Re: Packet gets stuck in NOLOCK pfifo_fast qdisc

[Cong Wang]

Hello, Kehuan

Can you test the attached one-line fix? I think we are overthinking,
probably all
we need here is a busy wait.

Thanks.

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index d60e7c39d60c..fc1bacdb102b 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -156,8 +156,7 @@ static inline bool qdisc_is_empty(const struct Qdisc *qdisc)
 static inline bool qdisc_run_begin(struct Qdisc *qdisc)
 {
 	if (qdisc->flags & TCQ_F_NOLOCK) {
-		if (!spin_trylock(&qdisc->seqlock))
-			return false;
+		spin_lock(&qdisc->seqlock);
 		WRITE_ONCE(qdisc->empty, false);
 	} else if (qdisc_is_running(qdisc)) {
 		return false;