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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v3)
Date: Wed, 15 Apr 2009 17:05:39 -0700 (PDT)
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From: Stephen Hemminger <shemminger@vyatta.com>
Date: Wed, 15 Apr 2009 17:01:11 -0700

> The counters are the bigger problem, otherwise we could just free table
> info via rcu.  Do we really have to support: replace where the counter
> values coming out to user space are always exactly accurate, or is it
> allowed to replace a rule and maybe lose some counter ticks (worst case
> NCPU-1).

I say this case doesn't matter until someone can prove that it's
any different from the IPTABLES replace operation system call
executing a few microseconds earlier or later.

There really is no difference, and we're making complexity out of
nothing just to ensure something which isn't actually guarenteed right
now.