netdev - RE: [PATCH net] net: xdp: don't call notifiers during driver init

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Message-ID: <6412a9aa92347_8961e20896@john.notmuch>
Date:   Wed, 15 Mar 2023 22:31:22 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com,
        Jakub Kicinski <kuba@...nel.org>, ast@...nel.org,
        daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com,
        lorenzo@...nel.org, tariqt@...dia.com, bpf@...r.kernel.org
Subject: RE: [PATCH net] net: xdp: don't call notifiers during driver init

Jakub Kicinski wrote:
> Drivers will commonly perform feature setting during init, if they use
> the xdp_set_features_flag() helper they'll likely run into an ASSERT_RTNL()
> inside call_netdevice_notifiers_info().
> 
> Don't call the notifier until the device is actually registered.
> Nothing should be tracking the device until its registered.
> 
> Fixes: 4d5ab0ad964d ("net/mlx5e: take into account device reconfiguration for xdp_features flag")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> CC: ast@...nel.org
> CC: daniel@...earbox.net
> CC: hawk@...nel.org
> CC: john.fastabend@...il.com
> CC: lorenzo@...nel.org
> CC: tariqt@...dia.com
> CC: bpf@...r.kernel.org
> ---
>  net/core/xdp.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index 87e654b7d06c..5722a1fc6e9e 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -781,6 +781,9 @@ void xdp_set_features_flag(struct net_device *dev, xdp_features_t val)
>  		return;
>  
>  	dev->xdp_features = val;
> +
> +	if (dev->reg_state < NETREG_REGISTERED)
> +		return;
>  	call_netdevice_notifiers(NETDEV_XDP_FEAT_CHANGE, dev);
>  }
>  EXPORT_SYMBOL_GPL(xdp_set_features_flag);
> -- 
> 2.39.2
> 

LGTM

Acked-by: John Fastabend <john.fastabend@...il.com>