netdev - [PATCH v2 net-next 10/11] net_sched: act_police: use RCU in tcf_police

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Message-ID: <20250709090204.797558-11-edumazet@google.com>
Date: Wed,  9 Jul 2025 09:02:02 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Jamal Hadi Salim <jhs@...atatu.com>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 10/11] net_sched: act_police: use RCU in tcf_police_dump()

Also storing tcf_action into struct tcf_police_params
makes sure there is no discrepancy in tcf_police_act().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tc_act/tc_police.h |  3 ++-
 net/sched/act_police.c         | 18 +++++++++---------
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/net/tc_act/tc_police.h b/include/net/tc_act/tc_police.h
index 490d88cb52338592f57e43fb79d1c6955a9684eb..a89fc8e68b1e4343bb3f6ecfc06737ebbc385f0c 100644
--- a/include/net/tc_act/tc_police.h
+++ b/include/net/tc_act/tc_police.h
@@ -5,10 +5,11 @@
 #include <net/act_api.h>
 
 struct tcf_police_params {
+	int			action;
 	int			tcfp_result;
 	u32			tcfp_ewma_rate;
-	s64			tcfp_burst;
 	u32			tcfp_mtu;
+	s64			tcfp_burst;
 	s64			tcfp_mtu_ptoks;
 	s64			tcfp_pkt_burst;
 	struct psched_ratecfg	rate;
diff --git a/net/sched/act_police.c b/net/sched/act_police.c
index a214ed68114206ed0770725ab91d867bab35aa09..0e1c611833790b4b1d941faf0a05ef1bde2adcb9 100644
--- a/net/sched/act_police.c
+++ b/net/sched/act_police.c
@@ -198,6 +198,7 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
 		psched_ppscfg_precompute(&new->ppsrate, pps);
 	}
 
+	new->action = parm->action;
 	spin_lock_bh(&police->tcf_lock);
 	spin_lock_bh(&police->tcfp_lock);
 	police->tcfp_t_c = ktime_get_ns();
@@ -254,8 +255,8 @@ TC_INDIRECT_SCOPE int tcf_police_act(struct sk_buff *skb,
 	tcf_lastuse_update(&police->tcf_tm);
 	bstats_update(this_cpu_ptr(police->common.cpu_bstats), skb);
 
-	ret = READ_ONCE(police->tcf_action);
 	p = rcu_dereference_bh(police->params);
+	ret = p->action;
 
 	if (p->tcfp_ewma_rate) {
 		struct gnet_stats_rate_est64 sample;
@@ -338,9 +339,9 @@ static void tcf_police_stats_update(struct tc_action *a,
 static int tcf_police_dump(struct sk_buff *skb, struct tc_action *a,
 			       int bind, int ref)
 {
+	const struct tcf_police *police = to_police(a);
 	unsigned char *b = skb_tail_pointer(skb);
-	struct tcf_police *police = to_police(a);
-	struct tcf_police_params *p;
+	const struct tcf_police_params *p;
 	struct tc_police opt = {
 		.index = police->tcf_index,
 		.refcnt = refcount_read(&police->tcf_refcnt) - ref,
@@ -348,10 +349,9 @@ static int tcf_police_dump(struct sk_buff *skb, struct tc_action *a,
 	};
 	struct tcf_t t;
 
-	spin_lock_bh(&police->tcf_lock);
-	opt.action = police->tcf_action;
-	p = rcu_dereference_protected(police->params,
-				      lockdep_is_held(&police->tcf_lock));
+	rcu_read_lock();
+	p = rcu_dereference(police->params);
+	opt.action = p->action;
 	opt.mtu = p->tcfp_mtu;
 	opt.burst = PSCHED_NS2TICKS(p->tcfp_burst);
 	if (p->rate_present) {
@@ -392,12 +392,12 @@ static int tcf_police_dump(struct sk_buff *skb, struct tc_action *a,
 	tcf_tm_dump(&t, &police->tcf_tm);
 	if (nla_put_64bit(skb, TCA_POLICE_TM, sizeof(t), &t, TCA_POLICE_PAD))
 		goto nla_put_failure;
-	spin_unlock_bh(&police->tcf_lock);
+	rcu_read_unlock();
 
 	return skb->len;
 
 nla_put_failure:
-	spin_unlock_bh(&police->tcf_lock);
+	rcu_read_unlock();
 	nlmsg_trim(skb, b);
 	return -1;
 }
-- 
2.50.0.727.gbf7dc18ff4-goog