netdev - Re: [PATCH] wireless extensions: play with netns

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Date:	Thu, 18 Jun 2009 02:02:06 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	John Linville <linville@...driver.com>,
	Netdev <netdev@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH] wireless extensions: play with netns

On Wed, 2009-06-17 at 16:54 -0700, Eric W. Biederman wrote:

> > Subject: net: make namespace iteration possible under RCU
> >
> > We already call rcu_barrier(), so all we need to take
> > care of is using proper RCU list add/del primitives.
> 
> This of course gives you a network namespace that can be found by for_each_net rcu
> while the per net exit functions are running.  I think that opens up to races
> that I don't want to think about.

Indeed. Can we move the rcu_barrier() up? Or we could insert a
synchronize_rcu() (which is sufficient for rcu_read_lock) before the
exit functions are run?

> I still haven't tracked down how I am occasionally getting time wait sockets
> with an invalid network namespace.

Ouch.

johannes

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