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net_sched: sch_skbprio: implement lockless skbprio_dump()

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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@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2024-04-18 07:32:48 +00:00 committed by David S. Miller
parent 6c00dc4fdb
commit c85cedb38f
1 changed files with 5 additions and 3 deletions
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8
net/sched/sch_skbprio.c
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@ -79,7 +79,9 @@ static int skbprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
prio = min(skb->priority, max_priority); prio = min(skb->priority, max_priority);
qdisc = &q->qdiscs[prio]; 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); __skb_queue_tail(qdisc, skb);
qdisc_qstats_backlog_inc(sch, skb); qdisc_qstats_backlog_inc(sch, skb);
q->qstats[prio].backlog += qdisc_pkt_len(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))) if (opt->nla_len != nla_attr_size(sizeof(*ctl)))
return -EINVAL; return -EINVAL;
sch->limit = ctl->limit; WRITE_ONCE(sch->limit, ctl->limit);
return 0; return 0;
} }
@ -200,7 +202,7 @@ static int skbprio_dump(struct Qdisc *sch, struct sk_buff *skb)
{ {
struct tc_skbprio_qopt opt; struct tc_skbprio_qopt opt;
opt.limit = sch->limit; opt.limit = READ_ONCE(sch->limit);
if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt)) if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
return -1; return -1;