On Thu, Feb 03, 2005 at 02:19:01PM -0800, David S. Miller wrote: > > They are for cases where you want strict ordering even for the > non-return-value-giving atomic_t ops.
I see. I got atomic_dec and atomic_dec_and_test mixed up. So the problem isn't as big as I thought which is good. sk_buff is only in trouble because of the atomic_read optimisation which really needs a memory barrier. However, instead of adding a memory barrier which makes the optimisation less useful, let's just get rid of the atomic_read. Signed-off-by: Herbert Xu <[EMAIL PROTECTED]> Thanks for the document, it's really helpful. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
===== include/linux/skbuff.h 1.59 vs edited ===== --- 1.59/include/linux/skbuff.h 2005-01-11 07:23:55 +11:00 +++ edited/include/linux/skbuff.h 2005-02-04 10:44:17 +11:00 @@ -353,14 +353,14 @@ */ static inline void kfree_skb(struct sk_buff *skb) { - if (atomic_read(&skb->users) == 1 || atomic_dec_and_test(&skb->users)) + if (atomic_dec_and_test(&skb->users)) __kfree_skb(skb); } /* Use this if you didn't touch the skb state [for fast switching] */ static inline void kfree_skb_fast(struct sk_buff *skb) { - if (atomic_read(&skb->users) == 1 || atomic_dec_and_test(&skb->users)) + if (atomic_dec_and_test(&skb->users)) kfree_skbmem(skb); }