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