netdev - [RFC PATCH net-next 02/15] net/sched: taprio: continue with other TXQs if one dequeue() failed

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Date:   Sat, 28 Jan 2023 03:07:06 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Kurt Kanzenbach <kurt@...utronix.de>
Subject: [RFC PATCH net-next 02/15] net/sched: taprio: continue with other TXQs if one dequeue() failed

This changes the handling of an unlikely condition to not stop dequeuing
if taprio failed to dequeue the peeked skb in taprio_dequeue().

I've no idea when this can happen, but the only side effect seems to be
that the atomic_sub_return() call right above will have consumed some
budget. This isn't a big deal, since either that made us remain without
any budget (and therefore, we'd exit on the next peeked skb anyway), or
we could send some packets from other TXQs.

I'm making this change because in a future patch I'll be refactoring the
dequeue procedure to simplify it, and this corner case will have to go
away.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 net/sched/sch_taprio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 375f445c1cfb..1504fdae723f 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -585,7 +585,7 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch)

 		skb = child->ops->dequeue(child);
 		if (unlikely(!skb))
-			goto done;
+			continue;

 skb_found:
 		qdisc_bstats_update(sch, skb);
-- 
2.34.1