netdev - Re: [PATCH net] net: dcb: flush lingering app table entries for unregistered devices

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Message-ID: <Yh+N2OCM+Mv3GWoO@shredder>
Date:   Wed, 2 Mar 2022 17:31:36 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Petr Machata <petrm@...dia.com>
Subject: Re: [PATCH net] net: dcb: flush lingering app table entries for
 unregistered devices

On Tue, Mar 01, 2022 at 04:36:32PM +0000, Vladimir Oltean wrote:
> On Tue, Mar 01, 2022 at 06:23:16PM +0200, Ido Schimmel wrote:
> > On Thu, Feb 24, 2022 at 06:01:54PM +0200, Vladimir Oltean wrote:
> > > +static void dcbnl_flush_dev(struct net_device *dev)
> > > +{
> > > +	struct dcb_app_type *itr, *tmp;
> > > +
> > > +	spin_lock(&dcb_lock);
> > 
> > Should this be spin_lock_bh()? According to commit 52cff74eef5d ("dcbnl
> > : Disable software interrupts before taking dcb_lock") this lock can be
> > acquired from softIRQ.
> 
> Could be. I didn't notice the explanation and I was even wondering in
> which circumstance would it be needed to disable softirqs...
> Now that I see the explanation I think the dcb_rpl -> cxgb4_dcb_handle_fw_update
> -> dcb_ieee_setapp call path is problematic, when a different
> DCB-enabled interface unregisters concurrently with a firmware event.

Yep. Can you please send a fix so that it gets into Jakub's PR tomorrow?