netdev - Re: [PATCH 10/16] ipv4: Cache output routes in fib

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Date:	Fri, 20 Jul 2012 00:19:22 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 10/16] ipv4: Cache output routes in fib_info nexthops.

On Thu, 2012-07-19 at 15:13 -0700, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Fri, 20 Jul 2012 00:09:03 +0200
> 
> > If we find orig not null, what can protect another cpu from reading
> > nh->nh_rth_output, then we dst_release(orig), and other cpu  does the
> > dst_use() too late ?
> 
> Indeed, we'd have to defer it somehow.
> 
> Actually, we might be able to fake this by using __dst_free() on it
> or something similar.
> 
> But safest would be RCU, whose protection we are still using on the
> read side.
> 
> Any better ideas?

Well, its very late for me in France and I really need to sleep.

I hope I really can, now that you gave me the silly idea to work on a
linux patch ;)

RCU seems a good idea at first glance.



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