[PATCH v3 net-next 12/15] net/sched: sch_choke: annotate data-races in choke_dump_stats()

Eric Dumazet
2026-04-10T18:23:27Z

choke_dump_stats() only runs with RTNL held,
reading fields that can be changed in qdisc fast path.

Add READ_ONCE()/WRITE_ONCE() annotations.

Fixes: edb09eb17ed8 ("net: sched: do not acquire qdisc spinlock in qdisc/class stats dump")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/sched/sch_choke.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c
index cd0785ad8e74314e6d5c88144ffcf64f286e02dd..73d3e673dc7b16cf2b9ac1d622da280c2ceb064a 100644
--- a/net/sched/sch_choke.c
+++ b/net/sched/sch_choke.c
@@ -229,7 +229,7 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch,

/* Draw a packet at random from queue and compare flow */
if (choke_match_random(q, skb, &idx)) {
- q->stats.matched++;
+ WRITE_ONCE(q->stats.matched, q->stats.matched + 1);
choke_drop_by_idx(sch, idx, to_free);
goto congestion_drop;
}
@@ -241,11 +241,13 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch,
qdisc_qstats_overlimit(sch);
if (use_harddrop(q) || !use_ecn(q) ||
!INET_ECN_set_ce(skb)) {
- q->stats.forced_drop++;
+ WRITE_ONCE(q->stats.forced_drop,
+ q->stats.forced_drop + 1);
goto congestion_drop;
}

- q->stats.forced_mark++;
+ WRITE_ONCE(q->stats.forced_mark,
+ q->stats.forced_mark + 1);
} else if (++q->vars.qcount) {
if (red_mark_probability(p, &q->vars, q->vars.qavg)) {
q->vars.qcount = 0;
@@ -253,11 +255,13 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch,

qdisc_qstats_overlimit(sch);
if (!use_ecn(q) || !INET_ECN_set_ce(skb)) {
- q->stats.prob_drop++;
+ WRITE_ONCE(q->stats.prob_drop,
+ q->stats.prob_drop + 1);
goto congestion_drop;
}

- q->stats.prob_mark++;
+ WRITE_ONCE(q->stats.prob_mark,
+ q->stats.prob_mark + 1);
}
} else
q->vars.qR = red_random(p);
@@ -272,7 +276,7 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch,
return NET_XMIT_SUCCESS;
}

- q->stats.pdrop++;
+ WRITE_ONCE(q->stats.pdrop, q->stats.pdrop + 1);
return qdisc_drop(skb, sch, to_free);

congestion_drop:
@@ -461,10 +465,12 @@ static int choke_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
{
struct choke_sched_data *q = qdisc_priv(sch);
struct tc_choke_xstats st = {
- .early = q->stats.prob_drop + q->stats.forced_drop,
- .marked = q->stats.prob_mark + q->stats.forced_mark,
- .pdrop = q->stats.pdrop,
- .matched = q->stats.matched,
+ .early = READ_ONCE(q->stats.prob_drop) +
+ READ_ONCE(q->stats.forced_drop),
+ .marked = READ_ONCE(q->stats.prob_mark) +
+ READ_ONCE(q->stats.forced_mark),
+ .pdrop = READ_ONCE(q->stats.pdrop),
+ .matched = READ_ONCE(q->stats.matched),
};

return gnet_stats_copy_app(d, &st, sizeof(st));
--
2.53.0.1213.gd9a14994de-goog