From c85cedb38f41bebc3da08c4a7bc58c5f62a2a950 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 18 Apr 2024 07:32:48 +0000 Subject: [PATCH] net_sched: sch_skbprio: implement lockless skbprio_dump() Instead of relying on RTNL, skbprio_dump() can use READ_ONCE() annotation, paired with WRITE_ONCE() one in skbprio_change(). Also add a READ_ONCE(sch->limit) in skbprio_enqueue(). Signed-off-by: Eric Dumazet Reviewed-by: Simon Horman Signed-off-by: David S. Miller --- net/sched/sch_skbprio.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/sched/sch_skbprio.c b/net/sched/sch_skbprio.c index b4dd626c309c..20ff7386b74b 100644 --- a/net/sched/sch_skbprio.c +++ b/net/sched/sch_skbprio.c @@ -79,7 +79,9 @@ static int skbprio_enqueue(struct sk_buff *skb, struct Qdisc *sch, prio = min(skb->priority, max_priority); qdisc = &q->qdiscs[prio]; - if (sch->q.qlen < sch->limit) { + + /* sch->limit can change under us from skbprio_change() */ + if (sch->q.qlen < READ_ONCE(sch->limit)) { __skb_queue_tail(qdisc, skb); qdisc_qstats_backlog_inc(sch, skb); q->qstats[prio].backlog += qdisc_pkt_len(skb); @@ -172,7 +174,7 @@ static int skbprio_change(struct Qdisc *sch, struct nlattr *opt, if (opt->nla_len != nla_attr_size(sizeof(*ctl))) return -EINVAL; - sch->limit = ctl->limit; + WRITE_ONCE(sch->limit, ctl->limit); return 0; } @@ -200,7 +202,7 @@ static int skbprio_dump(struct Qdisc *sch, struct sk_buff *skb) { struct tc_skbprio_qopt opt; - opt.limit = sch->limit; + opt.limit = READ_ONCE(sch->limit); if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt)) return -1;