linux-kernel - Re: [PATCH net 1/3] net: mscc: ocelot: extend ocelot->fwd_domain_lock to cover ocelot->tas

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Message-ID: <ZK2JxXusoKjkZq2m@corigine.com>
Date:   Tue, 11 Jul 2023 17:56:37 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/3] net: mscc: ocelot: extend
 ocelot->fwd_domain_lock to cover ocelot->tas_lock

On Wed, Jul 05, 2023 at 01:44:20PM +0300, Vladimir Oltean wrote:
> In a future commit we will have to call vsc9959_tas_guard_bands_update()
> from ocelot_port_update_active_preemptible_tcs(), and that will be
> impossible due to the AB/BA locking dependencies between
> ocelot->tas_lock and ocelot->fwd_domain_lock.
> 
> Just like we did in commit 3ff468ef987e ("net: mscc: ocelot: remove
> struct ocelot_mm_state :: lock"), the only solution is to expand the
> scope of ocelot->fwd_domain_lock for it to also serialize changes made
> to the Time-Aware Shaper, because those will have to result in a
> recalculation of cut-through TCs, which is something that depends on the
> forwarding domain.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Simon Horman <simon.horman@...igine.com>