From f83e07b29246f468bc7c99f98ca1897843fa8167 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 4 May 2026 16:38:42 +0000 Subject: net/sched: sch_fq_codel: annotate data-races from fq_codel_dump_class_stats() fq_codel_dump_class_stats() acquires qdisc spinlock only when requested to follow flow->head chain. As we did in sch_cake recently, add the missing READ_ONCE()/WRITE_ONCE() annotations. Fixes: edb09eb17ed8 ("net: sched: do not acquire qdisc spinlock in qdisc/class stats dump") Signed-off-by: Eric Dumazet Reviewed-by: Jamal Hadi Salim Link: https://patch.msgid.link/20260504163842.1162001-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/sched/sch_fq_codel.c | 39 ++++++++++++++++++++------------------- 1 file changed, 20 insertions(+), 19 deletions(-) diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c index 0664b2f2d6f2..24db54684e8a 100644 --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -117,7 +117,7 @@ static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow) { struct sk_buff *skb = flow->head; - flow->head = skb->next; + WRITE_ONCE(flow->head, skb->next); skb_mark_not_on_list(skb); return skb; } @@ -127,7 +127,7 @@ static inline void flow_queue_add(struct fq_codel_flow *flow, struct sk_buff *skb) { if (flow->head == NULL) - flow->head = skb; + WRITE_ONCE(flow->head, skb); else flow->tail->next = skb; flow->tail = skb; @@ -173,8 +173,8 @@ static unsigned int fq_codel_drop(struct Qdisc *sch, unsigned int max_packets, } while (++i < max_packets && len < threshold); /* Tell codel to increase its signal strength also */ - flow->cvars.count += i; - q->backlogs[idx] -= len; + WRITE_ONCE(flow->cvars.count, flow->cvars.count + i); + WRITE_ONCE(q->backlogs[idx], q->backlogs[idx] - len); q->memory_usage -= mem; sch->qstats.drops += i; sch->qstats.backlog -= len; @@ -204,13 +204,13 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch, codel_set_enqueue_time(skb); flow = &q->flows[idx]; flow_queue_add(flow, skb); - q->backlogs[idx] += qdisc_pkt_len(skb); + WRITE_ONCE(q->backlogs[idx], q->backlogs[idx] + qdisc_pkt_len(skb)); qdisc_qstats_backlog_inc(sch, skb); if (list_empty(&flow->flowchain)) { list_add_tail(&flow->flowchain, &q->new_flows); q->new_flow_count++; - flow->deficit = q->quantum; + WRITE_ONCE(flow->deficit, q->quantum); } get_codel_cb(skb)->mem_usage = skb->truesize; q->memory_usage += get_codel_cb(skb)->mem_usage; @@ -263,7 +263,8 @@ static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx) flow = container_of(vars, struct fq_codel_flow, cvars); if (flow->head) { skb = dequeue_head(flow); - q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb); + WRITE_ONCE(q->backlogs[flow - q->flows], + q->backlogs[flow - q->flows] - qdisc_pkt_len(skb)); q->memory_usage -= get_codel_cb(skb)->mem_usage; sch->q.qlen--; sch->qstats.backlog -= qdisc_pkt_len(skb); @@ -296,7 +297,7 @@ begin: flow = list_first_entry(head, struct fq_codel_flow, flowchain); if (flow->deficit <= 0) { - flow->deficit += q->quantum; + WRITE_ONCE(flow->deficit, flow->deficit + q->quantum); list_move_tail(&flow->flowchain, &q->old_flows); goto begin; } @@ -314,7 +315,7 @@ begin: goto begin; } qdisc_bstats_update(sch, skb); - flow->deficit -= qdisc_pkt_len(skb); + WRITE_ONCE(flow->deficit, flow->deficit - qdisc_pkt_len(skb)); if (q->cstats.drop_count) { qdisc_tree_reduce_backlog(sch, q->cstats.drop_count, @@ -328,7 +329,7 @@ begin: static void fq_codel_flow_purge(struct fq_codel_flow *flow) { rtnl_kfree_skbs(flow->head, flow->tail); - flow->head = NULL; + WRITE_ONCE(flow->head, NULL); } static void fq_codel_reset(struct Qdisc *sch) @@ -656,21 +657,21 @@ static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl, memset(&xstats, 0, sizeof(xstats)); xstats.type = TCA_FQ_CODEL_XSTATS_CLASS; - xstats.class_stats.deficit = flow->deficit; + xstats.class_stats.deficit = READ_ONCE(flow->deficit); xstats.class_stats.ldelay = - codel_time_to_us(flow->cvars.ldelay); - xstats.class_stats.count = flow->cvars.count; - xstats.class_stats.lastcount = flow->cvars.lastcount; - xstats.class_stats.dropping = flow->cvars.dropping; - if (flow->cvars.dropping) { - codel_tdiff_t delta = flow->cvars.drop_next - + codel_time_to_us(READ_ONCE(flow->cvars.ldelay)); + xstats.class_stats.count = READ_ONCE(flow->cvars.count); + xstats.class_stats.lastcount = READ_ONCE(flow->cvars.lastcount); + xstats.class_stats.dropping = READ_ONCE(flow->cvars.dropping); + if (xstats.class_stats.dropping) { + codel_tdiff_t delta = READ_ONCE(flow->cvars.drop_next) - codel_get_time(); xstats.class_stats.drop_next = (delta >= 0) ? codel_time_to_us(delta) : -codel_time_to_us(-delta); } - if (flow->head) { + if (READ_ONCE(flow->head)) { sch_tree_lock(sch); skb = flow->head; while (skb) { @@ -679,7 +680,7 @@ static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl, } sch_tree_unlock(sch); } - qs.backlog = q->backlogs[idx]; + qs.backlog = READ_ONCE(q->backlogs[idx]); qs.drops = 0; } if (gnet_stats_copy_queue(d, NULL, &qs, qs.qlen) < 0) -- cgit v1.2.3