net/sched: sch_cake: annotate data-races in cake_dump_stats() (III)

cake_dump_stats() runs without qdisc spinlock being held.

In this third patch, I add READ_ONCE()/WRITE_ONCE() annotations
for the following fields:

- packets
- tin_dropped
- tin_ecn_mark
- ack_drops
- peak_delay
- avge_delay
- base_delay

Other annotations are added in following patches, to ease code review.

Fixes: 046f6fd5daef ("sched: Add Common Applications Kept Enhanced (cake) qdisc")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: "Toke Høiland-Jørgensen" <toke@toke.dk>
Link: https://patch.msgid.link/20260427083606.459355-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index d7465ee4c5507467effd5aaaf8cfd05bcafde2cf..c5aae31565e984e40937b55201b498174a37180e 100644 (file)
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -1600,7 +1600,7 @@ static unsigned int cake_drop(struct Qdisc *sch, struct sk_buff **to_free)
        sch->qstats.backlog -= len;
 
        flow->dropped++;
-       b->tin_dropped++;
+       WRITE_ONCE(b->tin_dropped, b->tin_dropped + 1);
 
        if (q->config->rate_flags & CAKE_FLAG_INGRESS)
                cake_advance_shaper(q, b, skb, now, true);
@@ -1820,7 +1820,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                        numsegs++;
                        slen += segs->len;
                        q->buffer_used += segs->truesize;
-                       b->packets++;
+                       WRITE_ONCE(b->packets, b->packets + 1);
                }
 
                /* stats */
@@ -1844,7 +1844,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                        ack = cake_ack_filter(q, flow);
 
                if (ack) {
-                       b->ack_drops++;
+                       WRITE_ONCE(b->ack_drops, b->ack_drops + 1);
                        sch->qstats.drops++;
                        ack_pkt_len = qdisc_pkt_len(ack);
                        b->bytes += ack_pkt_len;
@@ -1860,7 +1860,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                }
 
                /* stats */
-               b->packets++;
+               WRITE_ONCE(b->packets, b->packets + 1);
                b->bytes            += len - ack_pkt_len;
                b->backlogs[idx]    += len - ack_pkt_len;
                b->tin_backlog      += len - ack_pkt_len;
@@ -2236,7 +2236,7 @@ retry:
                        b->tin_deficit -= len;
                }
                flow->dropped++;
-               b->tin_dropped++;
+               WRITE_ONCE(b->tin_dropped, b->tin_dropped + 1);
                qdisc_tree_reduce_backlog(sch, 1, qdisc_pkt_len(skb));
                qdisc_qstats_drop(sch);
                qdisc_dequeue_drop(sch, skb, reason);
@@ -2244,17 +2244,19 @@ retry:
                        goto retry;
        }
 
-       b->tin_ecn_mark += !!flow->cvars.ecn_marked;
+       WRITE_ONCE(b->tin_ecn_mark, b->tin_ecn_mark + !!flow->cvars.ecn_marked);
        qdisc_bstats_update(sch, skb);
        WRITE_ONCE(q->last_active, now);
 
        /* collect delay stats */
        delay = ktime_to_ns(ktime_sub(now, cobalt_get_enqueue_time(skb)));
-       b->avge_delay = cake_ewma(b->avge_delay, delay, 8);
-       b->peak_delay = cake_ewma(b->peak_delay, delay,
-                                 delay > b->peak_delay ? 2 : 8);
-       b->base_delay = cake_ewma(b->base_delay, delay,
-                                 delay < b->base_delay ? 2 : 8);
+       WRITE_ONCE(b->avge_delay, cake_ewma(b->avge_delay, delay, 8));
+       WRITE_ONCE(b->peak_delay,
+                  cake_ewma(b->peak_delay, delay,
+                            delay > b->peak_delay ? 2 : 8));
+       WRITE_ONCE(b->base_delay,
+                  cake_ewma(b->base_delay, delay,
+                            delay < b->base_delay ? 2 : 8));
 
        len = cake_advance_shaper(q, b, skb, now, false);
        flow->deficit -= len;
@@ -3042,17 +3044,17 @@ static int cake_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
                PUT_TSTAT_U32(INTERVAL_US,
                              ktime_to_us(ns_to_ktime(b->cparams.interval)));
 
-               PUT_TSTAT_U32(SENT_PACKETS, b->packets);
-               PUT_TSTAT_U32(DROPPED_PACKETS, b->tin_dropped);
-               PUT_TSTAT_U32(ECN_MARKED_PACKETS, b->tin_ecn_mark);
-               PUT_TSTAT_U32(ACKS_DROPPED_PACKETS, b->ack_drops);
+               PUT_TSTAT_U32(SENT_PACKETS, READ_ONCE(b->packets));
+               PUT_TSTAT_U32(DROPPED_PACKETS, READ_ONCE(b->tin_dropped));
+               PUT_TSTAT_U32(ECN_MARKED_PACKETS, READ_ONCE(b->tin_ecn_mark));
+               PUT_TSTAT_U32(ACKS_DROPPED_PACKETS, READ_ONCE(b->ack_drops));
 
                PUT_TSTAT_U32(PEAK_DELAY_US,
-                             ktime_to_us(ns_to_ktime(b->peak_delay)));
+                             ktime_to_us(ns_to_ktime(READ_ONCE(b->peak_delay))));
                PUT_TSTAT_U32(AVG_DELAY_US,
-                             ktime_to_us(ns_to_ktime(b->avge_delay)));
+                             ktime_to_us(ns_to_ktime(READ_ONCE(b->avge_delay))));
                PUT_TSTAT_U32(BASE_DELAY_US,
-                             ktime_to_us(ns_to_ktime(b->base_delay)));
+                             ktime_to_us(ns_to_ktime(READ_ONCE(b->base_delay))));
 
                PUT_TSTAT_U32(WAY_INDIRECT_HITS, READ_ONCE(b->way_hits));
                PUT_TSTAT_U32(WAY_MISSES, READ_ONCE(b->way_misses));