linux-kernel - Re: [PATCH v8 net-next 2/2] net: dsa: mv88e6xxx: mac-auth/MAB implementation

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Message-ID: <Y3Osehw6Ra28HhYv@shredder>
Date:   Tue, 15 Nov 2022 17:12:58 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     netdev@...io-technology.com
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 net-next 2/2] net: dsa: mv88e6xxx: mac-auth/MAB
 implementation

On Tue, Nov 15, 2022 at 11:36:38AM +0100, netdev@...io-technology.com wrote:
> On 2022-11-15 10:58, Ido Schimmel wrote:
> > On Sat, Nov 12, 2022 at 09:37:48PM +0100, Hans J. Schultz wrote:
> > > diff --git a/drivers/net/dsa/mv88e6xxx/global1_atu.c
> > > b/drivers/net/dsa/mv88e6xxx/global1_atu.c
> > > index 8a874b6fc8e1..0a57f4e7dd46 100644
> > > --- a/drivers/net/dsa/mv88e6xxx/global1_atu.c
> > > +++ b/drivers/net/dsa/mv88e6xxx/global1_atu.c
> > > @@ -12,6 +12,7 @@
> > > 
> > >  #include "chip.h"
> > >  #include "global1.h"
> > > +#include "switchdev.h"
> > > 
> > >  /* Offset 0x01: ATU FID Register */
> > > 
> > > @@ -426,6 +427,8 @@ static irqreturn_t
> > > mv88e6xxx_g1_atu_prob_irq_thread_fn(int irq, void *dev_id)
> > >  	if (err)
> > >  		goto out;
> > > 
> > > +	mv88e6xxx_reg_unlock(chip);
> > 
> > Why? At minimum such a change needs to be explained in the commit
> > message and probably split to a separate preparatory patch, assuming the
> > change is actually required.
> 
> This was a change done long time ago related to that the violation handle
> function takes the NL lock,
> which could lead to a double-lock deadlock afair if the chip lock is taken
> throughout the handler.

Why do you need to take RTNL lock? br_switchdev_event() which receives
the 'SWITCHDEV_FDB_ADD_TO_BRIDGE' event has this comment:
"/* called with RTNL or RCU */"
And it's using br_port_get_rtnl_rcu(), so looks like RCU is enough.