fix wait bug:
fix wait bug:

(gdb) p now
$2 = {tv_sec = 1473956470, tv_usec = 167936}
(gdb) p bq->bq_expire
$3 = {tv_sec = 1473956470, tv_usec = 167827}
(gdb) p bq->bq_cnt
$4 = 2048
(gdb) p now
$5 = {tv_sec = 1473956470, tv_usec = 167936}
(gdb) p stall
$6 = {tv_sec = -1, tv_usec = 999891}
(gdb)

pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable