[PATCH v3 net-next 10/15] net/sched: sch_fq_pie: annotate data-races in fq_pie_dump_stats()

Eric Dumazet
2026-04-10T18:31:47Z

fq_codel_dump_stats() acquires the qdisc spinlock a bit too late.

Move this acquisition before we fill tc_fq_pie_xstats with live data.

Alternative would be to add READ_ONCE() and WRITE_ONCE() annotations,
but the spinlock is needed anyway.

Fixes: ec97ecf1ebe4 ("net: sched: add Flow Queue PIE packet scheduler")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/sched/sch_fq_pie.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c
index 197f0df0a6eb06ab4ce25eefe01d32a35dbd84af..72f48fa4010bebbe6be212938b457db21ff3c5a0 100644
--- a/net/sched/sch_fq_pie.c
+++ b/net/sched/sch_fq_pie.c
@@ -509,18 +509,19 @@ static int fq_pie_dump(struct Qdisc *sch, struct sk_buff *skb)
static int fq_pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
{
struct fq_pie_sched_data *q = qdisc_priv(sch);
- struct tc_fq_pie_xstats st = {
- .packets_in = q->stats.packets_in,
- .overlimit = q->stats.overlimit,
- .overmemory = q->overmemory,
- .dropped = q->stats.dropped,
- .ecn_mark = q->stats.ecn_mark,
- .new_flow_count = q->new_flow_count,
- .memory_usage = q->memory_usage,
- };
+ struct tc_fq_pie_xstats st = { 0 };
struct list_head *pos;

sch_tree_lock(sch);
+
+ st.packets_in = q->stats.packets_in;
+ st.overlimit = q->stats.overlimit;
+ st.overmemory = q->overmemory;
+ st.dropped = q->stats.dropped;
+ st.ecn_mark = q->stats.ecn_mark;
+ st.new_flow_count = q->new_flow_count;
+ st.memory_usage = q->memory_usage;
+
list_for_each(pos, &q->new_flows)
st.new_flows_len++;

--
2.53.0.1213.gd9a14994de-goog