[PATCH 6.6 1383/1674] net_sched: sch_fifo: implement lockless __fifo_dump()
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COOLING5d
REVIEWED: 1 (1M)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2026-10-17 17:59:08
Also in:
linux-patches
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
1 review trailer (1 from subsystem maintainers).
6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <redacted>
[ Upstream commit 01daf66b791e1ddd1a4aae2a65ea65fa1d4a96ef ]
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 <redacted>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 4c660ee8c809 ("net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/sch_fifo.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/net/sched/sch_fifo.c b/net/sched/sch_fifo.c
index 1080d89f91780..ded0eac944068 100644
--- a/net/sched/sch_fifo.c
+++ b/net/sched/sch_fifo.c@@ -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);
@@ -38,11 +39,12 @@ static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) { unsigned int prev_backlog; + u32 limit = READ_ONCE(sch->limit); - if (unlikely(sch->limit == 0)) + if (unlikely(limit == 0)) return qdisc_drop(skb, sch, to_free); - if (likely(sch->q.qlen < sch->limit)) + if (likely(sch->q.qlen < limit)) return qdisc_enqueue_tail(skb, sch); prev_backlog = sch->qstats.backlog;
@@ -108,14 +110,14 @@ 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)
@@ -157,7 +159,7 @@ 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;
--
2.53.0