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

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Message-ID: <20180519211104.GB5488@localhost.localdomain>
Date:   Sat, 19 May 2018 18:11:04 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Vlad Buslov <vladbu@...lanox.com>, 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

On Mon, May 14, 2018 at 05:16:41PM +0200, Jiri Pirko wrote:
> 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".

Agreed. "rtnl_held" also removes the double negation, "!un...".