net-sched: When TX over-limit happens on netdev, what does kernel do?

Hi,

Could anybody tell me when TX over-limit happens on netdev, what does kernel do?
Is skb buffered in Qdisc->q and the sending process keeps running?
Or we block the sending process and make it scheduled?

Found some code in net/sched/sch_cbq.c
cbq_dequeue(struct Qdisc *sch) --> qdisc_watchdog_schedule(),  so I
guess the skb is buffered in Qdisc, but what about sending process?


Thanks and regards,
pingfan