linux-kernel - Re: [PATCH v5 net-next 01/15] net: bridge: mst: Multiple Spanning Tree (MST) mode

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Message-ID: <20230109100236.euq7iaaorqxrun7u@skbuf>
Date:   Mon, 9 Jan 2023 12:02:36 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     Tobias Waldekranz <tobias@...dekranz.com>, davem@...emloft.net,
        kuba@...nel.org, Nikolay Aleksandrov <razor@...ckwall.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Russell King <linux@...linux.org.uk>,
        Petr Machata <petrm@...dia.com>,
        Ido Schimmel <idosch@...dia.com>,
        Matt Johnston <matt@...econstruct.com.au>,
        Cooper Lees <me@...perlees.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH v5 net-next 01/15] net: bridge: mst: Multiple Spanning
 Tree (MST) mode

Hi Ido,

On Mon, Jan 09, 2023 at 10:05:53AM +0200, Ido Schimmel wrote:
> > +	if (on)
> > +		static_branch_enable(&br_mst_used);
> > +	else
> > +		static_branch_disable(&br_mst_used);
> 
> Hi,
> 
> I'm not actually using MST, but I ran into this code and was wondering
> if the static key usage is correct. The static key is global (not
> per-bridge), so what happens when two bridges have MST enabled and then
> it is disabled on one? I believe it would be disabled for both. If so,
> maybe use static_branch_inc() / static_branch_dec() instead?

Sounds about right. FWIW, br_switchdev_tx_fwd_offload does use
static_branch_inc() / static_branch_dec().