore);
 	}
 	return (F_STP_DONE);
 }

bin/varnishd/cache/cache_hash.c

@@ -911,15 +911,26 @@ HSH_Unbusy(struct worker *wrk, struct objcore *oc)
 
 void
 HSH_Kill(struct objcore *oc)
+{
+
+	HSH_Replace(oc, NULL);
+}
+
+void
+HSH_Replace(struct objcore *oc, const struct objcore *new_oc)
 {
 
 	CHECK_OBJ_NOTNULL(oc, OBJCORE_MAGIC);
 	CHECK_OBJ_NOTNULL(oc->objhead, OBJHEAD_MAGIC);
+	if (new_oc != NULL) {
+		CHECK_OBJ(new_oc, OBJCORE_MAGIC);
+		assert(oc->objhead == new_oc->objhead);
+	}
 
 	Lck_Lock(&oc->objhead->mtx);
 	oc->flags |= OC_F_DYING;
 	Lck_Unlock(&oc->objhead->mtx);
-	EXP_Remove(oc, NULL);
+	EXP_Remove(oc, new_oc);
 }
 
 /*====================================================================

bin/varnishd/cache/cache_objhead.h

@@ -67,6 +67,7 @@ enum lookup_e {
 
 void HSH_Fail(struct objcore *);
 void HSH_Kill(struct objcore *);
+void HSH_Replace(struct objcore *, const struct objcore *);
 void HSH_Insert(struct worker *, const void *hash, struct objcore *,
     struct ban *);
 void HSH_Unbusy(struct worker *, struct objcore *);

bin/varnishtest/tests/b00039.vtc

@@ -67,3 +67,5 @@ client c1 {
 } -run
 
 logexpect l1 -wait
+
+varnish v1 -expect MAIN.n_superseded == 2