netdev - Re: [PATCH net-next 2/9] net: hold instance lock during NETDEV

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Message-ID: <66a15c52d68a2317dfa65093ecd227b0ad4684cc.camel@nvidia.com>
Date: Wed, 26 Mar 2025 21:18:02 +0000
From: Cosmin Ratiu <cratiu@...dia.com>
To: "stfomichev@...il.com" <stfomichev@...il.com>
CC: "kuba@...nel.org" <kuba@...nel.org>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>, "pabeni@...hat.com"
	<pabeni@...hat.com>, "sdf@...ichev.me" <sdf@...ichev.me>
Subject: Re: [PATCH net-next 2/9] net: hold instance lock during
 NETDEV_REGISTER/UP/UNREGISTER

On Wed, 2025-03-26 at 21:57 +0100, Cosmin Ratiu wrote:
> 
> Am I missing some locking annotation patch? A quick search in net-
> next
> turned out nothing.

Soon after sending the previous email, I found
netdev_lockdep_set_classes and saw that it disables deadlock checking
for the instance lock. With it in place, it works.
I also saw your other email immediately after...

With that in place, things seem to work fine without further warnings
for a few quick tests.

However, it seems that this approach is dangerous, there is the
possibility of an actual deadlock with two concurrent
netif_change_net_namespace when the RTNL is removed from that path.

Cosmin.
>