smp_rmb() in consume_skb

Hi, When I was looking into consume_skb() routine (net/core/skbuff.c), there is smp_rmb() read barrier is present. It is not clear why this is needed here. Basically this routine frees sk_buff if only one user reference is theere void consume_skb(struct sk_buff * skb) { if (unlikely(!skb)) return; if (likley (atomic_read (&skb->users) == 1)) smp_rmb() --------------------------------------------------------> need for this barrier ...... __kfree_skb(); } Regards Kshemendra