• Menglong Dong's avatar
    net: skb: prevent the split of kfree_skb_reason() by gcc · c205cc75
    Menglong Dong authored
    Sometimes, gcc will optimize the function by spliting it to two or
    more functions. In this case, kfree_skb_reason() is splited to
    kfree_skb_reason and kfree_skb_reason.part.0. However, the
    function/tracepoint trace_kfree_skb() in it needs the return address
    of kfree_skb_reason().
    
    This split makes the call chains becomes:
      kfree_skb_reason() -> kfree_skb_reason.part.0 -> trace_kfree_skb()
    
    which makes the return address that passed to trace_kfree_skb() be
    kfree_skb().
    
    Therefore, introduce '__fix_address', which is the combination of
    '__noclone' and 'noinline', and apply it to kfree_skb_reason() to
    prevent to from being splited or made inline.
    
    (Is it better to simply apply '__noclone oninline' to kfree_skb_reason?
    I'm thinking maybe other functions have the same problems)
    
    Meanwhile, wrap 'skb_unref()' with 'unlikely()', as the compiler thinks
    it is likely return true and splits kfree_skb_reason().
    Signed-off-by: default avatarMenglong Dong <imagedong@tencent.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    c205cc75
skbuff.c 163 KB