netdev - Re: [PATCH net-next] devlink: Require devlink lock during device reload

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Message-ID: <YYt6Jyyz+K9Pj3oL@unreal>
Date:   Wed, 10 Nov 2021 09:52:07 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Jason Gunthorpe <jgg@...dia.com>, Jiri Pirko <jiri@...dia.com>,
        Ido Schimmel <idosch@...sch.org>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        edwin.peer@...adcom.com
Subject: Re: [PATCH net-next] devlink: Require devlink lock during device
 reload

On Tue, Nov 09, 2021 at 08:20:42AM -0800, Jakub Kicinski wrote:
> On Tue, 9 Nov 2021 11:33:35 -0400 Jason Gunthorpe wrote:
> > > > I once sketched out fixing this by removing the need to hold the
> > > > per_net_rwsem just for list iteration, which in turn avoids holding it
> > > > over the devlink reload paths. It seemed like a reasonable step toward
> > > > finer grained locking.  
> > > 
> > > Seems to me the locking is just a symptom.  
> > 
> > My fear is this reload during net ns destruction is devlink uAPI now
> > and, yes it may be only a symptom, but the root cause may be unfixable
> > uAPI constraints.
> 
> If I'm reading this right it locks up 100% of the time, what is a uAPI
> for? DoS? ;)
> 
> Hence my questions about the actual use cases.

It is important to add that this problem existed even before auxiliary
bus conversion.

Thanks