On Thu, 2016-03-31 at 13:50 +0800, Jason Wang wrote:
> We use a union for napi_id and send_cpu, this is ok for most of the
> cases except when we want to support busy polling for tun which needs
> napi_id to be stored and passed to socket during tun_net_xmit(). In
> this case, napi_id was overridden with sender_cpu before tun_net_xmit()
> was called if XPS was enabled. Fixing by not using union for napi_id
> and sender_cpu.
>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> include/linux/skbuff.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 15d0df9..8aee891 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -743,11 +743,11 @@ struct sk_buff {
> __u32 hash;
> __be16 vlan_proto;
> __u16 vlan_tci;
> -#if defined(CONFIG_NET_RX_BUSY_POLL) || defined(CONFIG_XPS)
> - union {
> - unsigned int napi_id;
> - unsigned int sender_cpu;
> - };
> +#if defined(CONFIG_NET_RX_BUSY_POLL)
> + unsigned int napi_id;
> +#endif
> +#if defined(CONFIG_XPS)
> + unsigned int sender_cpu;
> #endif
> union {
> #ifdef CONFIG_NETWORK_SECMARK
Hmmm...
This is a serious problem.
Making skb bigger (8 bytes because of alignment) was not considered
valid for sender_cpu introduction. We worked quite hard to avoid this,
if you take a look at git history :(
Can you describe more precisely the problem and code path ?
