From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] netns: remove useless synchronize_net()
Date: Thu, 05 Feb 2009 23:45:20 -0800 (PST)
Message-ID: <20090205.234520.149982266.davem@davemloft.net>
References: <498ABDA2.5040603@dev.6wind.com>
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From: Nicolas Dichtel <nicolas.dichtel@dev.6wind.com>
Date: Thu, 05 Feb 2009 11:21:22 +0100

> In dev_change_net_namespace(), synchronize_net() is called at the
> end of the function, but there is no reason (no deletion occurs).
>
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>

It is necessary to make sure all cpus stop looking at the
previous namespace the device was attached to, and only
see the new mapping.

That's why this function has two synchronize_net() calls.