netdev - Re: [PATCH v1 net] rtnetlink: Use register_pernet_subsys() in rtnl_net_debug

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Message-ID: <20250331154849.GC185681@horms.kernel.org>
Date: Mon, 31 Mar 2025 16:48:49 +0100
From: Simon Horman <horms@...nel.org>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net] rtnetlink: Use register_pernet_subsys() in
 rtnl_net_debug_init().

On Fri, Mar 28, 2025 at 03:04:48PM -0700, Kuniyuki Iwashima wrote:
> rtnl_net_debug_init() registers rtnl_net_debug_net_ops by
> register_pernet_device() but calls unregister_pernet_subsys()
> in case register_netdevice_notifier() fails.
> 
> It corrupts pernet_list because first_device is not updated
> in unregister_pernet_device().

Hi Iwashima-san,

Maybe I am confused, but should the above line refer to
unregister_pernet_subsys()?

And perhaps it would be yet clearer to say something like:

It corrupts pernet_list because first_device is not updated
in register_pernet_device() but not unregister_pernet_subsys()?

> 
> Let's fix it by calling register_pernet_subsys() instead.
> 
> The _subsys() one fits better for the use case because it keeps
> the notifier alive until default_device_exit_net(), giving it
> more chance to test NETDEV_UNREGISTER.
> 
> Fixes: 03fa53485659 ("rtnetlink: Add ASSERT_RTNL_NET() placeholder for netdev notifier.")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>

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