[Devel] Re: [PATCH 5/5] make netlink user -> kernel interface synchronious

[David Miller]

From: "Denis V. Lunev" <den at openvz.org>
Date: Fri, 5 Oct 2007 18:48:44 +0400

> This patch make processing netlink user -> kernel messages synchronious.
> This change was inspired by the talk with Alexey Kuznetsov about current
> netlink messages processing. He says that he was badly wrong when introduced 
> asynchronious user -> kernel communication.
> 
> The call netlink_unicast is the only path to send message to the kernel
> netlink socket. But, unfortunately, it is also used to send data to the
> user.
> 
> Before this change the user message has been attached to the socket queue
> and sk->sk_data_ready was called. The process has been blocked until all
> pending messages were processed. The bad thing is that this processing
> may occur in the arbitrary process context.
> 
> This patch changes nlk->data_ready callback to get 1 skb and force packet
> processing right in the netlink_unicast.
> 
> Kernel -> user path in netlink_unicast remains untouched.
> 
> EINTR processing for in netlink_run_queue was changed. It forces rtnl_lock
> drop, but the process remains in the cycle until the message will be fully
> processed. So, there is no need to use this kludges now.
> 
> Signed-off-by: Denis V. Lunev <den at openvz.org>
> Acked-by: Alexey Kuznetsov <kuznet at ms2.inr.ac.ru>

Applied.