On Thu, 13 May 2021 09:11:00 +0800 Yunsheng Lin wrote:
The netdev qeueue might be stopped when byte queue limit has reached or tx hw ring is full, net_tx_action() may still be rescheduled endlessly if STATE_MISSED is set, which consumes a lot of cpu without dequeuing and transmiting any skb because the netdev queue is stopped, see qdisc_run_end().
This patch fixes it by checking the netdev queue state before calling qdisc_run() and clearing STATE_MISSED if netdev queue is stopped during qdisc_run(), the net_tx_action() is recheduled again when netdev qeueue is restarted, see netif_tx_wake_queue().
As there is time window betewwn netif_xmit_frozen_or_stopped() checking and STATE_MISSED clearing, between which STATE_MISSED is set by net_tx_action() scheduled by netif_tx_wake_queue(), so set the STATE_MISSED again if netdev queue is restarted.
Fixes: 6b3ba9146fe6 ("net: sched: allow qdiscs to handle locking") Reported-by: Michal Kubecek mkubecek@suse.cz Signed-off-by: Yunsheng Lin linyunsheng@huawei.com
@@ -35,6 +35,25 @@ const struct Qdisc_ops *default_qdisc_ops = &pfifo_fast_ops; EXPORT_SYMBOL(default_qdisc_ops);
+static void qdisc_maybe_stop_tx(struct Qdisc *q,
nit: qdisc_maybe_clear_missed()?