On Tue, 2009-09-08 at 15:49 +0800, DDD wrote:
quoted text
> This race will break the messages order.
> 
> Sequence of events in the problem case:
> 
> Assume there is one skb "A" in skb_queue and the next action of
> netpoll_send_skb() is: sending out "B" skb.
> The right order of messages should be: send A first, then send B.
> 
> But as following orders, it will send B first, then send A.

I would say no, the order of messages A and B queued on different CPUs
is undefined. The only issue is that we can queue a message A on CPU0,
then causally trigger a message on CPU1 B that arrives first. But bear
in mind that the message A >>may never arrive<< because the message is
about a lockup that kills processing of delayed work.

Generally speaking, queueing should be a last ditch effort. We should
instead aim to deliver all messages immediately, even if they might be
out of order. Because out of order is better than not arriving at all.

-- 
http://selenic.com : development and support for Mercurial and Linux


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