From a17ef9e6c2c1cf0fc6cd6ca6a9ce525c67d1da7f Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Tue, 30 Apr 2024 18:00:15 +0000
Subject: [PATCH] net_sched: sch_sfq: annotate data-races around
q->perturb_period
sfq_perturbation() reads q->perturb_period locklessly.
Add annotations to fix potential issues.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240430180015.3111398-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
net/sched/sch_sfq.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index e66f4afb920d2..3b9245a3c767a 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -608,6 +608,7 @@ static void sfq_perturbation(struct timer_list *t)
struct Qdisc *sch = q->sch;
spinlock_t *root_lock;
siphash_key_t nkey;
+ int period;
get_random_bytes(&nkey, sizeof(nkey));
rcu_read_lock();
@@ -618,8 +619,12 @@ static void sfq_perturbation(struct timer_list *t)
sfq_rehash(sch);
spin_unlock(root_lock);
- if (q->perturb_period)
- mod_timer(&q->perturb_timer, jiffies + q->perturb_period);
+ /* q->perturb_period can change under us from
+ * sfq_change() and sfq_destroy().
+ */
+ period = READ_ONCE(q->perturb_period);
+ if (period)
+ mod_timer(&q->perturb_timer, jiffies + period);
rcu_read_unlock();
}
@@ -662,7 +667,7 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
q->quantum = ctl->quantum;
q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
}
- q->perturb_period = ctl->perturb_period * HZ;
+ WRITE_ONCE(q->perturb_period, ctl->perturb_period * HZ);
if (ctl->flows)
q->maxflows = min_t(u32, ctl->flows, SFQ_MAX_FLOWS);
if (ctl->divisor) {
@@ -724,7 +729,7 @@ static void sfq_destroy(struct Qdisc *sch)
struct sfq_sched_data *q = qdisc_priv(sch);
tcf_block_put(q->block);
- q->perturb_period = 0;
+ WRITE_ONCE(q->perturb_period, 0);
del_timer_sync(&q->perturb_timer);
sfq_free(q->ht);
sfq_free(q->slots);
--
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