netdev - Re: [PATCH 04/14] net: sched: implement unlocked action init API

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Date:   Mon, 14 May 2018 17:16:41 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com,
        xiyou.wangcong@...il.com, pablo@...filter.org,
        kadlec@...ckhole.kfki.hu, fw@...len.de, ast@...nel.org,
        daniel@...earbox.net, edumazet@...gle.com, keescook@...omium.org,
        linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, kliteyn@...lanox.com
Subject: Re: [PATCH 04/14] net: sched: implement unlocked action init API

Mon, May 14, 2018 at 04:27:05PM CEST, vladbu@...lanox.com wrote:
>Add additional 'unlocked' argument to act API init functions.
>Argument is true when rtnl lock is not taken and false otherwise.
>It is required to implement actions that need to release rtnl lock before
>loading kernel module and reacquire if afterwards.
>
>Signed-off-by: Vlad Buslov <vladbu@...lanox.com>

[...]


>@@ -721,9 +722,11 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
> 	a_o = tc_lookup_action_n(act_name);
> 	if (a_o == NULL) {
> #ifdef CONFIG_MODULES
>-		rtnl_unlock();
>+		if (!unlocked)
>+			rtnl_unlock();
> 		request_module("act_%s", act_name);
>-		rtnl_lock();
>+		if (!unlocked)
>+			rtnl_lock();

Although I don't like this conditional locking scheme, I see no other
way to solve this :/ But I think would be better perhaps to rename
"unlocked" to something like "rtnl_held".

[...]