Avoiding re-ordering in netif_rx()

From: Nagendra Singh Tomar (nagendra_tomar@adaptec.com)
Date: Wed Jul 30 2003 - 23:41:56 EST


I am modifying linux kernel 2.4.18 to add support for our TCP offload
card. The problem is:
The packets that I get from the card are fully TCP processed and in-order.
Now I feed these packets to netif_rx(). marking a flag in the skbuff which
says that the full TCP/IP processing is done on this packet and the higher
layers can just bypass the packet protocol processing. On an SMP m/c
different consequtive in-order packets received from the card can be
queued to different per-cpu queues and it might so happen that the later
received packet is added to the socket receive queue first ( bcos the
softirq on the later CPU got a chance to execute first). This maliciously
reorders the data.

My question is, what is an elegant way of avoiding this. I have a couple
of choices, but I want to know what people think. f.e one way is to queue
these packets to a single queue and not a per-cpu queue. In this case
order will be honoured.

brilliant suggestions are very welcome !!

Thanx
tomar

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