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

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Message-ID: <20211109082042.31cf29c3@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 9 Nov 2021 08:20:42 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Jiri Pirko <jiri@...dia.com>, Leon Romanovsky <leon@...nel.org>,
        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, 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.