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net_sched: sch_fifo: implement lockless __fifo_dump()

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Instead of relying on RTNL, __fifo_dump() can use READ_ONCE()
annotations, paired with WRITE_ONCE() ones in __fifo_init().

Also add missing READ_ONCE(sh->limit) in bfifo_enqueue(),
pfifo_enqueue() and pfifo_tail_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 07:32:42 +00:00 committed by David S. Miller
parent c5f1dde7f7
commit 01daf66b79
1 changed files with 7 additions and 6 deletions
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13
net/sched/sch_fifo.c
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@ -19,7 +19,8 @@
static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <=
READ_ONCE(sch->limit)))
return qdisc_enqueue_tail(skb, sch);
return qdisc_drop(skb, sch, to_free);
@ -28,7 +29,7 @@ static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
if (likely(sch->q.qlen < sch->limit))
if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
return qdisc_enqueue_tail(skb, sch);
return qdisc_drop(skb, sch, to_free);
@ -39,7 +40,7 @@ static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
{
unsigned int prev_backlog;
if (likely(sch->q.qlen < sch->limit))
if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
return qdisc_enqueue_tail(skb, sch);
prev_backlog = sch->qstats.backlog;
@ -105,14 +106,14 @@ static int __fifo_init(struct Qdisc *sch, struct nlattr *opt,
if (is_bfifo)
limit *= psched_mtu(qdisc_dev(sch));
sch->limit = limit;
WRITE_ONCE(sch->limit, limit);
} else {
struct tc_fifo_qopt *ctl = nla_data(opt);
if (nla_len(opt) < sizeof(*ctl))
return -EINVAL;
sch->limit = ctl->limit;
WRITE_ONCE(sch->limit, ctl->limit);
}
if (is_bfifo)
@ -154,7 +155,7 @@ static void fifo_destroy(struct Qdisc *sch)
static int __fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct tc_fifo_qopt opt = { .limit = sch->limit };
struct tc_fifo_qopt opt = { .limit = READ_ONCE(sch->limit) };
if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
goto nla_put_failure;