netdev - Re: [PATCH v2] ipv4: Restore old dst

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Message-Id: <20120731.144217.708886493005872001.davem@davemloft.net>
Date:	Tue, 31 Jul 2012 14:42:17 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v2] ipv4: Restore old dst_free() behavior.

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 31 Jul 2012 13:08:23 +0200

> [PATCH v2] ipv4: Restore old dst_free() behavior
> 
> commit 404e0a8b6a55 (net: ipv4: fix RCU races on dst refcounts) tried
> to solve a race but added a problem at device/fib dismantle time :
> 
> We really want to call dst_free() as soon as possible, even if sockets
> still have dst in their cache.
> dst_release() calls in free_fib_info_rcu() are not welcomed.
> 
> Root of the problem was that now we also cache output routes (in
> nh_rth_output), we must use call_rcu() instead of call_rcu_bh() in
> rt_free(), because output route lookups are done in process context.
> 
> Based on feedback and initial patch from David Miller (adding another
> call_rcu_bh() call in fib, but it appears it was not the right fix)
> 
> I left the inet_sk_rx_dst_set() helper and added __rcu attributes
> to nh_rth_output and nh_rth_input to better document what is going on in
> this code.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks Eric.
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