[Bridge] Re: [PATCH/RFC] Reduce call chain length in netfilter

David S. Miller davem at davemloft.net
Thu Jan 27 11:47:26 PST 2005


On Thu, 27 Jan 2005 18:50:50 +0100
Patrick McHardy <kaber at trash.net> wrote:

>  From what I can see it doesn't generate tail-calls currently:

Indeed... It even doesn't do this on Sparc64 either, even for
the okfn(skb) call which I was sure it would.

It won't tail-call for function pointers for some strance reason
as exhibited by this simple test:

struct sk_buff {
	int foo;
};

int invoke(struct sk_buff *skb, int (*okfn)(struct sk_buff *))
{
	return okfn(skb);
}

extern int test_func(struct sk_buff *);

int invoke2(struct sk_buff *skb)
{
	return test_func(skb);
}

In the generated asm on sparc64, invoke2() gets a tail-call
whereas invoke() does not.  Hmmm...



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