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Message-ID: <20240415132054.3822230-15-edumazet@google.com>
Date: Mon, 15 Apr 2024 13:20:54 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 14/14] 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 <edumazet@...gle.com>
---
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 b4dd626c309c36725e6030a338d21d1fabcb6704..20ff7386b74bd89c00b50a8f0def91b6c5cce7f4 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;
--
2.44.0.683.g7961c838ac-goog
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