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

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Message-ID: <20220301163632.pcag3zgluewlwnh3@skbuf>
Date:   Tue, 1 Mar 2022 16:36:32 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Ido Schimmel <idosch@...sch.org>
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 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.