linux-kernel - Re: [PATCH net v3 4/7] net/sched: act

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Message-ID: <1f63d057-ce11-4fdf-b9d4-7022ec356377@mojatatu.com>
Date: Wed, 21 Jan 2026 16:44:25 -0300
From: Victor Nogueira <victor@...atatu.com>
To: Paul Moses <p@....org>, netdev@...r.kernel.org
Cc: Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang
 <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH net v3 4/7] net/sched: act_gate: read schedule via RCU

On 21/01/2026 10:20, Paul Moses wrote:
> Switch dump/accessor reads to RCU read-side sections. This matches other
> actions that read params under rcu_read_lock(), e.g. act_tunnel_key dump
> (commit e97ae742972f6c), act_ctinfo dump (commit 799c94178cf9c9), and
> act_skbedit dump (commit 1f376373bd225c).
> 
> Dump reads tcf_action via READ_ONCE, following the lockless action reads used
> in act_sample (commit 5c5670fae43027) and act_gact.
> 
> Timer logic stays under tcf_lock and uses rcu_dereference_protected(), keeping
> RCU readers cheap while preserving lock-serialized timer updates.
> 
> diff --git a/include/net/tc_act/tc_gate.h b/include/net/tc_act/tc_gate.h
> index 05968b3822392..9587d9e9fa38f 100644
> --- a/include/net/tc_act/tc_gate.h
> +++ b/include/net/tc_act/tc_gate.h
> @@ -57,9 +57,10 @@ static inline s32 tcf_gate_prio(const struct tc_action *a)
>   	s32 tcfg_prio;
>   	struct tcf_gate_params *p;
>   
> -	p = rcu_dereference_protected(to_gate(a)->param,
> -				      lockdep_rtnl_is_held());
> +	rcu_read_lock();
> +	p = rcu_dereference(to_gate(a)->param);
>   	tcfg_prio = p->tcfg_priority;
> +	rcu_read_unlock();

These helper functions are called with the tcf_lock acquired, so you
don't need rcu_read_lock here. You can just do:

p = rcu_dereference_protected(to_gate(a)->param,
			      lockdep_is_held(&gact->tcf_lock));

cheers,
Victor