On 2020/11/5 14:16, Cong Wang wrote: > On Wed, Nov 4, 2020 at 10:04 PM Cong Wang <xiyou.wangc...@gmail.com> wrote: >> >> On Mon, Nov 2, 2020 at 11:24 PM Yunsheng Lin <linyunsh...@huawei.com> wrote: >>>>> From my understanding, we can do anything about the old qdisc (including >>>>> destorying the old qdisc) after some_qdisc_is_busy() return false. >>>> >>>> But the current code does the reset _before_ some_qdisc_is_busy(). ;) >>> >>> If lock is taken when doing reset, it does not matter if the reset is >>> before some_qdisc_is_busy(), right? >> >> Why not? How about the following scenario? >> >> CPU0: CPU1: >> dev_reset_queue() >> net_tx_action() >> -> sch_direct_xmit() >> -> dev_requeue_skb() >> some_qdisc_is_busy() >> // waiting for TX action on CPU1 >> // now some packets are requeued > > Never mind, the skb_bad_txq is also cleared by dev_reset_queue(). > TX action after resetting should get NULL.
Yes, maybe it is safe to remove qdisc_reset() now? or issue a warning if there are still skb in the qdisc. > > Thanks. > . >
