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From: David Miller <davem@davemloft.net>
Subject: Re: tun: Use netif_receive_skb instead of netif_rx
Date: Wed, 19 May 2010 13:14:48 -0700 (PDT)
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From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Wed, 19 May 2010 18:20:47 +1000

> On Wed, May 19, 2010 at 10:09:42AM +0200, Eric Dumazet wrote:
>> 
>> 6) netif_rx() pro is that packet processing is done while stack usage is
>> guaranteed to be low (from process_backlog, using a special softirq
>> stack, instead of current stack)
>> 
>> After your patch, tun will use more stack. Is it safe on all contexts ?
> 
> Dave also raised this but I believe nothing changes with regards
> to the stack.  We currently call do_softirq which does not switch
> stacks.

do_softirq() _does_ switch stacks, it's a per-arch function that
does the stack switch and calls __do_softirq() on the softirq
stack.