netdev - Re: [PATCH net] team: fix deadlock during setting of MTU

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Message-ID: <20210120132300.757b91b3@ceranb>
Date:   Wed, 20 Jan 2021 13:23:00 +0100
From:   Ivan Vecera <ivecera@...hat.com>
To:     Saeed Mahameed <saeed@...nel.org>
Cc:     netdev@...r.kernel.org, Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH net] team: fix deadlock during setting of MTU

On Fri, 15 Jan 2021 09:24:05 +0100
Ivan Vecera <ivecera@...hat.com> wrote:

> > according to your explanation in the commit message the team->lock
> > mutex will be also taken under this rcu lock, so this is bad even
> > if dev_set_mtu does not sleep.
> >   
> Hmm, you are right... btw do we need to take this mutex at this place?
> 
> team_change_mtu() is protected by RTNL, team_device_event() as a netdevice
> notifier as well... and team_{add,del}_slave() that modify port list
> also.
> 
> Thoughts?

After private discussion with Jiri, this is no-go as he would not like to
introduce a dependency on RTNL into team driver. The other solution is
to postpone features calculation in certain cases... the patch follows.

Ivan