linux-kernel - Re: [PATCH bpf v2] xdp: fix hang while unregistering device bound to xdp socket

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Date:   Fri, 7 Jun 2019 16:31:56 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Ilya Maximets <i.maximets@...sung.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, xdp-newbies@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>
Subject: Re: [PATCH bpf v2] xdp: fix hang while unregistering device bound
 to xdp socket

On Fri,  7 Jun 2019 20:31:43 +0300, Ilya Maximets wrote:
> +static int xsk_notifier(struct notifier_block *this,
> +			unsigned long msg, void *ptr)
> +{
> +	struct sock *sk;
> +	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> +	struct net *net = dev_net(dev);
> +	int i, unregister_count = 0;

Please order the var declaration lines longest to shortest.
(reverse christmas tree)

> +	mutex_lock(&net->xdp.lock);
> +	sk_for_each(sk, &net->xdp.list) {
> +		struct xdp_sock *xs = xdp_sk(sk);
> +
> +		mutex_lock(&xs->mutex);
> +		switch (msg) {
> +		case NETDEV_UNREGISTER:

You should probably check the msg type earlier and not take all the
locks and iterate for other types..