On Wed, 15 Apr 2009, David Miller wrote: > > I really think we should entertain the idea where we don't RCU quiesce > when adding rules. That was dismissed as not workable because the new > rule must be "visible" as soon as we return to userspace but let's get > real, effectively it will be. I never understood that dismissal. The new rule _will_ be visible as we return to user space. It's just that old packets may still be in flight in other queues. But that is true even _without_ the "synchronize_net()". The old packets just had to make it slightly further in the queueing - but as far as user space is concerned, there is absolutely _zero_ difference between the two. In both cases it may see packets queued with the old rules. > I almost cringed when the per-spinlock idea was proposed, but per-cpu > rwlocks just takes things too far for my tastes. I really personally would prefer the RCU approach too. I don't think rwlocks are any more cringe-worthy than spinlocks, although it is true that they tend to be slightly more expensive. The pure RCU "just get rid of the unnecessary 'serialze_net()'" approach seems to be clearly superior to either. Linus -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
