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

[Ilya Maximets <i.maximets@samsung.com>]

On 08.06.2019 2:31, Jakub Kicinski wrote:
> 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)

Hi.
I'm not a fan of mixing 'struct's with bare types in the declarations.
Moving the 'sk' to the third place will make a hole like this:

	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct net *net = dev_net(dev);
	struct sock *sk;
	int i, unregister_count = 0;

Which is not looking good.
Moving to the 4th place:

	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct net *net = dev_net(dev);
	int i, unregister_count = 0;
	struct sock *sk;

This variant doesn't look good for me because of mixing 'struct's with
bare integers.

Do you think I need to use one of above variants?

> 
>> +	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..

Yeah. I thought about it too. Will fix in the next version.

Best regards, Ilya Maximets.