Re: [PATCH net-next] fix unsafe set_memory_rw from softirq

[Eric Dumazet <eric.dumazet@gmail.com>]

On Wed, 2013-10-02 at 21:44 -0700, Alexei Starovoitov wrote:

> I think ifdef config_x86 is a bit ugly inside struct sk_filter, but
> don't mind whichever way.

Its not fair to make sk_filter bigger, because it means that simple (non
JIT) filter might need an extra cache line.

You could presumably use the following layout instead :

struct sk_filter
{
        atomic_t                refcnt;
        struct rcu_head         rcu;
	struct work_struct      work;

        unsigned int            len ____cacheline_aligned;    /* Number of filter blocks */
        unsigned int            (*bpf_func)(const struct sk_buff *skb,
                                            const struct sock_filter *filter);
        struct sock_filter      insns[0];
};