netdev - Re: [PATCH net-next v2] vxlan: synchronously and race-free destruction of vxlan sockets

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Message-ID: <CAM_iQpUbTz2dRS+ZTZSSL0AvkOb_2_HEfXo+ap9__aQZmajMjA@mail.gmail.com>
Date:	Fri, 8 Apr 2016 16:24:28 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Jiri Benc <jbenc@...hat.com>,
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net-next v2] vxlan: synchronously and race-free
 destruction of vxlan sockets

On Fri, Apr 8, 2016 at 1:55 PM, Hannes Frederic Sowa
<hannes@...essinduktion.org> wrote:
> Due to the fact that the udp socket is destructed asynchronously in a
> work queue, we have some nondeterministic behavior during shutdown of
> vxlan tunnels and creating new ones. Fix this by keeping the destruction
> process synchronous in regards to the user space process so IFF_UP can
> be reliably set.
>
> udp_tunnel_sock_release destroys vs->sock->sk if reference counter
> indicates so. We expect to have the same lifetime of vxlan_sock and
> vxlan_sock->sock->sk even in fast paths with only rcu locks held. So
> only destruct the whole socket after we can be sure it cannot be found
> by searching vxlan_net->sock_list.
>

I am wondering what is the reason why we used work queue from
the beginning?