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

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Message-ID: <20211109061729.32f20616@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 9 Nov 2021 06:17:29 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Ido Schimmel <idosch@...sch.org>, Jiri Pirko <jiri@...nulli.us>,
        "David S . Miller" <davem@...emloft.net>,
        Jiri Pirko <jiri@...dia.com>, 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 16:12:33 +0200 Leon Romanovsky wrote:
> > You'd need to tell me more about what the notifier is used for (I see
> > RoCE in the call trace). I don't understand why you need to re-register 
> > a global (i.e. not per netns) notifier when devlink is switching name
> > spaces.  
> 
> RDMA subsystem supports two net namespace aware scenarios.
> 
> We need global netdev_notifier for shared mode. This is legacy mode where
> we listen to all namespaces. We must support this mode otherwise we break
> whole RDMA world.
> 
> See commit below:
> de641d74fb00 ("Revert "RDMA/mlx5: Fix devlink deadlock on net namespace deletion"")

But why re-reg? To take advantage of clean event replay?

IIUC the problem is that the un-reg is called from the reload_down path.